Grant's dissector [16th edition, international edition.] 9781496316790, 1496316797

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ALAN J. DETTON, Ph D Lecturer Clinical Anatom y Stanford University School of Medicine Stanford, California

In Mem oriam

Pat rick W. Tan k, Ph D (1950–2012) Aut h or o f Th irt e e n t h , Fo urt e e n t h , an d Fift e e n t h Ed it io n s Professor of Anatom y (1978–2012) Course Director, Gross Anatom y; Director, Anatom ical Gift Program (1985–2011) Also served as Director of Education and Director of Anatom ical Education Dep artm ent of Neurobiology and Develop m ental Sciences University of Arkansas for Medical Sciences Little Rock, Arkansas

No t a u t h o rised fo r sa le in Un it ed St a t es, Ca n a d a , Au st ra lia , New Zea la n d , Pu er t o Rico , a n d U.S. Virgin Isla n d s. Acquisitions Editor: Crystal Taylor Product Developm ent Editor: Greg Nich oll Marketing Manager: Mich ael McMah on Production Project Manager: David Orzech owski Design Coordinator: Holly McLau gh lin Art Director: Jen n ifer Clem en ts Artist/Illustrator: Dragon y Med ia Grou p Manufacturing Coordinator: Margie Orzech Prepress Vendor: Absolu te Service, In c. Sixteen th Ed ition By P.W. Ta n k : Fifteen th Ed ition , 2013; Fou rteen th Ed ition , 2009; Th irteen th Edition , 2005 By E.K. Sa u erla n d : Twelfth Ed ition , 1999; Eleven th Ed ition , 1994; Ten th Ed ition , 1991; Nin th Ed ition , 1984; Eigh th Ed ition , 1978; Seven th Ed ition , 1974 By J.C.B. Gra n t : Sixth Ed ition , 1967; Fifth Edition , 1959 By J.C.B. Gra n t a n d H .A. Ca t es: Fou rth Edition , 1953; Th ird Edition , 1948; Secon d Ed ition , 1945; First Edition , 1940 Cop yrigh t © 2017 Wolters Klu wer. Cop yrigh t © 2013, 2009 Lip p in cott William s & Wilkin s, a Wolters Klu wer bu sin ess. Cop yrigh t © 2005, 1999 Lip p in cott William s & Wilkin s. Cop yrigh t © 1994, 1991, 1984, 1978, 1974, 1967, 1959, 1953, 1948, 1945, 1940 William s & Wilkin s. Prin ted in Ch in a All righ ts reserved . Th is book is p rotected by cop yrigh t. No p art of th is book m ay be rep rod u ced or tran sm itted in an y form or by an y m ean s, in clu d in g as p h otocop ies or scan n ed -in or oth er electron ic cop ies, or u tilized by an y in form ation storage an d retrieval system with ou t written p erm ission from th e cop yrigh t own er, excep t for brief q u otation s em bod ied in critical articles an d reviews. Materials ap p earin g in th is book p rep ared by in d ivid u als as p art of th eir of cial d u ties as U.S. govern m en t em p loyees are n ot covered by th e above-m en tion ed cop yrigh t. To req u est p erm ission , p lease con tact Wolters Klu wer at Two Com m erce Sq u are, 2001 Market Street, Ph ilad elp h ia, PA 19103, via em ail at p erm ission [email protected] , or via ou r website at lww.com (p rod u cts an d services). 9 8 7 6 5 4 3 2 1 Lib ra r y o f Co n gress Ca t a lo gin g-in -Pu b lica t io n Da t a Nam es: Detton , Alan J., au th or. | Tan k, Patrick W., 1950-2012. Gran t’s d issector. Preced ed by (work): Title: Gran t’s d issector / Alan J. Detton . Oth er titles: Dissector Descrip tion : Sixteen th ed ition . | Ph ilad elp h ia : Wolters Klu wer, [2017] | Preced ed by Gran t’s d issector. 15th ed . / Patrick W. Tan k. c2013. | In clu d es in d ex. Id en ti ers: LCCN 2015041288 | ISBN 9781496316790 Su bjects: | MESH: Dissection --Laboratory Man u als. Classi cation : LCC QM34 | NLM QS 130 | DDC 611--d c23 LC record available at h ttp :/ / lccn .loc.gov/ 2015041288 Th is work is p rovid ed “as is,” an d th e p u blish er d isclaim s an y an d all warran ties, exp ress or im p lied , in clu d in g an y warran ties as to accu racy, com p reh en siven ess, or cu rren cy of th e con ten t of th is work. Th is work is n o su bstitu te for in d ivid u al p atien t assessm en t based on h ealth care p rofession als’ exam in ation of each p atien t an d con sid eration of, am on g oth er th in gs, age, weigh t, gen d er, cu rren t or p rior m ed ical con d ition s, m ed ication h istory, laboratory d ata, an d oth er factors u n iq u e to th e p atien t. Th e p u blish er does n ot p rovid e m edical advice or gu id an ce an d th is work is m erely a referen ce tool. Health care p rofession als, an d n ot th e p u blish er, are solely resp on sible for th e u se of th is work in clu d in g all m ed ical ju d gm en ts an d for an y resu ltin g d iagn osis an d treatm en ts. Given con tin u ou s, rap id ad van ces in m edical scien ce an d h ealth in form ation , in d ep en d en t p rofession al veri cation of m ed ical diagn oses, in d ication s, ap p rop riate p h arm aceu tical selection s an d d osages, an d treatm en t op tion s sh ou ld be m ad e an d h ealth care p rofession als sh ou ld con su lt a variety of sou rces. W h en p rescribin g m ed ication , h ealth care p rofession als are ad vised to con su lt th e p rod u ct in form ation sh eet (th e m an u factu rer’s p ackage in sert) accom p an yin g each d ru g to verify, am on g oth er th in gs, con d ition s of u se, warn in gs, an d sid e effects an d id en tify an y ch an ges in d osage sch ed u le or con train d ication s, p articu larly if th e m ed ication to be adm in istered is n ew, in freq u en tly u sed , or h as a n arrow th erap eu tic ran ge. To th e m axim u m exten t p erm itted u n d er ap p licable law, n o resp on sibility is assu m ed by th e p u blish er for an y in ju ry an d/ or d am age to p erson s or p rop erty, as a m atter of p rod u cts liability, n egligen ce law or oth erwise, or from an y referen ce to or u se by an y p erson of th is work. LW W.com

To m y fam ily and friends who think Gross Anatomy is simply gross

Reviewers ANATOMY CONSULTANT Sh e rry A. Do w n ie , Ph D Professor, Dep artm en ts of An atom y an d Stru ctu ral Biology an d Ph ysical Med icin e an d Reh abilitation Albert Ein stein College of Med icin e, Bron x, New York

Facult y Re vie we rs Th o m as Ge st , Ph D Professor of An atom y Dep artm en t of Med ical Ed u cation Texas Tech Un iversity Health Scien ces Cen ter El Paso, Texas

Lisa M.J. Le e , Ph D Associate Professor Cell an d Develop m en tal Biology Un iversity of Colorad o Den ver, Colorad o

An t h o n y B. Olin g e r, Ph D Associate Professor Dep artm en t of An atom y Kan sas City Un iversity of Med icin e an d Bioscien ces Kan sas City, Missou ri

Gre g o ry Pag e , BMe d Sci, MBCh B Lectu rer in An atom y an d Clin ical Skills Sch ool of Med icin e, Ph arm acy an d Health Du rh am Un iversity Stockton -on -Tees, Un ited Kin gd om

David Rap ap o rt , Ph D Professor Dep artm en t of Su rgery Un iversity of Californ ia, San Diego, Sch ool of Med icin e San Diego, Californ ia

Ryan Sp lit t g e rb e r, Ph D Assistan t Professor Dep artm en t of Gen etics, Cell Biology an d An atom y Un iversity of Nebraska Med ical Cen ter Om ah a, Nebraska

Jo e l A. Vile n sky, Ph D Professor Dep artm en t of An atom y an d Cell Biology In d ian a Un iversity Sch ool of Med icin e Fort Wayn e, In d ian a

Laura We lke , Ph D Associate Professor an d Vice Ch air Ross Un iversity Sch ool of Med icin e Dom in ica, West In d ies

Law re n ce E. Win e ski, Ph D Professor an d Ch air Dep artm en t of Path ology an d An atom y Moreh ou se Sch ool of Med icin e Atlan ta, Georgia

St ud e n t Re vie we rs Sisay Ab rah am Meh arry Med ical College Nash ville, Ten n essee

Jo sh Ag ran at Boston Un iversity Sch ool of Med icin e Boston , Massach u setts

Sarah Co rral Oaklan d Un iversity William Beaum on t Sch ool of Medicin e Roch ester, Mich igan

Callie Hin t ze n Un iversity of Arizon a College of Med icin e Tu cson , Arizon a

Be n jam in Ho lle r Texas A&M Health Scien ce Cen ter, College of Med icin e Bryan , Texas

An d re w Me n d e lso n Lake Erie College of Osteop ath ic Med icin e Erie, Pen n sylvan ia

Niral Pat e l Lake Erie College of Osteop ath ic Med icin e Erie, Pen n sylvan ia

Sun ali Sh ah Boston Un iversity Sch ool of Med icin e Boston , Massach u setts

Sai Ve m ula Ru tgers New Jersey Med ical Sch ool Newark, New Jersey

vii

Preface Grant’s Dissector is in ten d ed to p rovid e d issection in stru ction s an d en ou gh an atom ical d etail to h elp stu den ts observe an d recogn ize im p ortan t relation sh ip s revealed th rou gh dissection . Th e sixteen th ed ition of Grant’s Dissector aim s to con tin u e th e stron g tradition of p reviou s ed ition s as a region al d issection in stru ction m an u al bu t h as been rewritten to m ake th e con ten t m ore ap p rop riate to tod ay’s gross an atom y d issection cou rses. As cu rricu la are con stan tly ch an gin g, th e m od i cation s d escribed h ere are in ten d ed to in crease th e ad ap tability of Grant’s Dissector to a variety of d issection n eed s.

KEY FEATURES Un it Org an izat io n Th e organ ization al ow in th e sixteen th ed ition h as been m od i ed to m ain tain con sisten cy th rou gh ou t every ch ap ter. Th e d issection u n its begin with a clearly labeled title followed by th ree key asp ects to each d issection : an overview, th e in stru ction s, an d a follow-u p .

Surface An at o m y an d Ost e o lo g y Th e Dissect io n O ver view in t ro d u ces wh at is t o be accom p lish ed d u rin g t h e d issect io n sessio n an d n ow in clu d es st ep -by-st ep in st ru ct ion s t o gu id e st u d en t s t h ro u gh relevan t su r fa ce a n a t o m y an d o st eo lo gy . Th e ch an ge from bu llet ed list s t o n u m bered in st ru ct ion s is m ean t t o assist t h e st u d en t in ap p ro ach in g t h ese t o p ics in each d issect ion regio n . By d rawin g m o re at t en t ion t o t h e o verview as a t ask-o rien t ed set o f in st ru ct io n s, it is h op ed t h e im p ortan ce of bo th su rface an d skelet al lan d m arks fo r t h e lo calizat io n o f so ft t issu e st ru ct u res will be bet t er u n d erst o od .

Im p ro ve d Disse ct io n In st ruct io n s Sign i can t effort h as been m ad e to create sm all ch an ges in th e word in g of each d issection step with in th e Dissect io n In st r u ct io n s. Th e ch an ges were m ad e to clarify an d im p rove th e d issection exp erien ce an d to m ove m u ch of th e in form ation in th e con ten t-rich step s to th e su m m ary tables. Ad d ition ally, m an y of th e d issection in stru ction s n ow in clu d e ad vice to p erform th e d eep d issection of a region on on ly on e sid e of th e bod y an d to m in im ize th e d isru p tive cu ts th rou gh overlyin g stru ctu res as often as p ossible.

Muscle Sum m ary Tab le s To m in im ize th e am ou n t of in form ation con tain ed in th e d issection in stru ction step s, th e sixteen th ed ition n ow in clu d es 33 su m m ary tables in th e Dissect io n Fo llo w -u p to p rovide su ccin ct in form ation related to m u scles. Th e su m m ary tables in clu d e th e n am es, attach m en ts, action s, an d in n ervation s of th e key m u scles id en ti ed d u rin g each d issection u n it. Th ese tables p rovide a key review op p ortu n ity for stu d en ts, wh ile sim u ltan eou sly m akin g th e d issection s step s in th e in stru ction s m ore task orien ted an d ap p roach able. In add ition to th e su m m ary tables, th e Dissection Follow-u p section s en d each d issection u n it th rou gh a n u m bered list of tasks for th e stu d en ts to p erform in th e lab followin g th e d issection . Th e n u m bered tasks illu strate th e im p ortan t featu res of th e dissection an d en cou rage th e syn th esis of in form ation th rou gh review of th e m aterial.

Ne w Alt e rn at ive Disse ct io n In st ruct io n s Th e re ection of th e abd om in al wall p resen ted in th e sixteen th ed ition n ow offers two ap p roach es. Dissection in stru ction s are p rovid ed on h ow to op en th e abd om in al wall in eith er a q u ad ran t ap p roach or re ection of th e en tire abd om in al wall. Offerin g two sets of in stru ction s m eets th e n eed s of stu d en ts an d facu lty d esirin g altern ative ap p roach es to a com p lex region of an atom y.

Ne w He ad Disse ct io n In st ruct io n s Th e in stru ction s for h ead d issection h ave been m odi ed in th e sixteen th ed ition in an effort to m ain tain th e su p er cial an atom y on on e sid e of th e h ead . Th e m ajority of th e d eep er d issection s are ad vised to be p erform ed exclu sively on on e sid e of th e h ead in an effort to p rovid e a m eth od of review for both th e su p er cial an d deep stru ctu res on th e sam e sp ecim en . Mod i cation s to th e cu ts th rou gh th e calvaria an d m an d ible h ave been m ad e in an effort to m ake d issection of th e in fratem p oral fossa an d in tern al featu res of th e cran ial cavity easier an d faster for stu d en ts.

Ne w Illust rat io n s Sign i can t effort h as been taken to com p lete th e art p rogram begu n in th e th irteen th ed ition of Grant’s Dissector.

ix

x

•

PREFACE

Man y of th e p reviou s im ages were altered to in clu d e n ew labels an d d etail, wh ereas oth ers were red rawn so th at all of th e im ages in th e book are con sisten t in style an d ton e. Ad d ition ally, several n ew illu stration s were eith er u sed as rep lacem en ts for p reviou s illu stration s or ad d ed to clarify th e in ten t of th e d escrip tion s in th e text an d to assist th e stu d en t in m akin g correct in cision s an d dissection p roced u res. In total, over 100 im ages were m od i ed , altered , u p d ated , or ad d ed to th e existin g illu stration collection .

REFERENCES TO ATLAS ILLUSTRATIONS Th e stu d en t is en cou raged to rely on Grant’s Dissector on ly for dissection in stru ction an d to u se a textbook su ch as

Clinically Oriented Anatom y to p rovid e an atom ical d etails in con ju n ction with a q u ality atlas su ch as Grant’s Atlas or th e oth ers referen ced th rou gh ou t th is volu m e. To h elp stu d en ts cross-referen ce Grant’s Dissector with an atom y atlases, d issection in stru ction s con tain referen ces to ap p rop riate illu stration s in fou r u n iq u e atlases: • Agu r AMR, Dalley AF. Gra n t ’s At la s of An a t om y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2016. • Tan k PW, Gest TR. Lippin cot t W illia m s & W ilkin s At la s of An a t om y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. • Netter FH. At la s of H u m a n An a t om y. 6th ed . Ph ilad elp h ia, PA: Elsevier; 2014. • Roh en JW, Yokoch i C, Lü tjen -Drecoll E. An a t om y: A Ph ot ogra ph ic At la s. 8th ed . Baltim ore, MD: Wolters Klu wer; 2015.

Acknowledgm ents Th e creation of th e sixteen th ed ition of Grant’s Dissector wou ld n ot h ave been p ossible with ou t th e su p p ort an d assistan ce from an in cred ible grou p of in d ivid u als. First an d forem ost, th e sign i can t con tribu tion s of au th ors in volved in th e develop m en t of p reviou s ed ition s of Grant’s Dissector m u st be recogn ized . I was n ot able to let Pat Tan k kn ow d irectly h ow h is work in u en ced m e, bu t I wan t to exp ress m y d esire to th ose wh o ch erish h im an d h is bod y of work th at I will d o m y best to carry on h is efforts in th is text. I wish to express m y sin cere th an ks to th e team at Wolters Kluwer for trustin g m e with such an am bitious un dertakin g on such a prom in en t piece of work. I would like to th an k Crystal Taylor for your reception of m y vision an d for your support an d trust th rough out th e duration of th is project. Greg Nich oll, th an k you for th e exten ded an d sign i can t h elp alon g th e path to publication as a rst-tim e auth or. I h ave n ot expressed suf cien tly m y gratitude to you for all th e tim e, patien ce, an d con structive advice you h ave

given . Rob Duckwall, your artwork h as been in strum en tal in creatin g th e n ew feel for th is work, an d I appreciate your h ard work to h elp m ake m y th ough ts an d ideas real. I wan t to recogn ize two in divid u als wh o h ave in sp ired an d assisted in in n u m erable ways. Bob Aclan d , you r work, d ed ication to th e eld , an d m asterfu l rep resen tation of h ow to p rofession ally create in stru ction al con ten t h as in sp ired m e m ore th an I can ad eq u ately exp ress. Sh erry A. Down ie, th an k you so m u ch for th e tim e, d ed ication , an d ad vice p rovid ed th rou gh th e m an y ed its of th is text. I feel at a loss to fu lly p ortray th e con tribu tion s th at you h ave m ad e to th is work an d wan t to exp ress m y sin cere an d d eep ap p reciation for you as both a p rofession al an d as an in d ivid u al. Last, th an ks to th e m an y in d ivid u als, stu d en ts, in stru ctors, m en tors, an d colleagu es wh o su p p orted m e alon g th is jou rn ey at Stan ford Un iversity, Th e Oh io State Un iversity, th e Un iversity of Californ ia, San Fran cisco, an d elsewh ere.

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Contents Preface

CHAPTER 2

ix

Th e Up p e r Lim b

Acknowledgm ents xi Figure Credits Introduction

SCAPULAR REGION AND POSTERIOR ARM Dissection Overview 23

xix

• SKELETON OF THE SCAPULAR REGION

1

Dissection Instructions

Dissection Follow-up

5

9

Dissection Follow-up 10

TRAPEZIUS MUSCLE 10 LATISSIMUS DORSI MUSCLE 11 RHOMBOID MAJOR AND RHOMBOID MINOR MUSCLES 11 LEVATOR SCAPULAE MUSCLE 12

12

INTERMEDIATE AND DEEP MUSCLES OF THE BACK 13 Dissection Overview 13 Dissection Instructions 13 • • • • • • •

SERRATUS POSTERIOR SUPERIOR MUSCLE 13 SERRATUS POSTERIOR INFERIOR MUSCLE 13 SPLENIUS MUSCLE 14 ERECTOR SPINAE MUSCLES 14 SEMISPINALIS CAPITIS MUSCLE 14 SEMISPINALIS CERVICIS MUSCLE 14 MULTIFIDUS MUSCLE 15

Dissection Follow-up

15

SUBOCCIPITAL REGION Dissection Overview 16

16

16 17

VERTEBRAL CANAL, SPINAL CORD, AND MENINGES 18 Dissection Overview 18 Dissection Instructions 19

• BREAST 31 • SUPERFICIAL FASCIA 31

Dissection Follow-up

32

MUSCLES OF THE PECTORAL REGION Dissection Overview 32 Dissection Instructions 33 • MUSCLES OF THE PECTORAL REGION

Dissection Follow-up

22

32

33

34

AXILLA 35 Dissection Overview 35 Dissection Instructions 35 • AXILLA 35 • AXILLARY ARTERY 36 • BRACHIAL PLEXUS 37

Dissection Follow-up

38

Dissection Instructions

39

40

• ANTERIOR COMPARTMENT OF THE ARM MUSCLES 40 • NEUROVASCULATURE OF THE ARM 41 • CUBITAL FOSSA 42

Dissection Follow-up

43

SUPERFICIAL MUSCLES OF THE BACK 44 SCAPULAR REGION AND POSTERIOR COMPARTMENT OF THE ARM 44 FLEXOR REGION OF THE FOREARM Dissection Overview 44

• LAMINECTOMY 19 • SPINAL MENINGES 20

Dissection Follow-up

PECTORAL REGION 31 Dissection Overview 31 Dissection Instructions 31

• SKELETON OF THE ARM AND CUBITAL REGION

• SUBOCCIPITAL MUSCLES 16 • CONTENTS OF THE SUBOCCIPITAL TRIANGLE 16

Dissection Follow-up

31

ARM (BRACHIUM) AND CUBITAL FOSSA 39 Dissection Overview 39

16

• SKELETON OF THE SUBOCCIPITAL REGION

Dissection Instructions

29

• SKIN INCISIONS 29 • SUPERFICIAL VEINS 29 • CUTANEOUS NERVES 30

SUPERFICIAL MUSCLES OF THE BACK 10 Dissection Overview 10 Dissection Instructions 10

Dissection Follow-up

27

Dissection Instructions

• SKIN INCISIONS 9 • SUPERFICIAL FASCIA 9

Dissection Follow-up

26

• SURFACE ANATOMY 28

• SURFACE ANATOMY 5 • VERTEBRAL COLUMN 6

• • • •

24

SUPERFICIAL VEINS AND CUTANEOUS NERVES 28 Dissection Overview 28

SKIN AND SUPERFICIAL FASCIA 5 Dissection Overview 5 Dissection Instructions

23

23

• POSTERIOR SHOULDER MUSCLES 24 • ROTATOR CUFF MUSCLES 25 • POSTERIOR COMPARTMENT OF THE ARM

CHAPTER 1

Th e Back

23

• SKELETON OF THE FOREARM

44

45

x iii

xiv

•

CONTENTS

Dissection Instructions • • • •

45

SUPERFICIAL LAYER OF FLEXOR MUSCLES 45 INTERMEDIATE LAYER OF FLEXOR MUSCLES 47 VESSELS AND NERVES OF THE ANTERIOR FOREARM DEEP LAYER OF FLEXOR MUSCLES 50

Dissection Follow-up

47

51

PALM OF THE HAND 52 Dissection Overview 52 • SKELETON OF THE HAND

Dissection Instructions • • • • • •

52

53

SKIN INCISIONS 53 SUPERFICIAL PALM 53 CARPAL TUNNEL 55 THENAR MUSCLES 56 HYPOTHENAR MUSCLES 57 DEEP PALM 57

Dissection Follow-up

58

EXTENSOR REGION OF THE FOREARM AND DORSUM OF THE HAND 59 Dissection Overview 59 Dissection Instructions 60 • SUPERFICIAL LAYER OF EXTENSOR MUSCLES 60 • DEEP LAYER OF EXTENSOR MUSCLES 62

Dissection Follow-up

64

JOINTS OF THE UPPER LIMB 65 Dissection Overview 65 Dissection Instructions 66 • • • • • • •

STERNOCLAVICULAR JOINT 66 ACROMIOCLAVICULAR JOINT 66 GLENOHUMERAL JOINT 67 ELBOW JOINT AND PROXIMAL RADIOULNAR JOINT 68 INTERMEDIATE RADIOULNAR JOINT 69 DISTAL RADIOULNAR JOINT AND WRIST JOINT 69 METACARPOPHALANGEAL AND INTERPHALANGEAL JOINTS 70

Dissection Follow-up

71

• MEDIASTINUM 83 • HEART IN THE THORAX 84 • REMOVAL OF THE HEART 86

Dissection Follow-up

86

EXTERNAL FEATURES OF THE HEART 86 Dissection Overview 86 Dissection Instructions 87 • SURFACE FEATURES 87 • CARDIAC VEINS 87 • CORONARY ARTERIES 88

Dissection Follow-up

89

INTERNAL FEATURES OF THE HEART 89 Dissection Overview 89 Dissection Instructions 89 • • • •

RIGHT ATRIUM 89 RIGHT VENTRICLE 90 LEFT ATRIUM 92 LEFT VENTRICLE 92

Dissection Follow-up

93

SUPERIOR MEDIASTINUM Dissection Overview 93 Dissection Instructions 93 • SUPERIOR MEDIASTINUM

Dissection Follow-up

73

PECTORAL REGION

73

INTERCOSTAL SPACE AND INTERCOSTAL MUSCLES 73 Dissection Overview 73 • SURFACE ANATOMY 73 • SKELETON OF THE THORAX 74

Dissection Instructions 75 Dissection Follow-up 76 REMOVAL OF THE ANTERIOR THORACIC WALL; THE PLEURAL CAVITIES 77 Dissection Overview 77 Dissection Instructions 77 • ANTERIOR THORACIC WALL 77 • PLEURAL CAVITIES 78

Dissection Follow-up

79

LUNGS 80 Dissection Overview 80 Dissection Instructions 80 • LUNGS IN THE THORAX 80 • REMOVAL OF THE LUNGS 80

Dissection Follow-up

83

93

POSTERIOR MEDIASTINUM Dissection Overview 95 Dissection Instructions 96 • POSTERIOR MEDIASTINUM

Dissection Follow-up

93

95 95

96

98

CHAPTER 4

Th e Ab d o m e n

CHAPTER 3

Th e Th o rax

MEDIASTINUM 83 Dissection Overview 83 Dissection Instructions 83

99

SUPERFICIAL FASCIA OF THE ANTEROLATERAL ABDOMINAL WALL 99 Dissection Overview 99 • SURFACE ANATOMY 99

Dissection Instructions

101

• SKIN INCISIONS 101 • SUPERFICIAL FASCIA 101

Dissection Follow-up

102

MUSCLES OF THE ANTEROLATERAL ABDOMINAL WALL 102 Dissection Overview 102 • SKELETON OF THE ABDOMINAL WALL 102

Dissection Instructions • • • • •

103

EXTERNAL OBLIQUE MUSCLE 103 INTERNAL OBLIQUE MUSCLE 104 TRANSVERSUS ABDOMINIS MUSCLE 105 RECTUS ABDOMINIS MUSCLE 106 DEEP INGUINAL RING 108

Dissection Follow-up

109

REFLECTION OF THE ABDOMINAL WALL 110 Dissection Overview 110 Dissection Instructions 110 • FOUR ABDOMINAL QUADRANTS 110 • ABDOMINAL WALL REFLECTION 111

Dissection Follow-up

113

CONTENTS PERITONEUM AND PERITONEAL CAVITY 113 Dissection Overview 113 Dissection Instructions 113 • ABDOMINAL VISCERA 113 • REFLECTION OF THE DIAPHRAGM • PERITONEUM 115

Dissection Follow-up

117

122

125

• INFERIOR MESENTERIC ARTERY 125 • LARGE INTESTINE 126

127

DUODENUM, PANCREAS, AND HEPATIC PORTAL VEIN 127 Dissection Overview 127 Dissection Instructions 127

Dissection Follow-up

128

129

REMOVAL OF THE GASTROINTESTINAL TRACT 129 Dissection Overview 129 Dissection Instructions 129 • OPENING THE STOMACH 129 • OPENING THE SMALL INTESTINE AND LARGE INTESTINE 129 • REMOVAL OF THE GASTROINTESTINAL TRACT 130

Dissection Follow-up

131

POSTERIOR ABDOMINAL VISCERA 131 Dissection Overview 131 Dissection Instructions 132 • KIDNEYS 133 • SUPRARENAL GLANDS 135 • ABDOMINAL AORTA AND INFERIOR VENA CAVA 136

Dissection Follow-up

136

POSTERIOR ABDOMINAL WALL 136 Dissection Overview 136 Dissection Instructions 137 • LUMBAR PLEXUS 137 • ABDOMINAL PART OF THE SYMPATHETIC TRUNK 138

Dissection Follow-up

ANAL TRIANGLE 141 Dissection Overview 141

Dissection Follow-up

INFERIOR MESENTERIC ARTERY AND LARGE INTESTINE 125 Dissection Overview 125 Dissection Instructions 125

• DUODENUM 127 • PANCREAS 127 • HEPATIC PORTAL VEIN

141

144

• SKIN AND SUPERFICIAL FASCIA REMOVAL 144 • ISCHIOANAL FOSSA 144

• SUPERIOR MESENTERIC ARTERY AND SMALL INTESTINE 123 • SMALL INTESTINE 124

Dissection Follow-up

Th e Pe lvis an d Pe rin e um

Dissection Instructions

SUPERIOR MESENTERIC ARTERY AND SMALL INTESTINE 122 Dissection Overview 122 Dissection Instructions 123 Dissection Follow-up

CHAPTER 5

• SKELETON OF THE PELVIS 142

PORTAL TRIAD 118 CELIAC TRUNK 118 SPLEEN 120 LIVER 120 GALLBLADDER 121

Dissection Follow-up

DIAPHRAGM 139 Dissection Overview 139 Dissection Instructions 139 Dissection Follow-up 140

114

CELIAC TRUNK, STOMACH, SPLEEN, LIVER, AND GALLBLADDER 117 Dissection Overview 117 Dissection Instructions 117 • • • • •

•

138

145

MALE EXTERNAL GENITALIA AND PERINEUM Dissection Overview 146 Dissection Instructions 146 • SCROTUM 146 • SPERMATIC CORD • TESTIS 147

147

Dissection Follow-up

148

MALE UROGENITAL TRIANGLE 148 Dissection Overview 148 Dissection Instructions 148 • • • • •

SKIN REMOVAL 148 MALE SUPERFICIAL PERINEAL POUCH 149 PENIS 151 SPONGY (PENILE) URETHRA 152 MALE DEEP PERINEAL POUCH 153

Dissection Follow-up

153

MALE PELVIC CAVITY 154 Dissection Overview 154 Dissection Instructions 154 • MALE PERITONEUM 154 • SECTION OF THE MALE PELVIS 155 • MALE INTERNAL GENITALIA 155

Dissection Follow-up

157

MALE URINARY BLADDER, RECTUM, AND ANAL CANAL 158 Dissection Overview 158 Dissection Instructions 158 • MALE URINARY BLADDER 158 • MALE RECTUM AND ANAL CANAL 159

Dissection Follow-up

160

MALE INTERNAL ILIAC ARTERY AND SACRAL PLEXUS 160 Dissection Overview 160 Dissection Instructions 160 • BLOOD VESSELS 160 • NERVES 161

Dissection Follow-up

163

MALE PELVIC DIAPHRAGM Dissection Overview 163 Dissection Instructions 163 Dissection Follow-up 165

163

146

xv

xvi

•

CONTENTS

FEMALE EXTERNAL GENITALIA, UROGENITAL TRIANGLE, AND PERINEUM 165 Dissection Overview 165 Dissection Instructions 165 • • • • •

LABIUM MAJUS 165 FEMALE EXTERNAL GENITALIA 166 SKIN REMOVAL 166 FEMALE SUPERFICIAL PERINEAL POUCH AND CLITORIS 167 FEMALE DEEP PERINEAL POUCH 169

Dissection Follow-up

170

FEMALE PELVIC CAVITY 171 Dissection Overview 171 Dissection Instructions 171 • • • •

Dissection Follow-up

205

207 207

210 211

ANTERIOR COMPARTMENT OF THE LEG AND DORSUM OF THE FOOT 213 Dissection Overview 213 Dissection Instructions 213

180 180

• ANTERIOR LEG MUSCLES 213 • DORSUM OF THE FOOT 215

Dissection Follow-up

215

SOLE OF THE FOOT 216 Dissection Overview 216 Dissection Instructions 216

183

• SURFACE ANATOMY 183 • SKELETON OF THE ANTERIOR THIGH 184

• • • • •

PLANTAR APONEUROSIS AND CUTANEOUS NERVES 216 FIRST LAYER OF THE SOLE 217 SECOND LAYER OF THE SOLE 218 THIRD LAYER OF THE SOLE 218 FOURTH LAYER OF THE SOLE 219

Dissection Follow-up

184

• SKIN INCISIONS 184 • SUPERFICIAL FASCIA OF THE POSTERIOR LOWER LIMB 185 • SUPERFICIAL FASCIA OF THE ANTERIOR LOWER LIMB 187

188

ANTERIOR COMPARTMENT OF THE THIGH Dissection Overview 188 Dissection Instructions 189

188

SAPHENOUS OPENING 189 FEMORAL TRIANGLE 189 ADDUCTOR CANAL AND SARTORIUS MUSCLE 191 QUADRICEPS FEMORIS MUSCLE 192 TENSOR OF FASCIA LATA MUSCLE 193

193

MEDIAL COMPARTMENT OF THE THIGH Dissection Overview 194 Dissection Instructions 194 Dissection Follow-up 196

204

LATERAL COMPARTMENT OF THE LEG Dissection Overview 211 Dissection Instructions 211 Dissection Follow-up 212

SUPERFICIAL VEINS AND CUTANEOUS NERVES 183 Dissection Overview 183

Dissection Follow-up

202

• SUPERFICIAL COMPARTMENT OF POSTERIOR LEG • DEEP COMPARTMENT OF POSTERIOR LEG 208

CHAPTER 6

• • • • •

POSTERIOR COMPARTMENT OF THE THIGH AND POPLITEAL FOSSA 201 Dissection Overview 201

Dissection Instructions

• BLOOD VESSELS 178 • NERVES 179

Dissection Follow-up

200

• SKELETON OF THE LEG 206 • SKELETON OF THE FOOT 206

FEMALE INTERNAL ILIAC ARTERY AND SACRAL PLEXUS 178 Dissection Overview 178 Dissection Instructions 178

Dissection Instructions

Dissection Follow-up

POSTERIOR COMPARTMENT OF THE LEG Dissection Overview 205

177

Th e Lo we r Lim b

198

• GLUTEUS MAXIMUS MUSCLE 198 • GLUTEUS MEDIUS AND MINIMUS MUSCLES 199 • EXTERNAL ROTATORS OF THE HIP 200

Dissection Follow-up

175

FEMALE PELVIC DIAPHRAGM Dissection Overview 180 Dissection Instructions 182 Dissection Follow-up 182

197

• POSTERIOR THIGH 202 • POPLITEAL FOSSA 202

• FEMALE URINARY BLADDER 175 • FEMALE RECTUM AND ANAL CANAL 176

Dissection Follow-up

Dissection Instructions

Dissection Instructions

FEMALE URINARY BLADDER, RECTUM, AND ANAL CANAL 175 Dissection Overview 175 Dissection Instructions 175 Dissection Follow-up

• SKELETON OF THE GLUTEAL REGION

• SKELETON OF THE POSTERIOR THIGH 201

FEMALE PERITONEUM 171 BROAD LIGAMENT 171 SECTION OF THE FEMALE PELVIS 172 FEMALE INTERNAL GENITALIA 173

Dissection Follow-up

GLUTEAL REGION 197 Dissection Overview 197

194

221

JOINTS OF THE LOWER LIMB 222 Dissection Overview 222 Dissection Instructions 222 • • • • •

HIP JOINT 222 KNEE JOINT POSTERIOR APPROACH 223 KNEE JOINT ANTERIOR APPROACH 225 ANKLE JOINT 225 JOINTS OF INVERSION AND EVERSION 226

Dissection Follow-up

227

CHAPTER 7

Th e He ad An d Ne ck SUPERFICIAL NECK 229 Dissection Overview 229 • SKELETON OF THE NECK 229 • ORGANIZATION OF THE NECK 230

229

CONTENTS Dissection Instructions

231

• SKIN REMOVAL 231 • POSTERIOR TRIANGLE OF THE NECK 231

Dissection Follow-up

233

ANTERIOR TRIANGLE OF THE NECK 234 Dissection Overview 234 • BONES AND CARTILAGES OF THE NECK 234

Dissection Instructions • • • • •

235

SUPERFICIAL FASCIA 235 MUSCULAR TRIANGLE 235 SUBMANDIBULAR TRIANGLE 235 SUBMENTAL TRIANGLE 236 CAROTID TRIANGLE 236

Dissection Follow-up THYROID Dissection Dissection Dissection

REMOVAL OF THE BRAIN Dissection Overview 266 • CRANIAL FOSSAE 266

Dissection Instructions 267 Dissection Follow-up 267 DURAL INFOLDINGS AND DURAL VENOUS SINUSES 267 Dissection Overview 267 Dissection Instructions 267 Dissection Follow-up

239

• BRAIN 269 • BLOOD SUPPLY TO THE BRAIN • CRANIAL NERVES 270

Dissection Follow-up

HEAD

Dissection Instructions

248

SKIN INCISIONS 248 SUPERFICIAL FASCIA AND FACIAL NERVE 248 FACIAL ARTERY AND VEIN 250 MUSCLES AROUND THE ORBITAL OPENING 250 MUSCLES AROUND THE ORAL OPENING 250 SENSORY NERVES OF THE FACE 251

251

PAROTID REGION 252 Dissection Overview 252 252

INTERIOR OF THE SKULL 263 Dissection Overview 263 Dissection Instructions 263 • REMOVAL OF THE CALVARIA 263 • CRANIAL MENINGES 264

Dissection Follow-up

265

• SKELETON OF THE ORBIT 276 • SURFACE ANATOMY OF THE EYEBALL 277

Dissection Instructions • • • •

278

EYELID AND LACRIMAL APPARATUS 278 RIGHT ORBIT FROM THE SUPERIOR APPROACH 279 CONTENTS OF THE ORBIT 280 LEFT ORBIT FROM THE ANTERIOR APPROACH 281

283

DISARTICULATION OF THE HEAD Dissection Overview 283

Dissection Follow-up

256

258

262

276

283 283

284

• RETROPHARYNGEAL SPACE 284 • DISARTICULATION OF THE HEAD 285 • PREVERTEBRAL AND LATERAL VERTEBRAL REGIONS 285

MASSETER MUSCLE AND REMOVAL OF THE ZYGOMATIC ARCH 258 TEMPORAL REGION 258 INFRATEMPORAL FOSSA 259 MAXILLARY ARTERY 259 PTERYGOID MUSCLES 260 TEMPOROMANDIBULAR JOINT 261

Dissection Follow-up

ORBIT 276 Dissection Overview

Dissection Instructions

TEMPORAL REGION 256 Dissection Overview 256

• • • • • •

275

• SKELETON OF THE SUBOCCIPITAL REGION

SCALP 254 Dissection Overview 254 Dissection Instructions 255 Dissection Follow-up 256

Dissection Instructions

273

Dissection Follow-up

Dissection Follow-up

Dissection Instructions 253 Dissection Follow-up 254

• SKELETON OF THE TEMPORAL REGION

271

• ANTERIOR CRANIAL FOSSA 273 • MIDDLE CRANIAL FOSSA 274 • POSTERIOR CRANIAL FOSSA 275

244

• SKELETON OF THE PAROTID REGION

269

• SKELETON OF THE CRANIAL BASE 271

244

Dissection Follow-up

269

CRANIAL FOSSAE 271 Dissection Overview 271

• SURFACE ANATOMY 244 • SKULL 245 • • • • • •

269

GROSS ANATOMY OF THE BRAIN Dissection Overview 269 Dissection Instructions 269

ROOT OF THE NECK 241 Dissection Overview 241 Dissection Instructions 241 Dissection Follow-up 243

Dissection Instructions

266

• DURAL INFOLDINGS 267 • DURAL VENOUS SINUSES 268

AND PARATHYROID GLANDS 240 Overview 240 Instructions 240 Follow-up 241

FACE 244 Dissection Overview

•

286

PHARYNX 286 Dissection Overview 286 Dissection Instructions 286 • • • • •

MUSCLES OF THE PHARYNGEAL WALL 286 NERVES OF THE PHARYNX 287 OPENING THE PHARYNX 288 BISECTION OF THE HEAD 288 INTERNAL ASPECT OF THE PHARYNX 289

Dissection Follow-up

290

NOSE AND NASAL CAVITY 290 Dissection Overview 290 • SKELETON OF THE NASAL CAVITY 291

Dissection Instructions

292

• EXTERNAL NOSE 292 • NASAL SEPTUM 292 • LATERAL WALL OF THE NASAL CAVITY 293

Dissection Follow-up

294

x vii

xviii

•

CONTENTS

HARD PALATE AND SOFT PALATE 294 Dissection Overview 294 • SKELETON OF THE PALATE 295

Dissection Instructions

296

• SOFT PALATE 296 • TONSILLAR BED 298 • SPHENOPALATINE FORAMEN AND PTERYGOPALATINE FOSSA 298

Dissection Follow-up

299

ORAL REGION 300 Dissection Overview 300 • SURFACE ANATOMY OF THE ORAL VESTIBULE 300 • SURFACE ANATOMY OF THE ORAL CAVITY PROPER 300

Dissection Instructions

301

• TONGUE 301 • BISECTION OF THE TONGUE AND MANDIBLE 301 • SUBLINGUAL REGION 301

Dissection Follow-up

303

LARYNX 303 Dissection Overview

303

• SKELETON OF THE LARYNX 304

Dissection Instructions 305 • INTRINSIC MUSCLES OF THE LARYNX 305 • INTERIOR OF THE LARYNX 306

Dissection Follow-up

307

EAR 307 Dissection Overview

307

• SURFACE ANATOMY OF THE EXTERNAL EAR 308 • SKELETON OF THE EAR 308

Dissection Instructions

309

• MIDDLE EAR (TYMPANIC CAVITY) 309 • WALLS OF THE TYMPANIC CAVITY 311 • INTERNAL EAR 312

Dissection Follow-up

Index

313

312

Figure Credits Ch ap t e r 1 FIGURE 1.1 Modi ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lippin cott William s & Wilkin s; 2009. FIGURE 1.2 Modi ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lippin cott William s & Wilkin s; 2009. FIGURE 1.15 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015.

Ch ap t e r 2 FIGURE 2.8 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.12 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.20A, B Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.23 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.24 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.25 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.26 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.38 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.39 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.40A, B Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.43 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.44C, D Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.45 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 2.46 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017.

Ch ap t e r 3 FIGURE 3.8 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 3.11 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 3.12 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009.

FIGURE 3.15 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 3.16 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 3.17A, B Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 3.18A, B Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 3.23 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 3.24 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 3.25 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 3.26 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 3.27 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009.

Ch ap t e r 4 FIGURE 4.18 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 4.19 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 4.20 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 4.29 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 4.30 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 4.31 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 4.33 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 4.34A Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 4.35 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009.

x ix

xx

•

FIGURE CREDITS

FIGURE 4.49 Mod i Anatom y. 14th ed . FIGURE 4.50 Mod i Anatom y. 14th ed .

ed from Agu r AMR, Dalley AR. Grant’s Atlas of Baltim ore, MD: Wolters Klu wer; 2017. ed from Agu r AMR, Dalley AR. Grant’s Atlas of Baltim ore, MD: Wolters Klu wer; 2017.

Ch ap t e r 5 FIGURE 5.3A, B Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 5.18 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 5.19 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 5.20 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 5.25A, B Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 5.29 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 5.34 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 5.35 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 5.37 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 5.41A, B Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015.

Ch ap t e r 6 FIGURE 6.14 Mod i ed from Tan k W illiam s & W ilkins Atlas of Anatom y. William s & Wilkin s; 2009. FIGURE 6.19 Mod i ed from Tan k W illiam s & W ilkins Atlas of Anatom y. William s & Wilkin s; 2009.

PW, Gest TR. Lippincott Baltim ore, MD: Lip p in cott PW, Gest TR. Lippincott Baltim ore, MD: Lip p in cott

FIGURE 6.23 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 6.28A, B Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 6.29 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 6.30 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 6.31 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009.

Ch ap t e r 7 FIGURE 7.1 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 7.11 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 7.12 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 7.13 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 7.16 Modi ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 7.17 Mod i ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017. FIGURE 7.20 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 7.24 Mod i ed from Tan k PW, Gest TR. Lippincott W illiam s & W ilkins Atlas of Anatom y. Baltim ore, MD: Lip p in cott William s & Wilkin s; 2009. FIGURE 7.37 Mod i ed from Moore KL, Agu r AMR, Dalley AR. Essential Clinical Anatom y. 5th ed . Baltim ore, MD: Lip p in cott William s & Wilkin s; 2015. FIGURE 7.66 Modi ed from Agu r AMR, Dalley AR. Grant’s Atlas of Anatom y. 14th ed . Baltim ore, MD: Wolters Klu wer; 2017.

Introduction YOUR FIRST PATIENT Th e op p ortu n ity to d issect a h u m an body is a on ce in a lifetim e exp erien ce. It is n ot p ossible to fu lly ap p reciate th e m otivation of an in d ivid u al to becom e a bod y d on or, bu t m ost of u s will try to im agin e th e circu m stan ces th at lead to th at d ecision . Th e valu e of th e gift th at h as been given to you can n ot be m easu red an d can on ly be rep aid by th e p rop er care an d u se of th e cadaver. Th e cad aver m u st be treated with th e sam e resp ect an d d ign ity th at are u su ally reserved for th e livin g p atien t. A

B

C

CADAVER CARE Upon en terin g th e laboratory, you will n d th at th e cadaver h as been em balm ed with a stron g xative. Th e wh ole body h as been kep t m oist by wrap p in gs or by su bm ersion u n der preservative u id. Desiccation of th e cad aver will q uickly ren der th e sp ecim en u seless for stu dy becau se on ce a part h as been allowed to becom e dry, it can n ever be fu lly restored . Th erefore, exp ose on ly th ose p arts of th e body th at you are cu rren tly workin g on an d m oisten an y exp osed region s p eriod ically th rou gh ou t th e dissection . At th e en d of each dissection session , m oisten th e wrap p in gs an d th e cadaver with wettin g solu tion an d p rop erly cover th e cad aver followin g th e p rotocols of you r laboratory.

DISSECTION INSTRUMENTS

D

E

It is gen erally true th at large dissection equipm en t (h am m ers, ch isels, saws, etc.) is provided for you, but person al dissection in strum en ts m ay n eed to be purch ased. Th e well-equipped dissector sh ould h ave th e followin g in strum en ts (FIG. I.1): • Pro b e —an excellen t blun t dissection tool to be u sed for in vestigation of a n ew region alon g with you r n gers. A probe is design ed to tear con n ective tissu e an d allow th e user to feel n erves an d vessels before th ey are d am aged. With practice, th e probe can becom e a p rim ary dissection in strum en t to isolate an d clean delicate stru ctu res. • Fo rcep s —u sed to lift an d h old vessels, n erves, an d oth er stru ctu res wh ile blu n t d issectin g with a p robe. Two p airs of forcep s are n eed ed . On e p air sh ou ld h ave tip s th at are blu n t an d rou n d ed, an d th e grip p in g su rfaces sh ou ld be corru gated . Th e secon d p air sh ou ld h ave teeth (also kn own as tissu e forcep s or rat-tooth ed forcep s) for grip p in g tissu e.

F

G

FIGURE I.1 Personal dissection instrum ents. A. Probe. B. Forceps. C. Tissue (rat-toothed) forceps. D. Scalpel and rem ovable blade. E. Large scissors. F. Sm all scissors. G. Hem ostat.

1

2

•

GRANT’S DISSECTOR

Artery

Nerve

FIGURE I.2 Scissors technique for separating structures. Closed scissors are inserted between structures into the connective tissue and then op ened to gently sp read the tissue.

• Scalp el —prim arily used as a skin n in g tool. Scalpels are n ot recom m en ded for gen eral dissection because th ey cut sm all structures with out allowin g you to feel th em . Th e scalpel h an dle sh ould be m ade of m etal (n ot plastic). Th e blade sh ould be about 3.5 to 4 cm lon g. Th e cuttin g edge m ust h ave som e con vexity n ear th e poin t. Th e scalpel sh ould be h eld in a grip sim ilar to h oldin g a pen cil, an d a sh arp blade m ust be used at all tim es for m ost effective im plem en tation . Th erefore, a suf cien t supply of blades will be n eeded. To avoid in jury, seek assistan ce th e rst tim e you place an d rem ove a scalpel blade. • Scisso rs —u sefu l in cu ttin g, blu n t d issection , an d tran section . Two p airs of scissors are recom m en d ed : a large, h eavy p air of d issectin g scissors (abou t 15 cm in len gth ) an d a sm all p air of scissors with two sh arp p oin ts for th e d issection of d elicate stru ctu res. • Hem ostat —a powerful graspin g tool th at is h elpful in skin rem oval. Th e advan tage of h em ostats is th e ability to lock th e grip on th e slippery surfaces such as skin to facilitate re ection or rem oval of tissue. However, th e h em ostat h as two disadvan tages: First, it crush es delicate structures. Secon d, it can n ot be reposition ed quickly like forceps can , th ereby slowin g progress. Hem ostats an d scissors sh ould be h eld with th e th um b an d fourth n ger in th e n ger loops for th e m ost con trol an d precision (FIG. I.2).

GLOSSARY OF DISSECTION TERMS Th is d issection m an u al rep eated ly u ses a n u m ber of d issection term s. Before begin n in g to d issect, learn th e m ean in g of th e followin g: • Dissect —to cut apart. In th e con text of th is dissection m an ual, th e m ean in g of dissect is to tear apart or separate. Th e recom m en ded dissection approach th rou gh out th is m an ual is blun t dissection . Th e scalpel sh ould on ly be u sed for skin in cision s or as a tool of last resort for crude cuts to dissect extrem ely tough con n ective tissues. • Blu n t d issect io n —to sep arate stru ctu res with you r n gers, a p robe, or scissors by tearin g (n ot cu ttin g) con n ective tissu es.

• Scissors tech n iqu e —a m eth od of blun t dissection in wh ich th e tips of a closed pair of scissors are in serted in to con n ective tissue an d th en open ed, tearin g th e con n ective tissue with th e back edge of th e tips (FIG. I.2). Th e scissors tech n ique is an effective way to dissect vessels an d n erves. • Sh a rp d issect io n —to d issect by u se of a scalp el or th e cu ttin g edge of th e scissors. Th e scalp el or scissors sh ou ld on ly be u sed in con ju n ction with forcep s. • Clea n —to rem ove fat an d con n ective tissu e, by m ean s of blu n t d issection (p referred ) or sh arp d issection , to exp ose th e su rface of an an atom ical stru ctu re for stu d y. Tissu e from th e su rface of a stru ctu re can be rem oved by sh arp d issection by cu ttin g th rou gh th e fascia an d con n ective tissu e after it h as been sep arated from th e d esired stru ctu re with blu n t d issection . Clea n t h e su rfa ce o f a m u scle —to rem ove all fat an d con n ective tissu e so th at th e m u scle fascicles becom e obviou s an d th e d irection of force can be u n d erstood . Clea n t h e b o rd er o f a m u scle —to de n e th e border of a m u scle with blu n t d issection by breakin g th e loose con n ective tissu e th at bin d s th e m u scle to su rrou n d in g stru ctu res. Clean a n erve —to use a probe (or scissors tech n ique) to strip th e con n ective tissue aroun d th e n erve for purposes of observin g its relation sh ips an d bran ch es. Clea n a vessel —to u se a p robe (or scissors tech n iq u e) to strip th e fat an d con n ective tissu e off th e su rface of a vessel, or its bran ch es, to illu strate its relation sh ip s. • De n e —to u se blu n t d issection to en h an ce a stru ctu re to better illu strate its relation sh ip s. De n in g a stru ctu re u su ally in volves blu n tly d issectin g th e loose con n ective tissu e away from it. • Ret ra ct —to p u ll a stru ctu re to on e side to visu alize an oth er stru ctu re th at lies m ore d eep ly. Retraction is a tem p orary d isp lacem en t an d is n ot in ten d ed to h arm th e retracted stru ctu re. • Tra n sect —to cu t a stru ctu re in two in th e tran sverse p lan e, as in tran section of a m u scle belly or ten d on . • Re ect —to fold back from a cu t ed ge, as in foldin g back a tran sected m u scle to view wh at is ben eath it. Th e reected tissu e sh ou ld rem ain attach ed to th e specim en . • Strip a vein —to rem ove a vein an d its tributaries from th e dissection eld so th at th e artery an d related structures can be seen m ore clearly. Vein s are stripped eith er by blun t dissection usin g a probe or carefully with scissors usin g a com bin ation of blun t an d sh arp dissection tech n iques.

ANATOMICAL POSITION An atom ists describe th e position an d relation of structures of th e body relative to th e anatom ical position . In th e an atom ical position , th e person stan ds erect with th e face an d feet directed forward an d arm s by th e sides with palm s facin g forward (FIG. I.3). Durin g dissection , structures are described as th ough th e body was in th e an atom ical position ,

INTRODUCTION Median plane Frontal (coronal) plane Sagittal plane

Median plane of hand

Transverse plane

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to th at p oin t, su ch as a sagittal p lan e p assin g m idway th rou gh th e clavicle. • Med ia n p la n e (m id -sa git t a l p la n e) is th e sagittal p lan e th at lies in th e m id lin e of th e bod y cu ttin g vertically th rou gh th e axis to divid e th e bod y in to “eq u al” righ t an d left h alves. Med ia l is a term u sed to d escribe stru ctu res closer to th e m ed ian p lan e, an d la t era l is a term u sed to d escribe stru ctu res fu rth er from th e m ed ian p lan e. • Fro n t a l (co ro n a l) p la n es cou rse vertically th rou gh th e body at a righ t an gle to th e m ed ian p lan e an d divid e th e body in to a n t erio r/ ven t ra l (th e p ortion of th e body in fron t of th e p lan e) an d p o st erio r/ d o rsa l (th e p ortion of th e bod y beh in d th e p lan e) p arts. • Tran sverse (h orizon tal, ax ial, t ran sax ial) p lan es course h orizon tally th rough th e body at righ t an gles to both th e fron tal an d sagittal plan es an d divide th e body in to su p erior (th e portion of th e body above th e plan e) an d in ferior (th e portion of th e body below th e plan e) parts. It is im p ortan t to n ote th at th e h an ds an d feet h ave th eir own u n iq u e m ed ian p lan es to referen ce m ovem en t of th e d igits. Th e m ed ian p lan e of th e h an d ru n s th rou gh th e th ird m etacarp al, wh ereas th e m ed ian p lan e of th e foot ru n s th rou gh th e secon d m etatarsal.

Median plane of foot

ANATOMICAL VARIATION FIGURE I.3 Anatom ical p osition and anatom ical p lanes. Anterolateral view.

even th ou gh th e cadaver is lyin g on a dissection table eith er supin e (face up) or p ron e (face down ). Wh en en coun terin g a stru cture durin g dissection , be aware of its position , its relation sh ip to oth er stru ctu res, its size an d sh ape, its fu n ction , its blood supp ly, an d its n erve su pply. Learn to give an accu rate accou n t of each im portan t stru ctu re in an orderly an d logical fash ion by describin g it to you r lab partn ers. Always base your description s on th e an atom ical position .

ANATOMICAL PLANES With th e body in an atom ical p osition , an atom ists describe th ree p lan es th at in tersect th e bod y as p oin ts of referen ce for eith er stru ctu re location or m ovem en t. With th e excep tion of th e m ed ia n (m id -sa git t a l) p la n e , th e an atom ical plan es m ay be fou n d at an y level parallel to th e origin al poin t of referen ce. A clear u n derstan din g of an atom ical plan es will assist you r un derstan din g of cross section al an atom y an d d iagn ostic im agin g. Th e cross section al im ages seen in th is dissection gu ide rep resen t axial views of variou s body region s as viewed from in ferior to su perior. • Sa git t a l p la n es cou rse vertically th rou gh th e bod y an d d ivid e th e bod y in to righ t an d left h alves. Often , sagittal p lan es are given a sp eci c p oin t of referen ce to assist p h ysician s in id en ti cation of stru ctu res correlatin g

All bod ies h ave th e sam e basic arch itectu ral p lan , bu t ju st as n o two bodies are iden tical on th e ou tside, it sh ou ld be n o su rp rise th at n o two bodies are iden tical on th e in sid e. Min or variation s, su ch as variation in size, color, an d p ath way of a vessel, com m on ly occu r in all region s of th e body an d sh ou ld be expected. At th e on set of dissection , th e focu s sh ou ld be on learn in g n orm al (average) an atom y rath er th an th e variation u n less sp eci cally in stru cted to d o oth erwise. Take tim e du rin g each dissection p eriod to view several d issection s on n eigh borin g cad avers so th at you can learn to ap p reciate an atom ical variation s an d be better prep ared for id en ti cation exam in ation s. Before begin n in g to d issect, con su lt you r textbook for ad d ition al t erm s o f rela t io n sh ip a n d co m p a riso n , t erm s o f la t era lit y , an d t erm s o f m o vem en t . Th ese term s form an im p ortan t p art of th e lan gu age of an atom y, an d it is n ot p ossible to u n d erstan d an atom ical d escrip tion s with ou t u n d erstan d in g an d u sin g th ese term s.

DAILY DISSECTION ROUTINE To get th e m ost ou t of d issection , it is recom m en d ed th at you establish a rou tin e ap p roach to each d ay’s d issection . Som e su ggestion s are offered : • Prep a re b efo re t h e la b . Read th e d issection assign m en t in th is book an d becom e fam iliar with th e n ew vocabu lary, th e stru ctu res to be d issected , an d th e d issection ap p roach . W h en actively d issectin g, you m u st

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d eliberately search for stru ctu res, an d a sm all am ou n t of ad van ce p rep aration will m ake th e exercise go m ore q u ickly an d be m u ch m ore p rod u ctive. Wa t ch t h e co rresp o n d in g d issect io n vid eo s eith er before or du rin g lab to gain a better visu al p erspective of th e tech n iqu es an d steps to be u sed in th e dissection . Use a good atlas in th e dissection lab. Th is dissection m an ual provides referen ces to four excellen t atlases to h elp you quickly n d illustration s th at support th e dissection . Pa lp a t e b o n y la n d m a rk s an d u se th em in th e search for soft tissu e stru ctu res. Rem o ve fa t , co n n ect ive t issu e, a n d sm a ller vein s to m ake th e d etails of th e m ore im p ortan t stru ctu res m ore obviou s. Review t h e co m p let ed d issect io n at th e en d of th e d issection p eriod an d again at th e start of th e n ext d issection p eriod. To h elp you d o th is, review exercises are in clu d ed at strategic p oin ts in each ch ap ter. Co m p let e ea ch d issect io n b efo re p ro ceed in g t o t h e n ex t becau se th e m ajority of th e d issection s will be an exten sion of th e p reviou s d issection .

LAB SAFETY W h ile in th e laboratory, eith er wear scru bs or p rotect you r cloth in g by wearin g a lon g laboratory coat or ap ron . For san itary reason s, th is ou ter layer of cloth in g sh ou ld n ot be worn ou tsid e of th e d issection laboratory, an d scru bs sh ou ld im m ed iately be ch an ged u p on exitin g th e lab. Do n ot wear san d als or op en -toed sh oes in th e laboratory becau se a d rop p ed scalp el, d issection in stru m en t, or oth er p iece of lab eq u ip m en t can seriou sly in ju re you r foot. Gloves m u st be worn to p reven t con tact with h u m an tissu e an d xatives. W h en u sin g a bon e saw, always wear glasses or goggles to p rotect you r eyes.

SKIN REMOVAL Skin rem oval is th e rst step in d issectin g a n ew region , an d a few su ggestion s are offered to h elp you get started . A variable am ou n t of su bcu tan eou s tissu e (also called su p er cial fascia) lies im m ed iately d eep to th e skin . Th e su bcu tan eou s tissu e con tain s fat, cu tan eou s n erves, an d su p er cial blood vessels. Th rou gh ou t th is d issection m an u al, wh en you are in stru cted to skin a region , t h e sk in sh o u ld b e rem o ved a n d t h e su b cu t a n eo u s t issu e sh o u ld b e left b eh in d . Su bseq u en t d issection in stru ction s will be p rovid ed for d issection an d rem oval of th e su bcu tan eou s tissu e. Th e th ickn ess of skin varies from region to region . For exam p le, th e skin is relatively th in on th e d orsu m of th e h an d an d it is con sid erably th icker over p alm of th e h an d . Gen erally, skin in cision s sh ou ld n ot exten d in to th e su bcu tan eou s tissu e; th erefore, a gen eral u n d erstan d in g of region al skin th ickn ess is im p ortan t.

Superficial fascia

Stab incision Skin

Taut collagen fibers

FIGURE I.4 Buttonhole technique. When rem oving skin, m ake a stab incision in a ap of skin. Place your nger through the hole and pull on the skin. Use the scalp el blade to cut the collagen bers from the deep surface of the skin where the bers are taut.

To begin skin n in g, m ake in cision lin es of th e ap p rop riate d ep th alon g th e recom m en d ed in cision lin es as in stru cted in th is m an u al. Th en , u se tooth ed forcep s or h em ostats to grasp th e skin at th e in tersection of two in cision lin es an d begin to rem ove it from th e u n d erlyin g su bcu tan eou s tissu e with th e scalp el blad e. On ce a skin ap h as been raised, p lace traction on th e skin as it is bein g rem oved an d d irect th e scalp el blad e toward th e d eep su rface of th e skin to cu t th e tau t collagen bers (FIG. I.4). Avoid d irectin g th e scalp el toward th e bod y becau se th e blade will read ily cu t th rou gh an d d estroy u n d erlyin g su bcu tan eou s tissu e, m u scle, an d n eu rovascu lar stru ctu res. To stead y you r scalp el h an d , rest it again st th e cad aver an d h old th e scalp el as you wou ld h old a p en cil an d m ake sh ort (5 to 10 cm ) sweep in g m otion s (FIG. I.5). To p reven t accid en ts, d o n ot work too close to you r lab p artn ers an d h old th e skin with d issection in stru m en ts wh en m akin g n ew in cision s.

FIGURE I.5 When dissecting, rest the hand to reduce unsteady m ovem ents.

CHAPTER 1

The Back ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

h e back is th e p osterior asp ect of th e tru n k an d exten d s from th e base of th e sku ll to th e tip of th e coccyx. Th e back con tain s th ree grou p s of m u scles: th e su p er cia l m u scles o f t h e b a ck , th e in t er m ed ia t e m u scles o f t h e b a ck , an d th e d eep m u scles o f t h e b a ck . All

T

of th ese m u scle grou p s attach to th e vertebral colu m n , wh ich form s th e axis of th e tru n k, su p p orts th e weigh t of th e body, tran sm its forces gen erated by m ovem en t, an d p rovid es a p rotective bon y coverin g for th e sp in al cord an d n erve roots.

SKIN AND SUPERFICIAL FASCIA Disse ct io n Ove rvie w The order of dissection will be as follows: The skin will be rem oved from the back, the posterior surface of the neck, and the posterior surface of the proxim al upp er lim b. Posterior cutaneous nerves will be studied. The super cial fascia will then be rem oved.

Surface An at o m y The surface anatom y of the back m ay be studied on a living subject or on a cadaver. On the cadaver, xation m ay m ake it dif cult to distinguish bone from well-preserved soft tissues. 1. With the cadaver in the prone position (face down), palpate the e xt e rn al o ccip it al p ro t ub e ran ce on the posterior asp ect of the head (FIG. 1.1). [G 30; L 5; N 152] 2. Posterior to the external ear, palpate the m ast o id p ro ce ss at the base of the skull. 3. Move inferiorly along the posterior m idline and palpate the ce rvical sp in o us p ro ce sse s. Depending on b ody type, the cervical spinous p rocesses are palpable, especially the sp in o us p ro ce ss o f t h e se ve n t h ce rvical ve rt e b ra (ve rt eb ra p ro m in e n s) at the base of the neck. 4. From the vertebra prom inens, palpate laterally to identify the sup e rio r b o rd e r o f t h e t rap e zius m uscle and follow it inferolaterally toward its attachm ent to the acro m io n o f t h e scap ula and lat e ral e n d o f t h e clavicle . 5. Palpate from the acrom ion posteriorly along the sp in e o f t h e scap ula (at vertebral level T3) toward the m e d ial (ve rt e b ral) b o rd e r o f t h e scap ula. 6. Follow the m edial border of the scapula inferiorly toward the in fe rio r an g le o f t h e scap ula (at vertebral level T7). 7. In the thoracic m idline, palpate the sp in o us p ro ce sses o f t h o racic ve rt e b rae . 8. Progress inferiorly to the lum bar vertebrae and identify the bilateral m asses of e re ct o r sp in ae m uscle located on either side of the vertebral colum n. 9. Palpate along the lateral m argin of the erector spinae inferiorly and identify the iliac cre st . Observe that the iliac crest is approxim ately at vertebral level L4. 10. Follow the iliac crest posteriorly and m edially and identify the p o st e rio r sup erio r iliac sp in e (PSIS). Observe that the PSIS is ap proxim ately at vertebral level S2. 11. Palpate laterally along the iliac crest toward the lateral aspect of the trunk and identify the lat e ral b o rd e r o f t h e lat issim us d o rsi m uscle . Follow the lateral border of the latissim us d orsi superiorly to the axilla and observe that it form s the p o st e rio r axillary fo ld .

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External occipital protuberance

Superior nuchal line C1 C2 Superior border of trapezius muscle

Clavicle Acromion of scapula

Vertebral prominens (C7)

Spine of scapula Medial border of scapula Posterior axillary fold

Spinous processes of vertebrae

Inferior angle of scapula Rib

Bulge of erector spinae muscles

Iliac crest

Ilium

Posterior superior iliac spine

Sacrum Coccyx

FIGURE 1.1

Surface anatom y of the back.

Ve rt e b ral Co lum n The ve rt e b ra l co lu m n con sists of 33 verteb rae: 7 cervical (C), 12 th oracic (T), 5 lum b ar (L), 5 sacral (S), an d 4 coccyg eal (Co) (FIG. 1.2). Th e verteb rae are n um b ered with in each reg ion from sup erior to in ferior. Th e up p er 24 verteb rae (cervical, th oracic, an d lum b ar) allow exib ility an d m ovem en t of th e verteb ral colum n , wh ereas th e sacral verteb rae are fused to p rovid e rig id sup p ort of th e p elvic g ird le and to tran sm it forces to and from the lower lim b . A typ ical th oracic verteb ra will b e d escrib ed , an d th e cervical an d lum b ar verteb rae will b e com p ared to it. [G 4 ; L 6 ; N 1 5 3 ; R 202] Refer to an articulated skeleton and identify the following skeletal features using FIGURE 1.2: 1. On the o ccip it al b o n e , identify the e xt e rn al o ccip it al p ro t ub e ran ce . 2. Arching laterally from the external occip ital p rotuberance, identify the sup e rio r n uch al lin e and observe that it runs in parallel to the m ore inferiorly located in fe rio r n uch al lin e. 3. On the t e m p o ral b o n e , identify the m ast o id p ro ce ss.

CHAPTER 1

4. Identify the spinous processes of the cervical vertebrae and ob serve the elongated sp in o us p ro ce ss o f t h e se ve n t h ce rvical ve rt e b ra (ve rt e b ra p ro m in e n s). 5. On the scap ula, identify the acro m io n p ro ce ss, the sp in e o f t h e scap ula, the sup e rio r an g le , the m e d ial (ve rt e b ral) b o rd e r, and the in fe rio r an g le . [G 65; L 32; N 406; R 383] 6. On the ilium , identify the iliac cre st and the PSIS. [G 27; L 5; N 473]

1. Refer to a disarticulated t h o racic ve rt e b ra and identify the ve rt e b ral b o d y, the ve rt e b ral arch , the p e d icle (2), the lam in a (2), and the ve rt e b ral fo ram e n (FIG. 1.3). 2. Identify the t ran sve rse p ro ce ss (2) and the associated t ran sve rse co st al face t s. 3. Articulation with ribs is a unique characteristic of thoracic vertebrae. Align a rib and observe that the head of the rib articulates with the bodies of two adjacent vertebrae at the d e m iface t s and with the in t e rve rt e b ral d isc (FIG. 1.3). 4. On an articulated skeleton, observe that the tubercle of a rib articulates with the transverse costal facet of the thoracic vertebra of the sam e num ber (i.e., the tubercle of rib 5 articulates with the transverse costal facet of vertebra T5). 5. Identify the sp in o us p ro ce ss and note that in a thoracic vertebra, it is long, slender, and directed inferiorly and posteriorly over the spinous process of the vertebra inferior to it. 6. Identify both the sup e rio r and in fe rio r art icular p ro ce sse s with their associated facet s and note that exion and extension are lim ited in the thoracic region d ue to this articulation. Superior articular facet Pedicle Transverse process

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Mastoid process External occipital protuberance

Atlas (C1) Axis (C2)

Cervical curvature Vertebra prominens

C7

Th o racic Ve rt e b rae

THE BACK

T1

Thoracic curvature

T12 L1

Lumbar curvature L5

Sacrum Sacral curvature Coccyx

FIGURE 1.2 eral view).

Skeleton of the back and vertebral colum n (lat-

Inferior articular facet T2

Body

T3

Transverse costal facet Inferior vertebral notch Superior vertebral notch

Intravertebral disc

T4

Intervertebral foramen Shaft of rib 5

Head of rib 5 T5

Spinal nerve T5

FIGURE 1.3

Typical thoracic vertebra in lateral view.

7. Identify the in ferio r ve rt eb ral n o t ch of one vertebra, along with the sup erio r vert eb ral n o t ch of the vertebra im m ediately inferior, and note how they form an in t ervert e b ral fo ram en . Note that a spinal nerve passes through the intervertebral foramen from the vertebral canal where it arose from the spinal cord (FIG. 1.3). [G 294; L 9; N 154; R 198]

Ce rvical an d Lum b ar Ve rt e b rae 1. Refer to a set of disarticulated ce rvical ve rt e b rae and observe that they differ from thoracic vertebrae because they have sm aller bodies, larger vertebral foram ina, shorter sp inous processes that bifurcate at the tip (except C7), and no transverse costal facets for rib attachm ent. [G 8; L 7; N 19; R 198]

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2. Identify the transverse processes and note that each contains a t ran sve rse fo ram e n (fo ram e n t ran sve rsarium ) (FIG. 1.4). 3. Identify C7 and observe that it has the m ost prom inent spinous process in the cervical region, hence its nam e, the ve rt e b ra p ro m in e n s (C7). 4. Refer to a set of disarticulated lum b ar ve rt e b rae and observe that they differ from thoracic vertebrae because they have larger bodies, b road spinous processes that p roject posteriorly, and no transverse costal facets for rib attachm ent (FIG. 1.4). 5. On an articulated skeleton, identify the lum bar vertebrae and observe that their spinous processes (spines) do not overlap like the spines of thoracic vertebrae. [G 16; L 11; N 155; R 198] 6. Id en tify th e sa cru m an d ob serve th at it is form ed b y ve fused verteb rae an d d oes n ot h ave id en ti ab le sp in ous or tran sverse p rocesses (FIG. 1.5). 7. On the posterior surface of the sacrum , identify the m e d ian sacral cre st , which represents the fused rudim entary spinous process of the upper three or four sacral vertebrae. Spinous process 8. On the sacrum , identify the an t e rior and p o st e rio r Lamina sacral fo ram in a, which allow the sp inal nerves to exit Vertebral foramen from the vertebral canal anteriorly and posteriorly as the sacrum articulates on its lateral surfaces with the ilia of the hip bones (FIG. 1.5). [G 24; L 12; N 157; Transverse foramen (foramen R 199] transversarium) 9. On the p osterior inferior asp ect of the sacrum , id entify the sa cra l h ia t u s, the inferior op ening at th e term ination of the verteb ral canal where the lam iBody nae of the fourth and fth sacral verteb rae fail to Cervical (C4) m eet. Superior articular 10. Inferior to the sacrum , identify the co ccyx, a sm all facet triangular bone form ed by the fusion of four rudiSpinous process m entary coccygeal vertebrae. Observe that the coccygeal vertebrae lack the features of typical vertebrae Transverse costal (FIG. 1.5). facet

Superior costal facet

Superior articular facet

Sacral canal

Body Thoracic (T6)

Spinous process Superior articular process Vertebral foramen

Posterior sacral foramina

Median sacral crest Transverse process

Sacral hiatus

Pedicle

Body

Coccyx

Lumbar (L4)

FIGURE 1.4 vertebrae.

Tip of coccyx

Com p arison of cervical, thoracic, and lum bar FIGURE 1.5

Sacrum and coccyx.

CHAPTER 1

Disse ct io n In st ruct io n s Skin In cisio n s 1. Refer to FIGURE 1.6. 2. Use a scalpel to m ake a skin incision in the m idline from the external occipital p rotuberance (X) to the tip of the coccyx (S). Note that the skin is approxim ately 6 m m thick in this region and thus only the tip of the scalpel need penetrate the surface of the skin. 3. To verify the thickness of the skin, m ake an initial cut and use forceps or hem ostats to pull the sides apart. Deep to the skin, you should see a little adipose tissue b ut no m uscle tissue. 4. Make an incision from the tip of the coccyx (S) to the m idaxillary line (T). This incision should pass just inferior and parallel to the iliac crest. 5. Make a transverse skin incision from the external occipital protuberance (X) laterally to the mastoid process (M). 6. Make a skin incision down the lateral surface of the neck and superior border of the trap ezius m uscle (M to B). Extend this incision to point F, about halfway down the arm .

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7. At point F, m ake an incision around the p osterior surface of the arm toward the m edial side (G). If the upper lim b has been dissected previously, this incision has already been m ade. 8. Make a skin incision that begins at G on the m edial surface of the arm and extends superiorly to the axilla. Extend this incision inferiorly along the lateral surface of the trunk, through V to T. 9. Make a transverse skin incision from R to B superior to the scap ula and superior to the acrom ion. 10. At the level of the inferior angle of the scapula, m ake a transverse skin incision from the m idline (U) to the m idaxillary line (V). 11. To facilitate skinning, m ake several parallel transverse incisions about 7.5 cm above and below the incision described in step 10. 12. Rem ove the skin from m edial to lateral using either a pair of locking forceps or the buttonhole technique. At any point, the portions of skin m ay be cut into sm aller segm ents to facilitate rem oval. Detach the skin and place it in the tissue container. 13. Repeat this process one section at a tim e until all the skin of the back has been rem oved.

Sup e r cial Fascia M

X

M

R

B

V

U

1. In the super cial fascia at the base of the skull, locate the occip ital artery and the g reater occip ital n erve (FIG. 1.7). The super cial veins in the region m ay serve as guides to identify the location of the occipital artery. 2. Observe that the greater occipital nerve pierces the t rap e zius m uscle about 3 cm inferolateral to the e xt e rn al o ccip it al p ro t ub e ran ce . Note that although the nerve arises on the medial side of the artery, it often

B

Greater occipital n. (C2)

V

F

F G

Scalp

External occipital protuberance

Occipital a.

G

T

T

S Deep fascia overlying trapezius

FIGURE 1.6

Skin incisions.

FIGURE 1.7

Cutaneous branches of dorsal primary rami

Greater occipital nerve and occipital artery.

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GRANT’S DISSECTOR

crosses over the artery along its path to the skin on the posterior aspect of the head. 3. Use blunt dissection to isolate the greater occipital nerve, the posterior (dorsal) ramus of spinal nerve C2. Note that the deep fascia in this area is very dense and tough, and it may be dif cult to nd the greater occipital nerve even though it is a large nerve. [G 31; L 16; N 175; R 230] 4. Read a description of the p o st e rio r (d o rsal) ram us o f a sp in al n erve . The p o st e rio r cut an e o us b ran ch e s of the posterior ram i p ierce the trapezius m uscle or the latissim us dorsi m uscle to enter the sup er cial fascia (FIG. 1.7) [G 212; L 21; N 188; R 233]. To save

tim e, m ake no deliberate effort to disp lay p osterior cutaneous branches of the posterior ram i. 5. Re ect the super cial fascia of the back by cutting it along sim ilar lines to the skin incision lines. Work from m edial to lateral to detach the super cial fascia and place it in the tissue container. 6. In the neck, re ect the super cial fascia only as far laterally as the sup erior border of the trapezius m uscle. Do not cut into the deep fascia along the superolateral border of the trapezius muscle because the accessory nerve is close to the surface at this location and is in danger of being cut.

Disse ct io n Fo llo w-up 1. Review the branching pattern of a typical spinal nerve and understand that cutaneous branches of the posterior ram i innervate the skin of the back. 2. Study a derm atom e chart and becom e fam iliar with the concept of segm ental innervation. [G 54; L 27; N 162]

SUPERFICIAL MUSCLES OF THE BACK Disse ct io n Ove rvie w The sup e r cial m uscle s o f t h e b ack are the t rap e zius, lat issim us d o rsi, rh o m b o id m ajo r, rh o m b o id m in o r, and le vat o r scap ulae . The order of dissection will be as follows: The super cial surface and borders of the trapezius m uscle will be cleaned. The trapezius m uscle will be exam ined and re ected. The latissim us dorsi m uscle will be cleaned, studied, and re ected. The rhom boid m ajor m uscle, rhom boid m inor m uscle, and levator scapulae m uscle will be identi ed. Dissection of the super cial back m uscles should be perform ed bilaterally.

Disse ct io n In st ruct io n s Trap e zius Muscle [G 31; L 17; N 171; R 230] 1. Place a block under each shoulder to take the tension off of the back m uscles. 2. Clean the fat and connective tissue from the surface of the t rap e zius m uscle (L. trapezoides, an irregular four-sided gure) (FIG. 1.8). 3. Clearly de ne the inferolateral border of the trapezius m uscle but do not disturb its superolateral border at this tim e. 4. Review the attachm ents and actions of the trapezius m uscle (see TABLE 1.1). 5. Prep are the trapezius m uscle for re ection. First, insert your ng ers d eep to the inferolateral b order of the m uscle (m ed ial to the inferior ang le of the scap ula) and m ove them sup eriorly as far as possib le to break the connective tissue that lies b etween the trap ezius m uscle and the deep er m uscles of the b ack.

6. Use scissors to d etach the trap ezius m uscle from the sp inous p rocesses inferiorly and extend the cut sup eriorly to the level of the nuchal lig am ent an d external occip ital p rotub erance (FIG. 1.8, d ashed line). 7. Use scissors to m ake a short transverse cut (2.5 cm ) across the superior end of the trapezius m uscle to detach it from the superior nuchal line. Spare the greater occipital nerve and the occipital artery and do not extend the transverse cut beyond the superolateral border of the trapezius m uscle. 8. Use scissors to cut th e trap ezius m uscle as close as p ossib le from its lateral attach m en ts on th e sup erior asp ect of th e sp in e an d acrom ion of th e scap ula (FIG. 1.8, d ash ed lin e). Leave th e trap ezius m uscle attach ed to th e clavicle an d the cervical fascia an d re ect th e m uscle sup erolaterally alon g th is b ord er. 9. Study the d eep surface of the re ected trapezius m uscle. Find the plexus of nerves form ed by the

CHAPTER 1

acce sso ry n e rve (cran ial n e rve [CN] XI) p roviding m otor innervation and b ran ch e s o f t h e an t e rio r (ve n t ral) ram i o f sp in al n e rve s C3 an d C4 providing proprioception. At this point in the dissection, it may not be possible to distinguish which portion of the plexus arises from which source. 10. The super cial branch of the t ran sverse ce rvical art e ry, along with its corresp onding vein, accom panies the nerves. The transverse cervical vein m ay be rem oved to clear the dissection eld. Note that superiorly, the accessory nerve passes through the posterior triangle of the neck but do not follow the nerve into the posterior triangle at this time because this will be dissected with the neck.

Lat issim us Do rsi Muscle [G 31; L 17; N 171; R 230] 1. Clean the surface and borders of the lat issim us d o rsi m uscle (L. latissim us, widest) (FIG. 1.8). 2. Review the attachm ents and actions of the latissim us dorsi m uscle (see TABLE 1.1). 3. Th e latissim us d orsi m uscle receives th e t h o ra co d o rsa l n e rve a n d a rt e ry on its an terior surface

External occipital protuberance Nuchal ligament Superolateral border of trapezius m.

Splenius m. Levator scapulae m. Trapezius m. (reflected) Rhomboid minor m.

4.

5.

6.

7.

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n ear its lateral attach m en t on th e h um erus. The lateral attachm ent of the latissim us dorsi m uscle, its nerve, and its artery will be dissected with the upper lim b and should not be dissected at this tim e. To re ect the latissim us dorsi m uscle, insert your ngers deep to the superior border of the m uscle (m edial to the inferior angle of the scapula) and break the plane of loose connective tissue that lies between it and the deeper m uscles. Elevate the latissim us dorsi m uscle enoug h to insert scissors and cut through its m edial attachm ent on the thoracolum bar fascia (dashed line). Do not cut close to the lum bar spinous processes; rather, cut through the m uscle where it attaches to the thoracolum bar fascia. Re ect the latissim us dorsi m uscle laterally m aking an effort to not disturb its attachm ent to the ribs or the possible attachm ent to the inferior angle of the scapula. Observe that deep to the latissim us dorsi m uscle is the serratus posterior inferior m uscle (FIG. 1.8).

Rh o m b o id Majo r an d Rh o m b o id Min o r Muscle s [G 32; L 17; N 174; R 230] 1. Clean the surface and borders of the rh o m b o id (rh o m b o id e us) m ajo r m uscle and the rh o m b o id m in o r m uscle (Gr. rhom bos, shap ed like a kite, or an equilateral parallelogram ). 2. Review the attachm ents and actions of the rhom boid m ajor and m inor m uscles (see TABLE 1.1). 3. Typ ically, the sep aration b etween the rhom b oid m uscles is not very ob vious and the two m uscles

Rhomboid major m.

CLIN ICA L CORRELATION

Triangle of auscultation Inferolateral border of trapezius m. Spinous process of T12 Lumbar triangle Iliac crest

FIGURE 1.8

Latissimus dorsi m. (reflected) Serratus posterior inferior m. External oblique m.

Thoracolumbar fascia

How to re ect the m uscles of the back.

Trian g le s o f t h e Back The t rian g le o f auscult at io n is bounded by the latissim us dorsi m uscle, the trapezius m uscle, and the rhom boid m ajor m uscle (FIG. 1.8). Within the triangle of auscultation, intercostal space 6 has no overlying m uscles. This area is particularly well suited for auscultation (listening to sounds p roduced by thoracic organs, particularly the lungs). The lum b ar t rian g le is b ound by the latissim us dorsi m uscle, the external oblique m uscle, and the iliac crest. The oor of the lum bar triangle is the internal obliq ue m uscle of the abdom en. On rare occasions, the lum bar triangle is the site of a lum bar hernia. [G 31, 32; L 17; N 250]

12

4.

5.

6.

7.

•

GRANT’S DISSECTOR

m ust b e sep arated from each other using their lateral attachm ents near the sp ine of the scap ula as a g uid e. To reflect t h e rh o m b o id m uscles, in sert your fin g ers d eep to th e in ferio r b o rd er o f th e rh o m b o id m ajo r m u scle an d sep arate it fro m d eep er m u scles. Working from inferior to sup erior, use scissors to detach the rhom boid m ajor m uscle from its m edial attachm ents on the spinous processes. Co n tin ue th e cu t sup eriorly an d d et ach th e rh o m b o id m in or m uscle from its m ed ial att ach m en ts o n th e sp in o u s p ro cesses an d lig am en tu m n u ch ae. Reflect b o th o f th e rh om b oid m uscles laterally. On th e d eep su rface o f th e two rh o m b o id m u scles, n ear th eir lateral attach m en ts on th e m ed ial b o rd er of th e scap ula, use b lun t d issection to fin d th e d o rsa l sca p u la r n e r ve an d d o rsa l sca p u la r ve sse ls. Note that the dorsa l sca p ula r a rt ery m ay branch directly from the subclavian artery, or from

the transverse cervical artery, in which case it is also known as the deep bra nch of t h e t ra nsverse cervica l a rt ery.

Le vat o r Scap ulae Muscle [G 32; L 17; N 171; R 226] 1. Identify the le va t o r scap ulae m uscle (L. levare, to raise) (FIG. 1.8). At this stag e of the d issection, the levator scap ulae m uscle can be seen only near its inferior attachm ent to the sup erior ang le of the scap ula. 2. Clean the surface and b ord ers of the levator scap ulae m uscle inferiorly but do not d issect its sup erior attachm ents to the transverse p rocesses of the up per four cervical verteb rae. Note that the dorsal scapular nerve and artery supply the levator scapulae m uscle and pass anterior (deep) to the inferior end of the m uscle. 3. Review the attachm ents and actions of the levator scapulae m uscle (see TABLE 1.1).

Disse ct io n Fo llo w-up 1. Replace the super cial m uscles of the back in their correct anatom ical positions. 2. Use the dissected specim en to review the attachm ents, action, innervation, and blood supply of each m uscle that you have dissected. 3. Review the m ovem ents that occur between the scapula and the thoracic wall. 4. Use an illustration to observe the origin of the transverse cervical artery and the orig in of the d orsal scap ular artery. 5. Observe two triangles associated with the latissim us dorsi m uscle: the t rian g le o f auscult at ion and the lum b ar t rian g le (FIG. 1.8).

TABLE 1.1

Sup e r cial Muscle s o f t h e Back

Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Trapezius

Superior nuchal line, external occipital protuberance, ligamentum nuchae, SP C7–T12

Lateral one-third of the clavicle and acromion and spine of scapula

Rotates, elevates (superior part), retracts (middle part), and depresses (inferior part) scapula

Motor: spinal accessory n. (CN XI) Proprioception: C3–C4

Latissimus dorsi

SP T7–L5, thoracolumbar fascia, sacrum, iliac crest, ribs 10–12

Floor of intertubercular sulcus of humerus

Extends, adducts, and medially rotates humerus

Thoracodorsal n. (middle subscapular n.)

Levator scapulae

TP C1–C4

Superior angle of scapula

Elevates and rotates the scapula to tilt the glenoid cavity inferiorly

Rhomboid major

SP T2–T5

Medial border of scapula below spine

Rhomboid minor

Ligamentum nuchae, SP C7–T1

Medial border of scapula at spine

Retracts and rotates the scapula to tilt the glenoid cavity inferiorly

Dorsal scapular n.

Abbreviations: C, cervical vertebrae; CN, cranial nerve; L, lumbar vertebrae; n., nerve; SP, spinous process; T, thoracic vertebrae; TP, transverse process.

CHAPTER 1

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INTERMEDIATE AND DEEP MUSCLES OF THE BACK Disse ct io n Ove rvie w The int erm ed iat e m uscles of th e b ack are the serrat us p osterior sup erior and the serrat us p ost erior in ferior. The interm ediate m uscles of the back are very thin respiratory m uscles attaching to the ribs and innervated by intercostal nerves. The d eep m uscles of t h e b ack act on the vertebral colum n and are innervated by posterior ram i of spinal nerves. There are several deep m uscles of the back, and m ost will be dissected including sp le n ius cap it is, sp le n ius ce rvicis, and the e re ct o r sp in ae m uscle s as well as som e of the t ran sve rso sp in ale s m uscles. The sp len ius cap itis and sp lenius cervicis m uscles are the m ost super cial of the deep m uscles of the back. They span the posterior neck and extend inferiorly to T6 (FIG. 1.9). The e re ct o r sp in ae m uscle s pass deep to the splenius m uscles and are com posed of three long colum ns of m uscle, spinalis, longissim us, and iliocostalis, on each side of the verteb ral colum n (FIG. 1.9). The t ran sve rso sp in ale s m uscle s lie deep to the erector sp inae m uscles and attach from transverse processes to sp inous p rocesses. Three m asses of m uscle com prise this group: the se m isp in alis, the m ult i d us, and m ost deep ly, the ro t at o re s. All of the deep m uscles of the back cause rotational and lateral bending m ovem ents between adjacent vertebrae and act to extend and stabilize the vertebral colum n. The order of dissection will be as follows: The deep m uscles of the posterior neck (splenius capitis and cervicis) will be studied and re ected. The erector spinae m uscles will be dissected and their com ponent parts identi ed. The sem ispinalis cap itis and sem ispinalis cervicis m uscles and the m ulti dus m uscles of the transversospinales group will be cleaned and identi ed.

Disse ct io n In st ruct io n s Se rrat us Po st e rio r Sup e rio r Muscle [G 32; L 17, 18; N 171; R 232] 1. Identify the serrat us p o st erio r sup erior m uscles deep to the rhom boid m uscles. If you do not see the serratus posterior superior muscles, look for them on the deep surface of the re ected rhomboid muscles (FIG. 1.9). 2. Review the attachm ents and actions of the serratus p osterior superior m uscles (see TABLE 1.2). 3. Clean the surface and borders of the serratus posterior superior m uscles. 4. Use scissors to cut the m edial attachm ents of the serratus posterior superior m uscles along the nuchal ligam ent and the spinous processes of verteb rae C7–T3.

Levator scapulae Serratus posterior superior Rhomboid minor (reflected)

Semispinalis capitis Splenius capitis Splenius cervicis

Rhomboid major (reflected)

Erector spinae

Latissimus dorsi (cut)

Longissimus

Spinalis Iliocostalis

Serratus posterior inferior

Thoracolumbar fascia

FIGURE 1.9 spinae.

Interm ediate m uscles of the back and erector

5. Re ect the m uscles laterally leaving their attachm ents intact along the superior borders of ribs 2 to 5, lateral to their angles.

Se rrat us Po st e rio r In fe rio r Muscle [G 32; L 17, 18; N 171; R 232] 1. Identify the serratus p osterior in ferior m uscles deep to the latissim us dorsi m uscles. If you do not see the serratus posterior inferior muscles, look for them on the deep surface of the re ected latissimus dorsi muscles (FIG. 1.9). 2. Review the attachm ents and actions of the serratus posterior inferior m uscles (see TABLE 1.2). 3. Continue re ecting the latissim us dorsi m uscles laterally along their attachm ents to the ribs to achieve greater visibility of the serratus posterior inferior m uscles.

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GRANT’S DISSECTOR

Semispinalis: Capitis m. Cervicis m. Thoracis m.

Longissimus capitis m.

Erector spinae: Spinalis m. Longissimus m. Iliocostalis m.

Multifidus m.

FIGURE 1.10

Deep m uscles of the back.

4. Clean the surface and borders of the serratus posterior inferior m uscles. 5. Use scissors to cut the medial attachments of the serratus posterior inferior muscles along the spinous processes of vertebrae T11–L2 and re ect the muscles laterally leaving their attachments intact lateral to the angle of the rib.

Sp le n ius Muscle [G 33; L 18; N 171; R 230] 1. Identify and clean the surface of the sp le n ius m uscle s deep to the serratus posterior superior m uscles (Gr. splenion, bandage) (FIG. 1.9). Observe that the bers of the splenius m uscles course obliquely across the neck from inferior to sup erior. 2. Identify the two parts of the sp lenius m uscles, which are nam ed according to their superior attachm ents. The sp le n ius cap it is (L. caput, head) attaches to the m astoid p rocess of the tem poral bone and the superior nuchal line of the occip ital bone, whereas the sp le n ius ce rvicis (L. cervix, neck) attaches to the transverse processes of vertebrae C1–C4. Note that the two parts of the splenius muscle are not easily distinguished from each other at this stage of the dissection.

3. Use a scalp el to detach both p arts of the splenius m uscles from their inferior attachm ents on the nuchal ligam ent and spinous processes of vertebrae C7–T6. 4. Re ect the m uscles laterally, leaving their superior attachm ents undisturbed.

Ere ct o r Sp in ae Muscle s [G 33; L 18; N 172; R 226] 1. Use scissors to carefully incise the posterior surface of the t h o raco lum b ar fascia beginning at the m idthoracic level (T6–T7) and extending to S3. Observe that the thoracolum bar fascia is very thin at thoracic levels but becom es very thick at lum bar and sacral levels. 2. Use blunt dissection to separate and re ect the thoracolum bar fascia from the posterior surface of the erector spinae m uscles. 3. Identify the sp in alis m uscle, the m ost m edial colum n of the erector spinae; the lon g issim us m uscle (L. longissimus, the longest), the interm ediate colum n of the erector spinae m uscle; and the iliocost alis m uscle, the lateral colum n of the erector spinae m uscle (FIG. 1.9). 4. Beginning at the midthoracic level, use your ngers to separate the three columns of the erector spinae. Continue to separate the columns inferiorly as far as possible. 5. Observe that the colum ns of the erector spinae m uscles are fused to each other at the level of the sacrum and ilium and cannot easily be separated. 6. Review the attachm ents and actions of the erector sp inae m uscles (see TABLE 1.2).

Se m isp in alis Cap it is Muscle [G 34; L 19; N 172; R 226] 1. Identify and clean the se m isp in alis cap it is m uscle s (L. semi, half; L. spinalis, sp ine) (FIG. 1.10). Note that the sem isp inalis cap itis m uscles are the m ost super cial m em bers of the transversospinales group of m uscles and lie deep to the splenius capitis and cervicis m uscles. [G 38, 39; L 19, 20; N 173; R 246] 2. Observe that the bers of the sem ispinalis capitis m uscles course vertically, parallel to the vertebral colum n. 3. Review the attachm ents and actions of the sem ispinalis capitis m uscle (see TABLE 1.2). 4. Find the g re at e r o ccip it al n e rve where it penetrates the sem isp inalis cap itis m uscle. 5. Use blunt dissection to follow the greater occipital nerve deeply through the semispinalis capitis muscle by widening the point of passage of the nerve through the muscle. 6. Detach the sem ispinalis capitis m uscles close to the occip ital bone while preserving the greater occipital nerve and re ect them inferiorly.

Se m isp in alis Ce rvicis Muscle [G 34; L 19; N 172; R 226] 1. Deep to the sem ispinalis capitis m uscles, identify and clean the se m isp in alis ce rvicis m uscle s.

CHAPTER 1

2. Verify that the superior attachm ent of the sem ispinalis cervicis m uscles is the spinous process of the axis (C2) (FIG. 1.10). Note that the semispinalis muscle additionally has a thoracic com ponent, semispinalis thoracis, but do not make an attem pt to dissect it.

Mult i dus Muscle [G 38, 39; L 19; N 172; R 226] 1. On one side of the body only, m ake a vertical incision through the erector sp inae tendon along the ipsilateral lum bar spinous p rocesses inferiorly to the m edian sacral crest. 2. From the inferior extent of the vertical incision, make a superolateral incision through the erector spinae

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tendon from the median sacral crest to the PSIS, essentially creating a “V”-shaped incision through the inferior extent of the attachments of the erector spinae tendon. 3. Detach the erector spinae tendon from its inferior attachm ents on the lum bar and sacral spinous p rocesses and re ect it sup erolaterally. 4. Identify and clean the m ult i d us m uscle im m ediately deep to the erector spinae tendon (FIG. 1.10). 5. Observe that the m ulti dus m uscle is very wide and thick over the sacrum and that it narrows in the lum bar region. Note that the multi dus muscle has com ponents in the lum bar, thoracic, and cervical regions and terminates superiorly at vertebral level C2. Do not follow it superiorly beyond the lum bar region.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the location, innervation, and action of each m uscle or colum n of m uscles in the deep group of back m uscles. 2. Replace the interm ediate m uscles of the back in their correct anatom ical positions. 3. Review the locations and actions of the interm ediate group of back m uscles. TABLE 1.2

In t e rm e d iat e an d De e p Muscle s o f t h e Back

INTERMEDIATE GROUP OF BACK MUSCLES Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Serratus posterior superior

SP C7–T3

Superior borders of ribs 2–5, lateral to their angles

Elevates ribs 2–5

Anterior rami T2–T5

Serratus posterior inferior

SP T11–L2

Inferior border of ribs 9–12, lateral to their angles

Depresses ribs 9–12

Anterior rami T9–T12

DEEP GROUP OF BACK MUSCLES Muscle

Inferior Atta chments

Superior Atta chments

Actions

Innerva tion

Splenius capitis

Ligamentum nuchae, SP C7–T4

Mastoid process, lateral onethird of superior nuchal line

Splenius cervicis

SP T3–T6

TP C1–C3

Unilateral—laterally exes and rotates head or neck to same side Bilateral—extends head and neck

Posterior rami of middle cervical nerves

Spinalis

SP of T and C

Iliocostalis

Median sacral crest, posterior surface sacrum, SP L and lower T, medial part iliac crest

Semispinalis capitis

TP C7–T6/T7, AP C4–C6

Between superior and inferior nuchal lines of occipital bone medially

Unilateral—extends and laterally rotates head to opposite side Bilateral—extends head

Semispinalis cervicis

TP T1–T5/T6

SP C2–C5

Unilateral—extends and laterally rotates neck to opposite side Bilateral—extends neck

Multi dus

Sacrum, ilium, TP T1– L5, and AP C4–C7

SP L5–C2

Extends and rotates VT to opposite side

Longissimus

Between tubercles and angles of ribs and TP of T and C Angles of lower ribs and TP of C

Unilateral—laterally exes VT to same side Bilateral—extends VT and head, stabilizes VT

Posterior rami of lower cervical nerves

Posterior rami of spinal nerves

Abbreviations: AP, articular process; C, cervical vertebrae; L, lumbar vertebrae; SP, spinous process; T, thoracic vertebrae; TP, transverse process; VT, vertebral column.

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GRANT’S DISSECTOR

SUBOCCIPITAL REGION Disse ct io n Ove rvie w The order of dissection will be as follows: The m uscles that bound the suboccipital triangle will be identi ed. The contents of the suboccipital region (vertebral artery and suboccip ital nerve) will be studied.

Ske le t o n o f t h e Sub o ccip it al Re g io n

Dens Transverse process

Refer to an articulated skeleton and identify the following skeletal features: [G 668; L 300, 301; N 10; R 32] 1. On the posterior aspect of the skull, identify the ext e rn al o ccip it al p ro t ub e ran ce and the bilaterally Foramen located sup e rio r and in fe rio r n uch al lin e s (FIG. 1.1). Groove for transversarium vertebral 2. Observe the relationship of the areas of m uscle atartery tachm ent between the nuchal lines and their proxim Transverse process ity to the base of the skull and fo ram e n m ag n um . 3. Observe that the atlas (C1) does not have a body and Posterior arch Spinous process the axis (C2) has the d en s, which is the body of C1 that Posterior tubercle of atlas (C1) of axis (C2) became fused to C2 during development (FIG. 1.11). FIGURE 1.11 Posterior view of the atlas (C1) and axis (C2). 4. On the atlas (C1), identify the p o st e rio r arch . App roxim ately at the m idpoint of the arch, observe the p o st e rio r t ub e rcle and note the atlas does not have a spinous p rocess (FIG. 1.11). [G 9; L 7; N 19; R 194] 5. On the superior aspect of the posterior arch, identify the g ro o ve fo r t h e ve rt e b ral art e ry bilaterally and observe its relationship to the t ran sve rse fo ram e n on the t ran sve rse p ro ce ss. 6. On the axis (C2), identify the bi d sp in ous p rocess, the tran sverse p rocesses, and the tran sverse foram en (FIG. 1.11).

Disse ct io n In st ruct io n s Subo ccipit al Muscle s [G 34; L 19; N 172; R 226] The spinous process of C2 and the external occipital protuberance will be key landm arks for this dissection and should be used as points of reference for the suboccipital region. 1. Identify the sp in o us p ro ce ss o f t h e axis (C2) using the sup erior extent of the sem ispinalis cervicis m uscle as a reference p oint (FIG. 1.12). 2. Identify and clean the o b liq uus cap it is in fe rio r m uscle and observe that it form s the inferior boundary of the suboccip ital triangle (FIG. 1.12). 3. Verify that the m edial attachm ent of the obliquus cap itis inferior m uscle is the spinous process of the axis (C2), whereas its lateral attachm ent is the transverse p rocess of the atlas (C1). 4. Follow the greater occipital nerve inferior to the inferior border of the o b liq uus cap it is in fe rio r m uscle . Note that the greater occipital nerve (posterior ram us of C2) em erges between vertebrae C1 and C2. 5. Identify and clean the re ct us cap it is p o st e rio r m ajo r m uscle , which form s the m edial boundary of the suboccipital triangle (FIG. 1.12). 6. Con rm that the m edial attachm ent of the rectus cap itis p osterior m ajor m uscle is the spinous p rocess of the axis, whereas its lateral attachm ent is the inferior nuchal line of the occipital bone laterally. 7. Identify and clean the re ct us cap it is p o st e rio r m in o r m uscle (FIG. 1.12).

8. Con rm that the inferior attachm ent of the rectus capitis posterior m inor m uscle is the posterior tubercle of the atlas (C1), whereas its superior attachm ent is the inferior nuchal line of the occip ital bone m ed ially. 9. Identify and clean the o b liq uus cap it is sup e rio r m uscle , which form s the lateral boundary of the suboccip ital triangle (FIG. 1.12). 10. Con rm that the inferior attachm ent of the obliquus capitis sup erior m uscle is the transverse process of the atlas and its superior attachm ent is the occipital bone between the lateral aspect of the superior and inferior nuchal lines. 11. Review the attachm ents and actions of the suboccipital m uscles (see TABLE 1.3).

Co n t e n t s o f t h e Sub o ccip it al Trian g le [G 34; L 19; N 172; R 226] 1. On one side, identify and clean the co n t e n t s o f t h e sub o ccip it al t rian g le , nam ely the sub o ccip it al n e rve and the ve rt e b ral art e ry (FIG. 1.12) [G 41; L 20; N 175; R 246]. Do not keep any of the veins found within the suboccipital region. 2. Observe that the suboccipital nerve (posterior ram us of C1) em erges between the occipital bone and the atlas (C1 vertebra). Note that the suboccipital nerve supplies motor innervation to all the m uscles of the suboccipital region and is the only posterior ram us of a cervical spinal nerve that has no cutaneous distribution.

CHAPTER 1

Greater occipital n. (C2)

THE BACK

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External occipital protuberance

Occipital a.

Rectus capitis posterior minor

Semispinalis capitis (cut)

Rectus capitis posterior major Obliquus capitis superior

Suboccipital n. (C1)

Vertebral a.

Suboccipital triangle

Transverse process (C1) Obliquus capitis inferior

Splenius capitis (reflected)

Trapezius (cut and reflected)

Spinous process (C2)

FIGURE 1.12

Semispinalis cervicis

Suboccipital region.

3. Deep within the suboccipital triangle, identify and clean the verteb ral artery superior to the posterior arch of C1. Do not follow the vertebral artery at this point in the dissection; rather, use an illustration to study the course of the vertebral artery through the neck and into the skull. [G 40, 41; L 13, 20; N 137; R 170]

4. If th e verteb ral artery is n ot visib le, cut th e ob liq uus cap itis sup erior m uscle from its attach m en t on th e lateral in ferio r n uch al lin e on on e sid e of th e b od y on ly an d reflect it laterally.

Disse ct io n Fo llo w-up 1. Review the locations and actions of the transversospinales m uscles. 2. Review the locations and actions of the suboccipital m uscles. 3. Review the distribution of the branches of a thoracic posterior ram us and com pare the thoracic pattern to the distribution of the posterior ram i of spinal nerves C1–C3.

TABLE 1.3

Sub o ccip it al Muscle s

SUBOCCIPITAL GROUP Muscle

Media l Atta chments

La tera l Atta chments

Actions

Rectus capitis posterior major

SP of C2 (axis)

Lateral inferior nuchal line of occipital bone

Extends head and rotates face to same side

Rectus capitis posterior minor

Posterior tubercle of C1 (atlas)

Medial inferior nuchal line of occipital bone

Extends head

Obliquus capitis superior

TP of C1 (atlas) (inferior attachment)

Between lateral aspect of superior and inferior nuchal lines of occipital bone (superior attachment)

Extends head

Obliquus capitis inferior

SP of C2 (axis)

TP of C1 (atlas)

Rotates face to same side

Abbreviations: C, cervical vertebrae; SP, spinous process; TP, transverse process.

Innerva tion

Posterior ramus C1

17

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GRANT’S DISSECTOR

VERTEBRAL CANAL, SPINAL CORD, AND MENINGES Disse ct io n Ove rvie w The ve rt e b ral can al is a bony tube form ed by the stacked ve rt e b ral fo ram in a of the ce rvical vert eb rae , t h o racic ve rt e b rae , lum b ar ve rt e b rae, and sacral can al. The vertebral canal encloses and protects the sp in al co rd , its m em branes (sp in al m e n in g e s), and blood vessels (FIG. 1.13). The spinal cord begins at the foram en m agnum of the occipital bone and typically term inates in the adult at the level of the second lum bar vertebra (FIG. 1.13). Because the spinal cord is shorter than the vertebral canal, the spinal cord segm ents are found at higher vertebral levels than their nam es would suggest. The spinal cord is not uniform in diam eter throughout its length. It has a ce rvical e n larg e m e n t corresponding to spinal cord segm ents C4–T1 and a lum b ar e n larg em e n t corresponding to spinal cord segm ents L2–S3. There are 31 pairs of sp in al n erves (8 cervical, 12 thoracic, 5 lum bar, 5 sacral, and 1 coccygeal), which em erge between adjacent vertebrae. The correlation between spinal nerves and the associated vertebral level varies in the cervical region as com pared to the other vertebral regions. In the cervical region, the spinal nerve C1 em erges superior to the corresponding vertebra C1. The cervical spinal nerves exiting the vertebral canal follow this pattern and em erge superior to the corresponding vertebra through C7. Sp inal nerve C8 exits inferior to the C7 vertebra. Beginning with spinal nerve T1 and

Frontal View 24 separate vertebrae and 2 composite vertebrae

Lateral View 31 pairs of spinal nerves

Brain Medulla oblongata C1 vertebra Cervical enlargement T1 vertebra

Lumbar enlargement L1 vertebra

C1 2 3 4 5 6 7 8 T1 2 3 4 5 6 7 8 9 10 11

Subarachnoid space

12

Conus medullaris

L1 2

Subarachnoid space

3

L5 vertebra

Cauda equina

4 5 S1

FIGURE 1.13

2

3

4 5 Co

The spinal cord within the vertebral canal.

CHAPTER 1

THE BACK

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19

progressing inferiorly, all the rem aining spinal nerves exit below the corresponding vertebra (i.e., spinal nerve T1 exits the vertebral canal below vertebra T1) (FIG. 1.13) The order of dissection will be as follows: The erector spinae and transversospinales m uscles will be rem oved to expose the lam inae of the vertebrae. The lam inae will then be cut and rem oved (lam inectom y) to expose the sp inal m eninges beginning at thoracic levels and extending into the sacrum . The spinal m eninges will be exam ined and will be opened to exp ose the spinal cord. The spinal cord will then be studied .

Disse ct io n In st ruct io n s Wear eye protection for all steps that require the use of a chisel, bone saw, or bone cutters. Skin

Lam in e ct o m y 1. Use a scalp el to rem ove the erector spinae and transversospinales m uscles bilaterally from vertebral levels T4–S3. To facilitate the rem oval of the m uscles, m ake a horizontal cut with the scalpel at the level of T4. Elevate the sup erior edge of the cut m uscles and re ect the entire group of m uscles inferiorly. As you prog ress inferiorly, detach the m uscles from the vertebral colum n to cleanly expose the lam inae. 2. Use scraping m otions with a chisel to clean the rem aining m uscle fragm ents off the lam inae. 3. Begin the lam inectom y in the thoracic region. Use a chisel or power saw to cut the lam inae of vertebrae T6–T12 on both sides of the spinous processes. Make this cut at the lateral end of the lam inae to gain wide exp osure to the vertebral canal. The cutting instrum ent should be angled at 45° to the vertical to m axim ize exposure of the vertebral canal (FIG. 1.14). Be careful to not cut through the transverse p rocesses and thus enter the thoracic cavity.

Pia mater on spinal cord

Supraspinous ligament

Subarachnoid space

Interspinous ligament Extradural (epidural) space

L2

CSF in lumbar cistern Arachnoid mater

Lumbar spinal puncture for CSF draw and spinal anesthesia

Spinous process of L4

Lumbar injection for epidural anesthesia Sacrum

Conus medullaris

Dural sac

S2

Extradural (epidural) space in sacral canal

Filum terminale

Sacral hiatus

FIGURE 1.15 Mid-sagittal cut of vertebral canal. CSF, cerebrosp inal uid. Posterior internal vertebral venous plexus

45

Edge of lamina

Chisel

Anterior spinal a. and v. Anterior internal vertebral venous plexus

FIGURE 1.14

Fat in epidural space

How to open the vertebral canal.

4. Use a scalp el to cut the in t e rsp in o us lig am e n t between vertebrae T6 and T7 and between vertebrae T12 and L1. Preserve the interspinous ligam ents between T7 and T12 levels to keep the intervening sp ines tog ether upon rem oval (FIG. 1.15). 5. Use a chisel to pry the spinous processes and their lam inae out as a unit p aying attention to not d am age the underlying structures. If done p roperly, the d ura m ater will rem ain in the vertebral canal with the spinal cord and will be undam aged. 6. On the deep surface of the rem oved sp inous specim en, identify the lig am e n t a ava. Observe that the ligam enta ava and interspinous ligam ents connect the lam inae and spinous processes of adjacent vertebrae, whereas the sup rasp in o us lig am e n t connects all the spinous processes from the sacrum to the C7

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GRANT’S DISSECTOR

CLIN ICA L CORRELATION

Ve rt e b ral Ve n o us Ple x use s The veins of the vertebral venous plexuses (FIG. 1.14) are valveless, perm itting blood to ow superiorly or inferiorly d ep ending on blood pressure gradients. The vertebral venous plexuses can serve as routes for sp read of infection or m etastasis of cancer from the p elvis to the vertebrae, verteb ral canal, and cranial cavity.

7. 8.

9.

10.

11.

vertebral level. At C7, the supraspinous ligam ent blends with the ligam entum nuchae, which continues to the external occipital protuberance (FIG. 1.15). Use a chisel to widen the canal and rem ove any sharp edges of bone rem aining after the initial cuts. Continue the lam inectom y p rocedure inferiorly in the lum bar and sacral regions to vertebral level S3. Use direct observation of the exposed vertebral canal to help you m ake the cuts correctly. Due to the curvature of the vertebral colum n (FIG. 1.2), the lower lum bar levels m ay be quite deep. Exercise caution in lower lum bar and sacral regions because the vertebral canal curves sharply p osteriorly (super cially). Make a “V”-shaped incision in the p osterior surface of the sacrum so the inferior point of the wedge term inates at vertebral level S3. Do not drive the chisel or push the saw through the sacrum because the tool m ay penetrate the rectum . Use a chisel to pry the spinous processes and their lam inae out as a unit, paying attention to not dam age the underlying structures, and place the rem oved sp inous specim en in the tissue container. When nished with the lam inectom y, you should see the posterior surface of the dura m ater from vertebral levels T6 to S2.

Sp in al Me n in g e s 1. Once the lam inectom y is com pleted, the e p id ural (e xt rad ural) sp ace is exp osed. The epid ural space contains fat and veins that m ay be dif cult to identify due to the em balm ing process. Use blunt dissection to rem ove the e p id ural fat and the p o st e rio r in t e rn al ve rt e b ral ve n o us p le xus from the epidural space. [L 26; N 166] 2. Identify the d ura m at e r, the external m eningeal layer. Observe that the d ural sac ends inferiorly at vertebral level S2 (FIG. 1.15). [G 44; L 22, 24; N 160; R 234] 3. In the thoracic region, lift a fold of d ura m a t e r with forcep s and use scissors to cut a sm all opening in its p osterior m id line. Use scissors to extend the cut inferiorly to vertebral level S2. Attem p t to d o this

4.

5.

6.

7.

8.

9.

10.

11.

without d am ag ing the und erlying arachnoid m ater by retracting the dura m ater laterally as you p rog ress inferiorly. Identify the m iddle m ening eal layer, the arach n o id m at e r (FIG. 1.15). Observe that the arachnoid m ater is very delicate and thin com pared to the overlying protective dura m ater. Incise the arachnoid m ater in the p osterior m idline and observe the sub arach n o id sp ace . Note that the subarachnoid space contains cerebrospinal uid (CSF) in the living person but not in the cadaver (FIG. 1.15). [G 45; L 23; N 165; R 240] Retract the arachnoid m ater and identify the sp in al co rd . The spinal cord is com pletely invested by the internal m ening eal layer, the p ia m at e r. The pia m ater is the thinnest of the m eningeal layers, lies directly on the surface of the spinal cord, and cannot be dissected. On the spinal cord at lower thoracic vertebral levels, identify the lum b ar e n larg e m e n t (spinal cord segm ents L2–S3) providing nerves to the lower lim b. [G 42; L 22, 24; N 160; R 234] Inferior to the lum bar enlargem ent, identify the co n us m e d ullaris (m e d ullary co n e ) dem arcating the end of the spinal cord between vertebral levels L1 and L2 (FIG. 1.16). Identify the collection of anterior and posterior nerve roots surrounding the conus m edullaris in the lower vertebral canal form ing the caud a e q uin a (L., tail of horse) (FIG. 1.16). Centrally within the cauda equina, identify the lum t e rm in ale in t e rn um , a delicate lam ent of pia m ater arising from the tip of the conus m edullaris and ending at vertebral level S2 (FIG. 1.16). Observe that inferiorly, the lum term inale internum becom es encircled by the lower end of the dural sac and continues as the lum t e rm in ale e xt e rn um (co ccyg e al lig am e n t ) (FIG. 1.16) below vertebral level S2. Note that the lum term inale externum passes through the sacral hiatus and ends by attaching to the coccyx.

CLIN ICA L CORRELATION

Lum b ar Pun ct ure CSF can be readily obtained in the adult from the subarachnoid space inferior to the conus m edullaris (FIG. 1.15). At this level, there is no danger of p enetrating the spinal cord with the p uncture needle. A lum bar injection m ay sim ilarly be perform ed in the lower lum bar region to safely introduce anesthesia into the epidural space. Epid ural injections provide spinal anesthesia to block sensations of pain for childbirth or surgery (FIG. 1.15).

CHAPTER 1

Splenius m.

Posterior rootlets

Erector spinae (cut) Spinal cord

Dural sac (cut edge)

Spinal nerves

Serratus posterior inferior (reflected)

Conus medullaris

Cauda equina

THE BACK

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21

15. In the thoracic region, expose one sp in al n e rve . Place a probe into an intervertebral foram en to protect the sp inal nerve. 16. Use bone cutters to rem ove the posterior wall of the intervertebral foram en and expose the sp in al g an g lio n (dorsal root ganglion) (FIG. 1.17A). Recall that the spinal ganglion is the location of the sensory cell bodies of the spinal nerves. 17. Distal to the spinal ganglion, identify the spinal nerve, the point where the posterior and anterior roots m erge. 18. Follow the spinal nerve distally a short distance to the point where it divides into a p osterior ram us and an an t e rio r ram us. Note that the posterior ram us will supply the deep muscles of the back and the overlying skin, whereas the ventral ram us will be responsible for the anterolateral trunk and lim bs.

Filum terminale internum

Arachnoid mater Pia mater

Dura mater

Anterior root Spinal nerve Filum terminale externum

Spinal ganglion

Denticulate ligament

A FIGURE 1.16 spinal cord.

Posterior root Subarachnoid space

Posterior view of lower vertebral canal and Dura mater Spinal nerve

12. The pia m ater form s two d e n t iculat e lig am e n t s, one on each side of the spinal cord (FIG. 1.17B). Note that each denticulate ligament has 21 teeth and each tooth is attached to the inner surface of the dura m ater anchoring the spinal cord laterally. [G 43; L 23; N 165; R 235] 13. Use a probe to follow the p o st e rio r and an t e rio r ro o t s to the point where they p ierce the dura m ater and enter the in t e rve rt e b ral fo ram e n (FIG. 1.17A). Observe that the posterior roots are on the posterior side of the denticulate ligam ent, whereas the anterior roots are on the anterior side of the denticulate ligam ent. 14. It m ay be p ossible to ob serve sm all b lo o d ve sse ls coursing along the anterior and p osterior roots. Dep ending on the vertebral level, these sm all blood vessels are branches of posterior intercostal, lum bar, or vertebral arteries. These sm all arteries pass into the vertebral canal through the intervertebral foram en and supply blood to the spinal cord. [G 48, 49; L 25; N 168]

Arachnoid mater

Posterior root

Anterior root

Spinal cord and pia mater

B

Denticulate ligament

Posterior root (reflected)

FIGURE 1.17 Relationships of the m eninges to the spinal cord and nerve roots. A. Transverse section. B. Posterior view.

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GRANT’S DISSECTOR

Disse ct io n Fo llo w-up 1. Review the form ation and branches of a typical spinal nerve. 2. Describe the way that the deep back m uscles receive their innervation. 3. Review the coverings and parts of the spinal cord and study an illustration that shows the blood supply to the spinal cord. 4. Consult a derm atom e chart and relate this pattern of cutaneous innervation to the spinal cord segm ents. [G 54; L 27; N 162]

CHAPTER 2

The Upper Lim b ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

h e u p p er lim b is d ivid ed in to fou r region s: sh o u ld er (p ect o ra l gird le), a rm (b ra ch iu m ), fo rea rm (a n t eb ra ch iu m ), an d h a n d (m a n u s). Th e u p p er lim b is stru ctu red for m obility so we can p lace ou r h an d s, wh ich are grasp in g organ s, in a large area of sp ace. Som e of th e m u scles th at con trol th e u p p er lim b are extrin sic, m ean in g th at th ey exten d in to oth er region s of th e bod y, sp eci cally th e an terior th orax an d th e back. If th e back h as p reviou sly been d issected , th e su p er cial m u scles an d bon y lan d m arks of th e back h ave been stu d ied . With th e body p ron e, com m en ce th e d issection

T

of th e u p p er lim b with th e scap u lar region . Begin n in g with th e scap u lar region m in im izes th e n u m ber of fu ll bod y rotation s req u ired an d con tin u es th e stu d y of th e su p er cial m u scles of th e back in to th e u p p er lim b. If th e u p p er lim b is you r rst d issect ion u n it an d t h e bod y is in a su p in e p o sit ion , it is reco m m en d ed to begin with th e su rface an at om y sect ion . At t h e ap p rop riat e tim e in t h e d issect ion , you will be in st ru ct ed to d issect th e su p er cial m u scles of t h e back an d t o ret u rn t o th e scap u lar regio n in st ru ct io n s aft er com p letin g th at d issection .

SCAPULAR REGION AND POSTERIOR ARM Disse ct io n Ove rvie w There are six shoulder (scapulohum eral) m uscles: d e lt o id , sup rasp in at us, in frasp in at us, t e re s m ajo r, t e res m in o r, and sub scap ularis. The order of dissection will be as follows: The skin and sup er cial fascia will be rem oved. The deltoid m uscle will be studied and detached from its proxim al attachm ent, and the course of its nerve and artery will be explored. Subsequently, the four m uscles arising from the posterior surface of the scapula (supraspinatus, infraspinatus, teres m ajor, teres m inor) will be dissected and their nerves and blood vessels will be dem onstrated. The posterior com partm ent of the arm (brachium ) contains two m uscles: the t rice p s b rach ii m uscle , which will be studied in this dissection sequence, and the an co n e us m uscle , which will be studied with the posterior com partm ent of the forearm (antebrachium ). In addition to the tricep s brachii m uscle, the radial nerve and the deep artery and vein of the arm will be identi ed. Further exam ination of the fascia, contents, and organization of the arm will be studied when the anterior com partm ent of the arm is dissected.

Ske le t o n o f t h e Scap ular Re g io n Refer to a skeleton or disarticulated scapula and hum erus to identify the following skeletal features (FIG. 2.1): [G 108, 109; L 32; N 406; R 383, 385]

Scap ula 1. On the posterior aspect of the scapula, observe that the sp in e o f t h e scap ula separates the sup rasp in o us fo ssa from the in frasp in o us fo ssa and term inates laterally as the acro m io n p ro ce ss. 2. Along the superior border of the scapula, identify the sup rascap ular n o t ch m edial to the anteriorly projecting co raco id p ro ce ss.

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GRANT’S DISSECTOR Intertubercular sulcus Supraglenoid tubercle Suprascapular notch Coracoid process Spine of scapula Superior angle Acromion

Supraspinous fossa

Clavicle Head of humerus

Greater tubercle

Infraspinous fossa Anatomical neck

Medial border

Lesser tubercle

Surgical neck Humerus

Lateral border Inferior angle

Deltoid tuberosity

Infraglenoid tubercle

Radial groove

FIGURE 2.1

Skeleton of the scapular region.

3. On the lateral aspect of the scapula, inferior to the acrom ion, identify the g le n o id cavit y form ing the “socket” of the glenohum eral joint. 4. Sup erior an d in ferior to th e d ep ression of th e g len oid cavity, id en tify th e su p ra g le n o id an d in fra g le n o id t u b e rcle s, resp ectively. Th e roug h en ed reg ion s of th e tub ercles serve as attach m en t sites for m uscles of th e up p er lim b .

Hum e rus 1. On the proxim al aspect of the hum erus m edially, identify the sm ooth surface of the h e ad o f t h e h um e rus form ing the “ball” of the glenohum eral joint. 2. Im m ediately inferior to the head of the hum erus, locate the an at o m ical n e ck. 3. On the proxim al aspect of the hum erus laterally, identify the g re at e r t ub ercle and note its sep aration from the m ore anteriorly oriented le sse r t ub e rcle by the in t e rt ub e rcular sulcus (b icip it al g ro o ve ). 4. Inferior to the greater and lesser tubercles, identify the surg ical n e ck o f t h e h um e rus. 5. Along the lateral aspect of the sh aft of the hum erus, identify the d e lt o id t ub e ro sit y im m ediately superior to the obliquely oriented rad ial g ro o ve .

Disse ct io n In st ruct io n s Po st e rio r Sh o uld e r Muscle s 1. With the cadaver in the prone position (face down), abduct the upper lim b to 45°. If a block is available, place it under the chest and shoulder. 2. Rem ove the skin of the posterior arm to the level of the elbow if this has not p reviously been done. 3. Rem ove the fat and super cial fascia of the shoulder and p osterior arm . 4. Re ect the trapezius m uscle superiorly, leaving it attached along the clavicle and “hinge” of cervical fascia created during the back dissection. 5. Clean the surface and borders of the d e lt o id m uscle . [G 103; L 36; N 409; R 394] 6. Review the attachm ents and actions of the deltoid m uscle (see TABLE 2.1). 7. Use a scalp el to d etach th e d eltoid m uscle from its p roxim al attach m en ts alon g the sp in e of th e

8.

9.

10.

11.

scap ula an d th e acrom ion p rocess. Leave th e m uscle attach ed an teriorly to th e clavicle an d d istally to th e h um erus. Re ect the deltoid m uscle laterally, taking care not to tear the vessels and nerve coursing along its deep surface. Observe the a xilla ry n e rve and the p o st e rio r circu m e x h u m e ra l a rt e ry a n d ve in on the d eep surface of the d eltoid m uscle near the surg ical neck of the hum erus (FIG. 2.2). Note that the axillary nerve innervates the deltoid m uscle and the teres minor muscle. Clean the nerve and vessels using blunt dissection and trace them around the posterior aspect of the surgical neck of the hum erus. [G 118; L 37; N 413; R 395] Follow the axillary nerve and the posterior circum ex hum eral vessels deep ly into the q uad ran g ular sp ace (FIG. 2.2).

CHAPTER 2

THE UPPER LIMB

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25

Posterior view Suprascapular nerve and artery Acromion

Superior transverse scapular ligament

Infraspinatus tendon (cut) Supraspinatus m. (cut)

Joint capsule of shoulder Deltoid m. (reflected)

Spine of scapula Teres minor m. Quadrangular space (green lines) transmitting axillary nerve and posterior circumflex humeral artery

Infraspinatus m. (cut)

Superior lateral cutaneous nerve of arm

Triangular space (green lines) with circumflex scapular artery deep to space

Deep artery of arm Radial nerve

Teres major m.

Lateral head of triceps brachii m.

Long head of triceps brachii m.

FIGURE 2.2

Neurovascular supply to the posterior aspect of the shoulder.

12. Observe that the q uad ran g ular sp ace is bound superiorly by the t e re s m in o r m uscle , inferiorly by the t e res m ajo r m uscle , and m edially by the lateral border of the lo n g h e ad o f t h e t rice p s b rach ii m uscle . The lateral border of the quadrangular space is the surgical neck of the hum erus, which cannot be seen at this tim e. 13. Identify and clean the proxim al end of the lo n g h e ad o f t h e t rice p s b rach ii m uscle . Observe that the long head passes posterior to the teres m ajor m uscle and anterior to the teres m inor m uscle. 14. Clean an d d efin e th e b ord ers of th e t e re s m a jo r m u scle . Th e teres m ajor m uscle m ay b e p artially covered b y th e latissim us d orsi m uscle. If th is is th e case, sim p ly loosen th e con n ective tissue surro un d in g th e latissim us d o rsi an d g en tly p ull it laterally. 15. Review the attachm ents and actions of the teres m ajor m uscle (see TABLE 2.1).

Ro t at o r Cuff Muscle s [G 106, 107, 124; L 45; N 405, 408; R 395] 1. Th e fo ur m uscles of th e ro t a t o r cu ff are th e su p ra sp in a t u s, in fra sp in a t u s, t e re s m in o r, an d

2.

3. 4.

5. 6.

7.

su b sca p u la ris. Th e sub scap ularis m uscle will b e d issected with th e axilla. Use an illustratio n to stud y th e lateral attach m en ts of th e rotator cuff m uscles. Identify and clean the t e re s m in o r m uscle along the lateral border of the scapula. Make an effort to clearly de ne its superior and inferior borders. Review the attachm ents and actions of the teres m inor m uscle (see TABLE 2.1). Clean the surface and de ne the borders of the in frasp in at us m uscle within the infraspinous fossa of the scapula. Review the attachm ents and actions of the infrasp inatus m uscle (see TABLE 2.1). Ob serve th at th e t ria n g u la r sp a ce is m ed ial to th e q uad ran g ular sp ace an d is b oun d sup eriorly b y th e in ferior b o rd er of th e teres m in o r m u scle, in ferio rly b y th e sup erio r b ord er o f th e teres m ajor m uscle, an d laterally b y th e m ed ial b o rd er of th e lon g h ead of th e tricep s b rach ii m u scle (FIG. 2.2). Ob serve th at th e circum flex scap ular artery an d vein can b e foun d with in th e trian g ular sp ace. Make n o d elib erate effort to follow th e vessel at th is tim e.

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GRANT’S DISSECTOR

8. Clean and de ne the borders of the sup rasp in at us m uscle within the suprascapular fossa. 9. Review the attachm ents and actions of the supraspinatus m uscle (see TABLE 2.1). 10. Use a scalpel to transect the supraspinatus m uscle about 5 cm lateral to the superior angle of the scapula but m edial to the sup rascap ular notch (FIG. 2.2). If a disarticulated scap ula is available, hold it over the scapula of the cadaver to help you locate the p roper level of the cut. 11. Use blunt dissection to loosen and re ect the lateral portion of the supraspinatus m uscle from the supraspinous fossa. 12. Id en tify th e su p ra sca p u la r a rt e ry a n d n e rve th at lie in th e sup rasp in ous fossa. Follow th e artery an d n erve an teriorly an d ob serve th eir relation sh ip with th e su p e rio r t ra n sve rse sca p u la r lig a m e n t . Th e sup rascap ular artery p asses sup erior to th e sup erior tran sverse scap ular lig am en t, an d th e sup rascap ular n erve p asses in ferior to it (FIG. 2.2). Th is relation sh ip can b e rem em b ered b y use of a m n em on ic: Arm y (a rtery) g oes over th e b rid g e; Navy (nerve) g oes un d er th e b rid g e. Th e “b rid g e” is th e sup erior tran sverse scap ular lig am en t. [G 1 1 8 ; L 3 7 ; N 4 1 3 ; R 416] 13. Transect the in frasp in at us m uscle about 5 cm lateral to the m edial border of the scap ula (FIG. 2.2). 14. Use blunt dissection to loosen and re ect the lateral portion of the infraspinatus m uscle from the infraspinous fossa. 15. Follow the sup rascap ular art e ry and the sup rascap ular n e rve around the spine of the scapula to the infraspinatus m uscle (FIG. 2.2). 16. The suprascapular artery contributes to the collateral circulation of the scapular region. Use an illustration to study the scap ular an ast o m o se s. [G 94; L 38; N 414; R 416]

5. Identify the t rice p s b rach ii m uscle and note the arrangem ent of its three m uscular heads (FIG. 2.3). Observe that the lo n g h e ad o f t h e t rice p s b rach ii m uscle is p ositioned m ore sup er cially than the lat e ral and m e d ial h e ad s o f t h e t rice p s b rach ii m uscle, which are nam ed for their location respective to the radial groove. 6. Review the attachm ents and actions of the triceps brachii m uscle (see TABLE 2.1). 7. Use your ngers to sep arate the long head from the lateral head of the triceps brachii inferior to where the teres m ajor m uscle crosses the anterior surface of the long head.

Posterior circumflex humeral a. Teres minor m.

Axillary nerve Deltoid m. (reflected)

Radial nerve and deep a. of the arm

Lateral head of triceps brachii m. Teres major m. Long head of triceps brachii m.

Po st e rio r Co m p art m e n t o f t h e Arm [G 117, 118; L 47; N 418; R 420, 421] 1. With the cadaver in the prone position, rotate the upp er lim b m edially to gain better access to the posterior com p artm ent of the arm . 2. Use scissors to open the posterior com p artm ent of the arm by m aking a longitudinal incision through the d eep (b rachial) fascia, from the teres m inor m uscle superiorly to the level of the olecranon of the ulna. 3. Use your ngers and blunt dissection to spread and elevate the brachial fascia. 4. Detach the brachial fascia from the m edial and lateral interm uscular sep ta and place it in the tissue container.

Lateral epicondyle of humerus Ulnar nerve Medial epicondyle of humerus Olecranon of ulna

Anconeus m.

FIGURE 2.3 How to transect the lateral head of the triceps brachii m uscle.

CHAPTER 2

8. Observe that the t rian g ular in t e rval is inferior to the quadrangular space and is bound m edially by the long head of the triceps brachii m uscle, laterally by the lateral head of the triceps brachii m uscle, and superiorly by the inferior border of the teres m ajor m uscle (FIG. 2.3). 9. Widen the triangular interval and identify the rad ial n e rve and the d e e p art e ry o f t h e arm (d e e p b rach ial art e ry). 10. Push a probe distally along the course of the radial nerve between the lateral head of the triceps brachii m uscle and the hum erus.

THE UPPER LIMB

•

27

11. On on e sid e of th e b od y, use a scalp el to tran sect th e lateral h ead of th e tricep s b rach ii over th e p ro b e. 12. Use blunt dissection to clean the radial nerve and the deep artery of the arm within the rad ial g ro o ve of the hum erus. 13. Do not follow the radial nerve or deep artery of the arm distally at this tim e. The path of the radial nerve will be continued in the dissection of the cubital fossa.

Disse ct io n Fo llo w-up 1. Replace the m uscles of the scapular region and posterior arm in their correct anatom ical positions. 2. Review the innervations and attachm ents of each m uscle of the scapular region. List the action of each m uscle and the com bined action of the rotator cuff group of m uscles. 3. Review the origin, course, and distribution of the transverse cervical artery, dorsal scapular artery, and suprascapular artery. 4. Review the scapular anastom oses. 5. Review the relationship of the suprascapular artery and the suprascapular nerve to the superior transverse scapular ligam ent. 6. Review th e b oun d aries an d con ten ts of th e trian g ular sp ace, th e q uad ran g ular sp ace, an d th e trian g ular interval.

TABLE 2.1

Muscle s o f t h e Sh o uld e r an d Po st e rio r Arm

SCAPULAR REGION Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Deltoid

Spine of the scapula, acromion of the scapula, lateral one-third of the clavicle

Deltoid tuberosity of the humerus

Abducts, exes, and extends the humerus

Axillary n.

Supraspinatus

Supraspinous fossa of the scapula

Superior facet of the greater tubercle of the humerus

Abducts the humerus

Suprascapular n.

Infraspinatus

Infraspinous fossa of the scapula

Middle facet of the greater tubercle of the humerus

Laterally rotates the humerus

Suprascapular n.

Teres major

Inferior angle of the scapula

Medial lip of the intertubercular sulcus of the humerus

Adducts and medially rotates the humerus

Lower subscapular n.

Teres minor

Lateral border of the scapula

Inferior facet of the greater tubercle of the humerus

Laterally rotates the humerus

Axillary n.

Subscapularis

Subscapular fossa

Lesser tubercle of the humerus

Medially rotates the humerus

Upper and lower subscapular nn.

POSTERIOR COMPARTMENT OF THE ARM Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Triceps brachii

Long head—infraglenoid tubercle of the scapula; medial and lateral heads— posterior surface of the humerus

Olecranon process of the ulna

Extends the forearm; long head—extends and adducts the arm

Radial n.

Abbreviations: n., nerve; nn., nerves.

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GRANT’S DISSECTOR

SUPERFICIAL VEINS AND CUTANEOUS NERVES Disse ct io n Ove rvie w The sup e r cial fascia of the upper lim b contains fat, sup e r cial ve in s, and cut an e o us n e rve s. In the living body, the sup er cial veins m ay be visible through the skin and are frequently used for drawing blood and injecting m edications. In the cadaver, the super cial veins are not conspicuous. The cutaneous nerves of the up per lim b p ierce the deep fascia to reach the sup er cial fascia and the skin. The ord er of d issection will b e as follows: The anterior th oracic wall and th e up p er lim b p roxim al to th e wrist will b e skinn ed , leavin g th e sup er cial fascia und isturb ed . The sup er cial vein s an d selected cutaneous nerves will b e d issected . Th e fat will th en b e rem oved to ob serve th e d eep fascia. [G 7 2 , 8 0 ; L 3 1 ; N 4 0 1 , 4 0 2 ; R 4 1 2 , 4 1 4 ]

Surface An at o m y The surface anatom y of the upper lim b can be studied on a living subject or on the cadaver. [G 64, 65; L 30; N 398; R 413, 414] 1. Place the cadaver in the supine (face up) position. 2. Beginning at the m idline of the neck, palpate the jug ular n o t ch between the sternal ends of the clavicle s (FIG. 2.4). 3. On the anterior chest wall, identify and palpate the st e rn al an g le at the level of the second costal cartilage. Palpate inferiorly along the sternum toward the xip h ist e rn al jun ct io n then laterally along the co st al m arg in s. 4. Return to the jugular notch and p alp ate laterally along the clavicle toward the acro m io n and feel the d e lt o id m uscle . 5. In the axilla (arm pit), palpate the free edges of b oth the an t erio r and p o st erio r axillary fo ld s. 6. On the anterior aspect of the arm , p alpate the b ice p s b rach ii m uscle working inferiorly toward the cub it al fo ssa. 7. On the m edial asp ect of the cubital fossa, p alpate the m e d ial e p ico n d yle and the associated e xo r m uscle m ass in the anterior forearm . 8. On the lateral aspect of the cubital fossa, palpate the lat e ral e p ico n d yle and the e xt e n so r m uscle m ass in the p osterior forearm . Jugular notch Clavicle Acromion

l

d

e

r

Deltoid m.

S

h

o

u

Axillary folds: Posterior Anterior Triceps brachii m.

m

Biceps brachii m. Xiphisternal junction

A

r

Cubital fossa Olecranon Lateral epicondyle

e

a

r

m

Extensor muscle mass

F

o

r

Styloid process of the radius

Costal margin Medial epicondyle Flexor muscle mass Styloid process of the ulna

H

a

n

d

Hypothenar eminence Carpal bones

FIGURE 2.4

Thenar eminence

Surface anatom y of the upper lim b.

CHAPTER 2

THE UPPER LIMB

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29

9. At the wrist, palpate the st ylo id p ro ce ss o f t h e rad ius laterally and the st ylo id p ro ce ss o f t h e uln a m edially just proxim al to the carp al b o n e s. 10. In the palm , palpate the t h e n ar e m in e n ce at the base of the thum b and the h yp o t h e n ar e m in e n ce on the m edial asp ect of the hand.

Disse ct io n In st ruct io n s Skin In cisio n s 1. Refer to FIGURE 2.5A. 2. Make a m idline skin incision from the jugular notch (A) to the xiphisternal junction (C) and verify that the skin on the thorax is thinner than the skin on the back. 3. Make a skin incision from the jugular notch (A) along the clavicle laterally to the acrom ion (B). Continue this incision d own the lateral side of the arm to a

4. 5.

6.

7. B

A

8.

9. F C

11.

G

12. 13.

V

A

10.

14. G

15. 16.

E

B FIGURE 2.5 Skin incisions for the pectoral region (A) and upper lim b (B).

point approxim ately halfway down the arm (F). If the back has previously been dissected, this cut has already been made. At point F, m ake an incision around the anterior surface of the arm toward the m edial surface of the arm (G). Make an incision from the xiphisternal junction (C) along the costal m argin inferolaterally to the m idaxillary line (V). Make an incision beginning at G on the m edial surface of the arm extending superiorly to the axilla. Extend this incision inferiorly along the lateral surface of the trunk to V. If the back has previously been dissected, this cut has already been m ade. Make an incision beginning in the axilla m edially and extending laterally around the arm toward the lateral surface of the arm just below the attachm ent of the deltoid. Make a transverse skin incision from the m iddle of the m anubrium to the m idaxillary line passing around the nipp le. The nip ple should be kep t attached to the super cial fascia and left intact for the breast dissection because it is a good super cial landm ark for the fourth intercostal space. Make a transverse skin incision from the xiphisternal junction (C) to the G–V incision. Make a transverse skin incision halfway between the A–B incision and the incision m ade in step 8. Rem ove the skin from m edial to lateral. Detach the skin along the m idaxillary line and place it in the tissue container. Refer to FIGURE 2.5B. Make an incision encircling the wrist (E). Note the skin is very thin (2 m m ) around the wrist—do not cut too deeply. Make a shallow longitudinal incision on the anterior surface of the up per lim b (E to G), p aying particular attention to rem ain shallow at the cubital fossa. Make an incision around the circumference of the forearm approximately midway between the cuts at E and G. Rem ove the skin from the arm and forearm and place it in the tissue container. While rem oving the skin, do not dam age the super cial veins and cutaneous nerves in the sup er cial fascia.

Supe r cial Ve ins [G 80; L 31; N 401, 402; R 410] 1. Use blunt dissection with a probe, forceps, or scissors to dem onstrate the super cial veins of the arm and forearm (FIG. 2.6).

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GRANT’S DISSECTOR

Supraclavicular nerves Superior lateral cutaneous nerve of arm Intercostobrachial nerve Medial cutaneous nerve of arm

between the deltoid and pectoralis m ajor m uscles. Near the clavicle, the cephalic vein penetrates the clavip e ct o ral fascia within the d e lt o p ect o ral t rian g le to join the axillary vein. 6. Follow the basilic vein proxim ally and note that a few centim eters above the m edial epicondyle it pierces the deep fascia to join the deep veins. 7. Use a probe to elevate the super cial veins and note that several p e rfo rat in g ve in s p enetrate the deep fascia connecting the super cial and deep veins of the upper lim b (FIG. 2.6).

Posterior cutaneous nerve of arm Inferior cutaneous nerve of arm Medial cutaneous nerve of forearm Median cubital vein

Posterior cutaneous nerve of forearm Lateral cutaneous nerve of forearm Cephalic vein Basilic vein

Superficial branch of radial nerve Dorsal branch of ulnar nerve Dorsal venous arch

Dorsal metacarpal veins

FIGURE 2.6

Super cial veins and cutaneous nerves.

2. In the posterior forearm , dem onstrate the b asilic ve in and the ce p h alic ve in . 3. Use a p rob e to follow th e cep h alic an d b asilic vein s p roxim ally, freeing them from the surround ing fat an d con n ective tissue. It m ay b e useful to ab d uct th e up p er lim b to 45° if p ossib le an d to h ave your d issection p artn er h old it in th e ab d ucted p osition. 4. Dem on strate th at th e cep h alic an d b asilic vein s are jo in ed across th e cub ital fossa b y th e m e d ia n cu b it a l ve in . Th e ven ou s p attern in th is reg io n can b e q u ite variab le an d sh o uld b e o b served o n o th er cad avers as an exam p le o f an atom ical variation . 5. Follow the cephalic vein proxim ally into the pectoral region where it courses in the d e lt o p ect o ral g ro o ve

Cut an e o us Ne rve s [G 72; L 31; N 401, 402; R 412] 1. Before d issectin g , use an illustration to fam iliarize yourself with th e course and d istrib ution of th e cu t a n e o u s n e rve s o f t h e a rm a n d fo re a rm (FIG. 2.6). 2. Within the super cial fascia, m ake an effort to identify the lat e ral cut an e o us n erve o f t h e fo re arm at the level of the elbow. Note its close relationship to the cephalic vein and the m edian cubital vein in the super cial fascia lateral to the biceps brachii distal tendon. 3. On th e m ed ial sid e of th e b icep s b rach ii ten d on , id en tify th e m e d ia l cu t a n e o u s n e rve o f t h e fo re a rm , n otin g its close relation sh ip to th e b asilic vein . 4. Near the wrist, identify the sup e r cial b ran ch o f t h e rad ial n e rve in the super cial fascia near the styloid process of the radius. Expose only 2 or 3 cm of this nerve, m aking an effort to not disrup t the nearby structures in the anatom ical snuffbox. 5. On the m edial aspect of the wrist and hand, locate the d o rsal b ran ch o f t h e uln ar n e rve in the super cial fascia near the styloid p rocess of the ulna. Expose only 2 or 3 cm of this nerve. 6. The cutaneous nerves to the digits will be studied when the hand is dissected. 7. Rem ove all rem aining super cial fascia from the arm and forearm preserving the dissected super cial veins and nerves. Do not disturb the deep fascia overlying the m uscles. Place the super cial fascia in the tissue container. 8. Exam in e th e d e e p fa scia of th e up p er lim b an d n ote th at it exten d s from th e sh ould er to th e n g ertip s. Th e d eep fascia of th e up p er lim b attach es to th e b on es of th e up p er lim b form in g com p artm en ts th at con tain g roup s of m uscles. Th e d eep fascia is n am ed reg ion ally: b ra ch ia l fa scia in th e arm , a n t e b ra ch ia l fa scia in th e forearm , p a lm a r fa scia on th e p alm ar surface of th e h an d , an d d o rsa l fa scia o f t h e h a n d on th e p osterior surface of th e h an d .

CHAPTER 2

THE UPPER LIMB

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31

Disse ct io n Fo llo w-up 1. Use the dissected specim en to trace the course of the super cial veins from distal to proxim al. 2. Review the location and drainage pattern of the cephalic vein, basilic vein, and m edian cubital vein and recall that these p rovide im portant access sites for venipuncture. 3. Use the dissected specim en to review the four cutaneous nerves that you have dissected. 4. Use an illustration to review the pattern of distribution of the cutaneous nerves that you did not dissect along with the derm atom es of the up per lim b. 5. Review and nam e the various com ponents of the deep fascia of the upper lim b. [G 83; L 31; N 399, 400]

PECTORAL REGION Disse ct io n Ove rvie w The p ect o ral re g io n (L. pectus, chest) covers the anterior thoracic wall and p art of the lateral thoracic wall. The order of dissection will be as follows: The breast will be dissected in fem ale cadavers only. Students with male cadavers must observe at another dissection table. In cadavers of both sexes, the sup er cial fascia will be rem oved to exp ose the pectoral m uscles.

Disse ct io n In st ruct io n s Bre ast [G 195, 196; L 39; N 179; R 298] The b re ast extends from the lateral border of the sternum to the m idaxillary line, and from rib 2 to rib 6. The breast is positioned anterior to the p e ct o ral fascia (the deep fascia of the pectoralis m ajor m uscle). The pectoral fascia is attached to the overlying skin by the susp e n so ry lig am e n t s o f t h e b reast that pass between the lobes of the m am m ary gland. The m am m ary gland is a m odi ed sweat gland contained within the sup er cial fascia of the breast (FIG. 2.7). Because of the advanced age of som e cadavers, it m ay be dif cult to d issect and identify all of the structures listed. Expect the lobes of the gland to be replaced by fat with advanced age. 1. Identify the are o la and the n ip p le (FIG. 2.7). 2. Make a parasagittal (superior to inferior) cut through the nip ple to divide the breast into m edial and lateral halves and rem ove the m edial half (FIG. 2.7). 3. On the cut edge of the breast, use a probe to dissect through the fat within 3 cm deep to the nipp le. Find and clean 1 of the 15 to 20 lact ife ro us d uct s converging on the nipp le. Identify a lact ife ro us sin us, which is an expand ed p art of the lactiferous duct. 4. Trace one lactiferous duct to the nipple and attem pt to identify its opening. 5. Use the handle of a forceps to scoop the fat out of several com p artm ents between susp en so ry lig am e n t s. These areas between suspensory ligam ents once contained lobes of functional glandular tissue. 6. Use an illustration to study the lym p h at ic d rain ag e o f t h e b re ast . [G 198; L 40; N 181; R 298] 7. Insert your ng ers deep to the breast and open the re t ro m am m ary sp ace im m ediately super cial to the deep fascia. Note that the norm al breast can be easily

sep arated from the underlying deep fascia of the pectoralis m ajor m uscle. 8. Carefully rem ove the breast from the anterior surface of the pectoralis m ajor m uscle with the aid of a scalpel.

Sup e r cial Fascia Dissection of the super cial fascia of the anterior thoracic wall m ust be perform ed on both m ale and fem ale cadavers. 1. Identify the p lat ysm a m uscle, a thin but broad m uscle of facial expression which extends inferiorly through Suspensory ligaments

Retromammary space (bursa)

Lactiferous sinus

2nd rib Subcutaneous tissue

Areola

Pectoralis minor m. Nipple Pectoralis major m. 4th intercostal space Mammary gland lobe Pectoral fascia

Opening of lactiferous duct

6th rib Lactiferous ducts

FIGURE 2.7

Breast in sagittal section.

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GRANT’S DISSECTOR

CLIN ICA L CORRELATION

Bre ast For descriptive purposes, clinicians divide the breast into four quadrants centered on the nipple. The superolateral (upper outer) quadrant contains a large am ount of glandular tissue and is a com m on site for breast cancers to develop. From this quadrant, an “axillary tail” of breast tissue often extends into the axilla. In advanced stages of breast cancer, the tum or m ay invade the underlying pectoralis m ajor m uscle and its fascia and becom e fused to the chest wall. During a physical exam ination, this fusion can be detected by palpation. As the breast tum or enlarges, it places traction on the suspensory ligam ents, resulting in d im pling of the skin overlying the tum or, giving the skin an “orange peel” ap pearance.

the neck into the super cial fascia of the superior thorax. Isolate the platysm a from the super cial fascia and re ect the m uscle superiorly out of the dissection eld superior to the clavicles. 2. Rem ove the sup er cial fascia of the pectoral region proceeding from m edial to lateral using the skin incisions A–B–F, C–V and G–V as guidelines (FIG. 2.5A). 3. The sm all an t erior cut an eous n erves em erge from the intercostal space lateral to the borders of the sternum . Although possible to identify, do not m ake an effort to nd them ; rather, study the typical branches of a spinal nerve from an illustration. [G 212; L 170; N 188; R 219] 4. As you p eel back the sup er cial fascia, identify an intercostal sp ace by palp ation. The lat e ral cut an e o us b ran ch e s of the intercostal nerves

Deltoid

Platysma

Cephalic vein Clavicle Intercostobrachial nerve (T2) (lateral cutaneous branch of 2nd intercostal nerve)

Sternum

S

Long thoracic nerve

S

Lateral thoracic a.

S S

Latissimus dorsi

S

Posterior branches of lateral cutaneous nerves

FIGURE 2.8

Pectoralis major

Nipple Serratus anterior (S)

S Anterior branches of lateral cutaneous nerves

Distribution of lateral cutaneous nerves of trunk.

are located near the m idaxillary line where they leave the intercostal sp ace to enter the sup er cial fascia (FIG. 2.8). Id entify one lateral cutaneous branch (from intercostal sp ace 4, 5, or 6) while the super cial fascia is being rem oved. If p ossible, trace its an t e rio r an d p o st e rio r b ran ch e s for a short distance. 5. Detach the super cial fascia along the m idaxillary line and place it in the tissue container, sparing any identi ed cutaneous nerves.

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Review the location and parts of the breast. Use an illustration to review the vascular sup ply to the breast. Discuss the pattern of lym phatic drainage of the breast and identify by nam e the involved lym ph node groups. Use an illustration of the branching pattern of a typical spinal nerve to review the innervation of the anterior thoracic wall and breast (FIG. 2.8).

MUSCLES OF THE PECTORAL REGION Disse ct io n Ove rvie w There are three m uscles in the pectoral region: pectoralis m ajor, pectoralis m inor, and subclavius. The m uscles of the pectoral region provide m ovem ent to the up per lim b and assist in attaching it to the axial skeleton. The order of dissection will be as follows: The pectoralis m ajor m uscle will be studied and re ected. The pectoralis m inor m uscle and clavipectoral fascia will be studied. The subclavius m uscle will be identi ed. The pectoralis m inor m uscle will be re ected, and the branches of the thoracoacrom ial artery will be dissected.

CHAPTER 2

Disse ct io n In st ruct io n s Muscle s o f t h e Pe ct o ral Re g io n 1. Clean the super cial surface of the p e ct o ralis m ajo r m uscle and clearly de ne its borders (FIG. 2.9). Note that the deep fascia on the sup er cial and deep surfaces of the pectoralis m ajor m uscle is called p e ct o ral fascia and that it is continuous with the axillary fascia form ing the base of the axilla. [G 88; L 41; N 409; R 418] 2. Identify the two heads of the pectoralis m ajor m uscle, the clavicular h e ad and the st e rn o co st al h e ad (FIG. 2.9). Observe that the juncture of these two heads is at the sternoclavicular joint. 3. Review the attachm ents and actions of the pectoralis m ajor m uscle (see TABLE 2.2). 4. Identify the d e lt o p ect o ral t rian g le located between the sup erior border of the clavicular head of the p ectoralis m ajor m uscle and the anterior border of the d eltoid m uscle near the clavicle (FIG. 2.9). Laterally, the deltopectoral triangle narrows to form the d e lt o p e ct o ral g ro o ve , a d epression between the p ectoralis m ajor and the deltoid m uscles. 5. Using blunt dissection, follow the ce p h alic ve in from the arm to the deltopectoral triang le where the vein p enetrates the deep fascia to enter the axilla. Make the effort to preserve the cephalic vein in subseq uent step s of this dissection. 6. Clean the anterior surface of the deltoid m uscle but do not disturb the cephalic vein. 7. To prepare the pectoralis m ajor m uscle for re ection, relax the sternal head of the pectoralis m ajor m uscle

8.

9.

10.

11.

12.

13.

14.

THE UPPER LIMB

Subclavius m. Coracoid process

Pectoralis major m. Clavicular head

Deltopectoral groove

Serratus anterior m.

Cut ends of pectoralis major m. 3 4 5

Pectoralis minor m. External intercostal muscles Serratus anterior m.

FIGURE 2.9

33

by exing and adducting the arm or by placing a dissection block under the ip silateral shoulder. Insert your ngers p osterior to the inferior border of the pectoralis m ajor m uscle and create a space between the pectoralis m ajor and the clavip e ct o ral fascia. Beginning at the inferior border of the m uscle, detach the sternocostal head of the pectoralis m ajor m uscle from its attachm ent to the costal cartilages and sternum (FIG. 2.9). Working from in ferior to sup erior, in sert your n g ers d eep to th e clavicular h ead and p alp ate th e m e d ia l a n d la t e ra l p e ct o ra l n e rve s a n d ve sse ls in serting on the d eep surface of th e p ectoralis m ajor m uscle. Detach the clavicular head of the pectoralis m ajor m uscle as close to the clavicle as possible (FIG. 2.9). Note that the lat e ral p e ct o ral n e rve and the p e ct o ral b ran ch o f t h e t h o raco acro m ial art e ry enter the deep surface of the clavicular head and are easily cut during detachm ent of the clavicular head. Re ect the pectoralis m ajor m uscle laterally, leaving it attached to the hum erus while preserving the nerves and vessels that enter its deep surface. Identify the clavip e ct oral fascia im m ediately d eep to the pectoralis m ajor m uscle. Superiorly, the clavipectoral fascia is attached to the clavicle and lies both super cial and deep to the subclavius and pectoralis m inor m uscles. Inferiorly, the clavipectoral fascia is attached to the axillary fascia. Identify the p e ct o ralis m in o r m uscle (FIG. 2.9). [G 88; L 41; N 412; R 419]

Deltopectoral triangle

Sternocostal head

•

Cuts for re ection of the pectoralis m ajor and pectoralis m inor m uscles.

34

•

GRANT’S DISSECTOR

15. Note that the cephalic vein passes through the co st o co raco id m e m b ran e (p art of the clavip ectoral fascia) on the m edial side of the pectoralis m inor m uscle. 16. Locate the m ed ial p ect oral n erve where it pierces the pectoralis m inor m uscle and follow it to where it enters the deep surface of the pectoralis m ajor m uscle. 17. Clean the surface of the pectoralis m inor m uscle and clearly de ne its borders sparing the m edial pectoral nerve. 18. Review the attachm ents and actions of the pectoralis m inor m uscle (see TABLE 2.2). 19. Identify and clean the visible portions of the sub clavius m uscle inferior to the clavicle (FIG. 2.9). 20. Review the attachm ents and actions of the subclavius m uscle (see TABLE 2.2). 21. Use scissors to detach the pectoralis m inor m uscle from its inferior attachm ents on ribs 3 to 5 (FIG. 2.9, dashed line). 22. Re ect the pectoralis m inor m uscle superiorly, leaving it attached to the coracoid process of the scapula. [G 90; L 42; N 414; R 424] 23. Medial to the re ected pectoralis m inor m uscle, identify branches of the t h o raco acro m ial art e ry (FIG. 2.10) and the lat e ral p ect o ral n e rve . Note these neurovascular structures also pass through the costocoracoid m em brane. 24. Identify and clean the branches of the thoracoacrom ial artery beginning with the p e ct o ral b ran ch . The pectoral branch is typically the largest of the b ranches and descends b etween the p ectoralis m ajor and p ectoralis m inor m uscles (FIG. 2.10).

Thoracoacromial a. Acromial branch Acromion process

Deltoid branch

Clavicular branch Clavicle

Subclavian a.

1 2

Pectoral branch 3

Pectoralis minor

FIGURE 2.10

Blood supply to the pectoral region.

25. The d e lt o id b ra n ch courses laterally in the d eltop ectoral g roove b etween the d eltoid m uscle and p ectoralis m ajor m uscle and accom p anies the cep halic vein. 26. The acro m ial b ran ch courses superior to the coracoid p rocess toward the acrom ion. 27. Th e cla vicu la r b ra n ch courses m ed ially to sup p ly th e sub clavius m uscle an d th e stern oclavicular join t.

Disse ct io n Fo llo w-up 1. Replace the pectoral m uscles into their correct anatom ical positions. 2. Review the attachm ents of the pectoralis m ajor, pectoralis m inor, and subclavius m uscles. Review their actions, innervations, and blood supply. 3. Review the relationship of the clavipectoral fascia to the m uscles, vessels, and nerves of this region. 4. Be sure that you understand the role played by the clavipectoral fascia to support the base of the axilla. 5. Nam e all branches of the thoracoacrom ial artery and the structures supplied by each branch.

TABLE 2.2

Muscle s o f t h e Pe ct o ral Re g io n

Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Pectoralis major

Medial half of clavicle, sternum, costal cartilages 1–7

Lateral lip of intertubercular sulcus

Medially rotates, exes, and adducts the humerus

Medial and lateral pectoral nn.

Pectoralis minor

Ribs 3–5

Coracoid process of scapula

Anteriorly tilts and depresses the scapula

Medial pectoral n.

Subclavius

Rib 1

Clavicle

Depresses the clavicle and stabilizes the SC joint

Nerve to subclavius

Abbreviations: n., nerve; nn., nerves; SC, sternoclavicular joint.

CHAPTER 2

THE UPPER LIMB

•

35

AXILLA Disse ct io n Ove rvie w The axilla (the “arm pit”) is the region between the p ectoral m uscles, the scap ula, the arm , and the thoracic wall (FIG. 2.11). It is a region of passage for vessels and nerves coursing between the root of the neck, the thorax, and the up per lim b. The co n t e n t s o f t h e axilla are the axillary sh e at h , the b rach ial p le xus, the axillary ve sse ls an d t h e ir b ran ch e s, lym p h n o d e s an d lym p h at ic ve sse ls, p o rt io n s o f t h re e m uscle s, and a considerable am ount of fat and connective tissue. The order of dissection will be as follows: The axillary vein and its tributaries will be rem oved. The branches of the axillary artery will be dissected. The brachial plexus will be studied.

Disse ct io n In st ruct io n s Axilla [G 92; N 412] 1. Refer to FIGURE 2.11. 2. Review the walls an d b o un d arie s o f t h e axilla b eginning superiorly at the ap e x o f t h e axilla. The ap ex of the axilla is bounded by the clavicle anteriorly, the superior border of the scapula posteriorly, and the rst rib m edially. 3. Observe that the b ase o f t h e axilla is the skin and fascia of the arm pit. 4. Observe that the an t e rio r wall o f t h e axilla is dened by the anterior axillary fold containing the p ectoralis m ajor m uscle, part of the pectoralis m inor m uscle, and the clavipectoral fascia. 5. Observe that the p osterior wall of th e axilla is de ned by the posterior axillary fold containing the teres m ajor and latissim us dorsi muscles inferiorly and the subscapularis muscle covering the anterior surface of the scapula. 6. The m e d ial wall o f t h e axilla is the upp er portion of the lateral thoracic wall and the serratus anterior m uscle, whereas the lat e ral wall o f t h e axilla is the intertubercular sulcus of the hum erus. 7. Re ect the pectoralis m ajor m uscle laterally and the p ectoralis m inor m uscle superiorly. 8. Abduct the upper lim b to approxim ately 45°. Apex of axilla (cervicoaxillary canal)

9. Observe that the axilla contains a large am ount of axillary fat to protect the contents of the region while allowing for m obility of the upper lim b (FIG. 2.12). 10. Within the axillary fat, identify the axillary sh eat h (FIG. 2.12), a thin connective tissue structure surrounding the axillary vessels and brachial plexus. The axillary sheath extends from the lateral border of the rst rib to the inferior border of the teres m ajor m uscle. 11. Use scissors or blunt dissection to open the anterior surface of the axillary sheath. 12. Identify the axillary ve in and observe that it is form ed at the lateral border of the teres m ajor m uscle b y the joining of the brachial vein and the basilic vein. Note that the axillary vein ends at the lateral border of the rst rib where its name changes to subclavian vein. 13. To increase visibility of the arteries and nerves in the axilla, the axillary vein m ust be rem oved. First, cut the cephalic vein where it joins the axillary vein and re ect it laterally. Next, cut the axillary vein at the lateral border of the rst rib. 14. Use blunt dissection to separate the axillary vein from the structures that lie posterior to it (axillary artery and brachial plexus) and then cut the axillary vein at the inferior border of the teres m ajor m uscle and rem ove it from the dissection eld. [G 91; N 415; R 423]

1st rib Clavicle

Intertubercular sulcus Axillary Boundaries

Lateral wall

Apex

Posterior wall

Base Anterior wall Lateral wall

Anterior wall

Medial wall

Base of axilla

Posterior wall Medial wall

FIGURE 2.11

Walls and boundaries of the axilla.

36

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GRANT’S DISSECTOR

Pectoralis major m. Pectoralis minor m.

Lateral cord of brachial plexus

Superior thoracic a.

Subclavian a.

Pectoralis minor m.

Coracobrachialis m.

Axillary sheath

Short head

Biceps brachii m. Long head Intertubular groove

Axillary v. Axillary a. Medial cord of brachial plexus

Head of humerus

Posterior cord of brachial plexus

Lymph nodes

Long thoracic n.

Axillary a. 1

Circumflex humeral aa.: Posterior Anterior Subscapular artery

2 3

Circumflex scapular artery Inferior border of teres major muscle Thoracodorsal artery

Deltoid m. Serratus anterior m.

Scapula Infraspinatus m. Inferior view

FIGURE 2.12

Thoracoacromial a.

Subscapularis m.

Lateral thoracic artery Brachial artery

Contents of the right axilla. Inferior view.

15. As the dissection proceeds, rem ove sm aller veins that are tributaries to the axillary vein while preserving the accom panying arteries. 16. Rem ove any lym ph nodes in the region associated with the veins.

FIGURE 2.13

5.

Axillary Art e ry [G 98, 99; L 44; N 414; R 425] The axillary artery is surrounded by the brachial plexus. The brachial plexus m ust be retracted and preserved during dissection of the axillary artery and its branches. 1. Identify t h e axillary art e ry. The axillary artery begins at the lateral border of the rst rib as the continuation of the sub clavian art e ry and ends at the inferior border of the teres m ajor m uscle where its nam e changes to the b rach ial art e ry (FIG. 2.13). 2. Identify the t h ree p art s of t h e axillary art ery (FIG. 2.13). The rst p art extends from the lateral border of the rst rib to the m edial border of the pectoralis m inor m uscle. The secon d p art lies posterior to the pectoralis m inor m uscle, and the t h ird p art extends from the lateral border of the pectoralis m inor m uscle to the inferior border of the teres m ajor m uscle. Dissect ion n ot e: The branching pattern of the axillary artery m ay vary from that which is com m only illustrated. If the pattern is different in your specim en, understand that the branches are nam ed according to their region of distribution rather than by their point of origin. 3. The rst part of the axillary artery has one branch. Identify and clean the sup e rio r t h o racic art e ry, which arises near the apex of the axilla and supplies b lood to the rst and second intercostal spaces. 4. The second part of the axillary artery has two b ranches: the t h oraco acro m ial art e ry and the

6.

7.

8.

Branches of the axillary artery.

lat e ral t h o racic art e ry (FIG. 2.13). Review the branches of the thoracoacrom ial artery previously dissected: the pectoral, acrom ial, deltoid, and clavicular. Identify and clean the lat e ral t h o racic art ery, which typically branches off the axillary artery near the lateral border of the p ectoralis m inor m uscle (FIG. 2.13). In a signi cant percentage of cases (35%), the lateral thoracic artery arises from the subscapular artery or the thoracoacrom ial artery. The lateral thoracic artery supplies the pectoral m uscles, the serratus anterior m uscle, the axillary lym ph nodes, and the lateral thoracic wall. In fem ales, the lateral thoracic artery also supplies the lateral portion of the breast. The third part of the axillary artery has three branches: the sub scap ular art e ry, the p o st e rio r circum e x h um e ral art e ry, and the an t e rio r circum e x h um e ral art e ry (FIG. 2.13). Identify and clean the sub scap ular art e ry. The subscapular artery is the largest branch of the axillary artery and courses inferiorly for a short distance before dividing into the circum e x scap ular art e ry (to m uscles on the posterior surface of the scapula) and the t h o raco d o rsal art e ry (to the latissim us d orsi m uscle). The subscapular artery also gives several unnam ed m uscular branches and m ay be the origin of the lateral thoracic artery. Make an effort only to identify the two term inal branches of the subscapular artery. Identify and clean the an t e rio r an d p o st e rio r circum e x h um e ral art e rie s, which arise from the lateral surface of the axillary artery distal to the origin of the subscapular artery. The circum ex hum eral arteries supply the deltoid m uscle and anastom ose around the surgical neck of the hum erus and m ay arise from a short com m on trunk.

CHAPTER 2

9. Note that the p o st erio r circum ex h um e ral art ery is typically the larger of the two circum ex hum eral arteries. Follow the posterior circum ex hum eral artery posterior to the surgical neck of the hum erus and observe its close proxim ity to the axillary nerve as these structures pass through the quadrangular space. 10. Follow the an t e rio r circum e x h um e ral art e ry for a short distance and observe that this vessel courses around the anterior surface of the hum erus at the surgical neck d eep to the tendon of the long head of the biceps brachii m uscle.

Brach ial Ple xus [G 98; L 43; N 415; R 425] The brachial plexus is a network of nerves innervating the upp er lim b orig inating from spinal cord levels C5–T1. The brachial plexus begins in the root of the neck superior to the clavicle, courses through the ap ex of the axilla, and then passes inferolaterally toward the base of the axilla where its t e rm in al b ran ch e s arise. Only the in fraclavicular p art o f t h e b rach ial p le xus (cords and branches) will be dissected at this tim e. The sup raclavicular p art (roots, trunks, and divisions) will be dissected with the neck. The t h re e cord s o f t h e b rach ial p le xus (lateral, m edial, and posterior) are nam ed according to their relationship to the second part of the axillary artery, posterior to the pectoralis m inor m uscle (FIG. 2.14). Minim al dissection is required to separate the cords and terminal branches of the brachial plexus, and much of the dissection can be done with your ngers. 1. Within the axilla, identify the coracobrachialis m uscle and observe that it shares an attachm ent to the coracoid process with the pectoralis m inor m uscle. The coracobrachialis is a m uscle of the anterior com partm ent of the arm (brachium ) and will be dissected later.

Axillary a. (1st part) Thoracoacromial a.

Pectoralis minor m. (reflected) Coracoid process

Clavicle

Lateral and medial cords of brachial plexus Pectoralis major m. (reflected) Musculocutaneous n. Median n. Ulnar n. Deltoid m. (cut) Teres major m. Medial cutaneous n. of arm and forearm Brachial a. Long thoracic n. Latissimus dorsi m.

FIGURE 2.14

Infraclavicular part of the brachial plexus.

THE UPPER LIMB

•

37

2. Find the m usculo cut an e o us n e rve where it p ierces the coracobrachialis m uscle. The m usculocutaneous nerve is the m ost lateral term inal branch of the brachial plexus. 3. Use blunt dissection to follow the m usculocutaneous nerve p roxim ally to the lat e ral co rd o f t h e b rach ial p le xus. 4. Observe that the lateral cord gives rise to one other large branch, the lat e ral ro o t o f t h e m e d ian n e rve . Follow the lateral root distally and identify the m e d ian n e rve . 5. Trace the m e d ial ro o t o f t h e m e d ian n erve proxim ally to nd the m e d ial co rd resting against the m edial aspect of the axillary artery. 6. Observe that the other term inal branch of the m edial cord continues distally as the uln ar n e rve . 7. Note that the three t e rm in al b ran ch e s you have just identi ed (m usculocutaneous nerve, m edian nerve, and ulnar nerve) form the letter M anterior to the third part of the axillary artery (FIG. 2.14). 8. Trace the m e d ial and lat e ral p ect o ral n e rve s from the re ected pectoral m uscles to their origins from the m edial and lateral cords, respectively. Note that the pectoral nerves are named for their origins from the medial and lateral cords, not for their relationship to each other relative to the median plane. 9. Identify the m e d ial cut an e ous n e rve o f t h e arm and the m e d ial cut an e o us n e rve o f t h e fo re arm originating from the m edial cord proxim al to the ulnar nerve (FIG. 2.14). Use your ngers and blunt dissection to trace these nerves a short distance (7.5 cm ) into the arm . 10. Retract the axillary artery, the lateral cord , and the m ed ial cord sup eriorly to exp ose the p o st e rio r co rd of th e b rach ial p lexus. The p osterior cord g ives rise to three nerves, the u p p e r a n d lo w e r su b sca p u la r n e rve s and th e t h o ra co d o rsa l n e rve , p rior to term inating as the a xilla ry and ra d ia l n e rve s (FIG. 2.15). 11. Use blunt dissection to clean the axillary n e rve . Observe that it courses through the q uadrangular space with the posterior circum ex hum eral artery to reach the deltoid and teres m inor m uscles (FIG. 2.15). 12. Use blunt dissection to clean the rad ial n e rve . Con rm that the radial nerve leaves the axilla by passing anterior to the latissim us dorsi and teres m ajor m uscles and runs toward the triceps m uscle posterior to the hum erus. 13. Observe that the radial nerve is larger than the axillary nerve. Note that the radial nerve is the only m otor and sensory nerve to the posterior com partm ents of the upper lim b. 14. Beg in n in g cen trally, id en tify an d isolate th e t h o ra co d o rsa l n e rve arising off th e p osterior cord and trace it in feriorly to th e latissim us d orsi m uscle.

38

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GRANT’S DISSECTOR

Coracoid process of scapula Lesser tubercle

Posterior cord

Greater tubercle Scapular nerves: Axillary nerve

Upper Thoracodorsal

Posterior circumflex humeral artery Quadrangular space

Lower Subscapularis m.

Radial nerve Circumflex scapular artery Deep artery of the arm

Thoracodorsal a. Teres major m.

Triceps brachii m. (long head) Latissimus dorsi m.

19. Identify the se rrat us an t e rio r m uscle and recall that it form s the m edial wall of the axilla (FIG. 2.14). [G 101; L 41; N 415; R 424] 20. Slide your hand into the axilla and verify that the serratus anterior attaches onto the m edial border of the scapula. With your palm against the subscapularis m uscle, the back of your hand is against the serratus anterior m uscle (FIG. 2.11). 21. On the super cial surface of the serratus anterior m uscle, identify and clean the lo n g t h o racic n e rve coursing vertically and observe its branches to the serratus anterior m uscle (FIG. 2.14). Follow the nerve superiorly, toward the apex of the axilla, as far as possible. 22. Clean the surface of the serratus anterior m uscle paying attention not to disrup t the long thoracic nerve. 23. Review the actions and innervations of the serratus anterior m uscle (see TABLE 2.3).

CLIN ICA L CORRELATION FIGURE 2.15 Posterior wall of the axilla and posterior cord of the brachial plexus.

15. Just distal to the branch point of the thoracodorsal nerve, identify and isolate the lower sub scap ular nerve tracing it to the subscapularis and teres m ajor m uscles. 16. Proxim al to the thoracodorsal nerve, identify the up p er sub scap ular n erve which is the rst of three branches from the posterior cord and the m ost dif cult to identify. Trace the upper subscapular nerve distally to the subscapularis m uscle. Note that all three branches of the posterior cord run in the loose connective tissue on the anterior surface of the subscapularis muscle (FIG. 2.15). 17. Identify the three m uscles form ing the posterior wall of the axilla: the lat issim us d o rsi, the t e re s m ajo r, and the sub scap ularis, which covers the anterior surface of the scapula (FIG. 2.15). 18. Review the attachm ents and actions of the subscapularis m uscle and recall that it is a m em ber of the ro t at o r cuff g ro up o f m uscle s (see TABLE 2.3).

Ne rve In jurie s The lo n g t h o racic n e rve is vulnerable to stab wounds and to surgical injury during m astectom y. Injury of the long thoracic nerve affects the serratus anterior m uscle. When a patient with paralysis of the serratus anterior m uscle is asked to push with both hands against a wall, the m edial border of the scapula protrudes on the affected side, a condition known as “winged scapula.” The t h o raco d o rsal n e rve is vulnerab le to com p ression injuries and surgical traum a during m astectom y. Injury of the thoracodorsal nerve affects the latissim us dorsi m uscle resulting in a weakened ability to extend, adduct, and m edially rotate the arm . The axillary n e rve courses around the surgical neck of the hum erus and m ay be injured during a fracture or during an inferior dislocation of the shoulder joint. Injury of the axillary nerve affects the deltoid m uscle and teres m inor m uscle, resulting in a weakened ability to abduct and laterally rotate the arm .

Disse ct io n Fo llo w-up 1. Replace the pectoralis m ajor and pectoralis m inor m uscles into their correct anatom ical positions and review their attachm ents. 2. Review the boundaries of the axilla. 3. Use the dissected specim en to review the relationship of the three parts of the axillary artery to the pectoralis m inor m uscle and recite the nam es of all the arterial branches of each part of the axillary artery on your dissected specim en. 4. Test your understanding of the brachial plexus by drawing a picture illustrating its structure and branches. Extend this exercise and demonstrate the cords and terminal branches of the infraclavicular portion of the brachial plexus on the cadaver. 5. Review the target structures of each branch of the brachial plexus. 6. Review the m ovem ents of the scapula and the groups of m uscles acting together to produce each m otion. 7. Exam ine other cadavers to gain an appreciation of variations in the branching pattern of arteries and nerves. 8. Use an illustration to review the lym phatic drainage of the axilla.

CHAPTER 2

TABLE 2.3

THE UPPER LIMB

39

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Muscle s o f t h e Axilla

MEDIAL WALL Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Serratus anterior

Anterior surface of the medial border of the scapula

Ribs 1–9 lateral parts

Protracts and rotates the scapula, holds it against the thoracic wall

Long thoracic n.

Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Subscapularis

Subscapular fossa

Lesser tubercle of the humerus

Medially rotates the humerus

Upper and lower subscapular nn.

Latissimus dorsi

Thoracolumbar fascia, iliac crest

Intertubercular groove ( oor)

Extends, adducts, and medially rotates the humerus

Thoracodorsal n.

Teres major

Inferior angle of the scapula

Medial lip of the intertubercular sulcus

Adducts and medially rotates the humerus

Lower subscapular n.

POSTERIOR WALL

Abbreviations: n., nerve; nn., nerves.

ARM (BRACHIUM) AND CUBITAL FOSSA Disse ct io n Ove rvie w The b rach ial fascia (d ee p fascia o f t h e arm ) is a sleeve of tough connective tissue continuous at its p roxim al end with the pectoral fascia, the axillary fascia, and the deep fascia covering the deltoid and latissim us dorsi m uscles. Distally, the brachial fascia is continuous with the an t e b rach ial fascia (d e e p fascia o f t h e fo rearm ). The brachial fascia is connected to the m edial and lateral sides of the hum erus by interm uscular septa (FIG. 2.16) creating an an t e rio r ( e xo r) co m p art m en t and a p o st e rio r (e xt e n so r) co m p art m e n t for the m uscles of the arm . The anterior com partm ent contains three m uscles (biceps brachii, brachialis, and coracobrachialis), whereas the posterior com partm ent predom inately contains the triceps brachii m uscle. The order of dissection will be as follows: The anterior com partm ent of the arm will be opened and its contents will be studied. Nerves and blood vessels will then be traced through the arm from the axilla to the cubital fossa.

Anterior compartment Musculocutaneous nerve territory

Lateral

Medial Skin intermuscular septum Cephalic v.

Medial Musculocutaneous nerve Median nerve

Biceps brachii

Brachial a.

Fascia Deep fascia

Ulnar n.

Brachialis Humerus

Medial head

Lateral head Lateral intermuscular septum

Long head of triceps brachii m.

Deep artery of the arm and radial nerve

Ske le t o n o f t h e Arm an d Cub it al Re g io n Refer to an articulated skeleton or isolated hum erus, radius, and ulna and identify the following skeletal features (FIG. 2.17): [G 134; L 32, 33; N 422; R 385, 386]

Posterior compartment Radial nerve territory

FIGURE 2.16 inferior view.

Com partm ents of the right arm . Axial cut

Hum e rus 1. On the distal end of the hum erus, identify the m e d ial e p ico n d yle m edially and the lat e ral e p ico n d yle laterally. 2. Between the epicondyles, identify the depression of the olecran on fossa posteriorly and the co ron o id fo ssa anteriorly. 3. Inferior to the epicondyles, identify the t ro ch le a m edially and the cap it ulum laterally.

Rad ius an d Uln a 1. On the proximal end of the radius, identify the head of the radius. Note that the depression of the head of the radius articulates with the capitulum and allows for exion and extension at the elbow as well as rotational movement of the forearm. 2. Inferior to the head of the radius, identify the narrowed n e ck o f t h e rad ius.

40

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GRANT’S DISSECTOR

Humerus

Olecranon

Olecranon fossa Lateral epicondyle

Medial epicondyle

Trochlear notch Coronoid process

Head

Olecranon

Neck

Radial notch Humerus Ulna

Radius

Ulna

Coronoid fossa

Medial epicondyle

Interosseous Capitulum margin Head Shaft Neck

Trochlea Coronoid process

Posterior view

Tuberosity Lateral view

Ulna

Radius

Anterior view

FIGURE 2.17

Skeleton of the elbow region.

3. Distal to the neck of the radius, identify the rad ial t ub e ro sit y, the attachm ent site of the biceps b rachii m uscle. 4. Place the radius and ulna together and observe the p ro xim al rad io uln ar jo in t where the head of the radius articulates with the rad ial n o t ch of the ulna. 5. On the proxim al end of the ulna, identify the t ro ch le ar n o t ch located between the o le cran o n p ro ce ss p roxim ally and the co ro n o id p ro ce ss distally. 6. Articulate the ulna with the hum erus and observe that exion is lim ited by contact of the coronoid process in the coronoid fossa. Sim ilarly observe that extension is lim ited by contact of the olecranon process in the olecranon fossa. 7. On a skeleton, exam ine the e lb o w jo in t . The elb ow joint is the articulation between the trochlear notch of the ulna and the trochlea of the hum erus and the articulation between the head of the radius and the cap itulum of the hum erus. These two articulations account for the hinge action ( exion/ extension) of the elbow joint.

Disse ct io n In st ruct io n s An t e rio r Co m p art m e n t o f t h e Arm Muscle s [G 112, 113; L 46; N 417; R 427] 1. With the cadaver in the supine position, use scissors to m ake a longitudinal incision in the anterior surface of the brachial fascia from the level of the pectoralis m ajor tendon to the elbow. 2. Use your ngers to separate the brachial fascia from the underlying m uscles. Work laterally and m edially from the incision and note the presence of the lat e ral in t e rm uscular se p t um and the m e d ial in t e rm uscular se p t um . Detach the brachial fascia from the interm uscular septa and place it in the tissue container. 3. Use your ngers to separate the three m uscles in the anterior com partm ent of the arm : co raco b rach ialis, b rach ialis, and b ice p s b rach ii (FIG. 2.18). 4. Use your ngers to separate the two m uscular bellies of the b ice p s b rach ii m uscle .

5. Identify the m ore m edially located sh o rt h e ad o f t h e b ice p s b rach ii m uscle and clean the surface of its tendon where it attaches to the coracoid p rocess of the scap ula. 6. Identify the m ore laterally located lo n g h e ad o f t h e b ice p s b rach ii m uscle . Superiorly, the tendon of the long head of the biceps brachii m uscle courses through the intertubercular sulcus of the hum erus deep to the t ran sve rse h um e ral lig am e n t . Within the glenohum eral joint, the tendon continues its course until reaching the sup rag len o id t ub e rcle . At this tim e, do not follow the tendon of the long head to its attachm ent on the scapula or deep to the transverse hum eral ligam ent. 7. Clean the surface of the biceps brachii m uscle and identify the b icep s b rach ii t e n d o n in the cubital fossa (FIG. 2.18). 8. Review the attachm ents and actions of the biceps brachii m uscle (see TABLE 2.4).

CHAPTER 2

Deltoid m.

Pectoralis minor m.

Transverse humeral ligament Pectoralis major m. (cut)

Lateral cord, medial cord of brachial plexus

Coracobrachialis m. Long head Short head

Brachial artery

Musculocutaneous nerve Median nerve Medial cutaneous nerve of arm Ulnar nerve

Brachialis m.

Superior ulnar collateral artery

Biceps brachii tendon

Medial cutaneous nerve of forearm

Radial recurrent artery

Inferior ulnar collateral artery

Radial artery

Medial epicondyle of humerus Pronator teres m. Ulnar artery Bicipital aponeurosis

Brachioradialis m.

FIGURE 2.18 the arm .

•

41

of the biceps brachii m uscle sup eriorly and inferiorly, respectively. 15. Review the attachm ents and actions of the brachialis m uscle (see TABLE 2.4).

Coracoid process

Biceps brachii m.

THE UPPER LIMB

Contents of the anterior com p artm ent of

9. Identify the b icip it al ap o n euro sis, an extension of the biceps tendon that broadens m edially and attaches to the antebrachial fascia (FIG. 2.18). 10. Clean the surface of the coracob rachialis m uscle paying attention to not disrupt the course of the m usculocutaneous nerve. 11. Use your ngers to con rm that the proxim al attachm ent of the coracobrachialis m uscle is the coracoid process and that its distal attachm ent is on the m edial side of the shaft of the hum erus. 12. Review the attachm ents and actions of the coracobrachialis m uscle (see TABLE 2.4). 13. Flex the elbow about 45 o and pull the bicep s brachii m uscle m edially or laterally to observe the m ore deeply located b rach ialis m uscle . 14. On one side of the cadaver, use scissors to transect the bicep s brachii m uscle about 5 cm p roxim al to the elbow (FIG. 2.18, dashed line). Do not cut the m usculocutaneous nerve. Re ect the two portions

Ne uro vasculat ure o f t h e Arm 1. Identify the m usculocutaneous nerve where it pierces the co raco b rach ialis m uscle and recall that the m usculocutaneous nerve innervates all three m uscles of the anterior com partm ent of the arm (FIG. 2.18). 2. Find the m usculo cut an e o us n e rve where it em erges from the coracobrachialis m uscle and follow it through the plane of loose connective tissue between the biceps brachii m uscle and brachialis m uscle. Observe that after the m usculocutaneous nerve gives its m uscular branches, it continues distally as the lat e ral cut an e o us n e rve o f t h e fo re arm . 3. Follow the lateral cutaneous nerve of the forearm to the cubital fossa where it em erges on the lateral side of the cubital fossa proxim al to the biceps brachii tendon. 4. Review the relationship of the lateral cutaneous nerve of the forearm to the cephalic vein. 5. On the m edial aspect of the arm , identify the m e d ial cut an e o us n e rve o f t h e forearm and follow it from the m edial cord of the brachial plexus to the level of the cubital fossa (FIG. 2.18). 6. Use blunt dissection to follow the m e d ian n e rve distally from the axilla, where it arises from the brachial plexus, to the cubital fossa (FIG. 2.18). The m edian nerve courses m edial to the biceps brachii m uscle within the m e d ial in t erm uscular se p t um . 7. Use blunt dissection to follow the uln ar n e rve from the m edial cord of the brachial plexus to the m edial epicondyle of the hum erus (FIG. 2.18). Note that the ulnar nerve courses in the m edial interm uscular septum in the p roxim al arm and then com es to lie on the posterior surface of the m edial interm uscular septum in the distal one-third of the arm . 8. Follow the ulnar nerve posteriorly at the elbow and ob serve that it is in contact with the p osterior surface of the m edial ep icondyle of the hum erus. At this location, the nerve is com m only referred to as the “funny bone” and induces the tingling sensation com m only felt with im pact to the elbow. 9. Identify the b rach ial art e ry, the continuation of the axillary artery. The brachial artery begins at the inferior b order of the teres m ajor m uscle and ends at the level of the elbow by branching into the uln ar art e ry and rad ial art e ry (FIG. 2.19). 10. Rem ove the surrounding brachial fascia covering the brachial artery and verify that the brachial artery courses with the m edian nerve within the m edial interm uscular septum . Observe that the m edian nerve is the only large structure to cross the anterior surface of the brachial artery. [G 115; L 46; N 419; R 427]

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GRANT’S DISSECTOR

Axillary a. Teres major m. Deep artery of arm

Brachial a.

Ulnar collateral arteries: Superior Inferior

Middle collateral a. Radial collateral a. Radial recurrent a. Interosseous recurrent a.

Ulnar recurrent arteries: Anterior Posterior

Radial a. Ulnar a.

FIGURE 2.19

Branches of the brachial artery.

11. Observe that the deep veins of the upper lim b drain into the basilic vein near the axilla. Note that the basilic vein changes its nam e to axillary vein after the deep veins of the arm have drained into it. 12. Identify the ven ae com it an t es, the paired veins coursing along the deep arteries of the arm . The two-to-one relationship of deep veins per deep artery will be seen throughout the lim bs and is a good way to differentiate the appearance of vessels and nerves in the lim bs. 13. The deep veins of the upper limb are named according to the corresponding artery that they follow. Remove the brachial veins and their tributaries to clear the dissection eld while preserving the branches of the brachial artery. 14. The brachial artery has three nam ed branches in the arm : d e e p art e ry o f t h e arm , sup e rio r uln ar co llat e ral art e ry, and in fe rio r uln ar co llat e ral art e ry. Several unnam ed m uscular branches also arise along the length of the brachial artery. 15. In the proxim al arm , nd the d e e p art e ry o f t h e arm (d e e p b rach ial art e ry or p ro fun d a b rach ii art e ry) where it arises from the brachial artery (FIG. 2.19). Recall that the deep artery of the arm courses around the p osterior surface of the hum erus where it accom panies the radial nerve in the radial groove. 16. Identify and clean the sup e rio r uln ar co llat eral art e ry where it arises from the brachial artery about halfway down the arm (FIG. 2.19). The superior ulnar

collateral artery courses distally with the ulnar nerve and p asses posterior to the m edial epicondyle of the hum erus. Note that the superior ulnar collateral artery may arise from the profunda brachii artery. 17. Identify and clean the in fe rio r uln ar co llat e ral art e ry where it arises from the brachial artery about 3 cm above the m edial epicondyle of the hum erus (FIG. 2.19). Observe that the inferior ulnar collateral artery passes anterior to the m edial ep icondyle, deep to the b rach ialis m uscle .

Cubit al Fo ssa [G 128–130; L 46; N 419; R 428–430] The cub it al fo ssa (L. cubitus, elbow) is the depression on the anterior surface of the elbow. The cubital fossa is clinically im portant because it contains brachial artery and accom panying veins and the super cial veins com m only used for venip uncture course across the cubital fossa. 1. Observe that the cub it al fo ssa is bound laterally by the b rach io rad ialis m uscle and m edially by the p ro n at o r t e re s m uscle (FIG. 2.20A, B). 2. Identify the sup e rio r b o un d ary o f t h e cub it al fo ssa, an im aginary line connecting the m edial and lateral epicondyles of the hum erus. 3. Observe that the sup e r cial b o un d ary (ro o f o f t h e cub it al fo ssa) is the antebrachial fascia reinforced by the bicipital aponeurosis and the d e e p b o un d ary ( o o r o f t h e cub it al fo ssa) is the brachialis and supinator m uscles. 4. Review the p ositions of the cephalic vein, basilic vein, and m edian cubital vein anterior to the cubital fossa. To gain access to deeper structures, it m ay be necessary to cut the p erforating veins that connect the deep veins to the super cial veins and retract the vessels either m edially or laterally as a group. 5. Identify and clean the t e n d o n o f t h e b ice p s b rach ii m uscle in the cubital fossa (FIG. 2.20A).

CLIN ICA L CORRELATION

Brach ial Art e ry Use an illustration to study the collateral circulation around the elb ow joint (FIG. 2.19). The brachial artery m ay becom e blocked at any level distal to the deep artery of the arm without com pletely blocking blood ow to the forearm and hand. In the arm , the brachial artery lies m edial to the biceps brachii m uscle and close to the shaft of the hum erus. The brachial artery is com pressed at this location when taking a blood pressure reading. Fractures to the hum erus can dam age the brachial artery and its branches. Midshaft fractures of the hum erus m ay sever the deep artery of the arm , whereas m ore distal fractures are m ore likely to dam age the brachial artery itself where it courses anteriorly. [G 140; L 48, 75; N 420; R 409]

CHAPTER 2

6. Insert a probe deep to the b icip it al ap o n e uro sis near the biceps brachii tendon and use scissors to cut the aponeurosis as distal as possible to allow for lateral re ection of the portion still attached to the b icep s tendon. Do not cut the brachial artery lying deep to the bicipital aponeurosis. 7. Follow the m ed ian n erve and the b rach ial art ery from the arm into the cubital fossa and rem ove any fat that m ay be obstructing your view of these structures. 8. On the lateral aspect of the forearm , identify and clean the proxim al end of the b rach io rad ialis m uscle (FIG. 2.20A). Use your ngers to op en the connective tissue p lane between the brachioradialis m uscle and the brachialis m uscle (FIG. 2.20B). 9. Deep to the brachioradialis m uscle in the plane of connective tissue, nd the radial nerve previously identi ed in the p osterior arm and follow it proxim ally to com plete its dissection in the arm .

Brachial fascia (cut) Cephalic vein (cut) Biceps brachii m.

Brachial artery

Brachialis m.

Brachial veins Median nerve

Lateral epicondyle (deep to muscle) Biceps brachii tendon Brachioradialis m. Radial artery

Brachialis m. Brachioradialis m. (retracted)

Brachial artery Inferior ulnar collateral artery Ulnar nerve (seen through brachial fascia) Median nerve

Medial epicondyle

Deep branch of radial nerve

Medial epicondyle

Cubital fossa (green lines)

Radial recurrent a.

Brachialis m.

Pronator teres m.

Superficial branch of radial nerve

Ulnar artery

Extensor carpi radialis longus m.

Pronator teres m.

Antebrachial fascia (cut)

43

Basilic vein

Radial nerve

Bicipital aponeurosis Cephalic vein (cut)

•

10. Note that the radial nerve passes on the exor side of the elbow joint and is accom panied by the rad ial recurre n t art e ry at this location (FIG. 2.20B). Do not follow the radial recurrent artery at this tim e. 11. Observe the relative positions of three im portant structures in the cubital fossa (FIG. 2.20B): The biceps brachii tendon is lateral, the brachial artery is interm ediate, and the m edian nerve is m edial. 12. Deep to the contents of the cubital fossa, identify and clean the oor of the cubital fossa form ed by the b rach ialis m uscle and sup in at o r m uscle . 13. Observe that the roof of the cubital fossa is reinforced by the bicipital ap oneurosis, which passes super cial to the brachial artery and m edian nerve but deep to the sup er cial veins. During venip uncture, the bicipital aponeurosis provides lim ited p rotection for the brachial artery and m edian nerve.

Branches of Cephalic medial cutaneous vein nerve of forearm Biceps Basilic vein brachii m. (cut)

Lateral cutaneous nerve of forearm

THE UPPER LIMB

Supinator m. Radial artery and veins

AAnterior view, superficial dissection FIGURE 2.20

BAnterior view, deep dissection

A. Super cial dissection of the cubital fossa. B. Deep dissection of the cubital fossa.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Replace the m uscles of the anterior com partm ent of the arm in their correct anatom ical positions. Review the attachm ents, innervations, and actions of each m uscle. Use the dissected specim en to review the origin, course, term ination, and branches of the brachial artery. Trace each nerve that you have dissected from the brachial plexus to the elbow, reviewing key relationships. Review a drawing of a cross section of the arm and notice the position of the brachial fascia and the interm uscular septa relative to the structures that you have dissected. 6. Review the pattern of com partm ent innervation of the arm and the nerve territories of the brachial region (FIG. 2.16).

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GRANT’S DISSECTOR

TABLE 2.4

Muscle s o f t h e Arm

ANTERIOR COMPARTMENT OF THE ARM Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Coracobrachialis

Coracoid process of the scapula

Medial side of shaft of humerus

Adducts and exes the humerus

Biceps brachii

Long head—supraglenoid tubercle of scapula; short head—coracoid process of the scapula

Radial tuberosity and antebrachial fascia

Supinates and exes the forearm

Brachialis

Anterior aspect of humerus

Tuberosity of the ulna

Flexes the forearm

Musculocutaneous n.

POSTERIOR COMPARTMENT OF THE ARM Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Triceps brachii

Long head—infraglenoid tubercle of the scapula; medial and lateral heads—posterior surface of the humerus

Olecranon process of the ulna

Extends the forearm

Radial n.

Abbreviation: n., nerve.

SUPERFICIAL MUSCLES OF THE BACK Instructions for dissection of the super cial m uscles of the back are found in Chapter 1, The Back. If you are dissecting the upp er lim b before the back, com plete the sup er cial m uscles for the back dissection, then return to this page.

SCAPULAR REGION AND POSTERIOR COMPARTMENT OF THE ARM If you are dissecting the upper lim b before the back, com p lete the p ortion of the dissection relating to the scapular region and p osterior com partm ent of the arm after having com pleted the dissection of the super cial m uscles of the back. Instructions for dissection of the scap ular region and p osterior com partm ent of the arm are found at the beginning of this chapter. Upon com pletion of the posterior com partm ent of the arm , return to this page.

FLEXOR REGION OF THE FOREARM Disse ct io n Ove rvie w The antebrachial fascia is a sleeve of connective tissue investing the forearm . Interm uscular septa project inward and attach the antebrachial fascia to the radius and ulna (FIG. 2.21). The interm uscular septa, the interosseous m em brane, the radius, and the ulna com bine to divide the forearm into an an t e rio r ( e xo r) co m p art m e n t and a p o st e rio r (e xt e n so r) co m p art m e n t . Th e m uscles in th e an terio r com p artm en t o f th e fo rearm can b e d ivid ed in to su p e r ficia l, in t e rm e d ia t e , an d d e e p la ye rs o f fle xo r m u scle s. Muscles o f th e sup erficial flexor layer arise from th e m ed ial ep icon d yle of th e h um erus an d its sup racon d ylar rid g e. Th e m uscle of th e in term ed iate layer arises from th e m ed ial ep ico n d yle of th e h um erus an d th e an terio r surface of th e rad ius. Muscles of th e d eep flexo r layer arise from th e an terio r surfaces of th e rad ius, uln a, an d in terosseo us m em b ran e. Stud y a tran sverse section th roug h th e m id level of th e forearm (FIG. 2.21) an d n ote th at th e uln ar

Lateral

Anterior compartment

Superficial branch of the radial n.

Medial

Median n. Ulnar a.

Radial a.

Superficial and intermediate

Ulnar n.

Deep

Deep Radius

Ulna Superficial

Interosseous membrane Posterior interosseous n. and a.

Posterior compartment

FIGURE 2.21 inferior view.

Com p artm ents of the right forearm . Axial cut

CHAPTER 2

THE UPPER LIMB

•

45

artery, uln ar n erve, an d m ed ian n erve are in th e con n ective tissue p lan e sep aratin g th e in term ed iate an d d eep layers of flexor m uscles. The order of dissection will be as follows: The structures in the super cial fascia of the forearm will be reviewed. The super cial fascia and the antebrachial fascia will be rem oved. At the level of the wrist, the relative positions of tendons, vessels, and nerves will be studied. The super cial and interm ediate layers of exor m uscles will be stud ied and re ected on one side. Vessels and nerves that lie between the interm ediate and deep layers of exor m uscles will be studied. The deep layer of exor m uscles will be dissected.

Ske le t o n o f t h e Fo re arm Refer to a skeleton or isolated hum erus, radius, and ulna to identify the following skeletal features (FIG. 2.22): [G 142, 164; L 33; N 422, 425; R 387]

Hum e rus 1. On the distal hum erus, identify the m e d ial sup raco n d ylar rid g e im m ediately sup erior to the m edial epicondyle as well as the lat e ral sup raco n d ylar rid g e superior to the lateral ep icondyle. 2. Review the location of the capitulum , trochlea, coronoid fossa, and olecranon fossa.

Rad ius an d Uln a

Medial epicondyle of humerus Supracondylar ridge Lateral Medial Olecranon fossa Olecranon

Lateral epicondyle Head Neck Tuberosity Anterior oblique line

Ulna

Capitulum Trochlea Radial notch of ulna Interosseous borders Ulna

Radius

Carpal bones

Styloid process

Ulnar notch of radius Head of ulna Pisiform bone

1. Review the location of the h e ad , n e ck, and rad ial t ub e ro sit y of the radius. 2. Review the location of o le cran o n p ro ce ss, the t ro ch le ar n o t ch , and the co ro n o id p ro ce ss o f t h e uln a. 3. On the anterior surface of the radius, identify the an t e rio r o b liq ue lin e . Posterior view Anterior view 4. Along the m edial edge of the radius, identify the FIGURE 2.22 Skeleton of the forearm . in t e ro sse o us b o rd e r, the thin region of the bone serving as the attachm ent site of the in t e ro sse o us m e m b ran e . 5. At the distal end of the radius, identify the uln ar n o t ch and the inferiorly oriented st ylo id p ro ce ss. 6. Articulate the radius and ulna and observe that the h e ad o f t h e uln a ts into the dep ression of the ulnar notch of the radius to create the d ist al rad io uln ar jo in t . 7. Observe that the interosseous border of each bone is oriented at the corresponding ridge of the other bone. 8. Pronate and supinate the forearm of the skeleton and notice the rotational m ovem ents that occur at the proxim al and distal radioulnar joints. In the position of supination (anatom ical position), note that the radius and ulna are parallel, whereas in the position of pronation, the radius crosses the ulna. 9. On the palm ar surface of the articulated hand, identify the p isifo rm b o n e (FIG. 2.22).

Disse ct io n In st ruct io n s Sup e r cial Laye r o f Fle x o r Muscle s [G 144; L 52; N 432; R 434] 1. With the cadaver in the supine position, abduct the upp er lim b. Actively sup inate the forearm and either use string to hold it in this position or have your dissection p artner assist in orienting the upp er lim b throughout the dissection. 2 . Rem o ve th e rem n an ts o f an y rem ain in g sup erficial fascia, takin g care to p reserve th e cep h alic an d

b asilic vein s. Th e o th er sm all vein s in th e reg io n m ay b e rem o ved t o clear t h e d issectio n field . 3. Use scissors to incise the anterior surface of the antebrachial fascia from the cubital fossa to the wrist. Use blunt dissection to separate the antebrachial fascia from the m uscles that lie deep to it. 4. Detach the antebrachial fascia from its attachm ents to the radius and ulna along the interm uscular sep ta and place it in the tissue container. 5. Beginning on the m edial aspect of the elbow, identify the four m uscles in the sup e r cial layer o f e xo r

46

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GRANT’S DISSECTOR

m uscles of the forearm : the p ro n at o r t e re s, the e xo r carp i rad ialis, the p alm aris lo n g us, and the e xo r carp i uln aris (FIG. 2.23). 6. Use your ngers to separate the tendons of the sup e r cial laye r o f exo r m uscle s from each

other. Observe that the bellies of the sup er cial m uscles cannot be easily separated from each other proxim ally. 7. Identify the co m m o n exo r t e n d o n attached to the m edial epicondyle of the hum erus and note that it

Median n.

Biceps brachii m.

Brachialis m.

Brachialis m.

Brachial a. and v.

Lateral cutaneous n. of forearm

Medial epicondyle of humerus Common flexor tendon

Bicipital aponeurosis (reflected) Biceps brachii tendon

Pronator teres m. Cut 3

Radial artery Flexor carpi radialis m.

Brachioradialis m.

Palmaris longus m.

Flexor carpi ulnaris m. Radial a.

Superficial branch of radial n. Flexor pollicis longus m. Cut 2 Abductor pollicis longus tendon Superficial palmar branch of radial artery

Flexor digitorum superficialis m.

Flexor carpi radialis tendon Palmaris longus tendon Median n. Cut 1 Flexor carpi ulnaris tendon Ulnar a. Ulnar n. Pisiform bone Palmaris brevis m.

Palmar aponeurosis

FIGURE 2.23

Super cial layer of exor m uscles in the rig ht forearm . Anterior view.

CHAPTER 2

8.

9. 10. 11.

12.

13. 14.

15.

16.

17.

form s part of the proxim al attachm ent of the m uscles of the sup er cial layer (FIG. 2.23). Use your nger to trace the belly of the p ro n at o r t e re s m uscle toward the m iddle of the lateral surface of the radius. Clean the proxim al surface of the pronator teres m uscle. Clean the surface of the e xo r carp i rad ialis m uscle and follow its tendon toward its distal attachm ent. In the m iddle of the forearm , identify the p alm aris lo n g us t e n d o n . Follow and clean the palm aris longus distally toward its attachm ent to the p alm ar ap oneurosis in the hand. Note that this m uscle and tendon are absent in approximately 14% of upper limbs. On the m edial aspect of the forearm , identify and clean the e xo r carp i uln aris m uscle and follow its tend on toward its distal attachm ents. Review the attachm ents and actions of the sup e r cial laye r o f e xo r m uscle s (see TABLE 2.5). On the anterior surface of the wrist, deep and lateral to the tendon of the exor carp i rad ialis m uscle, identify and clean the rad ial art ery (FIG. 2.23). Note that the pulse of the radial artery can be felt at this location on the anterior distal surface of the radius in living individuals. Deep and lateral to the p alm aris lo n g us t en d o n , identify the m e d ian n e rve . Note that the m edian nerve is super cial at the wrist and can be easily injured. Deep and lateral to the tendon of the e xo r carp i uln aris m uscle , id entify and clean the uln ar art ery and uln ar n e rve . [G 148, 149; L 52; N 432; R 434] In your own wrist, palpate the tendons listed previously. Feel the pulse of the radial artery between the abductor pollicis longus and exor carpi radialis tendons. Flex your wrist and palpate the pisiform bone in the tendon of the exor carpi ulnaris muscle. Palpate the ulnar nerve and artery, which lie immediately lateral to the pisiform bone.

In t e rm e d iat e Laye r o f Fle x o r Muscle s [G 145; L 53; N 446] Perform the following dissection sequence on only one side of the cadaver. Maintain the sup er cial relationship s on the contralateral side. On the side where the deep dissection cuts are not m ade, sim ply use blunt dissection with your ngers to retract the m uscles and tendons and expose m any of the underlying structures. 1. Identify the exor d ig it orum sup er cialis m uscle, the only m uscle of the interm ediate layer of forearm exor m uscles (FIG. 2.23). To see it fully, several m uscles of the super cial layer m ust be transected and re ected. 2. Use scissors to cut the tendon of the palm aris longus m uscle about 3 cm proxim al to the wrist (FIG. 2.23, cut 1). Re ect the tendon and m uscle belly superiorly. 3. Cut the tendon of the exor carpi radialis m uscle about 5 cm p roxim al to the wrist (FIG. 2.23, cut 2) and re ect it superiorly.

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47

4. The pronator teres m uscle has two heads: a super cial (hum eral) head and a deep (ulnar) head. Observe that the m edian nerve passes between the two heads of the pronator teres. 5. Insert a probe through the pronator teres m uscle along the anterior surface of the m ed ian nerve (FIG. 2.23, cut 3). 6. Transect the portion of the pronator teres m uscle that lies anterior to the p robe. Re ect the hum eral head of the pronator teres m edially and the p alm aris longus and exor carpi radialis m uscles superiorly. 7. Observe the exor dig itorum super cialis m uscle. Proxim ally, the exor digitorum super cialis has three attachm ents that create a tendinous arch (FIG. 2.24). The ulnar artery and m edian nerve pass posterior (deep) to this arch. 8. Distally, the exor digitorum super cialis m uscle gives rise to four tendons that attach to the m iddle phalanges of digits 2 to 5 (FIG. 2.24). 9. Proxim al to the wrist, observe that the four tendons of the exor digitorum super cialis m uscle lie between the m edian nerve and the ulnar artery and nerve (FIG. 2.24). 10. Review the attachm ents and actions of the e xo r d ig it o rum sup e r cialis m uscle (see TABLE 2.5)

Ve sse ls an d Ne rve s o f t h e An t e rio r Fo re arm [G 146; L 53, 54; N 433, 434; R 435] 1. On the lateral side of the proxim al forearm , identify the brachioradialis m uscle (FIG. 2.24). 2. At the point where the pronator teres m uscle passes deep to the brachioradialis m uscle, use your ngers to op en the connective tissue p lane that is deep to the brachioradialis m uscle and identify the sup e r cial b ran ch o f t h e rad ial n e rve (FIG. 2.24). 3. Follow the super cial branch of the radial nerve to the distal one-third of the forearm and con rm that it em erges on the p osterior side of the b rachioradialis tend on and distributes to the dorsum of the hand. 4. In the cubital fossa, use blunt dissection to follow the b rach ial art e ry distally until it bifurcates into the rad ial art e ry and the uln ar art e ry (FIG. 2.24). 5. Clean the radial artery and follow it distally as far as the level of the wrist. The radial vein and its tributaries m ay be rem oved to clear the dissection eld. Note that the radial artery gives rise to several unnamed m uscular branches in the forearm. 6. Find the radial recurrent artery, which arises from the radial artery near its origin from the brachial artery (FIG. 2.24). The radial recurrent artery courses superiorly in the connective tissue plane between the brachioradialis muscle and the brachialis muscle and anastomoses with the radial collateral branch of the deep artery of the arm. Recall that the radial recurrent artery is part of the anastomotic network around the elbow (FIG. 2.19).

48

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Ulnar n.

Biceps brachii m.

Triceps brachii m.

Median n. Brachial a.

Pronator teres m. (reflected)

Brachioradialis m. (retracted)

Flexor carpi radialis m. (reflected) Common flexor tendon

Radial nerve: Deep branch Superficial branch

Brachialis m.

Radial recurrent a. Flexor digitorum superficialis m., humeral head

Radial a. Ulnar a.

Anterior ulnar recurrent a.

Supinator m. Tendinous arch Cut 2 Flexor carpi ulnaris m. (retracted)

Pronator teres m. (cut)

Flexor digitorum profundus m. Ulnar a. and n.

Flexor digitorum superficialis m., radial head

Flexor digitorum superficialis m.

Cut 2 Flexor pollicis longus m. Dorsal (cutaneous) branch of ulnar n. Dorsal carpal branch of ulnar a.

Palmar carpal branch of radial a. (cut)

Flexor digitorum superficialis tendons

Superficial palmar branch of radial a.

Flexor digitorum profundus tendon Cut 1 Median n.

Flexor carpi radialis tendon (reflected)

Pisiform bone

FIGURE 2.24

Palmaris longus tendon (reflected)

Interm ediate layer of exor m uscles in the right forearm . Anterior view.

7. Find the m ed ian n erve in the cubital fossa and observe that it is positioned m edial to the brachial artery and passes deep to the exor digitorum super cialis m uscle (FIG. 2.24). The m edian nerve innervates m ost of the m uscles of the exor com partm ent of the forearm . 8. To expose the distal part of the m edian nerve, the exor digitorum super cialis m uscle m ust be cut and retracted m edially. On only one upper lim b, use scissors to cut the four tendons of the exor digitorum

super cialis m uscle proxim al to the wrist at the level shown in FIGURE 2.24 (cut 1). On the other lim b, use blunt dissection to sep arate the layers and tendons of the m uscles. 9. Detach the exor digitorum super cialis m uscle from its attachm ent on the anterior obliq ue line of the radius (FIG. 2.24, cut 2). Do not cut the radial artery. Retract the m uscle m edially, leaving it attached to the ulna and m edial ep icondyle of the hum erus.

CHAPTER 2

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49

Musculocutaneous n. Brachialis m. Medial epicondyle of humerus

Brachioradialis m. (retracted) Radial n.:

Brachial a. Median n.

Superficial branch Deep branch

Common flexor tendon (cut) Biceps brachii tendon (cut)

Supinator m.

Anterior and posterior ulnar recurrent aa.

Interosseous aa.:

Anterior interosseous n.

Common Posterior Anterior

Flexor carpi ulnaris m. (retracted)

Pronator teres m. (cut) Extensor carpi radialis longus m. Extensor carpi radialis brevis m.

Ulnar a. and n.

Flexor digitorum superficialis m., radial head (cut)

Flexor pollicis longus m.

Flexor digitorum profundus m. Median n.

Radial a.

Dorsal branch of ulnar n. Pronator quadratus m. Flexor carpi radialis tendon (cut) Abductor pollicis longus tendon Flexor retinaculum

FIGURE 2.25

Dorsal carpal branch of ulnar a. Pisiform bone Flexor digitorum superficialis tendons (cut) Deep branch of ulnar a. and n.

Deep layer of exor m uscles in the right forearm . Anterior view.

10. Use a probe to free the m edian nerve from the loose connective tissue that lies between the interm ediate and deep layers of forearm exor m uscles (FIG. 2.25). 11. Observe that the m edian nerve gives sm all m uscular b ranches to the palm aris longus, exor carpi radialis, exor digitorum super cialis, and pronator teres m uscles. 1 2 . Id entify the a n t e rio r in t e ro sse o u s n e rve , which arises from the m ed ian n erve and in nervates the d eep layer of forearm exor m uscles (FIG. 2.25). 13. Find the uln ar art e ry in the cubital fossa and observe that it p asses posterior to the deep head of the pronator teres m uscle.

14. Insert a probe along the anterior surface of the ulnar artery, posterior to the deep head of the pronator teres m uscle. 15. Use scissors to cut the deep head of the pronator teres m uscle. The pronator teres m uscle is now com pletely transected and m ay be re ected to broaden the dissection eld . 16. Clean the ulnar artery and follow it from the cubital fossa to the wrist. The ulnar vein and its tributaries m ay be rem oved to clear the dissection eld. 17. Observe that the ulnar artery that passes posterior to the m edian nerve in the cubital fossa is layered between the exor digitorum super cialis and the

50

18.

19.

20.

21.

22.

23.

24.

•

GRANT’S DISSECTOR

exor digitorum profundus m uscles and is joined by the ulnar nerve about one-third of the way down the forearm (FIG. 2.25). Observe that the ulnar artery and nerve lie deep to the exor carpi ulnaris m uscle in the distal forearm and pass into the hand on the lateral side of the pisiform bone at the wrist (FIG. 2.25). Find the co m m o n in t e ro sse o us art e ry, a branch of the ulnar artery that arises ab out 3 cm distal to the origin of the ulnar artery. Ob serve that the com m on interosseous artery passes p osterolaterally toward the interosseous m em b rane b efore d ivid ing into the an t e rio r in t e ro sse o u s art e ry and the p o st e rio r in t e ro sse o us a rt e ry. The com m on interosseous artery is usually q uite short and m ay b e ab sent (i.e., the anterior and posterior interosseous arteries m ay arise directly from the ulnar artery). Identify the an t e rio r in t ero sse o us art e ry and follow it distally on the anterior surface of the interosseous m em brane between the m uscles of the deep layer of forearm exor m uscles (FIG. 2.26). At the p roxim al end of the interosseous m em brane, identify the p o st e rio r in t e ro sse o us art e ry and observe that it passes posteriorly to enter the posterior com p artm ent of the forearm (FIG. 2.26). The posterior interosseous artery supplies the extensor group of forearm m uscles. Do not attem pt to follow it into the posterior com partm ent at this tim e. Two other nam ed vessels arise from the ulnar artery in the proxim al forearm : the an t e rio r uln ar re curre n t art e ry and the p o st e rio r uln ar re curre n t art ery. The anterior and posterior ulnar recurrent arteries anastom ose with the inferior and superior ulnar collateral branches of the brachial artery, respectively (FIG. 2.19). Note that several unnam ed m uscular branches arise from the ulnar artery in the forearm . Identify the ulnar nerve in the distal forearm and follow it proxim ally. Near the elbow, observe that the ulnar nerve penetrates the exor carp i ulnaris m uscle and courses posterior to the m edial epicondyle of the hum erus. The ulnar nerve innervates the exor

carpi ulnaris m uscle and the m edial half of the exor digitorum profundus m uscle.

De e p Laye r o f Fle x o r Muscle s [G 147; L 54; N 434; R 435] 1. Th ree m uscles com p rise th e d e e p la ye r o f fo re a rm e xo r m u scle s: e xo r d ig it o ru m p ro fu n d u s, e xo r p o llicis lo n g u s, an d p ro n a t o r q u a d ra t u s (FIG. 2.25). 2. Identify and clean the surface of the e xo r d ig it o rum p ro fun d us m uscle . Note that the exor digitorum

Olecranon Trochlear notch Coronoid process

Annular ligament of radius Tuberosity of radius

Median n.

Tuberosity of ulna Common

Anterior

Posterior

Anterior interosseous n.

Interosseous membrane

Interosseous border

Pronator quadratus m.

CLIN ICA L CO RRELATIO N

Hig h Bifurcat io n o f t h e Brach ial Art e ry In about 3% of up per lim bs, the brachial artery bifurcates in the arm . When it does, the ulnar artery m ay course super cial to the super cial layer of exor m uscles and m ay be m istaken for a vein. When certain drugs are injected into an artery, the capillary bed is dam aged, followed by gangrene. In the exam ple of an injection into a super cial ulnar artery, the hand could be severely injured.

Interosseous arteries

Distal radioulnar joint Styloid process

Head of ulna Styloid process Articular disc

FIGURE 2.26 Pronator quadratus and interosseous m em brane. Anterior view.

CHAPTER 2

profundus m uscle has two motor nerves: The lateral half of the m uscle is innervated by the anterior interosseous branch of the m edian nerve and the medial half is innervated by the ulnar nerve. 3. Review the attachm ents and actions of the e xo r d ig it o rum p ro fun d us m uscle (see TABLE 2.5). 4. On the radial side of the forearm , identify and clean the e xo r p o llicis lo n g us m uscle (FIG. 2.25). 5. Review the attachm ents and actions of the e xo r p o llicis lo n g us m uscle (see TABLE 2.5).

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51

6. Retract the tendons of the exor digitorum profundus and exor pollicis longus m uscles m edially and laterally, resp ectively, and identify the p ro n at o r q uad rat us m uscle (FIG. 2.26). Observe that the bers of the pronator quadratus m uscle run transversely from the ulna to the radius. 7. In the distal forearm , observe that the an t e rio r in t e ro sse o us art e ry an d n e rve p ass between the pronator quadratus m uscle and the interosseous m em brane (FIG. 2.26).

Disse ct io n Fo llo w-up 1. Rep lace the exor m uscles in their correct anatom ical positions, taking care to align the cut tendons correctly. 2. Use the dissected sp ecim en to review the attachm ents and action of each m uscle dissected. 3. Organize the exor m uscles into super cial, interm ediate, and deep layers and recall that the nerves and vessels coursing through the forearm are found between the interm ed iate and deep layers. 4. Follow the brachial artery from its origin in the p roxim al arm to its bifurcation in the cubital fossa. 5. Review all of the branches of the radial and ulnar arteries and trace the course of these two arteries from the elbow to the wrist. 6. Review the course of the m edian nerve from the brachial plexus to the wrist. 7. Review the course of the ulnar nerve from the brachial p lexus to the wrist. 8. Recall that all m uscles of the anterior com p artm ent of the forearm are innervated by the m edian nerve or its branch, the anterior interosseous nerve, with the excep tion of the exor carpi ulnaris m uscle and m edial half of the exor d igitorum p rofundus m uscle, which are innervated by the ulnar nerve. [L 77, 78]

TABLE 2.5

An t e rio r Co m p art m e n t o f t h e Fo re arm

SUPERFICIAL GROUP OF MUSCLES Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Pronator teres

Medial epicondyle, supraepicondylar ridge, medial side of coronoid process

Lateral midshaft of radius

Pronates and exes the forearm

Median n.

Base of metacarpals 2–3

Flexes and abducts the wrist

Palmar aponeurosis

Flexes the wrist

Pisiform bone and base of metacarpal 5

Flexes and adducts the wrist

Ulnar n.

Flexor carpi radialis Palmaris longus Flexor carpi ulnaris

Medial epicondyle of humerus

INTERMEDIATE GROUP OF MUSCLES Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Flexor digitorum super cialis

Medial epicondyle of humerus and oblique line of radius

Middle phalanges of digits 2–5

Flexes PIP of digits 2–5

Median n.

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Flexor digitorum profundus

Anterior and medial surface of ulna and interosseous membrane

Distal phalanges of digits 2–5

Flexes DIP of digits 2–5

Lateral half—anterior interosseous n.; medial half— ulnar n.

Flexor pollicis longus

Anterior surface of radius and interosseous membrane

Base of distal phalanx of thumb

Flexes IP of thumb

Pronator quadratus

Distal radius

Distal ulna

Pronates the forearm

DEEP GROUP OF MUSCLES

Abbreviations: DIP, distal interphalangeal joint; IP, interphalangeal joint; n., nerve; PIP, proximal interphalangeal joint.

Anterior interosseous branch of median n.

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PALM OF THE HAND Disse ct io n Ove rvie w In t rin sic h an d m uscle s have both their p roxim al and distal attachm ents within the hand. There are two super cial group s of intrinsic hand m uscles: the t h e n ar g ro up o f m uscle s, which form s the t h e n ar e m in e n ce , and the h yp o t h e n ar g ro up o f m uscle s, which form s the h yp o t h e n ar e m in e n ce . Deep in the hand, the in t e ro sse o us m uscle s and the ad d uct o r p o llicis m uscle abduct and adduct the digits. The lum b ricals are unique intrinsic m uscles of the hand because they do not attach to bone. The lum bricals assist in exion of the m etacarpophalangeal (MCP) joint and extension of the p roxim al interphalangeal (PIP) and distal interphalangeal (DIP) joints. Ext rin sic h an d m uscle s reach the hand through the carp al tunnel and are responsible for exing the digits. The palm ar fascia overlies the m uscles of the hand and is thinner over the thenar and hypothenar em inences and thicker in the m iddle of the palm form ing the palm ar aponeurosis. In the palm , two arterial arches course between the m uscle layers. The super cial palm ar arch is m ainly derived from the ulnar artery and the deep palm ar arch from the radial artery. The nerve supply of the palm ar aspect of the hand is from the m edian and ulnar nerves. The order of dissection will be as follows: The palm ar aponeurosis will be studied and rem oved. The super cial palm ar arch will be dissected, followed by the tendons of the m uscles of the anterior com partm ent of the forearm . The transverse carpal ligam ent will be cut and the exor tendons will be released from the palm . The exor tendons will be followed into the p alm and the lum bricals will be studied. The m uscles of the thenar group will be dissected, followed by the m uscles of the hypothenar group. The deep palm ar arch will be dissected along with the deep branch of the ulnar nerve. The adductor pollicis and interosseous m uscles will be studied.

Ske le t o n o f t h e Han d

A

N

G

E

S

Index finger (digit 2): Distal phalanx

P

H

A

L

Middle phalanx Proximal phalanx Thumb (digit 1):

A

C

A

R

P

A

L

S

Distal phalanx

M

E

T

Proximal phalanx

A

R

P

A

L

S

5

C

Refer to a skeleton or an articulated hand and identify the following skeletal features (FIG. 2.27): [G 142, 164; L 60, 61; N 443; R 388, 389] 1. Identify the e ig h t carp al b o n es (Gr. karpos, wrist) collectively and observe that they are positioned in two rows of four. 2. In the proxim al row of carpal bones on the lateral asp ect of the wrist, identify the scap h o id , lun at e , t riq uet rum , and p isifo rm . 3. In the distal row of carpal bones, again beginning laterally, identify the t rap e zium , t rap e zo id , cap it at e , and h am at e . 4. Identify the ve m e t acarp als, num bered from 1 to 5 beginning laterally. 5. Observe that digit 1 (the thum b) has two phalanges: a proxim al and a distal. 6. Observe that digits 2 to 5 (the ngers) have three phalanges: a proxim al, a m iddle, and a distal. 7. Identify on the m edial side of the carpal bones the pisiform b one and the h o o k o f t h e h am at e as well as the t ub e rcle o f t h e scap h o id and the t ub e rcle o f t h e t rap e zium on the lateral side. Using FIGURE 2.28, note that a portion of the e xo r ret in aculum , the t ran sve rse carp al lig am e n t , bridges these four bones. 8. The space between the carpal bones and the transverse carpal ligam ent is the carp al t un n e l, which allows p assage of nine of the exor tendons and the m edian nerve into the hand.

Hamate Pisiform Triquetrum Lunate

Ulna

4

3

2 1

Hook of hamate Trapezium Trapezoid Capitate Scaphoid Radius

FIGURE 2.27 Skeleton of the hand (p alm ar view). The eig ht carp al b ones includ e a p roxim al row of four b ones (scap hoid : L, lunate; Tq, triq uetrum ; P, p isiform ) and a d istal row of four b ones (trap ezium : trap ezoid ; C, cap itate; H, ham ate).

CHAPTER 2

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53

CARPAL TUNNEL WITH CONTENT Flexor digitorum superficialis tendons Transverse carpal ligament Flexor carpi Median n. radialis tendon

Ulnar a.

Ulnar n.

Pisiform

Scaphoid Triquetrum

Flexor pollicis longus tendon Lunate Flexor digitorum profundus tendons

FIGURE 2.28 Section through the right carp al tunnel. Axial cut inferior view.

Disse ct io n In st ruct io n s Skin In cisio n s In m any cadavers, the hand m ay be stuck in a clenched position after the em balm ing process, m aking it very dif cult to dissect to the palm . If this is the case, ex the wrist and force open the clenched hand. Have a dissection partner hold it open or use string to straighten the clenched ngers. 1. With the cadaver in the supine position, refer to FIGURE 2.29. 2. Make a longitudinal incision down the palm (E to M). 3. Make a transverse incision proxim al to the level of the webs of the ngers (N to O). 4. Make a longitudinal incision on the anterior surface of d igits 2 to 5 from the incision line N/ O to points P on each digit. 5. Make a longitudinal incision along the palm ar surface of the thum b (E to Q).

Q

N E P

Supe r cial Palm [G 151; L 62; N 446, 447; R 442]

M

P O

P P FIGURE 2.29

6. Beginning in the m idline of the palm , rem ove the thick skin from the p alm ar surface of the hand staying super cial to the p alm ar aponeurosis. Rem ove the skin by cutting along the m edial and lateral aspects of the hand and carefully freeing it from the underlying aponeurosis. Place it in the tissue container. 7. Re ect the skin of the dig its away from the m idlines paying attention to not dam age the underlying digital nerves and vessels laterally and brous digital sheaths im m ediately deep to the skin (FIG. 2.30). 8. Make short horizontal cuts just p roxim al to the ngertips and rem ove the anterior skin of the digits by cutting along the periphery of the digits. When skinning the digits, proceed with caution because the subcutaneous tissue on the palmar surface of the digits is very thin, especially at the skin creases. 9. Turn the hand over and rem ove the skin on the dorsum of the hand. Note that the skin on the dorsum of the hand is m uch thinner and more loosely attached than the skin on the palm . Exercise caution while rem oving the thin skin to not dam age the underlying super cial veins on the dorsum of the hand. 10. Rem ove the skin on the dorsum of the hand to just below the carpom etacarpal joint leaving the skin on the posterior surface of the digits intact at this point in the dissection.

Skin incisions for the hand.

1. Carefully use scraping m otions with a scalpel blade to clean the fat from the p alm ar ap o n e uro sis (FIG. 2.30). Observe that the p alm ar ap oneurosis has four bands of lo n g it ud in al b e rs, one band to each of the digits 2 to 5, which end by attaching to the brous digital sheath near the base of the proxim al phalanx of each digit.

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GRANT’S DISSECTOR

Proper palmar digital arteries and nerves Fibrous digital sheath Longitudinal digital bands of palmar aponeurosis Palmar aponeurosis Hypothenar fascia over hypothenar eminence Palmaris brevis m. Palmaris longus tendon

Recurrent branch of median n. Thenar fascia over thenar eminence

FIGURE 2.30 Super cial dissection of the hand showing the palm ar ap oneurosis.

2. Identify the palm ar fascia covering the t h e n ar m uscle s lateral to the p alm ar ap oneurosis and observe that it is a m uch thinner fascia. 3. Identify the palm ar fascia covering the hypothenar m uscles m edial to the palm ar aponeurosis and the p alm aris b re vis m uscle (FIG. 2.30). The palm aris brevis m uscle is a thin, fragile m uscle responsible for contracting the skin at the base of the m edial palm and m ay not be readily visible in m any cadavers. 4. Detach the palm aris brevis m uscle from the palm ar ap oneurosis and re ect it m edially. 5. Find the tendon of the p alm aris lo n g us m uscle in the forearm and follow it distally into the palm to where it is attached to the palm ar aponeurosis (FIG. 2.30). 6. Near its distal attachm ents, use a probe to elevate the p alm ar aponeurosis away from the underlying structures in the palm . Note that although the palmaris longus m uscle m ay be absent, the palm ar aponeurosis is always present. 7. In the forearm where the palm aris longus tendon was cut, use the distal p alm aris longus tendon to ap ply traction to the p alm ar ap oneurosis during its rem oval. Use a scalpel and skinning m otions to detach the p alm ar aponeurosis from the underlying structures. 8. While re ecting the palm ar aponeurosis, do not cut too deeply because the super cial palm ar arch is in contact with its deep surface. Similarly, be careful to preserve the recurren t b ran ch of th e m ed ian n erve entering the thenar em inence along its distal m argin (FIG. 2.30). 9. Near the proxim al end of digits 2 and 3, rem ove the band of longitudinal bers of the palm ar aponeurosis.

10. On the upper lim b with the super cial dissection, rem ove the palm ar ap oneurosis beginning distally. Using the sam e techniq ues with the scalp el, carefully detach the palm ar aponeurosis from the underlying structures and re ect it sup eriorly, leaving it attached to the tendon of the palm aris longus. 11. Find the uln ar art e ry in the forearm and, using blunt dissection, follow it into the palm . Observe that the ulnar artery p asses lateral to the pisiform bone with the ulnar nerve, then divides into a sup e r cial b ran ch and a d e e p b ran ch . The super cial branch of the ulnar artery crosses the palm to form the sup e r cial p alm ar arch . The super cial palm ar arch is com pleted by a sm aller contribution from the sup e r cial p alm ar b ran ch o f t h e rad ial art e ry (FIG. 2.31). [G 156; L 63; N 447; R 442] 12. Use blunt dissection to clean the super cial palm ar arch and the co m m o n p alm ar d ig it al art e rie s that arise from it. 13. Trace one or two com m on palm ar digital arteries distally and note that they divide into two p ro p e r p alm ar d ig it al art e rie s supplying the adjacent sides of two digits (FIG. 2.31). 14. Find the uln ar n erve lateral to the p isiform bone and use a probe to dissect the sup e r cial b ran ch o f t h e uln ar n e rve , which sup plies cutaneous innervation to digit 5 and the m edial side of digit 4. The d ee p

Flexor digitorum profundus tendons

Proper palmar digital nn. and aa. Fibrous digital sheath

Flexor digitorum superficialis tendon

Adductor pollicis m.

Common palmar digital nn. and aa. Superficial palmar arch Superficial branch of ulnar n. Deep branch of ulnar n. and palmar branch of ulnar a. Transverse carpal ligament (flexor retinaculum) Pisiform bone Ulnar n. and a. Flexor digitorum superficialis and profundus tendons Flexor carpi ulnaris m.

Flexor pollicis brevis m. Recurrent branch of median nerve Abductor pollicis brevis m. Superficial palmar branch of radial a. Radial a. Median n.

Flexor carpi radialis tendon Flexor pollicis longus tendon

FIGURE 2.31 Super cial dissection of the palm showing the super cial palm ar arch and exor dig itorum super cialis tendons.

CHAPTER 2

b ran ch o f t h e uln ar n e rve disap pears between the hypothenar m uscles (FIG. 2.31). Identify the initial portion of the deep branch of the ulnar nerve but do not follow it at this tim e.

Carp al Tun n e l [G 157; L 63, 65; N 449; R 443] 1. Identify the transverse carp al lig am ent between the thenar and hypothenar eminences (FIG. 2.31). Use an illustration to review the transverse carpal ligament and its role in the formation of the carpal tunnel (FIG. 2.28). 2. Insert a probe deep to the transverse carpal ligam ent from proxim al to distal (FIG. 2.32). Use a scalpel to cut through the transverse carp al ligam ent super cial to the probe and open the carp al tunnel (FIG. 2.32, dashed line). 3. Exam ine the co n t e n t s o f t h e carp al t un n e l: m e d ian n e rve , fo ur t e n d o n s of t h e e xor d ig it o rum sup e r cialis m uscle , fo ur t e n d o n s o f t h e e xo r d ig it o rum p ro fun d us m uscle , and the t e n d o n o f t h e e xo r p o llicis lo n g us m uscle (FIG. 2.33). 4. Find the m edian nerve at the level of the wrist and follow it through the carpal tunnel. 5. Identify and clean the m edian nerve in the hand as well as its various proxim al branches. The m edian nerve innervates ve m uscles in the hand: lum b rical m uscle s 1 an d 2, via com m on palm ar digital nerves, as well as the three thenar m uscles via the re curre n t b ran ch o f t h e m e d ian n e rve (FIG. 2.33). 6. Follow the co m m o n p alm ar d ig it al b ran ch e s of the m edian nerve toward the lateral 3.5 digits (FIG. 2.34). Note that the com m on p alm ar digital nerves typically divid e to give rise to two p ro p e r p alm ar d ig it al n e rve s, which accom pany the p roper palm ar digital arteries. Use an illustration to study the

Adductor pollicis m.

Recurrent branch of median n.

Superficial palmar arch Flexor digiti minimi brevis m. Transverse carpal ligament (being reflected) Abductor digiti minimi m. Cut line

Flexor pollicis brevis m. Abductor pollicis brevis m.

Pisiform bone Ulnar n. and a.

Superficial palmar branch of radial a.

Flexor digitorum superficialis and profundus tendons Flexor carpi ulnaris m.

Flexor carpi radialis tendon Median n. Radial a.

FIGURE 2.32

Flexor pollicis longus tendon

How to open the carpal tunnel.

THE UPPER LIMB

Flexor digitorum profundus tendons Flexor digitorum superficialis tendon Common palmar digital aa. and nn. Flexor digiti minimi brevis m.

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55

Proper palmar digital nn. and aa. Fibrous digital sheath Superficial palmar arch Recurrent branch of median n.

Abductor digiti minimi m. Superficial branch of ulnar n. Deep branch of ulnar n. and palmar branch of ulnar a. Pisiform bone Ulnar n. and a. Contents of carpal tunnel: Median n. Flexor digitorum profundus tendons Flexor digitorum superficialis tendons Flexor pollicis longus tendon Flexor carpi radialis tendon

Adductor pollicis m. Flexor pollicis brevis m. Abductor pollicis brevis m. Transverse carpal ligament (cut) Superficial palmar branch of radial a. Radial a.

FIGURE 2.33 Interm ediate dissection of the palm showing the contents of the carpal tunnel.

cutaneous distribution of the m edian nerve in the hand. [G 167; L 62; N 459; R 435] 7. Identify and clean the exor tendons that pass through the carp al tunnel. Observe that the exor tendons pass through the p alm of the hand deep to the sup er cial p alm ar arch and digital nerves and enter the brous digital sheaths on the anterior surfaces of the digits (FIG. 2.33). 8. There are four synovial sheaths associated with the tend ons of the ngers: a co m m o n e xo r syn o vial sh e at h (uln ar b ursa) and three d ig it al syn o vial sh e at h s. The tendon of the exor p ollicis longus m uscle has its own synovial sheath (rad ial b ursa). Use an illustration to study the extent of the synovial tend on sheaths deep to the transverse carp al ligam ent and extending into the palm . [G 158, 159; L 65; N 449, 450; R 402, 403] CLIN ICA L CORRELATION

Carp al Tun n e l Syn d ro m e A swelling of the com m on exor synovial sheath, com m only caused by repetitive m ovem ent, m ay encroach on the available space in the carpal tunnel. As a result, the m edian nerve m ay be com p ressed resulting in pain and paresthesia of the thum b, index, and m iddle ngers and weakness of the thenar m uscles.

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Proper palmar digital nn. and aa.

Flexor digitorum profundus tendons

Fibrous digital sheath Flexor digitorum superficialis tendons (cut and reflected)

Common palmar digital aa. (cut) and nn.

Lumbrical mm. 3 and 4 Flexor digiti minimi brevis m. Adductor pollicis m.

Superficial palmar arch (cut)

Lumbrical mm. 1 and 2

Abductor digiti minimi m.

Flexor pollicis brevis m.

Superficial branch of ulnar n.

Recurrent branch of median nerve

Deep branch of ulnar n. and palmar branch of ulnar a.

Abductor pollicis brevis m.

Pisiform bone Ulnar n. and a. Flexor digitorum profundus tendons

Median n. Flexor pollicis longus tendon

Transverse carpal ligament (cut)

Flexor carpi Radial a. radialis tendon

FIGURE 2.34 Interm ediate dissection of the palm showing the exor digitorum profundus tendons and lum brical m uscles.

9. In the distal forearm , use your ngers to separate the tendons of the e xo r d ig it o rum sup er cialis m uscle from the tendons of the e xo r d ig it o rum p ro fun d us m uscle. Perform the following dissection steps only on the upper lim b with the deep dissection already perform ed in the forearm . 10. Cut the super cial palm ar arch in the m idline of the palm and retract the com m on digital branches of the m edian and ulnar nerves laterally and m edially, respectively. 11. Pull the tendons of the exor digitorum super cialis anteriorly to free them from the carpal tunnel (FIG. 2.34). Note that during this procedure, the comm on exor synovial sheath will be destroyed. 12. Clean surface of the tendons of the exor digitorum super cialis m uscle toward the base of each digit. 13. In the palm , identify and clean the tendons of the e xo r d ig it o rum p ro fun d us m uscle . 14. Follow the tendons of exor digitorum profundus distally and observe the relationship of the four attached lum b rical m uscle s (FIG. 2.34). 15. Clean the surface of the lum bricals but do not disrupt their points of attachm ent to exor digitorum p rofundus.

16. Review the attachm ents and actions of the e xo r d ig it o rum p ro fun d us m uscle and the lum b ricals (see TABLES 2.5 and 2.6). 17. Use a scalpel to carefully m ake a m idline incision through the b ro us d ig it al sh e at h on the exor surface of at least one digit and rem ove the sheath from the digit. 18. Study the re lat io n sh ip o f t h e t e n d o n s o f t h e e xo r d ig it o rum sup e r cialis and e xo r d ig it o rum p ro fun d us m uscle s. Verify that the exor digitorum super cialis tendon attaches to the m iddle phalanx and that the exor digitorum profundus tendon passes through the split distal end of the super cialis tendon and attaches to the distal phalanx (FIG. 2.34). This pattern is true for digits 2 to 5. 19. Id entify the e xo r p o llicis lo n g us m uscle in the forearm and follow its tend on d istally through the carp al tunnel into the p alm (FIGS. 2.26 and 2.33). Pull on the tend on to con rm that the exor p ollicis long us m uscle exes the d istal p halanx of the thum b.

The nar Muscle s [G 158–160; L 63; N 452; R 442] 1. Clean the thin layer of palm ar fascia off the thenar m uscles and m ake an effort to preserve the recurrent branch of the m edian nerve (FIG. 2.34). 2. Identify the three m uscles of the thenar group: ab d uct o r p o llicis b re vis, e xo r p o llicis b re vis, and o p p o n e n s p o llicis (L. pollex, thum b; genitive, pollicis) (FIGS. 2.34 and 2.35). 3. Review the attachm ents and actions of the t h e n ar g ro up o f m uscle s (see TABLE 2.6). 4. Exam ine the re curre n t b ran ch o f t h e m ed ian n e rve . 5. Use a p rob e to follow th e recurren t b ran ch of th e m ed ian n erve an d sep arate th e ab d ucto r p ollicis b revis m u scle fro m th e flexo r p o llicis b revis m uscle. 6. Use a prob e to elevate the abductor p ollicis brevis m uscle and transect it and the exor pollicis brevis with scissors near their distal attachm ents.

CLIN ICA L CORRELATION

Re curre n t Bran ch o f t h e Me d ian Ne rve The recurrent branch of the m edian nerve is super cial and can easily be severed by “m inor” cuts over the thenar em inence. If the recurrent branch of the m edian nerve is injured, the thenar m uscles are paralyzed and the thum b cannot be op posed. Com m only, the recurrent branch of the m edian nerve is referred to as the thenar branch, or “the m illion dollar nerve,” due to its im portance and potential value if severed.

CHAPTER 2

Proper palmar digital nn. and aa. Flexor digitorum superficialis and profundus tendons (cut) Common palmar digital a. (cut) Palmar metacarpal aa.

1st dorsal interosseous m. Transverse head of adductor pollicis m.

Flexor digiti minimi brevis m. Abductor digiti minimi m.

Oblique head of adductor pollicis m.

Deep palmar arch Superficial branch of ulnar n. Deep branch of ulnar n. and palmar branch of ulnar a.

Opponens pollicis m. Recurrent branch of median nerve

Pisiform bone Ulnar n. and a.

Flexor pollicis brevis and abductor pollicis brevis mm. (cut)

Flexor carpi ulnaris m.

Transverse carpal ligament (cut)

Ulnar and radial contributions to superficial palmar arch (cut)

Radial a.

FIGURE 2.35 Deep dissection of the p alm showing the deep p alm ar arch and deep branch of ulnar nerve.

7. Observe the o p p o n e n s p o llicis m uscle deep to the abductor and exor p ollicis brevis m uscles (FIG. 2.35). Note that the opponens pollicis m uscle attaches to the lateral side of the entire length of the shaft of the rst m etacarpal bone.

Hyp o t h e n ar Muscle s [G 158–160; L 63, 64; N 452; R 442] 1. Clean the thin layer of palm ar fascia off the hypothenar m uscles (FIG. 2.30). 2. Id en tify th e th ree m uscles of th e h yp oth en ar g roup : a b d u ct o r d ig it i m in im i, e xo r d ig it i m in im i b re vis, an d o p p o n e n s d ig it i m in im i (FIGS. 2.34 an d 2.35). 3. Find the tendons of the abductor digiti m inim i and exor digiti m inim i brevis m uscles near their distal attachm ents on the base of the proxim al phalanx of d igit 5. Use a probe to separate and de ne the bord ers of the m uscles along their tendons. 4. Review the attachm ents and actions of the h yp o t h e n ar g ro up o f m uscle s (see TABLE 2.6). 5. Use a probe to elevate the abductor digiti m inim i m uscle and observe the underlying o p p o n e n s d ig it i m in im i m uscle .

THE UPPER LIMB

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6. If the opp onens digiti m inim i is not visible, detach the abductor digiti m inim i from its distal attachm ent and re ect the m uscle toward its attachm ent on the exor retinaculum . Preserve the deep branches of the ulnar artery and ulnar nerve.

De e p Palm [G 160, 161; L 64; N 452, 453; R 443] 1. Transect the exor digitorum profundus m uscle in the distal forearm proxim al to the carpal tunnel (FIG. 2.34). 2. Re ect the tend ons of the exor d igitorum p rofund us and the associated lum b rical m uscles inferiorly as far as p ossib le to exp ose the d eep p alm (FIG. 2.35). 3. Find the ulnar nerve and the ulnar artery on the lateral side of the pisiform bone and identify the d e e p b ran ch o f t h e uln ar n e rve and the d e e p p alm ar b ran ch o f t h e uln ar artery. 4. Follow the deep branches of the ulnar artery and nerve to the proxim al attachm ents of the exor digiti m inim i brevis and abductor digiti m inim i m uscles (FIG. 2.35). 5. Push a probe parallel to the deep branch of the ulnar nerve where it p ierces the op ponens digiti m inim i m uscle. 6. Use a scalpel to cut down to the inserted probe and release the nerve. 7. Use blunt dissection to follow the deep branch of the ulnar nerve laterally across the palm and observe that it lies on the anterior surface of the interosseous m uscles then passes into the adductor pollicis m uscle (FIG. 2.35). 8. Identify the d e e p p alm ar art e rial arch and ob serve that it arises from the rad ial art e ry laterally and the deep branch of the ulnar artery m edially. 9. Identify the p alm ar m e t acarp al arteries and use an illustration to study the branches of the deep p alm ar arch (FIG. 2.35). 10. Identify the ad d uct o r p o llicis m uscle in the deep palm and use blunt dissection to de ne its borders (FIG. 2.35). 11. Identify the two heads of the adductor pollicis m uscle: o b liq ue and t ran sve rse . 12. Review the attachm ents and actions of the ad d uct o r p o llicis m uscle (see TABLE 2.6). 13. Identify the three p alm ar in t e ro sse o us m uscle s and observe their unipennate appearance (FIG. 2.36A). [G 155; L 64; N 452; R 443] 14. The dorsal interossei are bipennate m uscles and will be seen on the dorsal surface of the hand occupying the intervals b etween the m etacarpal bones. Use an

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GRANT’S DISSECTOR

AXIAL LINE

AXIAL LINE

1st palmar interosseous m.

3rd palmar interosseous m.

Adductor pollicis m. Transverse head (cut)

4th dorsal interosseous m. 1st dorsal interosseous m.

Oblique head

A Palmar view

B

Dorsal view

FIGURE 2.36 A. The three unipennate Palm ar interosseous m uscles ADduct (PAD) the ngers (arrows) in relation to the axial line. B. The four bipennate Dorsal interosseous m uscles ABduct (DAB) the ngers (arrows).

illustration to study the four d o rsal in t e ro sse o us m uscles at this tim e and do not m ake attem pts to dissect these m uscles (FIG. 2.36B). Note that in spite of their visibility on the dorsal side of the hand, dorsal interossei are considered intrinsic m uscles of the palm . 15. Study the actions of the interosseous m uscles (FIG. 2.36A, B). Observe that the three Palm ar interosseous m uscles are ADductors (PAD), which

adduct digits 2, 4, and 5 toward an im aginary axial line drawn through the long axis of digit 3. The four Dorsal interosseous m uscles are ABductors (DAB), which m ove digits 2, 3, and 4 away from the im aginary axial line. The two dorsal interosseous m uscles attaching to digit 3 m ove it to either side of the im aginary axial line back and forth. Note that all the interosseous m uscles are innervated by the deep branch of the ulnar nerve.

Disse ct io n Fo llo w-up 1. Place the dissected m uscles, tendons, and nerves back into their correct anatom ical positions. 2. Review the m ovem ents of the ngers and thum b. De ne exion, extension, abduction, and adduction and review the m uscles responsible for each action. 3. Use the dissected specim en to follow the m edian nerve from the forearm into the hand, review its recurrent branch, and list the three m uscles that it innervates. 4. Follow the ulnar artery from the elbow to the hand, trace the super cial branch and deep palm ar branches, and review the form ation of the palm ar arterial arches. 5. Follow the ulnar nerve from the m edial epicondyle of the hum erus to the hand, and trace the super cial and deep branches of the ulnar nerve. 6. Review an illustration dem onstrating the cutaneous distribution of the ulnar and m edian nerves in the hand. 7. Recall that all intrinsic m uscles of the hand are innervated by the ulnar nerve, except the m uscles of the thenar group and the rst two lum bricals, which are innervated by the m edian nerve. [L 77, 78; N 459]

CHAPTER 2

TABLE 2.6

THE UPPER LIMB

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59

In t rin sic Han d Muscle s

SUPERFICIAL PALM Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Palmaris brevis

Medial aspect of the palmar aponeurosis

Skin over the hypothenar eminence

Wrinkles skin of medial palm

Ulnar n.

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Lateral side, base of proximal phalanx of the thumb

Abducts the thumb

Volar side, base of proximal phalanx of the thumb

Flexes the thumb

Lateral side of the shaft of the rst metacarpal bone

Rotates the rst metacarpal toward the palm

Dista l Atta chments

Actions

Medial side, base of the proximal phalanx of digit 5

Abducts digit 5

Volar side, base of the proximal phalanx of digit 5

Flexes digit 5

Medial border of the fth metacarpal bone

Rotates fth metacarpal toward the palm

THENAR GROUP OF MUSCLES Muscle Abductor pollicis brevis Flexor pollicis brevis

Transverse carpal ligament and tubercle of scaphoid and trapezium

Opponens pollicis

Recurrent branch of the median n.

HYPOTHENAR GROUP OF MUSCLES Muscle

Proxima l Atta chments

Abductor pollicis brevis Flexor digiti minimi brevis

Pisiform, hamate, and transverse carpal ligament

Opponens digiti minimi

Innerva tion

Ulnar n.

DEEP PALM Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Lumbricals

Flexor digitorum profundus tendons

Radial side of the extensor expansions of digits 2–5

Flexes MCP and extends PIP and DIP of digits 2–5

1 and 2—median n.; 3 and 4—deep branch of ulnar n.

Adductor pollicis muscle

Transverse head—anterior surface of the shaft of third metacarpal Oblique head—second and third metacarpals and adjacent carpal bones

Medial side of base of proximal phalanx of thumb

Draws the thumb toward the plane of the palm (adduction)

Palmar interossei

Palmar surface of metacarpals of digits 2, 4, and 5

Base of the proximal phalanges and extensor expansion of digits 2, 4, and 5

Adducts digits 2, 4, and 5 and assists lumbricals in MCP exion

Dorsal interossei

Metacarpal bones 1–5

Base of the proximal phalanges and the extensor expansion of digits 2–4

Abducts digits 2–4 and assists lumbricals in MCP exion

Deep branch of ulnar n.

Abbreviations: DIP, distal interphalangeal; MCP, metacarpophalangeal; n., nerve; PIP, proximal interphalangeal.

EXTENSOR REGION OF THE FOREARM AND DORSUM OF THE HAND Disse ct io n Ove rvie w The posterior com partm ent of the forearm contains the extensor m uscles of the hand and digits and can be divided into super cial and deep layers. The m uscles of the super cial layer extend the wrist and the proxim al phalanges. The m uscles of the deep layer cause supination of the forearm , extension of the index nger, and abduction and extension of the thum b. The nerves and vessels of the posterior com partm ent run in the connective tissue plane dividing the super cial and deep layers of extensor m uscles (FIG. 2.21).

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In the dorsum of the hand, the skin is thinner and looser than the palm , intrinsic m uscles are absent, and the bones are relatively super cial. Because there are no intrinsic m uscles in the dorsum of the hand, no m otor innervation is req uired and the radial, ulnar, and m edian nerves share the cutaneous innervation. The order of dissection will be as follows: The antebrachial fascia will be rem oved from the elbow to the wrist. The m uscles of the super cial extensor layer will be identi ed and followed to their distal attachm ents in the hand. On the side where you did the deep dissection of the exor m uscles, the tendons of the super cial extensor m uscles will be released from the extensor retinaculum and retracted to expose the m uscles of the deep extensor layer. The contents of the anatom ical snuffbox will b e identi ed.

Disse ct io n In st ruct io n s Sup e r cial Laye r o f Ex t e n so r Muscle s [G 166; L 58; N 430; R 433] 1. With the cadaver in the supine position, ex the elbow and rotate the up per lim b to achieve increased visibility of the posterior com partm ent of the forearm . Either use string to hold it in this position or have your dissection partner assist in orienting the upper lim b throughout the dissection 2. Use blunt dissection to rem ove the rem nants of the super cial fascia from the p osterior forearm and dorsum of the hand, taking care to p reserve the dorsal venous arch and its contributions to the basilic and cephalic veins (FIG. 2.3). 3. Identify the super cial branch of the radial nerve and follow it onto the dorsum of the hand. 4. Identify the dorsal cutaneous branch of the ulnar nerve and follow it onto the dorsum of the hand. 5. Rem ove any rem aining skin from the posterior aspect of the forearm and hand as well as the posterior surface of at least one digit. 6. Follow the dorsal venous network toward the digits and verify that the digital veins drain into this network on the dorsum of the hand. 7. Identify the e xt e n so r re t in aculum , a transversely oriented sp ecialization of the antebrachial fascia, on the p osterior surface of the distal forearm (FIG. 2.37). 8. Use scissors to incise the posterior surface of the antebrachial fascia from the olecranon to the wrist while p reserving the extensor retinaculum . 9. Use blunt dissection to separate the antebrachial fascia from the underlying m uscles, detach it from its attachm ents to the radius and ulna, and place it in the tissue container. Note that in the proxim al extensor forearm , the fascia will be hard to separate from the m uscles and it m ay be necessary to use sharp dissection. 10. Identify and clean the an co n e us m uscle near the olecranon process of the ulna (FIG. 2.37). Recall that the anconeus is a m uscle of the posterior com partm ent of the arm and thus receives radial nerve innervation along with the tricep s m uscle. 11. Review the attachm ents and actions of the an co n e us m uscle (see TABLE 2.7).

12. Identify and clean the b rach io rad ialis on the lateral aspect of the forearm . Recall that the brachioradialis m uscle form s the lateral border of the cubital fossa. 13. Adjacent to the brachioradialis m uscle, identify and clean the e xt e n so r carp i rad ialis lo n g us and the ext e n so r carp i rad ialis b re vis m uscle s. 14. In the m iddle of the posterior forearm , identify and clean the ext en so r d ig it o rum m uscle. Observe that the extensor digitorum splits distally into four tendons that pass deep to the extensor retinaculum to reach digits 2 to 5. Note that all of the extensor tendons travel across the dorsal wrist deep to the extensor retinaculum within osseo brous tunnels. As on the exor side, the tendons are enveloped in synovial tendon sheaths. 15. Observe that the tendons of the extensor digitorum m uscle are connected to each other by in t e rt e n d in o us co n n e ct io n s on the posterior surface of the hand near the MCP joints (FIG. 2.37). [G 170; L 58; N 457; R 436] 16. Identify and clean the e xt e n so r d ig it i m in im i m uscle on the ulnar side of the extensor digitorum m uscle belly. Note that the extensor digiti m inim i m uscle sends two tendons distally to digit 5. 17. On the ulnar side of the forearm , identify and clean the e xt e n so r carp i uln aris m uscle . 18. Note that four of the m uscles in the super cial extensor layer (extensor carpi radialis brevis, extensor digitorum , extensor digiti m inim i, and extensor carpi ulnaris) originate on the lateral epicondyle of the hum erus by way of a com m o n ext en so r t en d on (FIG. 2.37). 19. Review the attachm ents, actions, and innervations of the sup e r cial laye r o f e xt e n so r m uscle s (see TABLE 2.7). 20. Observe the e xt e n so r e xp an sio n on the dorsum of the digits on which the skin was rem oved. The “hoodlike” exp ansion retains the extensor tend on in the m idline of the digit (FIG. 2.38). The extensor expansion wraps around the dorsum and sides of the proxim al phalanx and distal end of the m etacarpal bone. Recall that the tendons of the lum bricals and interossei m uscles attach into the extensor expansion, which continues across the PIP and the DIP to insert on the base of the distal p halanx. [G 171; L 59; N 451; R 433]

CHAPTER 2

THE UPPER LIMB

Anconeus m. Brachioradialis m.

Common extensor tendon

Antebrachial fascia (opened)

Extensor carpi radialis longus m.

Extensor carpi radialis brevis m.

Extensor digitorum m.

Extensor carpi ulnaris m. Abductor pollicis longus Extensor digiti minimi m.

Extensor indicis m.

Extensor pollicis brevis Extensor pollicis longus

Outcropping muscles of the thumb

Extensor digitorum tendons

Extensor pollicis longus tendon

Extensor retinaculum

Extensor pollicis brevis tendon

Cut line

Radial artery in the anatomical snuffbox

Dorsal carpal branch of ulnar a. Extensor carpi ulnaris tendon Dorsal carpal arch Extensor digitorum tendons Extensor digiti minimi tendon Intertendinous connections

Extensor carpi radialis longus tendon Extensor carpi radialis brevis tendon

1st dorsal interosseous m. Extensor expansion: Expansion Central band Lateral bands

FIGURE 2.37

Extensor indicis tendon

Super cial layer of extensor m uscles in the right forearm . Posterior view.

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GRANT’S DISSECTOR

Phalanges: Distal Middle Proximal Vincula brevia

Central band

Vincula longa

Flexor digitorum superficialis tendon

Lateral band Extensor (dorsal) expansion

2nd lumbrical m.

2nd dorsal interosseous m.

Extensor digitorum tendon

Flexor digitorum profundus tendon

FIGURE 2.38

3rd metacarpal bone

Extensor expansion of the right third digit. Lateral view.

De e p Laye r o f Ex t e n so r Muscle s [G 166; L 59; N 431; R 433] 1. On the upper lim b with the deep exor dissections, cut through the e xt e n so r re t in aculum to release the tendons of the extensor digitorum m uscle (FIG. 2.37, dashed line). 2. Use blunt dissection to separate the super cial layer of extensor m uscles from the ve m uscles com prising the d ee p laye r o f e xt en so r m uscles (FIG. 2.39). 3. Near the elbow, use your ngers to retract the brachioradialis m uscle and observe the sup in at o r m uscle wrapp ed around the p roxim al end of the radius (FIG. 2.39). 4. On the lateral aspect of the elbow, nd the radial nerve in the connective tissue plane between the b rachioradialis m uscle and the brachialis m uscle. Observe that the radial nerve divides into a super cial b ranch and a deep branch. The d e e p b ran ch o f t h e rad ial n e rve enters the sup inator m uscle. 5. Look for the deep branch of the radial nerve where it em erges from the distal border of the supinator

6.

7.

8.

9.

m uscle. Note that at this point, the deep branch of the radial nerve becom es the p o st e rio r in t e ro sse o us n e rve (FIG. 2.39). Observe that the posterior interosseous nerve is accom panied by the p o st e rio r in t e ro sse o us art e ry, a branch of the com m on interosseous artery. Identify and clean the ab d uct o r p o llicis lo n g us, e xt e n so r p o llicis b re vis, and ext e n so r p o llicis lo n g us m uscle s. Observe that the tendons of these three m uscles em erge from the interval between the extensor digitorum m uscle and the extensor carpi radialis brevis m uscle. For this reason, these deep m uscles are often referred to as the “outcropping” m uscles of the thum b (FIG. 2.39). Use blunt dissection to identify and clean the e xt e n so r in d icis m uscle lying deep to the extensor digitorum m uscle. Note that its tendon travels in the fourth dorsal compartm ent with the tendons of the extensor digitorum m uscle. Review the attachm ents, actions, and innervations of the d e ep laye r o f e xt e n so r m uscle s (see TABLE 2.7).

CHAPTER 2

THE UPPER LIMB

Lateral epicondyle of humerus Deep branch of radial n.

Brachioradialis m.

Supinator m. Extensor carpi radialis longus m.

Interosseous recurrent a.

Extensor carpi radialis brevis m. Branches of posterior interosseous n.

Posterior interosseous n. Posterior interosseous a.

Extensor digitorum m. (retracted)

Abductor pollicis longus m. Extensor pollicis brevis m. Extensor indicis m. Extensor pollicis longus tendon Extensor retinaculum Extensor carpi radialis tendons: Brevis Longus

Radial a. Abductor pollicis longus tendon Extensor pollicis brevis tendon Extensor pollicis longus tendon

1st dorsal interosseous m. Extensor digitorum tendon

FIGURE 2.39

Adductor pollicis m.

Deep layer of extensor m uscles in the right forearm . Lateral view.

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10. Identify the an at o m ical sn uffb o x, a d epression on the posterolateral surface of the wrist bound ed laterally by the ab d uct o r p o llicis lo n g us and the e xt e n so r p o llicis b re vis t e n d o n s and p osteriorly by the ext e n so r p o llicis lo n g us t en d o n (FIG. 2.40A, B). [G 173; L 58; N 456; R 436] 11. Within the anatom ical snuffbox, identify the rad ial art e ry (FIG. 2.40B).

Extensor tendons (cut) Dorsal carpal branch of ulnar a. Dorsal carpal arch

12. Use blunt dissection to clean the radial artery and follow it distally until it disappears between the two heads of the rst d o rsal in t e ro sse o us m uscle (FIG. 2.40A). Note that the dorsa l ca rpa l a rch supplies arterial blood to the dorsum of the hand and receives a branch of the radial artery that arises in the anatomical snuffbox. Do not dissect its branches.

Abductor pollicis longus tendon

Extensor retinaculum Dorsal carpal branch of radial a.

Extensor pollicis brevis tendon

Radial a. in anatomical snuffbox

Extensor pollicis longus tendon

Perforating a.

1st dorsal interosseous m.

Dorsal interosseous mm. Dorsal metacarpal aa. Dorsal digital aa. Extensor tendons and dorsal fascia of the hand (reflected)

APosterior view

Radialis indicis artery

Adductor pollicis m.

Insertion of 1st dorsal interosseous m.

B Lateral view

FIGURE 2.40 Dorsum of hand showing radial artery in anatom ical snuffbox. Boundaries of anatom ical snuffbox are outlined in green.

Disse ct io n Fo llo w-up 1. Replace the m uscles of the posterior com partm ent of the forearm into their correct anatom ical positions. 2. Use the dissected specim en to review the attachm ents of the extensor tendons. 3. Note that the tendons of three strong extensor m uscles (extensor carpi radialis longus, extensor carpi radialis brevis, and extensor carp i ulnaris) attach to the proxim al ends of m etacarp al bones and work synergistically with the exors of the digits to p roduce a rm grip. 4. Review the extensor expansion and recall the m uscles that insert into it. 5. Review the action of each m uscle in the posterior com partm ent of the forearm . 6. Review the course of the com m on interosseous branch of the ulnar artery and observe how the posterior interosseous artery enters the posterior com partm ent of the forearm . 7. Review the course of the radial artery from the cubital fossa to the deep palm ar arch. 8. Palpate the anatom ical snuffbox on yourself. Feel the pulsations of the radial artery within its boundaries. 9. Recall that the radial nerve innervates all of the m uscles in the posterior com partm ent of the forearm either directly or via one of its branches. [L 79] 10. Recall that there are no intrinsic m uscles in the dorsum of the hand and therefore no m uscles in the hand that are innervated by the radial nerve.

CHAPTER 2

TABLE 2.7

THE UPPER LIMB

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Po st e rio r Co m p art m e n t o f t h e Fo re arm

SUPERFICIAL GROUP OF MUSCLES Muscle

Proxima l Atta chment(s)

Dista l Atta chment(s)

Actions

Anconeus

Lateral epicondyle of humerus

Lateral surface of olecranon and posterior surface of proximal ulna

Assists triceps in extension of the elbow Flexes the forearm in neutral (midpronated) position

Brachioradialis

Proximal two-thirds of lateral supracondylar ridge

Lateral surface of distal radius (radial styloid process)

Extensor carpi radialis longus

Distal lateral supracondylar ridge

Base of second metacarpal

Radial n.

Extends and abducts the hand

Extensor carpi radialis brevis

Base of third metacarpal

Extensor digitorum

Extensor expansions of digits 2–5

Extends digits 2–5

Extensor expansion of digit 5

Extends fth digit

Base of fth metacarpal

Extends and adducts the hand

Extensor digiti minimi

Lateral epicondyle of humerus via common extensor tendon

Extensor carpi ulnaris

Innerva tion

Radial n. Deep branch of radial n.

Posterior interosseous n.

DEEP GROUP OF MUSCLES Muscle

Proxima l Atta chment(s)

Dista l Atta chment(s)

Actions

Innerva tion

Supinator

Lateral epicondyle of humerus, radial collateral and annular ligaments, crest of ulna

Lateral, posterior, and anterior surfaces of proximal ulna

Supinates forearm

Deep branch of the radial n.

Abductor pollicis longus

Base of rst metacarpal

Abducts and extends CMC of thumb

Extensor pollicis brevis

Base of the proximal phalanx of digit 1

Extends MCP of thumb

Base of the distal phalanx of digit 1

Extends MCP and IP of thumb

Extensor expansion of digit 2

Extends digit 2

Extensor pollicis longus

Posterior surfaces of the radius, ulna, and interosseous membrane

Extensor indicis

Posterior interosseous n.

Abbreviations: CMC, carpometacarpal joint; IP, interphalangeal joint; MCP, metacarpophalangeal joint; n., nerve.

JOINTS OF THE UPPER LIMB Disse ct io n Ove rvie w In ord er to d issect th e join ts in th e up p er lim b , it will b e n ecessary to re ect or rem ove th e m ajority of th e surroun d in g m uscles. Because th e join t d issection s will m ake it d if cult to review key m uscular relation sh ip s later, it is recom m en d ed to lim it th e join t d issection s to on e up p er lim b an d to keep th e soft tissue structures of th e oth er lim b intact for review p urp oses. Altern atively, if en oug h cad averic sp ecim en s are availab le in th e lab , p erform on ly select d issection s on each lim b an d altern ate th e d issection s p erform ed on each cad aver. Wh ile rem ovin g th e m uscles of th e selected up p er lim b , take ad van tag e of th is op p ortun ity to review th e attach m en ts, action s, an d in n ervation of each m uscle as it is rem oved . The order of dissection will be as follows: The sternoclavicular and acrom ioclavicular joints will be dissected. The glenohum eral joint will be dissected. The elbow joint and radioulnar joints will be studied. The wrist joint will be d issected. Finally, the joints of the digits will be studied.

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Disse ct io n In st ruct io n s St e rn o clavicular Jo in t [G 96; L 71; N 404] 1. On an articulated skeleton, identify the jug ular n o t ch o f t h e m an ub rium between the m e d ial (st e rn al) en d s o f t h e clavicle s. 2. With the cadaver in the supine position, identify the st e rn o clavicular jo in t . Note that the clavicles articulate with the m anubrium at each clavicular n o t ch and the adjacent part of the rst co st al cart ilag e (FIG. 2.41). 3. Observe that the tendon of the st e rn o cle id o m ast o id m uscle is attached to the anterior surface of the sternoclavicular joint. 4. Use a scalpel to detach the sternocleidom astoid tend on and re ect it and the sternocleidom astoid m uscle superiorly. Be careful only to re ect the m uscle and tendon of the sternocleidom astoid and not to disrupt the other structures in the area. 5. Id entify and clean the a n t e rio r st e rn o cla vicu lar lig a m e n t , which sp ans from the sternum to the clavicle. 6. Identify and clean the co st o clavicular lig am e n t , which runs obliq uely from the rst costal cartilage to the inferior surface of the clavicle near its m edial end. 7. Use a scalpel to rem ove the anterior sternoclavicular ligam ent to exp ose the joint cavity. 8. Identify the art icular d isc within the joint cavity. Observe that inferiorly, the articular disc is attached to the rst costal cartilage, whereas sup eriorly, it is attached to the clavicle. Note that the articular disc is attached in such a manner that it resists m edial displacement of the clavicle. 9. Palpate the m ovem ents of the sternoclavicular joint either on yourself, or if possible on the cadaver. Circum duct the up per lim b and observe that the sternoclavicular joint allows a lim ited am ount of m ovem ent in every direction.

Anterior sternoclavicular ligament

Acro m io clavicular Jo in t [G 122, 543; L 71; N 408; R 390] 1. On an articulated skeleton, identify the acro m io clavicular jo in t (FIG. 2.42). Observe that the acrom ioclavicular joint is located where the lat e ral (acro m ial) e n d o f t h e clavicle articulates with the acro m io n of t h e scap ula. 2. Inferom edial to the acrom ion, identify the coraco id p ro ce ss o f t h e scap ula and note its proxim ity to the sup rascap ular n o t ch . 3. Detach the trapezius m uscle from the lateral end of the clavicle and supraclavicular fascia. 4. Detach the coracobrachialis m uscle from its attachm ent to the coracoid process and re ect it laterally. 5. Detach the pectoralis m inor m uscle from its attachm ent to the coracoid process and re ect it inferiorly. If the p ectoralis m inor m uscle was previously detached from its inferior attachm ent to the ribs, rem ove the m uscle and place it in the tissue container. 6. Identify the acrom ioclavicular joint, a plane synovial joint between the acrom ion and the lateral end of the clavicle. 7. Identify and clean the coracoclavicular lig am en t located between the clavicle and coracoid process (FIG. 2.42). Observe that the coracoclavicular ligam ent has two parts which help support the acrom ioclavicular joint. Identify the m ore laterally located t rap ezoid lig am en t and the m ore m edially located con oid lig am en t . 8. Open the acrom ioclavicular joint by com pletely rem oving the joint capsule. 9. Separate the acrom ion from the lateral end of the clavicle and ob serve the shape of the articulating surfaces. Note that the angle of the articulating surfaces causes the acrom ion to slide inferior to the distal end of the clavicle when the acrom ion is forced m edially. The conoid and trapezoid ligam ents prevent the acrom ion from m oving inferiorly relative to the clavicle, thus strengthening the joint.

Articular disc of sternoclavicular joint Articular cavities of sternoclavicular joint

Clavicle Subclavius m. Costoclavicular ligament

Costoclavicular ligament

1st rib Costal cartilages Manubrium

FIGURE 2.41

Sternoclavicular joint. Surface view and sectional view.

CHAPTER 2

THE UPPER LIMB

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Acromioclavicular joint capsule Clavicle Acromion Trapezoid ligament

Coracoacromial ligament

Conoid ligament

Supraspinatus tendon (cut) Greater tubercle and lesser tubercle of humerus

Coracoclavicular ligament

Superior transverse scapular ligament and suprascapular notch

Transverse humeral ligament Coracoid process Subscapularis tendon (cut) Biceps brachii tendon (long head)

Capsular ligaments

FIGURE 2.42 Acrom ioclavicular joint and anterior asp ect of g lenohum eral joint; coracoclavicular and coracoacrom ial ligam ents.

Gle n o h um e ral Jo in t [G 122–125; L 71; N 408; R 390] The g le n o h um e ral jo in t (sh o uld e r jo in t ) is a ball-andsocket synovial joint with a greater degree of m ovem ent than any other joint in the body. The large range of m otion of the shoulder is due to the large difference in size of the articular surfaces between the bones involved (head of the hum erus [large articular area] and the glenoid fossa of the scapula [sm all articular area] and the loose joint capsule. With such a large range of m obility, the stability of the shoulder joint largely depends on the p roper function of the m uscles of the rotator cuff. 1. On an articulated skeleton, identify the g le n o h um e ral (sh o uld e r) jo in t (FIG. 2.1). Observe that the glenohum eral joint is the articulation between the g le n o id fo ssa o f t h e scap ula and the h e ad o f t h e h um e rus. 2. Identify the an at o m ical n e ck o f t h e h um erus and note its obliq ue orientation distal to the sm ooth articulating surface of the head of the hum erus. 3. With the cadaver in the supine position, cut the anterior attachm ent of the deltoid to clavicle and re ect the m uscle laterally. 4. Re ect the pectoralis m ajor m uscle laterally and m ake an incision through its tendon near the attachm ent to the intertubercular sulcus. Cut any adhering neurovascular structures and place the m uscle and associated tissue in the tissue container.

5. Detach the short head of the biceps brachii m uscle from the coracoid process. 6. Cut the tend on of the long head of the b icep s ap p roxim ately 3 cm inferior to the tran sverse h um eral lig am en t. Re ect th e b icep s b rachii m uscle in feriorly. 7. Cut through the proxim al attachm ent of the coracobrachialis m uscle, detach any adhering neurovascular structures, and re ect the m uscle inferiorly. 8. De ne and clean the co raco acro m ial lig am e n t , which spans from the coracoid process to the acrom ion. Note that the coracoacrom ial ligament, the acromion, and the coracoid process prevent superior displacement of the head of the humerus. 9. Elevate and cut the tendons of the supraspinatus and subscap ularis m uscles near their lateral attachm ents. 10. Identify the cap sule o f t h e g le n o h um e ral jo in t and rem ove the m uscles and tendons overlying the capsule on its sup erior and anterior surfaces. 11. Verify that the joint capsule is attached to the anatom ical neck of the hum erus. Recall that posteriorly, the tendons of the infrasp inatus and teres m inor m uscles blend with and reinforce the joint capsule. 12. Observe that the g le n o h um e ral lig am e n t strengthens the anterior wall of the brous cap sule. The glenohum eral ligam ent can be divided into three portions: superior, m iddle, and inferior, which are not easily identi able.

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Tendon of long head of biceps brachii in joint capsule Tendon of supraspinatus (cut)

Acromion process Coracoacromial ligament Supraglenoid tubercle Coracoid process

Fibrous capsule of shoulder joint

Suprascapular notch

Greater tubercle Transverse humeral ligament Tendon of scapularis (cut) Intertubular tendon sheath Surgical neck of humerus

Subscapular fossa

Glenoid fossa

Tendon of long head of biceps brachii m.

FIGURE 2.43

Cut edge of head of humerus

Glenoid labrum Lateral border of scapula

Op ened g lenohum eral joint capsule with rem oved head of the hum erus.

13. Use a scalpel to carefully open the anterior surface of the joint capsule by m aking an oblique cut m edial to the anatom ical neck of the hum erus (FIG. 2.43). 14. Within the capsule, identify the t e n d o n o f t h e lo n g h e ad o f t h e b ice p s b rach ii m uscle and observe that the tendon passes through the glenoid cavity to attach to the sup raglenoid tubercle. 15. Observe the relative thickness of the capsule and m ake horizontal incisions or rem ove portions of the capsule to increase visibility within the space, while sparing the biceps tend on. 16. Ab d uct an d rotate th e up p er lim b to in crease visib ility of th e h um eral h ead an d use a saw or a ch isel to rem o ve th e h ead of th e h um erus at th e an atom ical n eck. Make an effort to p reserve th e attach m en t of th e cap sule wh ile rem ovin g th e h um eral h ead . 17. Use a probe to explore the g le n o id cavit y and identify the g le n o id lab rum (FIG. 2.43). 18. Use the dissected specim en to perform the m ovem ents of the glenohum eral joint: exion, extension, abduction, adduction, and rotation. Note that this freedom of m otion is obtained at the loss of joint stability.

Elb o w Jo in t an d Pro x im al Rad io uln ar Jo in t [G 136, 137; L 72; N 424; R 391] 1. On an articulated skeleton, verify that the elbow joint consists of three bones and three distinct joints that allow exion and extension as well as pronation and supination. 2. Identify the h in g e jo in t between the trochlea of the hum erus and the trochlear notch of the ulna.

3. Id en tify th e g lid in g jo in t b etween th e cap itulu m of th e h um erus an d th e h ead o f th e rad ius (FIG. 2.44A) . 4. Identify the p ivo t jo in t between the head of the radius and the radial notch of the ulna. 5. With the cadaver in the sup ine p osition, cut the bicep s brachii tendon where it crosses the cubital fossa and re ect the m uscle superiorly. 6. Rem ove the brachialis m uscle from the anterior surface of the joint cap sule. 7. Rotate the upp er lim b either laterally or m edially and detach the triceps brachii tendon from the olecranon and the posterior surface of the joint capsule and reect the m uscle superiorly. If all the joint dissections are being performed on one upper lim b, increase the mobility and decrease the weight of the upper lim b by rem oving the bulk of the triceps brachii m uscle and placing it in the tissue container. 8. Cut and detach the super cial exor m uscles of the forearm by cutting through their attachm ent to the m edial epicondyle via the com m on exor tendon and re ect the m uscles inferiorly. 9. Identify the uln ar co llat e ral lig am e n t on the m edial side of the elbow joint and observe that it consists of a strong anterior cord and a fanlike posterior portion (FIG. 2.44D). 10. Cut the brachioradialis m uscle proxim ally near its attachm ent to the lateral supracondylar ridge and reect the m uscle inferiorly. 11. Cut and re ect the super cial extensor m uscles of the forearm by cutting through their attachm ent to the lateral epicondyle of the hum erus.

CHAPTER 2

A Radial fossa

Coronoid fossa Trochlea

Head of radius

B Lateral epicondyle

Neck

Medial epicondyle

Radial notch

Olecranon

Head Coronoid process

Neck Tuberosity of radius

Radial collateral ligament Annular ligament

Ulna

C LATERAL VIEW Annular ligament

Interosseous membrane

THE UPPER LIMB

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69

14. Identify the rad ial co llat e ral ligam ent and observe that it fans out from the lateral ep icondyle of the hum erus to the an n ular lig am e n t (FIG. 2.44C). 15. On an articulated skeleton, verify that the p ro xim al rad io uln ar jo in t is a p ivot joint b etween the head of the radius and the radial notch of the ulna. 16. On the cadaver, identify and clean the an n ular lig am e n t (FIG. 2.44B). 17. Once again, actively pronate and supinate the forearm and observe that the radius can freely rotate in the annular ligam ent. Note that the annular ligament com pletely encircles the head of the radius along with the radial notch of the ulna. 18. Open the elbow joint by m aking a transverse cut through the anterior surface of the joint cap sule between the ulnar and the radial collateral ligam ents. 19. Use a probe to explore the extent of the syn o vial cavit y. Observe the sm ooth articular surfaces of the hum erus, ulna, and radius. 20. Use the d issected sp ecim en to p erform the m ovem ents of th e elb ow joint: exion and extension, p ronation and sup ination. Ob serve the joint surfaces and the collateral lig am ents d uring th ese m ovem ents.

In t e rm e d iat e Rad io uln ar Jo in t [G 141; L 72, 73; N 425; R 392] Joint capsule

Radial collateral ligament

Annular ligament

D

Biceps brachii tendon

Ulnar collateral ligament

Joint capsule

MEDIAL VIEW

FIGURE 2.44 Elb ow joint. A. Disarticulated elb ow anterior view. B. Annular ligam ent. C. Elbow joint lateral view. D. Elb ow joint m edial view.

12. Take a m om ent to observe the attachm ents of the supinator m uscle. Observe its role in supination while actively pronating and supinating the forearm . Recall that the biceps brachii m uscle also supinates the forearm by pulling on the radial tuberosity while the forearm is pronated. 13. Detach the supinator from its proxim al and distal attachm ents and place it in the tissue container.

1. The radius and ulna are joined along their length by the in t e ro sse o us m e m b ran e creating a strong brous (syndesm osis) joint. 2. In the forearm , identify the interosseous m em brane and observe its attachm ents along the interosseous m argins of the radius and ulna. 3. Observe that the interosseous m em brane does not connect to the elbow but has a gap proxim ally allowing for passage of the nerves and vessels from the anterior com partm ent of the forearm to the posterior com partm ent.

Dist al Rad io uln ar Jo in t an d Wrist Jo in t [G 177–179; L 73, 74; N 441, 442; R 392, 393] 1. On an articulated skeleton, observe that the distal radioulnar joint is a pivot joint between the head of the ulna and the ulnar notch of the radius (FIG. 2.45). 2. Verify th at th e w rist jo in t (ra d io ca rp a l jo in t ) is th e articulation b etween the d istal end of the ra d iu s and the p roxim al row of ca rp a l b o n e s (FIG. 2.45). The wrist is a cond yloid joint and allows for m ovem ent in two p lanes: exion/ extension in the sag ittal p lan e an d ab d uction / ad d uction in th e coron al p lane. 3. Use an illustration to observe that the proxim al row of carpal bones articulates with the radius proxim ally

70

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GRANT’S DISSECTOR

MEDIAL

Transverse carpal ligament (flexor retinaculum)

LATERAL

Carpal tunnel Pisiform Lunate

Scaphoid

Triquetrum

Synovial membrane Synovial fold

Styloid process of ulna

Styloid process of radius

Articular disc

Distal end of radius

Ligamentous anterior border of articular disc

Pronator quadratus ANTERIOR VIEW

FIGURE 2.45

4.

5.

6.

7.

8.

9.

ones m ost com m only fractured in a fall on the outstretched hand. 10. Identify the art icular d isc o f t h e wrist (FIG. 2.45). Verify that the articular disc hold s the distal end s of the radius and the ulna together and articulates with the triquetrum when the hand is adducted. 11. Use the dissected specim en to perform the m ovem ents of the wrist joint: exion, extension, adduction, abduction, and circum duction. Observe the articular surfaces during these m ovem ents.

Distal radioulnar and radiocarpal joints.

and the distal row of carpal bones distally (FIG. 2.45). The articulation between the two rows of carpal bones is the m id carp al jo in t . Note that the distal row of carpal bones articulates distally with the m e t acarp als to form the carp o m e t acarp al jo in t s. In the anterior com partm ent of the forearm , rem ove all the tendons and soft tissue structures crossing the wrist. Review the distal attachm ents, actions, and innervations of each m uscle during rem oval. Observe that the anterior and p osterior surfaces of the wrist joint are reinforced by the rad io carp al lig am e n t s. Note that each ligam ent is nam ed according to its speci c sites of attachment. Extend the wrist and cut transversely through the radiocarp al ligam ents on the anterior surface of the joint capsule proxim al to the transverse carpal ligam ent and carpal tunnel. Do not cut com pletely through the joint capsule; rather, leave the hand attached to the forearm posteriorly. Use a probe to exp lore the distal radioulnar joint and identify the joint space between the radius and ulna (FIG. 2.45). Identify the art icular surface o f t h e rad ius on its distal end and verify that it articulates with the scap h o id and lun at e carp al bones. Identify the sm ooth p roxim al surfaces of the sca p h o id , lun a t e , and t riq u e t rum . Note that the sca phoid and luna te bones are positioned to transm it forces from the hand to the forearm and therefore are the

Me t acarp o p h alan g e al an d In t e rp h alan g e al Jo in t s [G 181; L 74; N 445; R 393] 1. On an articulated skeleton, identify the m e t acarp o p h alan g e al jo in t s. Con rm that the MCP joints are condyloid joints like the wrist and support exion/ extension and abduction/ adduction. 2. Identify the proxim al and distal interphalangeal joints of digits 2 to 5 and the interp halangeal joint of the thum b. Con rm that the interphalangeal joints are hinge joints and allow only exion and extension. 3. Select a digit to use as a representative exam ple for the other digits. 4. Cut the attachm ents of the exor digitorum super cialis from the m iddle phalanx and the exor digitorum profundus m uscle from the distal phalanx. 5. Rem ove the interosseous m uscles, lum brical, and the extensor expansion to expose the MCP joint cap sule. 6. Identify and clean the co llat e ral lig am e n t s o f t h e m e t acarp o p h alan g e al jo in t (FIG. 2.46A). 7. Move the digit to con rm that the collateral ligam ents are slack during extension and taut during exion. Therefore, the digits cannot be spread (abducted) unless they are extended. 8. Use the dissected specim en to perform the m ovem ents of the digit at the MCP joint: exion, extension, abduction, and adduction. 9. Identify and clean the co llat e ral lig am e n t s of t h e in t e rp h alan g e al jo in t s of the selected digit (FIG. 2.46A, B). 10. Use a scalpel to m ake an incision along the anterior surface of one PIP joint. 11. Use a probe to explore the synovial cavity of the interp halangeal joint and insp ect the articular surfaces covered with sm ooth cartilage. 12. Identify the vo lar p lat e , a brocartilaginous extension of the base of the m iddle phalanx. 13. Use the dissected specim en to perform exion and extension of the interphalangeal joints and conrm that the collateral ligam ents lim it the range of m otion.

CHAPTER 2

Metacarpal bone

A In extension: medial view

Dorsal surface

Palmar surface Palmar ligament (plate)

Metacarpophalangeal joint Joint capsule Collateral ligament

Proximal

THE UPPER LIMB

•

Proximal interphalangeal joint

Middle

Distal interphalangeal joint

Distal

Phalanges

B In flexion: medial view

Joint capsule Collateral ligaments

FIGURE 2.46 A. Metacarpophalang eal and interphalangeal joints in extension. B. Metacarpop halangeal and interphalangeal joints in exion.

Disse ct io n Fo llo w-up 1. Review the nam es of the bones articulating at each joint of the upper lim b. 2. Review the m ovem ents perm itted at each joint of the upper lim b. 3. Use the dissected specim en to identify the key ligam ents associated with each joint and review their respective points of attachm ent. 4. Return the re ected m uscles of the upper lim b back to their anatom ical positions.

71

CHAPTER 3

The Thorax ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

h e h eart an d lu n gs are fragile organ s, an d th e m ain fu n ction of th e th orax is to h ou se an d p rotect th em . Th e p rotective fu n ction of th e th oracic wall is com bin ed with m obility to accom m od ate volu m e ch an ges du rin g resp iration . Th ese two d issim ilar fu n ction s, p rotection an d m obility, are accom p lish ed by th e altern atin g arran gem en t of th e ribs an d in tercostal m u scles.

T

Th e su p er cial fascia of th e th orax con tain s th e u su al elem en ts th at are com m on to su p er cial fascia in all bod y region s: blood vessels, lym p h vessels, cu tan eou s n erves, an d sweat glan d s. In ad d ition , th e su p er cial fascia of th e an terior th oracic wall con tain s th e m am m ary glan d s, wh ich are h igh ly sp ecialized organ s u n iq u e to th e su p ercial fascia of th e th orax.

PECTORAL REGION Instructions for dissection of the pectoral region are found in Chapter 2, The Upper Lim b. If you are dissecting the thorax before the upper lim b, com plete the pectoral region dissection, then return to this page.

INTERCOSTAL SPACE AND INTERCOSTAL MUSCLES Disse ct io n Ove rvie w The interval between adjacent ribs is called the in t e rco st al sp ace . The intercostal sp ace is truly a space only in a skeleton because three layers of m uscle ll the intercostal spaces in the living body and in the cadaver. From super cial to deep, the three layers of m uscle are e xt e rn al in t e rco st al m uscle , in t e rn al in t e rco st al m uscle , and in n erm o st in t e rco st al m uscle . There are 11 intercostal spaces on each side of the thorax, and each is num bered according to the rib that form s its superior boundary. For exam ple, the fourth intercostal space is located between ribs 4 and 5. Th e o rd er of d issection will b e as follows: Th e extern al in tercostal m uscle will b e stud ied in th e fourth in tercostal sp ace an d will b e reflected . Th e in tern al in tercostal m uscle will b e stud ied in th e fourth in terco stal sp ace an d reflected . Bran ch es of in tercostal n erves an d b lood vessels will b e id en tified . Th e in n erm ost in tercostal m uscle will b e id en tified .

Surface An at o m y The surface anatom y of the thorax can be studied on a living subject or on the cadaver. [G 192; L 160; N 178] 1. Turn the cadaver to the supine position (face up) and palpate the jug ular n o t ch (sup rast e rn al n o t ch ) on the superior asp ect of the m an ub rium between the sternal ends of the clavicle s (FIG. 3.1). 2. Feel along the clavicle laterally to the acro m io n o f t h e scap ula and note its relationship sup erior to the an t e rio r axillary fo ld (lat e ral b o rd e r o f t h e p e ct o ralis m ajo r m uscle ) . 3. Palpate the st e rn al an g le (m an ub rio st e rn al jun ct io n ) between the m anubrium and b o d y o f t h e st e rn um . 4. Inferior to the body of the sternum , p alpate the xip h o id p ro ce ss just below the xip h ist e rn al jun ct io n and feel laterally along the co st al m arg in s .

73

74

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GRANT’S DISSECTOR Jugular notch

Clavicle Acromion Manubrium Sternal angle

Tubercle

Body of sternum

Neck

Head

Costal angle

Articular facets or bodies of vertebrae

Anterior axillary fold Xiphisternal joint Xiphoid process

Shaft

Articular facet for transverse process

Seventh costal cartilage Costal margin

FIGURE 3.1

Surface anatom y of the anterior thoracic wall.

Costal groove

FIGURE 3.2

Typical left rib. Posterior view.

Ske le t o n o f t h e Th o rax If you have previously dissected the back, review the parts of a t h o racic ve rt e b ra . If you have not com pleted the dissection of the back, turn to the section on the verteb ral colum n and com plete the associated exercise, then return to this page.

Rib s [G 205; L 61, 164; N 82; R 205] Refer to a skeleton or isolated ribs and sternum and identify the following skeletal features (FIGS. 3.2 and 3.4): 1. On rib 6 or 7 , identify the h e ad and n eck o f t h e rib . 2. On the head of the rib, observe the art icular face t s . Observe that the h e ad of a rib usually articulates with two vertebral bodies and their intervertebral disc. For exam ple, the head of rib 5 articulates with vertebral bodies T4 and T5 (FIG. 3.3). The 1st, 10th, 11th, and 12th ribs are exceptions to this rule because their heads articulate with only one vertebral body. 3. Identify the t ub e rcle of a rib and observe that it Superior articular facet articulates with the t ran sve rse co st al face t on the Pedicle transverse process of the thoracic vertebra of the Transverse process sam e num ber (FIG. 3.3). Inferior articular facet 4. Lateral to the tubercle, where the rib changes direcT2 Body tion along the sh aft (b o d y) , id entify the co st al an g le Transverse costal facet and the co st al g ro o ve along its inferior surface. 5. On an articulated thoracic cage, observe how the ribs Inferior vertebral notch T3 angle inferiorly approxim ately two vertebral levels as they wrap laterally and anteriorly around the thorax. Superior vertebral notch Intravertebral 6. Observe that the rst rib is the highest, shortest, disc Intervertebral foramen T4 b road est, and m ost sharply curved rib. 7. Anteriorly along the lateral aspect of the st e rn um , Shaft of rib 5 Head of observe that co st al cart ilag e is attached to the anrib 5 T5 terior end of each rib. Note that ribs are classi ed by the way their costal cartilag es articulate m edially. 8. Identify the t rue rib s (rib s 1 t o 7) , in which the cosSpinal nerve T5 tal cartilages articulate d irectly to the sternum . 9. Identify the false rib s (rib s 8 t o 12) , in which the costal cartilages articulate with the costal cartilage of FIGURE 3.3 Part of the thoracic vertebral colum n. Right the rib above, as seen along the co st al m arg in . lateral view.

CHAPTER 3

10. Identify the two false or oatin g rib s (rib s 11 and 12) , which do not articulate anteriorly with a skeletal elem ent but end in the abdom inal m usculature.

Acromioclavicular joint Sternoclavicular joint 1

St e rn um [G 204; L 163; N 184; R 202] 1. Exam ine the st e rn um and observe that the st e rn al an g le is at the level of the se co n d co st al cart ilag e anteriorly and the level of the T4/ T5 in t e rve rt e b ral d isc p osteriorly (FIG. 3.4). 2. Review the location of the jug ular n o t ch (suprasternal notch), the m an ub rium (L. m anubrium , handle), the b o d y o f t h e st e rn um , and the xip h o id p ro ce ss (Gr. xiphos, sword). 3. Exam ine a scap ula and identify the acro m io n p rocess laterally and co raco id p ro ce ss anteriorly (FIG. 3.4). [G 69; L 32; N 183; R 381] 4. Observe that the m edial end of the clavicle articulates with the m anubrium of the sternum (sternoclavicular joint) and that the lateral end of the clavicle articulates with the acrom ion of the scapula (acrom ioclavicular joint) (FIG. 3.4).

7

External intercostal m. (cut edge)

8

FIGURE 3.5 Structures in the intercostal space. A. Anterior view. B. Coronal section at the m idaxillary line.

Body of sternum 11 T11

L1

Xiphoid process Costal margin

10

Inferior thoracic aperture (thoracic outlet)

FIGURE 3.4

5.

6.

7.

10.

B

Sternal angle

9

Innermost intercostal m. Internal intercostal m. External intercostal m.

Costal groove

Manubrium

12 T12

9.

Collateral vessels

Scapula

6

Rib

External intercostal m. (reflected)

Coracoid process

5

Internal intercostal m.

A

T1

4

Innermost intercostal m.

Intercostal: Vein Artery Nerve

75

Superior thoracic aperture Jugular (suprasternal) notch Clavicle Acromion

3

8.

Internal intercostal m. (reflected)

•

2

Disse ct io n In st ruct io n s 1. Detach the se rrat us an t erio r m uscle , one attachm ent at a tim e, from its proxim al attachm ents on the upp er eight or nine ribs. 2. Re ect the serratus anterior m uscle, along with the long thoracic nerve and lateral thoracic artery, laterally. 3. Palpate the ribs and the intercostal spaces beginning at the level of the sternal angle (attachm ent of the second costal cartilage) and identify each intercostal space by num ber. 4. Identify the ext ern al in t ercost al m uscle in intercostal space 4 (between ribs 4 and 5) (FIG. 3.5). Observe

THE THORAX

Skeleton of the thoracic region.

that the bers of the external intercostal m uscle are oriented inferoanteriorly. [G 211; L 166; N 186; R 211] Identify the e xt e rn al in t e rco st al m em b ran e , which is located at the anterior end of the intercostal space, between the co st al cart ilag e s . Observe that the bers of the external intercostal m uscle end at the lateral edge of the external intercostal m em brane. Insert a probe deep to the external intercostal m em brane just lateral to the border of the sternum in the fourth intercostal space and push the probe laterally deep to the external intercostal m em brane and m uscle. With the probe as a guide, use scissors to cut the external intercostal m em brane and m uscle from the rib above and re ect them inferiorly (FIG. 3.5). Continue the cut laterally toward the m idaxillary line. Identify the in tern al in tercostal m uscle and observe that the ber direction of the internal intercostal m uscle is perpendicular to the ber direction of the external intercostal m uscle (superoanterior) (FIG. 3.5). Observe that the internal intercostal m uscle bers occupy the intercostal space all the way to the sternum and are visible deep to the external intercostal m em brane. Begin at the lateral border of the sternum and detach the internal intercostal m uscle from its attachm ent on rib 5. Continue to detach the internal intercostal m uscle as far laterally as the m idaxillary line and reect the m uscle superiorly (FIG. 3.5). Look for the fourth in t e rco st al n e rve and the fourth p o st e rio r in t e rco st al art e ry an d vein inferior to rib 4. Observe that the intercostal nerve and vessels run in the p lane between the in t e rn al in t e rco st al m uscle and in n e rm o st in t e rco st al m uscle (FIGS. 3.5 and 3.6).

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11. Deep to the intercostal neurovascular structures, identify the in n erm ost in t ercost al m uscle and observe that it has the sam e ber direction as the internal intercostal m uscle but does not extend as far anteriorly in the intercostal space. [G 212; L 170; N 188; R 219] 12. Use FIGURE 3.6 to study the course and distribution of a typical intercostal nerve and note that it supplies the intercostal m uscles, the skin of the thoracic wall, and the parietal pleura.

13. The anterior end of the intercostal space is sup plied by an t erio r in t e rco st al b ran ch es of the in t ern al t h o racic art e ry. The internal thoracic artery runs a vertical course inside the thorax just lateral to the border of the sternum where it crosses the deep surfaces of the costal cartilages. Do not attem pt to dissect the anterior intercostal branches at this tim e. [G 214; L 167, 168; N 186; R 212]

External intercostal membrane

Anterior cutaneous branches of 4th intercostal nerve: Lateral branch Medial branch Sternum

External intercostal muscle Internal intercostal muscle

Transversus thoracis muscle

Innermost intercostal muscle Parietal pleura

Lung

Lateral cutaneous branches of 4th intercostal nerve: Anterior branch Posterior branch Body of 4th thoracic vertebra

Spinal cord

Spinal ganglion 4th thoracic spinal nerve Anterior ramus (intercostal nerve) Posterior ramus

Posterior cutaneous branches of posterior ramus of 4th thoracic nerve: Lateral branch Medial branch

FIGURE 3.6

Course and distribution of the fourth thoracic spinal nerve.

Disse ct io n Fo llo w-up 1. Replace the internal and external intercostal m uscles in their correct anatom ical positions. 2. Review the m uscles that lie in the intercostal space along with their actions and understand how they assist respiration by elevating and dep ressing the ribs. 3. Use an illustration and your dissected specim en to review the origin, course, and branches of the posterior intercostal artery and intercostal nerve. 4. Consult a derm atom e chart and com pare the derm atom e pattern to the distribution of the intercostal nerves. [G 54; L 162; N 162; R 209]

CHAPTER 3

TABLE 3.1

THE THORAX

•

77

In t e rco st al Muscle s

Muscle

Superior Atta chment

Inferior Atta chment

Actions

External intercostal Internal intercostal

Innerva tion

Elevates the rib below Inferior border of the rib above

Depresses the rib above

Superior border of the rib below

Intercostal nn.

Innermost intercostal Abbreviation: nn., nerves.

REMOVAL OF THE ANTERIOR THORACIC WALL; THE PLEURAL CAVITIES Disse ct io n Ove rvie w The thorax has two ap ertures or openings, which allow the passage of structures either superiorly or inferiorly (FIG. 3.4). The sup e rio r t h o racic ap e rt ure (t h o racic in le t ) is sm aller and bounded com pletely by bone. Anteriorly, the superior thoracic aperture is de ned by the m anubrium of the sternum , laterally by the right and left rst ribs, and p osteriorly by the body of the rst thoracic vertebra. Structures pass between the thorax, the neck and head, and the upper lim b through the superior thoracic aperture (e.g., t rach e a , e so p h ag us , vag us n e rve s , t h o racic d uct , m ajo r b lo o d ve sse ls ). The in fe rio r t h o racic ap e rt ure is larger and bounded anteriorly b y the xip histernal joint and the costal m argin, laterally by ribs 11 and 12, and posteriorly by the body of vertebra T12. The d iap h rag m attaches to the structures form ing the boundaries of the inferior thoracic ap erture and sep arates the thoracic and abdom inal cavities. Several large structures (e.g., ao rt a , t h oracic d uct , in fe rio r ve n a cava , e so p h ag us , vag us n e rve s ) pass between the thorax and abdom en through op enings in the diaphragm . The thorax contains two p le ural cavit ie s (right and left) and the m e d iast in um . The two pleural cavities occup y the lateral p arts of the thoracic cavity and each contains one lun g . The m ediastinum (L. quod per medium stat , that which stands in the m iddle) is the region between the two pleural cavities. [G 220; L 173; N 193; R 251] To view the contents of the thoracic cavity, the anterior thoracic wall m ust be rem oved. The goal of this dissection is to rem ove a portion of the thoracic wall along with the co st al p le ura attached to its inner surface and then observe the contents of the pleural cavities. The order of dissection will be as follows: The sternocleidomastoid and infrahyoid neck muscles will be detached from the sternum and clavicle. The clavicles will be cut at their midpoint. The costal cartilages and sternum will be cut at the level of the xiphisternal joint. The ribs and intercostal structures will be cut at the midaxillary line. The anterior thoracic wall will be removed along with the associated costal parietal pleura. The inner surface of the thoracic wall and contents of the pleural cavities will be studied.

Disse ct io n In st ruct io n s An t e rio r Th o racic Wall 1. Re ect the pectoralis m ajor m uscle laterally, the pectoralis m inor m uscle superiorly, and the serratus anterior m uscle laterally. 2. Detach the sternocleidom astoid m uscle from the superior m argin of the sternum and the superior surface of the clavicle. 3. Use b lun t d issection to loosen th e d istal 5 cm of th e stern ocleid om astoid m uscle an d re ect it sup eriorly. 4. Use your ngers or a probe to push the infrahyoid m uscles posteriorly. Follow the infrahyoid m uscles inferiorly and detach them from the deep surface of the sternum . 5. Use a saw to cut both clavicles at their m idpoint (FIG. 3.7, cuts 1 and 2). 6. At the level of the xiphisternal joint (approxim ately at the level of intercostal space 5), use a saw to m ake

Cut 1

Cut 2

Cut 3

Cut ribs and intercostal muscles along green lines

FIGURE 3.7

Cuts used to rem ove the anterior thoracic wall.

78

7.

8.

9. 10.

11.

12.

13.

14.

15.

16. 17.

18.

•

GRANT’S DISSECTOR

a transverse cut across the sternum and costal cartilages (FIG. 3.7, cut 3). Allow the saw to p ass through the bone and cartilage but not into the deep er tissues within the thorax. Continue the saw cut bilaterally ap proxim ately 4 cm superior to the inferior border of the costal m argin following the curve of the m argin inferolaterally. Extend the cut to the m idaxillary line at approxim ately intercostal space 8. Use a saw or bone cutters to cut ribs 2 to 8 in the m idaxillary line on both sides of the thorax, beginning inferiorly and p rogressing sup eriorly. Elevate the cut portion of ribs or push against the cut rib one at a tim e to verify you have cut com p letely through each rib. Palpate the rst rib and use blunt dissection to push the contents of the axilla p osteriorly. Use the saw or bone cutters to cut through the rst rib near the costal cartilage. While m aking the cut, pay attention to not dam age any of the neurovascular structures passing into the axilla, in particular the subclavian vein. With a scalpel or scissors, m ake a series of vertical cuts through the m uscles in intercostal spaces 1 to 8 in the m idaxillary line. The cuts should be aligned with the cut ribs and deep enough to cut the parietal pleura but not the surface of the lungs. Gently elevate the inferior end of the sternum along with the attached portions of the costal cartilages and ribs and re ect the anterior thoracic wall sup eriorly. Near the inferior end of the sternum , identify the rig h t an d left in t ern al t h oracic vessels. If they have not already been severed, use scissors to cut the internal thoracic vessels at the level of the fth intercostal space. Continue to elevate the inferior end of the anterior thoracic wall and use scissors to cut any adhesions of parietal pleura from the inner surface of the thoracic wall onto the m ediastinum . Cut the internal thoracic vessels at the level of the rst rib and remove the anterior thoracic wall along with the attached portions of the internal thoracic vessels. Observe the internal surface of the anterior thoracic wall and identify the co st al p arie t al p le ura . Peel off a p ortion of the costal parietal p leura from the inner surface of the anterior thoracic wall and note the d istinct tearing sound as you separate the pleura from the thoracic wall. The sound is the tearing of the bers of the e n d o t h o racic fascia , the loose connective tissue attaching the costal pleura to the thoracic wall. Identify the t ran sve rsus t h o racis m uscle on the deep surface of the sternum and costal cartilages [G 215; L 168; N 187; R 210]. Observe that the inferior attachm ent of the transversus thoracis m uscle is on the sternum , and its superior attachm ents are

CLIN ICA L CORRELATION

An t e rio r Th o racic Wall In thoracic surgery, the anterior and lateral approaches to the contents of the thorax are the two m ost com m on approaches. In the anterior approach, the sternum is split vertically in the m idline to avoid any m ajor vessels and allow for good access to the heart. The incision through the sternum is closed with stainless steel wires. In the lateral approach, an intercostal space is incised to provide access to the lungs or structures posterior to the heart.

on costal cartilages 2 to 6. The transversus thoracis m uscle depresses the ribs. 19. Identify and clean the in t e rn al t h o racic art e ry an d ve in s between the transversus thoracis m uscle and the costal cartilages. 20. Follow the internal thoracic artery inferiorly and identify at least one of its an t e rio r in t e rco st al b ran ch e s . 21. Observe that posterior to the sixth or seventh costal cartilage, the internal thoracic artery term inates by dividing into the sup e rio r e p ig ast ric art e ry and the m usculo p h re n ic art e ry.

Ple ural Cavit ie s [G 220; L 172; N 193; R 275] 1. Use your hands to carefully explore the right and left pleural cavities paying attention because the cut ends of the ribs are sharp and can cut you. To reduce the risk of injury, fold the serratus anterior m uscle into the thoracic cavity over the cut ends of the ribs before you begin palpating the pleural cavities. 2. Use paper towels or a turkey baster to rem ove uid that m ay have collected in the p leural cavity during the em balm ing p rocess. 3. Identify the subdivisions of p arie t al p le ura , the outer lining of the serous m em brane enclosing the pleural cavities, beginning with the co st al p le ura on the inner surface of the thoracic wall (FIG. 3.8). Observe that som e of the costal p arietal pleura was cut and rem oved with the anterior thoracic wall. 4. Identify the m e d iast in al p arie t al p le ura lining the m ediastinum m edially and the d iap h rag m at ic p arie t al p le ura covering the superior surface of the diaphragm . Note that endothoracic fascia underlies all the subdivisions of parietal pleura. 5. Identify the ce rvical p le ura (p le ural cup ula) extending superior to the rst rib. 6. Observe that the parietal pleura is folded sharply at the lin e s o f p le ural re e ct io n , where the costal pleura m eets the diaphragm atic pleura and where the costal pleura m eets the m ediastinal p leura. 7. The areas where one parietal pleura contacts another parietal pleura are called p le ural re ce sse s .

CHAPTER 3

Trachea Cervical pleura Apex of left lung

Superior lobe

Root of lung containing: Main bronchus Pulmonary artery Pulmonary veins

10.

11.

12. Ribs and intercostal muscles Endothoracic fascia

Mediastinal pleura

13.

Costal pleura Inferior lobe Diaphragm Visceral pleura Pleural cavity Diaphragmatic pleura Costodiaphragmatic recess Line of pleural reflection

FIGURE 3.8

The pleurae, pleural cavity, and pleural re ections.

Identify the two co st o d iap h rag m at ic rece sse s (left and right), which are located at the m ost inferior lim its of the parietal pleura. 8. Using the rem oved p ortion of the anterior thoracic wall, appreciate the relative location of the two co st o m e d iast in al re ce sse s (larger on the left than the right), which occur p osterior to the sternum where costal pleura m eets m ediastinal pleura. 9. Inferiorly along the lateral border of the diaphragm , place your ngers in the co st o d iap h rag m at ic re ce ss and follow it p osteriorly observing the acute angle that the diap hragm m akes with the inner surface of the thoracic wall. Note that during quiet inspiration,

14.

THE THORAX

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the inferior border of the lung does not extend into the costodiaphragmatic recess. Place your hand between the lung and the mediastinum and palpate the root of the lung , comprised the physical structures passing from the mediastinum in and out of the lung. Note that here, at the root of the lung, the mediastinal pleura is continuous with the visceral pleura and demarcates the boundary of the hilum of the lung. Palpate the p ulm o n ary lig am e n t , which extends inferior to the root of the lung, anchoring the inferior lobe of each lung to the m ediastinum . Observe that each lung is com pletely covered with visce ral p le ura (p ulm o n ary p le ura) . Make no attem p t to rem ove the visceral p leura because this will destroy the lung tissue. Observe that the root of the lung is attached to the m ediastinum but that all other parts of the lung should slide freely against the parietal p leura as the lung m oves within the p le ural cavit y, the space between the visceral pleura and the parietal pleura (FIG. 3.8). Note that in the living body, the pleural cavity is a potential space, and visceral pleura touches parietal pleura separated only by a thin layer of serous uid. Use your ngers to trace the periphery of the lung within the pleural cavity and break any pleural adhesions between visceral and parietal pleurae that m ay be present because they are the result of disease processes.

CLIN ICA L CORRELATION

Ple ural Cavit y Under p athologic conditions, the potential sp ace of the pleural cavity m ay becom e a real space. With traum a, air m ay enter the p leural cavity (pneum othorax) causing the lung to collapse due to the change in intrathoracic p ressure and the elasticity of the lung tissue. Excess uid m ay also accum ulate in the pleural cavity and com press the lung producing breathing difculties. The uid could be excess serous uid from pleural effusion or blood accum ulation resulting in hem othorax.

Disse ct io n Fo llo w-up 1. Replace the anterior thoracic wall, the serratus anterior, and pectoralis m inor and m ajor m uscles in their correct anatom ical p ositions. 2. Use an illustration, and the dissected specim en, to project the lines of pleural re ection to the anterior thoracic wall. 3. Review the attachm ents and the actions of the pectoralis m ajor and m inor, the serratus anterior, and the transversus thoracis m uscles. 4. Study the course of the internal thoracic artery from its origin on the subclavian artery to its term inal bifurcation and nam e its branches. 5. Review the course of the intercostal nerves and understand that they provide som atic innervation (including pain bers) to the costal pleura.

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LUNGS Disse ct io n Ove rvie w The lungs are the prim ary respiratory organs in hum ans and form part of the lower aspect of the conducting portion of the resp iratory system . Though they are bilateral organs, the right and left lungs have distinct anatom ical differences. The alveoli, which are the gas exchange portion of the lungs, are not visible without the aid of a m icroscope; however, the gross structures of the lungs and the conducting system are readily visible for study. The order of dissection will be as follows: The surface features and relationships of the lung s seen from an anterior view will be studied with the lungs in the thorax. The lungs will then be rem oved, and the study of surface features and relationships of the lungs will be com p leted. The hilum and root of the lung will be studied .

Disse ct io n In st ruct io n s Lun g s in t h e Th o rax [G 214; L 174, 175; N 195; R 278] 1. Observe the lungs in situ and identify their three surfaces beginning with the co st al surface , which, as its nam e infers, is the surface of the lung adjacent to the ribs (FIG. 3.9). 2. Gently pull a lung laterally and identify the m e d iast in al surface of the lung, which rests in contact with the centrally located m ediastinum . 3. Elevate the inferior aspect of the lung and identify the d iap h rag m atic surface of the lung lying directly over the diaphragm . Contraction of diaphragm atic m uscle bers pulls the diaphragm inferiorly and increases the volum e of the thoracic cavity and lungs. The increased volume consequently lowers the atmospheric pressure in the lungs and draws air into the lungs. 4. Observe that the right lung has three lobes (sup e rio r , m id d le , and in fe rio r ), whereas the left lung has two lobes (sup e rio r and in fe rio r ) (FIG. 3.9). Note that variations in the number of lobes are comm on.

Apex Trachea and esophagus Superior vena cava

Aortic arch Superior lobe

Superior lobe

Re m o val o f t he Lung s [G 224, 225; L 189; N 196; R 257]

Horizontal fissure Middle lobe

Oblique fissure

Oblique fissure

Inferior lobe

Inferior lobe Diaphragm

FIGURE 3.9

Pericardium

5. Observe the o b liq ue ssure (m ajo r ssure) on both lungs just superior to the inferior lobe. Using the anterior thoracic wall as a guide, observe that the oblique ssure lies deep to the fth rib laterally and deep to the sixth costal cartilage anteriorly. 6. Identify the h o rizo n t al ssure (m in o r or t ran sve rse ssure ) on the right lung between the superior and m iddle lobes. Using the anterior thoracic wall as a guide, observe that the horizontal ssure lies deep to the fourth rib and fourth costal cartilage. Observe that the ap e x of the lung lies sup erior to the bod y of the rst rib along with the associated cervical pleura and therefore lies superior to the plane of the superior thoracic aperture in the neck. 7. Between the right and left pleural cavities, identify the p e ricard ium . The pericardium occupies the m idline between the lung s, lies posterior to the sternum and costal cartilages, and contains the heart. 8. Insert your hand into the pleural cavity between the pericard ium and the lung and p alpate the hard structures within the ro o t o f t h e lun g . The structures within the root of the lung are the pulm onary vessels and the m ain bronchus. 9. On the lateral surface of the pericardium , identify the p h re n ic n e rve and the p e ricard iaco p h re n ic ve ssels , travelling together, deep to the m ediastinal pleura. 10. Observe that the phrenic nerve and p ericardiacophrenic vessels pass anterior to the root of the lung. Do not dissect the phrenic nerve or pericardiacophrenic vessels at this tim e because they will be dissected with the m ediastinum .

Cardiac notch

The lungs in situ. Anterior view.

1. Place your hand into the right pleural cavity between the lung and m ediastinum and retract the lung laterally to stretch the root of the lung while preserving the phrenic nerve and pericardiacophrenic vessels m edially. 2. While retracting the lung, use scissors or a scalpel to transect the root of the lung halfway between the lung and the m ediastinum . Take care not to cut into the m ediastinum or the lung.

CHAPTER 3

Apex

Apex Horizontal fissure

Posterior border

Anterior border

Superior lobe

Superior lobe Cardiac notch Middle lobe

Inferior lobe

Inferior lobe

Lingula Oblique fissure

Right lung

Inferior border

FIGURE 3.10

Left lung

The lungs in lateral view.

3. Gently pull the lung laterally and use your ngers to determ ine that the root of the lung is com pletely transected. Be sure to transect the pulm onary ligam ent. 4. Slide your hands under the right lung and lift it from the pleural cavity paying attention not to cut the lung or yourself on the sharp edges of the ribs. Note that the lung tissue is quite delicate and the lungs must be removed gently to avoid damaging the tissue or separating the lobes.

THE THORAX

Superior lobe

Oblique fissure Inferior lobe Structures of hilum: Bronchi Pulmonary artery Bronchial artery

Anterior border

Bronchopulmonary lymph nodes Superior and inferior pulmonary veins Horizontal fissure Posterior border Esophagus impression

Middle lobe

Pulmonary ligament

Inferior border Diaphragmatic surface

FIGURE 3.11

81

5. On the right lung, identify the sup e rio r , m id d le , an d in fe rio r lo b es and the h o rizo n t al ssure (FIG. 3.10). 6. Identify the co st al, m e d iast in al, and d iap h rag m at ic surface s o f t h e rig h t lun g . 7. Identify the an t e rio r , p o st e rio r , and in fe rio r b o rd e rs o f t h e rig h t lun g . 8. On the m ediastinal surface of the rig h t lun g , identify the shallow card iac im p re ssio n anterior to the e so p h ag e al im p ressio n . 9. Identify the im p re ssio n o f t h e arch o f t h e azyg o s ve in arching superior to the root of the lung toward the sup e rio r ve n a cava im p re ssio n (FIG. 3.11). 10. Perform steps 1 to 4 of this dissection sequence on the left lung and rem ove it from the left pleural cavity. To facilitate the rem oval of the left lung, have som eone hold the pericardium and heart to the right. 11. Identify the co st al, m e d iast in al, and d iap h rag m at ic surface s o f t h e le ft lun g . 12. Identify the an t e rio r , p o st e rio r , and in fe rio r b o rd e rs o f t h e le ft lun g . 13. On the m ediastinal surface of the left lun g , id entify the m ore prom inent card iac im p re ssio n inferior to the ao rt ic arch im p re ssio n and anterior to the t h o racic ao rt a im p re ssio n (FIG. 3.12). 14. On the left lung, identify the card iac n ot ch on the anterior border of the superior lobe and verify that in

Apex Arch of azygos vein impression Right brachiocephalic vein impression Superior vena cava impression Cardiac impression

•

Mediastinal surface of the right lung.

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GRANT’S DISSECTOR

Apex Superior lobe

Oblique fissure

Aortic arch impression Cardiac impression

Inferior lobe

Structures of hilum: Pulmonary artery Bronchial artery Main bronchus

Anterior border

Bronchopulmonary lymph nodes Superior and inferior pulmonary veins Posterior border Thoracic aorta impression Cardiac notch Pulmonary ligament Lingula Diaphragmatic surface

FIGURE 3.12

15.

16.

17.

18.

19.

20.

Inferior border

Mediastinal surface of the left lung.

the anatom ical position, it is p ositioned anterior to the heart (FIGS. 3.9 and 3.10). On the left lung, identify the lin g ula , the inferior, m edial portion of the superior lobe, and verify that it is the hom olog of the m iddle lobe of the right lung. Com pare the two lungs and observe that the right lung is shorter but has greater volum e than the left lung (FIG. 3.10). Verify that each lung has a sup e rio r and in fe rio r lo b e separated by the o b liq ue ssure and observe that m ost of the inferior lobe lies posteriorly and that m ost of the sup erior lobe lies anteriorly in the thorax (FIG. 3.10). On the m edial surface of each lung, exam ine the ro o t o f t h e lun g and identify the m ain b ro n ch us , p ulm o n ary art e ry, and p ulm o n ary ve in s (FIGS. 3.11 and 3.12). Observe that the pulm onary artery is usually superior to the pulm onary veins (FIGS. 3.11 and 3.12). Note that the pulm onary artery contains oxygen-poor blood and the pulm onary veins contain oxygen-rich blood. Observe at the hilum of the left lung that the left m ain bronchus contains cartilage and com m only lies inferior to the pulm onary artery. Observe at the hilum of the right lung that the right m ain bronchus lies posterior to the pulm onary artery but m ay have already divid ed into lo b ar (se co n d ary) b ro n ch i.

21. At the hilum of each lung, insert a probe to follow the m ain b ro n ch us into the lung and verify its p attern of branching. 22. In the left lung, identify the sup erior and inferior lob ar (secon d ary) b ron ch i. [G 233; L 192; N 200; R 255] 23. In the right lung, identify the sup e rio r , m id d le , and in fe rio r lo b ar b ro n ch i. Note that the rig h t sup e rio r lo b ar b ro n ch us passes superior to the right pulm onary artery and therefore is also called the “ e p art e rial b ro n ch us .” 24. Use blunt dissection to follow one lobar bronchus approxim ately 3 to 4 cm deeper into the lung tissue until it branches into several seg m en t al (t ert iary) b ro n ch i. Note that the right lung contains 10 segmental bronchi and the left lung contains either 9 or 10, each of which supply one bronchopulmona ry segment of the lung. 25. Identify a b ro n ch ial art e ry coursing along the surface of the m ain or lobar bronchi. 26. In addition to the already identi ed structures, the hilum of the lung contains bronchial arteries and veins, lym ph nodes, lym ph vessels, and autonom ic nerves. Note that the lungs have a rich nerve sup ply via the anterior and posterior pulm onary plexuses with sym pathetic contributions from the right and left sym pathetic trunks and parasym pathetic contributions from the right and left vagus nerves. [G 235, 236; L 190; N 205, 206; R 285]

CHAPTER 3

THE THORAX

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83

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5. 6. 7. 8. 9.

Review the surfaces, borders, and com ponent parts of the lungs. Review the structures of the root of the lung. Review the parts of the parietal pleura. Note that the transition from parietal to visceral pleura occurs at the hilum of the lung. Com pare and contrast the structures that can be seen in the hilum of the right lung to those that can be seen in the hilum of the left lung. Review the relationship of the phrenic nerve to the root of the lung and the pericardium . Replace the lungs in their correct anatom ical positions within the pleural cavities. Replace the anterior thoracic wall and project the borders, surfaces, and ssures of the lungs to the surface of the thoracic wall. Review the relationship of the pleural re ections to the thoracic wall and the location of the costom ediastinal and costodiaphragm atic recesses.

MEDIASTINUM Disse ct io n Ove rvie w The m ediastinum is the region between the two pleural cavities. For descriptive purposes, the m ediastinum can be divided into four parts based on their relative locations (FIG. 3.13). An im aginary transverse plane at the level of the st e rn al an g le intersects the intervertebral disc between ve rt e b rae T4 an d T5 and separates the sup e rio r m e d iast in um from the in fe rio r m e d iast in um . The inferior m ediastinum is further subdivided by the pericardium into three parts [G 221; L 194, 195; R 253]. The an t e rio r m e d iast in um lies between the sternum and the pericardium and in children and adolescents contains part of the thym us. The m id d le m e d iast in um is Superior centrally located and contains the pericardium , the heart, and the roots of the great vessels. The p o st e rio r m e d iasSternal angle t in um lies posterior to the pericardium and anterior to the bodies of vertebrae T5–T12 and contains structures that 4 pass between the neck, thorax, and abdom en (esophagus, 5 vagus nerves, azygos system of veins, thoracic duct, thoAnterior 6 racic aorta). It is worth noting that som e structures that 7 course through the m ediastinum (esophagus, vagus nerve, Middle 8 phrenic nerve, and thoracic duct) pass through m ore than Pericardium one m ediastinal subdivision. The order of dissection will be as follows: The m ediastinal pleura will be exam ined, and m ediastinal structures will be palpated. The costal and m ediastinal pleurae will then be rePosterior 12 m oved. The pericardium will be opened and its relationship to the heart and great vessels will be explored. The characteristics of the parietal serous pericardium will then be studied. The heart will be rem oved by cutting the great vessels. FIGURE 3.13 Boundaries and subdivisions of the mediastinum.

Disse ct io n In st ruct io n s Me d iast in um 1. Observe that the m e d iast in um has a sup e rio r b o un d ary of the superior thoracic ap erture, an in fe rio r b o un d ary of the diaphragm , an an t e rio r b o un d ary of the sternum , a p o st e rio r b o un d ary of vertebral bodies T1–T12, and lat e ral b o un d arie s of m ediastinal pleurae (left and right).

2. Use the anterior thoracic wall to identify the location of the sternal angle relative to the m ediastinum . Verify that the sternal angle is at the sam e height as the intervertebral disc between vertebrae T4 and T5. 3. Palpate the m e d iast in al p le ura and observe that the plane of the sternal angle is at the level of the sup e rio r b o rd e r o f t h e p e ricard ium , the b ifurcat io n o f t h e t rach e a , the e n d o f t h e asce n d in g aorta, the b e g in n in g a nd e n d o f t h e arch o f t h e ao rt a , and

84

4.

5.

6.

7. 8.

9.

•

GRANT’S DISSECTOR

the b e g in n in g o f t h e t h o racic ao rt a . [G 272, 273; L 194, 195; N 227, 228; R 290, 291] Observe that as you m ove from anterior to posterior, the m ediastinal pleura is in contact with the p ericard ium and root of t h e lun g and either the eso p h ag us on the right side or the t h o racic ao rt a on the left side. Follow the m ediastinal p leura further posteriorly until it contacts the sides of the vertebral bodies where it transitions to co st al p le ura . Detach the costal p leura in the m idaxillary line near the cut ends of ribs 1 to 5 and p eel the costal p leura off the inner surface of the posterior thoracic wall, m oving from lateral to m edial. Note that the e n d o t h o racic fascia p rovides a natural cleavage p lane for separation of costal pleura from the thoracic wall. Rem ove the costal p leura up to the p oint where it covers the vertebral colum n. Identify the left and rig ht p h re n ic n e rve s and the left and right p e ricard iaco p h re n ic ve sse ls coursing deep to the m ediastinal pleura. Observe that the phrenic nerve and pericardiacop hrenic vessels are located between the m ediastinal pleura and the pericardium about 1.5 cm anterior to the root of the lung. Clean and follow the phrenic nerve and pericardiacophrenic vessels inferiorly toward the diaphragm . Recall that the phrenic nerves arise from vertebral levels C3–C5 and that each phrenic nerve is the only m otor innervation to the ipsilateral half of the diaphragm .

He art in t h e Th o rax [G 241; L 177, 178; N 209; R 278] 1. Identify the p e ricard ial sac (p e ricard ium ) that encloses the heart and observe that it is p ierced by the ao rt a , the p ulm o n ary t run k, and the sup e rio r ve n a cava superiorly; the fo ur p ulm o n ary ve in s posterolaterally; and the in fe rio r ven a cava inferiorly. 2. Observe that the pericardial sac lies deep to the m e d iast in al p arie t al p le ura . Note that the pericardial sac consists of two layers: the b ro us p e ricard ium externally and the sm ooth se ro us p e ricard ium lining the inner surface. 3. Rem ove the m ediastinal parietal pleura and associated fat covering the anterior surface of the pericardial sac between the right and left phrenic nerves and pericardiacophrenic vessels. 4. Observe that the pericardial sac is attached to the ce n t ral t en d o n o f t h e d iap h rag m and thus will m ove up and down with the diaphragm during inspiration and expiration carrying the heart with it. 5. Use forceps to elevate the anterior surface of the pericardium and use scissors to m ake a vertical cut through the pericardium from just above the d iaphragm toward the ascending aorta (FIG. 3.14).

Vertical cut Transverse cuts

Pericardium

Diaphragm

FIGURE 3.14

How to open the pericardium .

6. Make the two parallel transverse cuts around the periphery of the pericardium as illustrated in FIGURE 3.14. Take care to not cut the p hrenic nerves and accom panying vessels. Op en the aps of pericardium widely. 7. On the inner surface of the pericardial sac, identify the sm ooth surface of the p arie t al laye r o f se ro us p e ricard ium . Use the cadaver and an illustration to observe that the parietal layer of serous pericardium re ects onto the heart as the visce ral laye r o f se ro us p e ricard ium (e p icard ium ) . The line of re ection of parietal serous pericardium to visceral serous pericardium occurs at the roots of the great vessels. [G 241; L 178; N 209; R 279] 8. Use your ngers to p alpate and observe the now visible p e ricard ial cavit y, a potential space between the parietal and visceral layers of the serous pericardium (FIG. 3.15). Norm ally, the p ericardial cavity contains only a thin lm of serous uid that lubricates the serous surfaces and allows free m ovem ent of the heart within the pericardium . 9. Place your right hand in the pericardial cavity with your ngers posterior to the heart in the o b liq ue p e ricard ial sin us and lift the heart gently while p ushing your ng ers superiorly until they are stopp ed by the re ection of serous pericardium (FIG. 3.16). [G 243; L 179; N 212; R 282] 10. Within the pericardial cavity, identify the sup e rio r ve n a cava , asce n d in g ao rt a , p ulm o n ary t run k, p ulm o n ary ve in s , and the in fe rio r ve n a cava (FIG. 3.15). 11. Push your right index nger posterior to the pulm onary trunk and ascending aorta, p roceeding from

CHAPTER 3

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85

Arch of aorta Left vagus nerve Right phrenic nerve and pericardiacophrenic vessels

First rib (cut) Left recurrent laryngeal nerve

Superior vena cava

Ligamentum arteriosum

Right lung (retracted)

Ascending aorta

Right auricle

Pulmonary trunk

Right atrium

Left auricle

Right border

Left lung (retracted) Left ventricle

Right coronary artery in coronary sulcus

Left border Anterior interventricular artery in anterior interventricular sulcus

Pericardium (cut) Diaphragm Inferior border Apex

Right ventricle

FIGURE 3.15

Anterior view of the heart in situ.

left to right, until your ngertip em erges between the sup erior vena cava and the ascending aorta. Your nger is in the t ran sve rse p e ricard ial sin us (FIG. 3.15). 12. Use your ngers to explore the lines of re ection of the serous p ericardium where the great vessels (aorta, pulm onary trunk, superior vena cava, inferior vena cava, and four pulm onary veins) enter and exit the heart (FIG. 3.16).

Ascending aorta Superior vena cava Transverse pericardial sinus

Left phrenic nerve and pericardiacophrenic vessels

13. Exam ine the surface of the heart and observe that the rig h t b o rd e r o f t h e h e art is form ed by the rig h t at rium . 14. Observe that the m ajority of the anterior surface of the heart and the in ferio r b o rd er are form ed by the rig h t ven t ricle and a sm all part of the left ven t ricle and that the left b o rd er is form ed by the left ventricle. 15. Though dif cult to see, the sup e rio r b o rd e r o f t h e h e art is form ed by the rig h t and le ft at ria

Superior limit of pericardium Pulmonary trunk Left lung (retracted)

Right lung (retracted)

Structures in root of lung

Right pulmonary veins

Left pulmonary veins Pericardium (cut)

Inferior vena cava Diaphragm

Oblique pericardial sinus

FIGURE 3.16 Inner surface of the posterior wall of the pericardium showing pericardial sinuses and re ections of the serous pericardium .

86

16.

17.

18. 19.

20.

21.

22.

23.

•

GRANT’S DISSECTOR

and auricle s . Note that the right, inferior, and left borders of the heart are easily seen on a chest radiograph. The superior heart border is not easily seen on a chest radiograph. Identify the ap e x o f t h e h e art on the inferior left side of the heart and observe that it is p art of the left ventricle. Note that the apex of the heart is norm ally located deep to the left fth intercostal space, approximately 9 cm lateral to the m idline. Identify the b ase o f t h e h e art form ed by the left atrium and part of the right atrium . Clinicians often refer to the em ergence of the great vessels from the heart as its base. External to the pericardium , identify the arch o f t h e ao rt a (FIG. 3.16). Use blunt dissection to identify and clean the le ft vag us n e rve where it crosses the left side of the aortic arch. Observe that the vag us n e rve descends within the thorax p osterior to the root of the lung, whereas the phrenic nerve passes anterior to the root of the lung. [G 272, 273; L 194, 195; N 227, 228; R 290, 291] Identify the initial portion of the le ft re curren t laryn g e al n e rve where it branches from the left vagus nerve inferior to the aortic arch and posterior to the ligam entum arteriosum (FIG. 3.16). Use your ngers to gently open the interval between the concavity of the aortic arch and pulm onary trunk and identify the lig am e n t um art e rio sum , connecting the left pulm onary artery to the inferior aspect of the arch of the aorta (FIG. 3.16). Replace the anterior thoracic wall into its correct anatom ical position. Use the cadaver and an illustration to project the outline of the heart to the surface of the thoracic wall. [G 218; L 172, 173; N 193; R 262]

CLIN ICA L CORRELATION

Pe ricard ium In am m atory diseases can cause uid to accum ulate in the pericardial cavity (pericardial effusion). Bleeding into the pericardial cavity (hem opericardium ) m ay result from penetrating heart wounds or from perforation of weakened heart m uscle following m yocardial infarction. Because the pericardium is com posed of brous connective tissue, it cannot stretch, thus uids that collect in the p ericardial cavity will com p ress the heart (cardiac tam p onade).

Re m o val o f t h e He art 1. Place a probe through the transverse pericardial sinus (FIG. 3.16). 2. Cut the ascen d in g ao rt a and the p ulm o n ary t run k anterior to the probe about 1.5 cm superior to the point where the aorta and pulm onary trunk em erge from the heart. 3. Cut the sup e rio r ve n a cava about 1 cm superior to its junction with the right atrium . 4. Lift the apex of the heart superiorly and cut the in ferio r ve n a cava close to the surface of the diap hragm . 5. Continue lifting the apex of the heart and cut the fo ur p ulm o n ary ve in s very close to the inner surface of the pericardial sac where they form the lateral boundaries of the oblique pericardial sinus (FIG. 3.16). 6. Cut the rem aining re ections of the serous pericardium from its posterior surface to the inner surface of the pericardial sac and rem ove the heart from the pericardial sac (FIG. 3.16). 7. Exam ine the posterior aspect of the pericardium and identify the op enings of eight vessels and the lines of the pericardial re ections (FIG. 3.16).

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Review the parts of the m ediastinum and state their boundaries. Review the attachm ents of the pericardium to the diaphragm and to the roots of the great vessels. Review the em bryonic origin of the transverse and oblique pericardial sinuses. Com pare the appearance and functional properties of the parietal and visceral serous pericardia to those of the parietal and visceral pleurae.

EXTERNAL FEATURES OF THE HEART Disse ct io n Ove rvie w Dissection of the heart will p roceed in two stages: The external features of the heart will be studied, including its vascular supp ly. The internal features of each cham ber of the heart will then be studied.

CHAPTER 3

Disse ct io n In st ruct io n s Surface Features [G 238, 239; L 180; N 211; R 262] 1. Examine the external surface of the heart and identify the coronary (atrioventricular) sulcus (L. sulcus, a groove; pl. sulci) coursing around the circumference of the heart, separating the atria from the ventricles (FIG. 3.15). 2. Identify the an t e rio r in t e rve n t ricular sulcus sep arating the right and left ventricles on the st e rn o co st al (an t e rio r) surface of the heart and observe that the right ventricle predom inantly form s the anterior surface of the heart. Note that the interventricular sulci indicate the location of the interventricular septum internally, which lies at a right angle to the coronary sulcus. 3. On the anterior surface of the heart, identify the rig h t auricle extending from the right atrium and the le ft auricle extending from the left atrium (FIG. 3.15). 4. Observe that left ventricle predom inantly form s the d iap h rag m at ic (in fe rio r) surface of the heart. 5. On the inferior surface of the heart, identify the o p e n in g o f t h e in fe rio r ve n a cava and the p o st e rio r in t e rve n t ricular sulcus running from the apex of the heart to the coronary sulcus. Note that the cardiac veins and coronary arteries are located in the coronary and interventricular sulci. 6. Observe that the le ft p ulm o n ary surface of the heart is form ed m ainly by the left ventricle and is aligned with the cardiac im pression of the left lung. 7. Observe that the rig h t p ulm o n ary surface of the heart is form ed m ainly by the right atrium . 8. Beginning superiorly, at the base of the heart, identify the rem aining portion of the ascen d in g ao rt a and, from a superior view, exam ine the ao rt ic se m ilun ar valve . Use a p robe to gently op en the aortic valve to view the connection of the aorta to the left ventricle through the aortic valve. 9. Identify the p ulm o n ary t run k on the left side of the aorta and, from a superior view, exam ine the p ulm o n ary valve . Use a probe to gently open the p ulm onary valve to view the connection of the pulm onary trunk to the right ventricle. 10. Identify the sup e rio r ve n a cava on the right side of the heart and observe that it is vertically aligned with the inferior vena cava on the inferior aspect of the right atrium .

THE THORAX

coronary sinus is a dilated p ortion of the venous system of the heart located in the coronary sulcus. 2. Use blunt dissection to clean the fat and portions of the ep icardium overlying the coronary sinus. Note that the coronary sinus is about 2 to 2.5 cm in length and opens into the right atrium . The opening of the coronary sinus will be seen when the internal features of the right atrium are dissected. 3. Use a probe to de ne the borders and surface of the coronary sinus and follow its path around the heart in the coronary sulcus to the point where it receives the g re at card iac ve in (FIG. 3.17B). 4. Use blunt dissection to follow the great cardiac vein onto the sternocostal surface of the heart. Along its path, observe that the g reat cardiac vein p asses deep to the arteries on the anterior aspect of the heart. Coronary sinus (ghosted) Superior vena cava

Oblique vein of left atrium (ghosted) Great cardiac vein

Anterior cardiac veins

Small cardiac vein Inferior vena cava

A

Middle cardiac vein (ghosted) Superior vena cava

Great cardiac vein Oblique vein of left atrium

Inferior vena cava

Coronary sinus

Card iac Ve in s [G 247; L 183; N 215; R 270] As you stud y the vessels of the heart, realize that they (and the fat that surrounds them ) are located between the visceral pericardium (epicardium ) and the m uscular wall of the heart. Because the card iac ve in s course super cial to the co ro n ary art erie s , they will be dissected rst. 1. Identify the co ro n ary sin us on the diap hragm atic surface of the heart (FIG. 3.17B). Observe that the

87

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Small cardiac vein

B

Posterior vein of left ventricle

Middle cardiac vein

FIGURE 3.17 Cardiac veins and coronary sinus. A. Anterior view. B. Posterior view.

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5. Clean the great cardiac vein suf ciently to verify its course from the apex of the heart toward the coronary sinus in the anterior interventricular sulcus (FIG. 3.17A). Note that additional veins assist in draining the left ventricle back to the great cardiac vein or coronary sinus. 6. In the posterior interventricular sulcus, identify and clean the m id d le card iac ve in and trace it to the coronary sinus. 7. Near the location of inferior vena cava, toward the term ination of the coronary sinus, identify the sm all card iac vein coursing laterally around the heart from the right (FIG. 3.17B). 8. Use a probe to dissect the sm all cardiac vein and follow it to the anterior surface of the heart where it courses along the inferior border of the heart (FIG. 3.17A). 9. On the anterior surface of the heart, identify the an t e rio r card iac ve in s , which bridge the atrioventricular sulcus between the right atrium and the right ventricle, and pass super cial to the right coronary artery (FIG. 3.17A). 10. Observe that m ost veins of the heart are tributaries to the coronary sinus, with the exception of the anterior cardiac veins, which drain the anterior wall of the right ventricle directly into the right atrium .

Co ro n ary Art e rie s [G 246; L 182; N 215; R 270] 1. Begin the dissection of the coronary arteries by observing the ao rt ic valve in the lum en of the ascending aorta. Identify the rig h t , le ft , and p o st e rio r se m ilun ar cusp s of the aortic valve and observe that behind each valve cusp is a sm all pocket called an ao rt ic sin us (rig h t , le ft , and p o st e rio r , respectively). 2. In the left aortic sinus, identify the o p e n in g o f t h e le ft co ro n ary art e ry by inserting the tip of a blunt p robe into the opening. On the surface of the heart, p alp ate the tip of the probe between the left auricle and the pulm onary trunk and observe that this is the initial portion of the left coronary artery. 3. Use blunt dissection to clean the left coronary artery b eginning at the ascending aorta inferior to the left auricle. Observe that the left coronary artery is q uite short and that it divides into the an t e rio r in t e rve n t ricular b ran ch and the circum e x b ran ch within the coronary sulcus (FIG. 3.18A). 4. Use blunt dissection to clean and follow the path of the an t erior in t erven t ricular b ran ch in the anterior interventricular sulcus toward the apex of the heart. Do not disrupt the great cardiac vein. Note that clinicians call the anterior interventricular branch of the left coronary artery the left a nterior descending (LAD) a rtery. 5. Use blunt dissection to clean and follow the circum ex b ran ch of t h e left coron ary art ery in the coronary sulcus around the left side of the heart (FIG. 3.18B).

6. Observe that the circum ex branch of the left coronary artery accom panies the coronary sinus in the coronary sulcus and has several unnam ed branches that supply the posterior wall of the left ventricle. 7. To begin the dissection of the rig h t co ro n ary art e ry, identify its opening in the right aortic sinus and then insert the tip of a probe into its opening. 8. On the surface of the heart, palpate the tip of the probe in the coronary sulcus between the right auricle and the ascending aorta and observe that this is the beginning of the rig ht coronary artery. 9. Elevate the right auricle and use blunt dissection to clean the right coronary artery. 10. Identify the an t e rio r rig h t at rial b ran ch , which arises close to the origin of the right coronary artery and

Ascending aorta Pulmonary trunk Sinuatrial (SA) nodal branch (ghosted) Site of SAnode Anterior right atrial branch Right auricle (ghosted) Right coronary artery

Right marginal branch of right coronary artery

Left coronary artery (ghosted) Left auricle (ghosted) Circumflex branch of left coronary artery (ghosted) Anterior interventricular branch (left anterior descending) of left coronary artery Left marginal branch of circumflex branch Apex

A

Left coronary artery (ghosted) Circumflex branch of left coronary artery Posterior left ventricular branch

SA nodal branch Right pulmonary veins Right coronary artery (ghosted) Site of atrioventricular (AV) node AVnodal branch (ghosted) Crux of heart

Posterior interventricular branch (posterior descending) of right coronary artery

B

FIGURE 3.18 Coronary arteries and their branches. A. Anterior view. B. Posterior view.

CHAPTER 3

11.

12.

13.

14.

15.

ascends along the anterior wall of the right atrium toward the superior vena cava. (FIG. 3.18A). Follow and clean the anterior right atrial branch as well as its sin uat rial n o d al b ran ch , which supplies the sinuatrial node. Follow the right coronary artery in the coronary sulcus and, if possible, preserve the anterior cardiac veins arching over the artery toward the right atrium . Identify and clean the rig h t m arg in al b ran ch of the right coronary artery, which usually arises near the inferior border of the heart where it accom p anies the sm all cardiac vein. Continue to follow and clean the right coronary artery in the coronary sulcus onto the diaphragm atic surface of the heart. Follow the right coronary artery until it reaches the posterior interventricular sulcus and gives rise to the p o st e rio r in t e rve n t ricular b ran ch , which accom panies the m iddle cardiac vein (FIG. 3.18B). Follow and clean the posterior interventricular branch toward the ap ex of the heart where it anastom oses with the anterior interventricular branch of the left coronary artery.

THE THORAX

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CLIN ICA L CORRELATION

Co ro n ary Art e rie s In ap proxim ately 75% of hearts, the right coronary artery gives rise to the p osterior interventricular branch and supplies the left ventricular wall and posterior p ortion of the interventricular septum , com m only referred to as right dom inance. In approxim ately 15% of hearts, the left coronary artery gives rise to the p osterior interventricular branch, a condition referred to as left d om inance. Other variations in the branching p attern of the coronary vessels account for the rem aining 10%.

16. Identify the crux o f t h e h e art , the point where the posterior interventricular sulcus m eets the coronary sulcus, and note that the art e ry t o t h e at rio ven t ricular n o d e arises from the rig ht coronary artery at this location (FIG. 3.18B). 17. Rem ove the rem aining fat and visceral pericardium from the surface of the heart to better visualize the heart vasculature.

Disse ct io n Fo llo w-up 1. Review the borders of the heart. 2. On the surface of the heart, review the boundaries and locations of the four cham bers. 3. Review the location of the coronary sulcus and interventricular sulci of the heart and nam e the vessels that course within them . 4. Trace the path of blood from the right aortic sinus to the coronary sinus, nam ing all vessels that are involved. 5. Trace the path of blood from the left aortic sinus to the apex of the heart and follow the venous return to the coronary sinus, nam ing all vessels that are involved.

INTERNAL FEATURES OF THE HEART Disse ct io n Ove rvie w The atria and ventricles of the heart will be opened and studied in the sequence that blood passes through the heart: rig h t at rium , rig h t ve n t ricle , le ft at rium , and le ft ve n t ricle . The cuts that will be perform ed are designed to preserve m ost of the vessels that have previously been dissected on the surface of the heart. The cham bers of the heart will contain clotted blood that m ust be rem oved in order to study their internal features. The clots will be hard and m ay need to be broken before they can be extracted. Observe the lab rules and regulations for discarding the clotted blood in the proper tissue containers. The following descriptions are based on the heart in the anatom ical position.

Disse ct io n In st ruct io n s Rig h t At rium [G 252; L 184; N 217; R 266] 1. Gently elevate the right auricle with a pair of forceps and use scissors to m ake a cut through the free edge of the right auricle near its sup erior border. Insert one blade of the scissors through the opening and m ake a short horizontal cut toward the right, below

the junction of the sup erior vena cava and the right atrium (FIG. 3.19, cut 1). 2. Next, cut inferiorly down through the lateral edge of the right atrium , stop ping sup erior to the junction with the inferior vena cava (FIG. 3.19, cut 2). 3. At the inferior extent of cut 2, m ake a short horizontal cut toward the left, stopp ing just short of the coronary sulcus (FIG. 3.19, cut 3).

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CLIN ICA L CORRELATION

Ascending aorta Superior vena cava

Fo ssa Ovalis The fossa ovalis is the rem nant of the foram en ovale. In fetal life, blood from the placenta is delivered to the heart by way of the inferior vena cava. This oxygen-rich and nutrient-rich blood is directed toward the foramen ovale, which allows direct passage into the left atrium . Bypassing the right ventricle enables the enriched fetal blood to reach the body without passing through the lungs.

Pulmonary trunk Left auricle

Cuts for right atrium

1 2 4

Cut for left ventricle

5 3

7 6

Inferior vena cava

Cuts for right ventricle

FIGURE 3.19 Cuts used to open the right atrium , right ventricle, and left ventricle of the heart.

4. Use a pair of forceps to grasp the free edge of the ap of atrial wall and g ently p ull it to the left to open the right atrium widely (FIG. 3.20). 5. Rem ove the blood clots from the right atrium using forceps and, if p erm itted, take the heart to the sink to rinse the right atrium with water. 6. On the inner surface of the anterior wall of the right atrium , identify the pectinate m uscles forming horizontal ridges directed at the crista term inalis, a vertical ridge of muscle connecting the pectinate muscles (FIG. 3.20).

Right auricle

Superior vena cava

Pectinate muscles Crista terminalis

Site of: Sinuatrial node Atrioventricular node

Rig h t Ve n t ricle [G 253; L 184; N 217; R 269]

Limbus fossa ovalis Fossa ovalis Valve of inferior vena cava Inferior vena cava

7. On the superior aspect of the right atrium , identify the o p e n in g o f t h e sup e rio r ve n a cava . 8. Identify the op e n in g an d valve o f t h e in fe rio r ve n a cava on the inferior asp ect of the right atrium (FIG. 3.20). 9. On the p o st e rio r wall o f t h e rig h t at rium , identify the o p e n in g an d valve o f t h e co ro n ary sin us . Insert a probe into the opening of the coronary sinus and verify its location within the coronary sinus along the coronary sulcus. 10. On the m edial asp ect of the right atrium , identify the fo ssa o valis , a sm all depression on the in t e rat rial se p t um , and observe its relative location inferior to the thickened ridge of the lim b us fo ssa o valis (L. lim bus, a border) (FIG. 3.20). 11. Parts of the co n d uct in g syst e m o f t h e h e art are located in the walls of the right atrium but cannot b e seen in dissection. The sin uat rial n o d e (SA node) lies at the superior end of the crista term inalis at the junction between the right atrium and the superior vena cava, whereas the at rio ve n t ricular n o d e (AV node) is located in the interatrial septum above the opening of the coronary sinus (FIG. 3.20). 12. Identify the opening of the rig h t at rio ve n t ricular valve , which leads into the right ventricle, and use a probe to observe the path of blood from the right atrium to the right ventricle.

Valve of coronary sinus

Opening of right atrioventricular valve

FIGURE 3.20 Interior of the right atrium showing approxim ate locations of the sinuatrial and atrioventricular nodes. Anterior wall re ected to the left.

1. Use a probe or your nger to determ ine the level of the p ulm o n ary valve in the pulm onary trunk. 2. Use scissors or a scalpel to m ake a short horizontal cut through the an t e rio r wall o f t h e rig h t ve n t ricle im m ediately inferior to the level of the pulm onary valve (FIG. 3.19, cut 4). 3. Insert one blade of the scissors into the right end of cut 4 and m ake a cut parallel to the coronary sulcus about 1 cm from the coronary sulcus, ending at the inferior border of the heart (FIG. 3.19, cut 5). While beginning the cut, verify the thickness of the ventricular wall to ensure the atrioventricular valve cusp is not cut on the deep surface.

CHAPTER 3

4. Insert your nger through the opening in the ventricular wall and palp ate the in t e rve n t ricular se p t um using the LAD as a guide. 5. From the left end of cut 4, m ake a cut toward the inferior border of the heart about 2 cm to the right of the anterior interventricular sulcus, parallel to the right side of the interventricular septum , to a level just above the right m argin of the heart (FIG. 3.19, cut 6). 6. Use your ngers or a pair of forceps to turn the ap of the right ventricular wall inferiorly (FIG. 3.21). 7. Within the right ventricle, use forceps to carefully rem ove blood clots. Once the clots have been rem oved, gently rinse the right ventricle with water to rem ove any rem aining loose m aterial. 8. Identify the o p e n in g o f t h e rig h t at rio ve n t ricular valve or t ricusp id valve and observe that it has t h re e cusp s: an t e rio r , se p t al, and p o st e rio r , which are nam ed for their resp ective locations (FIG. 3.21). 9. Identify the ch o rd ae t e n d in e ae and observe that these delicate tendons p ass from the valve cusp s to the apices of p ap illary m uscle s arising from the walls of the right ventricle. 10. Identify the t h ree p ap illary m uscles beginning with the an t erior p ap illary m uscle , which is the largest and easiest to identify. The sep t al p ap illary m uscle is very sm all and m ay actually be m ultiple sm aller m uscles arising from the interventricular septum , whereas the

11.

12.

13.

14.

15.

Aorta

THE THORAX

Right auricle

R

A L Conus arteriosus

Right atrium Right atrioventricular valve: Anterior cusp

Septal papillary muscle Interventricular septum

Septal cusp Posterior cusp Chordae tendineae

Septomarginal trabecula

Posterior papillary muscle Anterior papillary muscle Trabeculae carneae

FIGURE 3.21

91

p ost erior p ap illary m uscle lies deep within the cham ber. Note that the chordae tendineae of each papillary muscle attach to the adjacent sides of two valve cusps. Id entify the t rab e culae carn e ae (L. trabs, wooden beam ; carneus, eshy), the roughened m uscular rid ges on the inner surface of the wall of the right ventricle. Id entify the se p t o m arg in al t rab e cula (m o d e rat o r b an d ) near the inferior extent of the right ventricle arching from the interventricular septum to the base of the anterior papillary m uscle. Note that the septomarginal trabecula contains the part of the right bundle of the conducting system that stim ulates the anterior papillary m uscle. Id entify the o p e n in g o f t h e p ulm o n ary t run k superiorly within the right ventricle and observe the sm ooth cone-shap ed region nam ed the co n us art erio sus , or in fun d ib ulum , inferior to the opening (FIG. 3.21). Observe that the p ulm o n ary valve consists of t h re e se m ilun ar cusp s: an t e rio r , rig h t , and le ft (FIG. 3.21). [G 256, 257; L 184; N 219; R 267] Look into the pulm onary trunk from a superior view and exam ine the superior surface of the pulm onary valve. Observe that each sem ilunar valve cusp has one brous n o d ule and two lun ule s , which help to seal the valve cusp s and prevent back ow of blood during diastole.

Pulmonary trunk

Superior vena cava

•

Interior of the right ventricle. Anterior wall re ected inferiorly.

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Le ft At rium [G 254; L 185; N 218; R 266] 1. Exam ine the posterior surface of the heart and observe the openings of the fo ur p ulm o n ary ve in s into the left atrium . The pulm onary veins are usually arranged in pairs: two from the right lung and two from the left lung. 2. Use scissors to m ake an inverted U-shaped cut through the posterior wall of the left atrium using the op enings of the p ulm onary veins as reference points laterally (FIG. 3.22). 3. Use a pair of forceps to grasp the free edge of the ap and gently p ull it inferiorly. 4. Rem ove the large blood clots within the left atrium and then gently rinse out any rem aining clots with water. 5. Id en tify th e o p e n in g in t o t h e le ft a u ricle an d o b serve p ectin ate m uscles on th e in n er surface o f th e wall. Note th at th e rest of th e left atrium is sm ooth . 6. Identify the valve o f t h e fo ram e n o vale o n t h e in t e rat rial se p t um in the left atrium (FIG. 3.22). 7. Place your n g er on th e surface of th e in teratrial sep tum with in th e left atrium , an d your th um b on th e surface of th e in teratrial sep tum with in th e rig h t atrium , an d verify th e relative th in n ess of th e fossa ovale com p ared to th e rest of th e in teratrial sep tum . 8. Identify the o p e n in g o f t h e le ft at rio ve n t ricular valve and use a probe to observe the p ath of blood from the left atrium to the left ventricle.

Left pulmonary a.

Le ft Ve n t ricle [G 255; L 185; N 218; R 266] The following procedure will cut the anterior interventricular branch of the left coronary artery and the great cardiac vein. Alternate ap proaches m ay be taken to spare these vessels. 1. Look into the aorta from a superior view and identify the aort ic valve and its t h ree sem ilun ar valve cusp s: rig h t , left , and p ost erior . [G 256, 257; L 185; N 217, 219; R 267] 2. Insert one blade of the scissors between the left and right sem ilunar cusp s and m ake a cut inferiorly through the anterior wall of the ascending aorta anterior and parallel to the left coronary artery (FIG. 3.19, cut 7). 3. Cut through the junction of the ascending aorta and left ventricle and bisect the anterior interventricular branch of the left coronary artery and the great cardiac vein. 4. Continue the cut to the apex of the heart about 2 cm to the left of the anterior interventricular sulcus, m aking it parallel to the left side of the interventricular septum . 5. Open the left ventricle and the ascending aorta widely (FIG. 3.23). 6. Use forceps to carefully rem ove blood clots in the left ventricle. Once the m ajority of the clots have been rem oved, gently rinse the left ventricle with water to rem ove the rem aining clots. 7. In the left ventricle, identify the le ft at rio ve n t ricular valve (b icusp id valve , m it ral valve ) . Distinguish the an t e rio r cusp from the p o st e rio r cusp (FIG. 3.23).

Aorta

Pulmonary trunk

Ascending aorta (opened) Posterior cusp of aortic valve: Lunule Nodule

Left auricle Superior vena cava

Left ventricle

Valve of foramen ovale Left pulmonary veins

Pulmonary trunk

Aortic sinus (behind valve cusp)

Opening of right coronary artery

Opening of left coronary artery Left cusp of aortic valve

Right cusp of aortic valve

Chordae tendineae

Right pulmonary vv. Left atrium Inferior vena cava Coronary sinus

Posterior wall of left atrium (reflected)

Interior of the left atrium . Posterior wall reFIGURE 3.22 ected inferiorly.

Anterior papillary muscles

Interventricular septum: Membranous part Muscular part

Anterior cusp of left atrioventricular valve

Posterior papillary muscle Trabeculae carneae

FIGURE 3.23

Left atrioventricular orifice Posterior cusp of left atrioventricular valve Left ventricle Apex of heart

Interior of the left ventricle. Oblique view.

CHAPTER 3

8. Identify the anterior pap illary m uscle and the posterior p apillary m uscle and observe that the chordae tendineae of each papillary muscle attach to both valve cusps. 9. Observe that the inner surface of the wall of the left ventricle is roughened by t rab e culae carn e ae . 10. Exam ine the sp lit ao rt ic valve and identify its rig h t , le ft , and p o st e rio r sem ilun ar cusp s observing that each has one nodule and two lunules. 11. Superior to the aortic valve, identify the openings of the coron ary arteries and study their relationship to the sem ilunar valve cusps and the aortic sin uses. Note that the posterior cusp is also called the noncorona ry cusp because there is no coronary artery arising from its sinus. 12. Palpate the m uscular p art o f t h e in t e rve n t ricular se p t um and observe its thickness by placing the thum b of your right hand in the right ventricle and your index nger in the left ventricle.

THE THORAX

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93

13. Move your thum b and index nger superiorly along the interventricular sep tum and palp ate the thin m e m b ran o us p art o f t h e in t e rve n t ricular se p t um inferior to the attachm ent of the right cusp of the aortic valve. 14. Use an illustration to stud y the co n d u ct in g syst e m o f t h e h e a rt [G 2 5 0 ; L 1 8 7 ; N 2 2 2 ; R 2 6 9 ] . Recall that the SA nod e is in the wall of the rig ht atrium , at the sup erior end of the crista term inalis near the sup erior vena cava. Im p ulses from the SA nod e p ass throug h the wall of the rig ht atrium to the AV n o d e , which then p ass in the AV b un d le throug h the m em b ranous p art of the interventricular sep tum . Sub seq uently, the AV b und le d ivid es into rig h t a n d le ft b u n d le s , which lie within the m uscular p art of the interventricular sep tum and stim ulate the ventricles to contract.

Disse ct io n Fo llo w-up 1. Review the internal features of each of the cham bers of the heart. 2. Review the course of blood as it passes through the cham bers and valves of the heart beginning in the superior vena cava and ending in the ascending aorta. 3. Review the connections of the great vessels to the heart. 4. Use an illustration to review the conducting system of the heart and relate the illustration to the dissected specim en. 5. Replace the heart into the thorax in its correct anatom ical position. Return the anterior thoracic wall to its anatom ical position. Use an illustration, a textbook description, and the dissected specim en to project the heart valves to the surface of the anterior thoracic wall. 6. Read a description of the auscultation point used to listen to each heart valve. Locate each auscultation point on the anterior thoracic wall and then lift the anterior thoracic wall to observe the location of the auscultation point relative to the heart.

SUPERIOR MEDIASTINUM Disse ct io n Ove rvie w The superior m ediastinum is located sup erior to the plane connecting the sternal angle anteriorly and the intervertebral disc between vertebral bodies T4 and T5. The superior m ediastinum contains structures that pass between the thorax and the neck, the thorax and the upp er lim b, or the thorax and the abdom en, including several of the great vessels and their prim ary branches, the trachea, the esophagus, and the thoracic duct. The order of dissection will be as follows: The brachiocephalic veins will be studied and cleaned to exp ose the aortic arch. The aortic arch and the p roxim al ends of its branches will be dissected. The d istal parts of these vessels will be dissected with the neck or the upp er lim b. The trachea and its bifurcation will be studied. The upp er part of the esophagus and the vagus nerves will be dissected.

Disse ct io n In st ruct io n s Sup e rio r Me d iast in um 1. Review the b o un d arie s o f t h e sup e rio r m e d iast in um beginning with the sup e rio r b o un d ary of the sup erior thoracic ap erture and the in fe rio r b o un d ary of the p lane of the sternal angle. The an t e rio r b o un d ary of the superior m ediastinum is

the m anub rium of the sternum , and the p o st e rio r b o un d ary is the bodies of vertebrae T1–T4. Laterally, the sup erior m ediastinum is bound by right and left m ediastinal pleurae (FIG. 3.13). 2. Rem ove the anterior thoracic wall. 3. Identify the t h ym us , an organized fatty m ass that lies im m ediately posterior to the m anubrium of the sternum . The thym us can be recognized in the cadaver by

94

4.

5. 6.

7.

8.

9.

10.

11.

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GRANT’S DISSECTOR

the thym ic veins on its posterior surface, which drain to the brachiocephalic veins. In the newborn, it is an active lym phatic organ that can be easily visualized on a chest radiograph. [G 258–261; L 177; N 209; R 278] Re ect superiorly the thin layer of m uscles extending from the neck down into the superior aspect of the superior m ediastinum . Rem ove the thym us from the superior m ediastinum by blunt dissection. Identify and clean the sup e rio r ve n a cava and follow it superiorly until its two tributaries, the left an d rig h t b rach io ce p h alic ve in s , are visible (FIG. 3.24). Note that the two brachiocephalic veins m eet to form the superior vena cava posterior to the inferior border of the right rst costal cartilage. Use blunt dissection to clean the left and rig ht brachiocephalic veins and free them from the structures that lie posterior. Follow the sup erior vena cava inferiorly and ob serve that it p asses anterior to the sup erior asp ect of the root of the rig ht lung . [G 272; L 179, 194; N 227; R 29 0] Identify and clean the azyg o s ve in on the right side of the m ediastinum . Observe that the arch o f t h e azyg o s ve in p asses superior to the root of the right lung and drains into the posterior side of the superior vena cava. Cut the left brachiocephalic vein just lateral to the superior vena cava and re ect the sup erior vena cava and the attached right brachiocephalic and azygos veins to the right. Re ect the left brachiocephalic vein superiorly and to the left. Identify the rig h t and le ft p h re n ic n e rve s where they were previously dissected in the m iddle m ediastinum .

Right internal jugular vein and right common carotid artery Right phrenic nerve Right vagus nerve Right subclavian artery and vein Right recurrent laryngeal nerve Brachiocephalic trunk Right and left brachiocephalic veins

Left common carotid artery and left internal jugular vein

14.

15.

16.

17.

18.

19.

20.

21.

22.

Left vagus nerve Left subclavian artery and vein Thoracic duct Left recurrent laryngeal nerve Ligamentum arteriosum Arch of aorta Pulmonary trunk

Azygos vein

Thoracic aorta Esophagus Esophageal plexus

Diaphragm

13.

Left phrenic nerve

Superior vena cava Right phrenic nerve

12.

Left phrenic nerve

FIGURE 3.24 Relationship s of the phrenic nerves and the vagus nerves to the great vessels in the superior m ediastinum .

23.

Recall that the phrenic nerves pass anterior to the roots of the right and left lungs, respectively. Follow the p hrenic nerves superiorly and observe that they pass posterior to the brachiocephalic veins (FIG. 3.24). Clean the phrenic nerves along their full extent, from the level of the thoracic inlet to where they enter the superior surface of the diap hragm , and dem onstrate that they accom p any the p ericardiacop hrenic vessels. Identify and clean the arch o f t h e ao rt a , which begins and ends at the level of the sternal angle (FIG. 3.24). [G 273; L 179, 195; N 228; R 291] On the superior aspect of the arch of the aorta, identify and clean its branches, from anterior to p osterior, the b rach io ce p h alic t run k, the le ft co m m o n caro t id art e ry, and the le ft sub clavian art e ry. Identify the ligam entum arteriosum , the brous cord that connects the concavity of the arch of the aorta to the left pulm onary artery (FIG. 3.24). Identify the left vag us n e rve and the le ft re curre n t laryn g e al n e rve on the left side of the arch of the aorta. Note the relationship of the left recurrent laryngeal nerve to the ligam entum arteriosum (FIG. 3.24). Follow and clean the left vagus nerve inferiorly and note that it p asses p osterior to the root of the left lung along its path toward the esophagus. On the right side of the sup erior m ediastinum , note that the rig h t vag us n e rve passes posterior to the root of the right lung (FIG. 3.25). Identify and clean the inferior aspect of the rig h t re curre n t laryn g e al n e rve , a branch of the right vagus nerve, which loop s around the right subclavian artery. Note that if the right upper lim b has not been dissected, the right subclavian artery will not be readily visible. Identify the t rach e a and observe that the esop hagus lies directly posterior to it in the superior m ediastinum . Do not attem pt to dissect it. At the plane of the sternal angle, identify the b ifurcat io n o f t h e t rach e a into the rig h t m ain b ro n ch us and the le ft m ain b ro n ch us . Use blunt dissection to clean these structures. Observe that the arch of the azygos vein passes superior to the right m ain bronchus and the arch of

CLIN ICA L CORRELATION

Le ft Re curre n t Laryn g e al Ne rve The left recurrent laryngeal nerve has a close relationship to the aortic arch as it passes through the superior m ediastinum . In cases of m ediastinal tum ors or an aneurysm of the aortic arch, the left recurrent laryngeal nerve m ay be com pressed. Com pression of the left recurrent laryngeal nerve results in paralysis of the left vocal fold and hoarseness.

CHAPTER 3

Right recurrent laryngeal nerve Right vagus nerve Trachea

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Esophagus

CLIN ICA L CORRELATION

Left vagus nerve

Bifurcat io n o f t h e Trach e a During bronchoscopy, the carina serves as an im portant landm ark because it lies between the superior ends of the rig ht and left m ain bronchi. The carina is usually positioned slightly to the left of the m edian plane of the trachea. When foreign bodies are aspirated , they usually enter the right m ain bronchus because it is wider and m ore vertically oriented than the left m ain bronchus.

Left recurrent laryngeal nerve

Arch of azygos vein

Ligamentum arteriosum

Root of right lung

Root of left lung

Azygos vein

THE THORAX

Cardiac plexus Esophageal plexus

Thoracic duct

Diaphragm

Anterior and posterior vagal trunks

FIGURE 3.25 Branches of the arch of the aorta. The m ajor veins have been rem oved.

the aorta p asses superior to the left m ain bronchus (FIG. 3.25). 24. Look for t rach e o b ro n ch ial lym p h n o d e s located b etween the two m ain bronchi at the bifurcation of the trachea. 25. Palpate the anterior and posterior surfaces of the trachea near its bifurcation. You can feel that the t rach e al rin g s are C-shaped with the op en part of the “C” located p osteriorly.

26. Observe that the esophagus is located posterior to the trachea in close relationship to the op en part of the tracheal cartilages. 27. Com pare the rig ht and left m ain bronchi and observe that the right m ain bronchus is larger in diam eter, shorter, and oriented m ore vertically than the left m ain bronchus. 28. Use an im age to study the inner surface of the tracheal bifurcation or carefully m ake an inverted “Y”-shaped cut following the branching pattern of the m ain bronchi. Observe that inside the trachea, at the inferior border of the tracheal bifurcation, is a ridge of cartilage called the carin a (L. carina , keel-shaped ridge). 29. Identify and clean the pulm onary trunk to its bifurcation point into the rig h t an d le ft p ulm o n ary art e rie s . Observe that the right pulm onary artery p asses posterior to the superior vena cava and that the left pulm onary artery passes anterior to the d e sce n d in g (t h o racic) ao rt a (FIG. 3.25).

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Replace the contents of the superior m ediastinum into their correct anatom ical positions. Review the form ation of the superior vena cava and the position of the arch of the azygos vein. Review the position of the ascending aorta, the arch of the aorta, and its branches. Com pare the positions of the phrenic and vagus nerves relative to the root of the lung. Contrast the thoracic course of the left recurrent laryngeal nerve with the cervical course of the right recurrent laryngeal nerve. Relate these differences in pathway to the em bryonic origin of the arteries. 6. Return the anterior thoracic wall to its correct anatom ical position and project the structures of the superior m ediastinum to the surface of the thoracic wall.

POSTERIOR MEDIASTINUM Disse ct io n Ove rvie w The p osterior m ediastinum lies posterior to the pericardium and contains structures that course between the neck and thorax and between the thorax and abdom en. To em phasize their close relationship to the heart, the structures in the posterior m ediastinum will be approached through the p o st e rio r wall o f t h e p e ricard ium . The order of dissection will be as follows: The pericardium will be reviewed and its posterior wall rem oved. The esop hagus will be studied. The azygos vein and its tributaries will be studied. The thoracic duct will be identi ed. The descending aorta and its branches will be dissected. The thoracic portion of the sym pathetic trunk and its branches will be dissected.

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Disse ct io n In st ruct io n s Po st e rio r Me d iast in um

11.

1. The p o st erio r m e d iast in um has its sup e rio r b o un d ary at the plane of the sternal angle, its in fe rio r b o un d ary at the diaphragm , its an t e rio r b o un d ary at the pericardium , its p osterior boundary at the bodies of vertebrae T5–T12, and its lat e ral b o un d arie s at the right and left m ediastinal p leurae (FIG. 3.13). 2. Review the inner surface of the posterior wall of the pericardium (FIG. 3.16). 3. Place the heart in the pericardial cavity and exam ine the relationship of the heart to the esop hagus from the right side of the thorax. Note that the esophagus lies im m ediately posterior to the left atrium and part of the left ventricle. 4. Rem ove the heart from the pericardial cavity. 5. Use your ngers to gently separate the esophagus from the posterior aspect of the pericardium . 6. Use scissors to carefully m ake a vertical cut through the posterior wall of the p ericardium in the are a o f t h e o b liq ue p e ricard ial sin us (FIG. 3.26). 7. Spread the posterior wall of the pericardium and identify the e so p h ag us , a m uscular tube just to the right of the m idline. 8. Identify the large t h o racic ao rt a to the left and slightly p osterior to the esophag us coursing inferiorly through the posterior m ediastinum . 9. Use blunt dissection to elevate and re ect the rem ainder of the posterior wall of the pericardium leaving the portion adhering to the diap hragm undisturbed. 10. Use scissors to cut the pericardium near its attachm ents to the great vessels and diaphragm and place

Pulmonary trunk Aortic arch

12.

13.

14.

15.

16.

17.

18.

Left main bronchus

Superior vena cava

Left lung (retracted)

Right main bronchus Right pulmonary veins

Left pulmonary veins Right lung (retracted)

Thoracic aorta

Azygos vein

19. 20.

Esophagus

Mediastinal pleura (cut)

Phrenic nerve and pericardiacophrenic vessels

Posterior intercostal veins and arteries Inferior vena cava Thoracic duct

Pericardium (cut edge) Esophageal plexus on esophagus

FIGURE 3.26 Structures located posterior to the heart and pericardium . The p ericardium has been rem oved.

21.

the pericardium in the tissue container. [G 274; L 196; N 229; R 284] Use blunt dissection to clean the e so p h ag us and observe that the surface of the esophagus is covered by the e so p h ag e al p le xus o f n e rve s , which innervates the inferior portion of the esophag us (FIG. 3.26). Find the rig h t vag us n e rve where it crosses the anterior surface of the right subclavian artery and follow it posterior to the root of the right lung. Use blunt dissection to dem onstrate that the bers of the right vagus nerve sp read out on the surface of the esophagus (FIG. 3.25). Identify the le ft vag us n e rve as it crosses the left side of the arch of the aorta and follow it posterior to the root of the left lung. Use blunt dissection to dem onstrate that its bers contribute to the esop hageal plexus (FIG. 3.25). Note that the esophageal plexus condenses to form the an t erior vag al t run k on the anterior surface of the esophagus and the p o st erio r vag al t run k on the posterior surface of the esophagus, just superior to the esophageal hiatus in the diaphragm (FIG. 3.25). Note that due to the curvature of the diaphragm, the vagal trunks may not be visible at this stage of the dissection. Identify the azyg o s vein where it arches superior to the root of the right lung and follow it inferiorly to the level of the diap hragm (FIGS. 3.25 and 3.27). Clean the azygos vein on the right side of the thorax as well as the p o st erio r in t erco st al ve in s , which drain into it. [G 270; L 194, 198; N 234; R 289] Retract the esophagus to the left and explore the area between the azyg o s ve in and the t h o racic ao rt a and identify the t h o racic d uct , which has the appearance of a sm all vein without blood in it (FIG. 3.27). Observe that the thoracic duct lies p osterior to the esophagus between the azygos vein and the aorta. Use b lunt dissection to carefully free the thoracic duct from the surrounding connective tissue, paying attention because it is thin walled and easily torn. Note that the thoracic duct m ay be a network of several smaller ducts instead of a single duct. [G 268; L 199; N 295; R 287] Follow the thoracic duct inferiorly to where it passes through the diap hragm with the thoracic aorta. Observe that the thoracic duct crosses the anterior surface of the rig h t p ost erior in t ercost al art eries , the h e m iazyg os vein , and the accessory h e m iazyg os vein . Note that superiorly, the thoracic duct terminates by draining into the junction of the left internal jugular vein and left subclavian vein. Do not attempt to demonstrate its superior termination at this time (FIG. 3.27). On the left side of the posterior thorax, clean the h e m iazyg os vein inferiorly and the acce sso ry h e m iazyg o s vein superiorly. Identify and clean a few posterior intercostal veins that drain into the azygos system .

CHAPTER 3

THE THORAX

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97

Thoracic duct Left brachiocephalic vein Superior vena cava

Left superior intercostal vein

Arch of azygos vein

Esophageal veins (cut)

Azygos vein Right posterior intercostal veins Sympathetic trunk

Accessory hemiazygos vein Innermost intercostal muscles Left posterior intercostal veins Hemiazygos vein

Thoracic splanchnic nerves: Greater Lesser Least Subcostal vein (cut)

Thoracic aorta (ghosted) Thoracic duct 12th rib

FIGURE 3.27 Contents of the posterior m ediastinum . The esophagus and diap hragm have been rem oved and the thoracic aorta is ghosted to expose the veins and thoracic duct.

22. Follow the hem iazygos and accessory hem iazygos veins across the bodies of the eighth and ninth thoracic vertebrae, respectively, and observe that they term inate by draining into the azygos vein. Note that variations of the azygos system are comm on. 23. Exam ine the branches of the t h o racic ao rt a . Identify and clean the e so p h ag e al art e rie s on the deep surface of the esophagus and the le ft b ro n ch ial art e rie s coursing along the m ain bronchi (if visible). Note that these sm all arteries are unpaired vessels that arise from the anterior surface of the aorta and are distinguished by their area of distribution. 24. Dissect one pair of p o st e rio r in t e rco st al art e rie s (right and left) and follow them to their intercostal sp ace. Observe that the right p osterior intercostal arteries cross the m idline on the anterior surface of the vertebral bodies and pass p osterior to all other contents of the posterior m ediastinum . 25. On b oth sides of the thorax, identify and clean one in t e rco st a l n e rve and follow it laterally until it d isap p ears p osterior to the in n e rm o st in t e rco st a l m u scle . 26. On both sides of the thorax, identify the sym p at h e t ic t run k (ch ain ) . 27. Starting high in the thorax, clean and follow the sym pathetic trunk inferiorly and observe that it crosses the heads of ribs 2 to 9.

28. Inferior to rib 9, observe that the sym pathetic trunk lies m ore anteriorly, on the sides of the thoracic vertebral bodies. [G 274; L 194, 195; N 236; R 290] 29. Observe that the sym pathetic trunk has one sym p at h et ic g an g lio n for each thoracic vertebral level (FIG. 3.27). 30. Dem onstrate that two ram i co m m un ican t e s (wh it e ram us co m m un ican s , g ray ram us co m m un ican s) connect each intercostal nerve with its corresponding thoracic sym p athetic ganglion. Note that during dissection, it is im possible to distinguish white and gray ram i from each other based on color, however, the m ore lateral of the two rami is the white ram us com municans. 31. Use a probe to clean the contributions to the g re at e r sp lan ch n ic n e rve s arising on both the rig ht and left sides from the respective sym pathetic trunk. Follow the contributions from the fth through the ninth thoracic sym pathetic ganglia on the lateral surfaces of vertebral bodies T5–T9 and observe that the greater sp lanchnic nerves are not com pletely form ed until lower thoracic levels (FIG. 3.27). 32. The le sse r sp lan ch n ic n e rve s arise from the 10th and 11th thoracic sym pathetic ganglia, and the le ast sp lan ch n ic n e rve s arise from the 12th thoracic sym pathetic ganglion (FIG. 3.27). Due to the curvature of the diaphragm , these two pairs of nerves cannot be seen at this tim e.

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Disse ct io n Fo llo w-up 1. Review the boundaries of the anterior, m iddle, and posterior m ediastina. 2. Study a transverse section through the m idlevel of the thorax and identify the contents of the posterior m ediastinum and observe the relationship of the contents of the posterior m ediastinum to the heart and vertebral bodies. 3. Review the course and function of an intercostal nerve, nam ing all structures that it innervates. 4. Review the parts of the aorta (ascending, arch, and thoracic), nam ing all branches derived from each region and their areas of distribution. 5. Review the origin and course of the right and left posterior intercostal arteries. 6. Nam e the structures in the posterior m ediastinum that cross anterior to the right posterior intercostal arteries.

CHAPTER 4

The Abdom en ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

h e abd om en is th e p ortion of th e tru n k between th e th orax an d th e p elvis. Su p eriorly, th e abdom in al cavity is p h ysically d ivid ed from th e th oracic cavity by th e diap h ragm . In feriorly, th e abd om in al cavity is con tin u ou s with th e p elvic cavity, an d th u s, th is region is com m on ly

T

referred to as th e abd om in op elvic cavity. Th e abdom in al organ s (viscera) are n ot bilaterally sym m etrical. Th erefore, it is worth n otin g th at u se of th e word s “righ t” an d “left” in n am es an d in stru ction s refers to th e righ t an d left sid es of th e cad aver in th e an atom ical p osition .

SUPERFICIAL FASCIA OF THE ANTEROLATERAL ABDOMINAL WALL Disse ct io n Ove rvie w Unlike the thoracic cavity where the contents were protected by the thoracic cage, the contents of the abd om inal cavity are not protected by bony structures. Although the m uscular anterolateral abdom inal wall offers less protection than the thoracic cage, it adds the bene t of increased body m ovem ent, and expansion and m otility that accom m odates changes in the internal organs. The organization of the layers form ing the anterolateral abdom inal wall is illustrated in FIGURE 4.1. The sup er cial fascia is unique in this region in that it form s two distinct layers: a super cial fat t y laye r called Cam p e r’s fascia and a deep m e m b ran o us laye r called Scarp a’s fascia . The m em branous layer is noteworthy b ecause it attaches to the fascia lata of the thigh and is continuous with nam ed fascias in the perineum . [G 299; L 218; N 248; R 217]

Skin Superficial fascia: Fatty layer (Camper’s) Membranous layer (Scarpa’s) External oblique m. Internal oblique m. Transversus abdominis m. Transversalis fascia Extraperitoneal fascia Parietal peritoneum

FIGURE 4.1

Layers of the anterior abdom inal wall.

Surface An at o m y The surface anatom y of the abdom en m ay be studied on a living subject or on a cadaver. Firm xation of tissues in the cadaver m ay m ake it dif cult to palpate abdom inal organs. To prepare patient notes, you will need to understand the term inology used to describe the abdom en. The quadrant and regional system s are both com m only used and rely on surface anatom y for p roper orientation. The q uadrant system is suitable for general descriptions and will be used to describe the position of organs in this dissection guide. [G 290; L 213; N 242] 1. With the cadaver in the supine p osition, p alp ate the xip h o id p ro cess in the m idline, just below the xip h ist e rn al jun ct io n (FIG. 4.2). 2. At the m idpoint of the abdom en, identify the um b ilicus . The q uad ran t syst e m divides the abdom en into four quadrants by a vertical line along the m edian plane and a horizontal line across the transum bilical plane. Note that the two lines intersect at the um bilicus (FIG. 4.3). 3. Trace your nger inferiorly along the m idline from the um bilicus to the p ub ic sym p h ysis .

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4. Palpate laterally from the pubic sym physis along the p ub ic cre st to the p ub ic t ub e rcle . 5. Use your nger to trace the path of the in g uin al lig am e n t from the p ubic tub ercle, superolaterally, to the palpable an t e rio r sup erio r iliac sp in e (ASIS) on the anterior aspect of the hip. 6. Use your nger to trace the planes used in the re g io n al syst e m to subdivide the abdom en. Begin with the vertical m id clavicular lin e s . Observe that the m idclavicular lines begin at the m idp oint of each clavicle and course inferiorly to the m idpoint between the ASIS and the p ubic tubercle, effectively bisecting each inguinal ligam ent (FIG. 4.4). 7. Progressing posteriorly from the ASIS, palpate the iliac cre st and the iliac t ub e rcle located on the superolateral asp ect of the ilium about 5 cm p osterior to the ASIS. The t ran st ub e rcular p lan e passes through the right and left iliac tubercles (FIG. 4.4). 8. Return to the xiphoid process and palpate bilaterally along the co st al m arg in to the lowest p alpable level. This is the location of the sub co st al p lan e (FIG. 4.4). 9. Refer to FIGURE 4.4 to review the nam es and locations of the nine abdom inal regions. Note that clinical com plaints m ay be more speci cally described using the regional system than the quadrant system , and thus, you should be fam iliar with both descriptive m ethods.

Xiphoid process Costal margin

Tubercle of the iliac crest Anterior superior iliac spine Pubic tubercle Pubic crest Pubic symphysis Inguinal ligament

FIGURE 4.2

Surface anatom y of the abdom en.

Midclavicular lines Median plane

Right upper quadrant

Left upper quadrant

Right hypochondriac

Epigastric

Left hypochondriac

Subcostal plane Right lumbar Transumbilical plane Right lower quadrant

FIGURE 4.3

Transtubercular plane Left lower quadrant

The four abdom inal quadrants.

Right inguinal

FIGURE 4.4

Umbilical Hypogastric (pubic)

Left lumbar

Left inguinal

The nine abdom inal regions.

CHAPTER 4

Disse ct io n In st ruct io n s Skin In cisio n s 1. Refer to FIGURE 4.5. 2. Make a m idline skin incision from the xiphisternal junction (C) to the pubic sym physis (E), encircling the um bilicus. 3. Make an incision from the xiphoid process (C) along the costal m arg in to a point on the m idaxillary line (V). Note that if the thorax has been dissected previously, this incision has already been made. 4. Make a skin incision beginning 3 cm inferior to the p ubic crest (E) running parallel to the line of the ing uinal ligam ent to a point 3 cm inferior to the ASIS. 5. Continue the incision posteriorly, 3 cm below the iliac crest to a point on the m idaxillary line (F). 6. Make a vertical skin incision along the m idaxillary line from point V to p oint F. Note that if the back has been dissected previously, this incision has already been made. 7. Make a transverse skin incision from the encircling cut around the um bilicus to each m idaxillary line. 8. Rem ove the skin, but not the super cial fascia, from m edial to lateral using either a pair of locking forceps or the buttonhole technique. At any point, the portions of skin m ay be cut into sm aller segm ents to facilitate rem oval. Detach the skin and place it in the tissue container.

C

THE ABDOMEN

101

Sup e r cial Fascia 1. Just lateral to the m idclavicular line, use blunt dissection to create a vertical cut through the super cial fascia about 7.5 cm lateral to the m idline (FIG. 4.6). Note that the super cia l epiga stric a rtery a nd vein are in the super cial fascia in this area but do not m ake a special effort to nd them . 2. Dissect through the super cial fascia down to the ap o n euro sis o f t h e e xt e rn al o b liq ue m uscle . 3. On the m edial side of the vertical cut, use your ngers to separate the super cial fascia from the aponeurosis of the external oblique m uscle (FIG. 4.6, arrow 1). 4. As you rem ove the super cial fascia inferior to the um bilicus, observe that its deep surface is brous connective tissue containing relatively little fat (Scarpa’s fascia) and its super cial layer is com posed alm ost entirely of fat (Cam per’s fascia). 5. As you approach the m idline, palpate the an t e rior cut an e o us n e rve s that enter the sup er cial fascia 2 to 3 cm lateral to the m idline. 6. Make an effort to clean and isolate at least one anterior cutaneous nerve from within the super cial fascia. Note that the abdominal anterior cutaneous nerves are branches of intercosta l nerves (T7–T11), the subcosta l nerve (T12), and the iliohypoga stric nerve (L1).

Superficial fascia: Fatty layer (Camper’s)

1

Membranous layer (Scarpa’s)

V

Umbilicus 2

External oblique aponeurosis

F

E

FIGURE 4.5

•

Skin incisions.

Inguinal ligament

FIGURE 4.6

Rem oval of the abdom inal super cial fascia.

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CLIN ICA L CORRELATION

Sup e r cial Ve in s o f t h e Ab d o m in al Wall The super cial epigastric vein anastom oses with the lateral thoracic vein in the super cial fascia of the abdom en, creating an im portant collateral venous channel from the fem oral vein to the axillary vein. In patients who have obstruction of the inferior vena cava or hepatic portal vein, the super cial veins of the abdom inal wall m ay be engorged and m ay becom e visible around the um bilicus (cap ut m e d usae ).

7. While rem oving the super cial fascia, consult a derm atom e chart [G 54; L 162; N 162; R 209] and note that T6 innervates the skin sup er cial to the xiphoid process, T10 innervates the skin of the um bilicus, T12 innervates the skin superior to the pubic

8.

9.

10.

11.

sym p hysis, and L1 innervates the skin overlying the pubic sym physis. [G 296; L 214; N 253; R 220] Lateral to the vertical cut m ade in step 1, use your ngers to separate the super cial fascia from the external oblique m uscle (FIG. 4.6, arrow 2). As you near the m idaxillary line, p alpate the lat e ral cut an e o us n e rve s entering the super cial fascia and clean the branches of at least one lateral cutaneous nerve. Note that the lateral cutaneous nerves are branches of intercostal and subcostal nerves. Rem ove the super cial fascia from superior to inferior and clearly dem onstrate the lower border of the external oblique m uscle. Extend the sup er cial fascia rem oval inferiorly to a point approxim ately 2.5 cm into the p roxim al thigh. Detach the super cial fascia from the m idline, m idaxillary line, and proxim al thigh and place it in the tissue container.

Disse ct io n Fo llo w-up 1. Use an illustration to review the distribution of the super cial epigastric vessels. 2. Review the abdom inal distribution of the anterior ram i of spinal nerves T6–L1.

MUSCLES OF THE ANTEROLATERAL ABDOMINAL WALL Disse ct io n Ove rvie w The rect us ab d o m in is m uscle form s the bulk of the anterior abdom inal wall from the fth rib sup eriorly to the pubic crest inferiorly. Between the right and left rectus abdom inis m uscles lies the m idline tendinous structure, the lin e a alb a . Because there are no bones in the anterior abdom inal wall, the linea alba serves as a site of m uscle attachm ent. Three at m uscles (e xt e rn al o b liq ue , in t e rn al o b liq ue , and t ran sve rsus ab d o m in is) form m ost of the anterolateral abdom inal wall. The three at m uscles have broad, eshy proxim al attachm ents (to the ribs, vertebrae, and pelvis) and broad, aponeurotic distal attachm ents (to the ribs, linea alba, and pubis). Each of the three at m uscles contributes to the form ation of the rectus sheath and the inguinal canal. In the m ale, the testes are housed in the scrotum , which is an outpouching of the anterior abdom inal wall. Each testis passes through the abdom inal wall during developm ent, dragging its ductus deferens behind it. The passage of the testis occurs through the in g uin al can al, which is located superior to the m edial half of the inguinal ligam ent, and extends from the sup e r cial (e xt ern al) in g uin al rin g to the d e e p (in t e rn al) in g uin al rin g . In the fem ale, the inguinal canal is sm aller in diam eter and less distinct. It m ust be noted that the structures form ing the inguinal canal are identical in the two sexes, but the contents of the inguinal canal differ. In the m ale, the inguinal canal contains the sp e rm at ic co rd , whereas in the fem ale, the inguinal canal contains the ro un d lig am e n t o f t h e ut e rus . Dissection instructions are referenced to m ale cadavers, but these instructions also ap ply to fem ale cadavers. The order of dissection will be as follows: The three at m uscles of the anterolateral abdom inal wall will be studied. Em phasis will be placed on the inguinal region. The com position and contents of the rectus sheath will be explored. The anterior abdom inal wall will be re ected.

Ske le t o n o f t h e Ab d o m in al Wall Use an articulated skeleton to identify the following structures (FIG. 4.7): [G 202, 200; L 215; N 243; R 381]

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Th o racic Cag e [G 204; L 163; N 184; R 202] 1. Identify the location of the xip h ist e rn al jun ct io n at the inferior border of the body of the sternum and the sup erior border of the xip h o id p ro ce ss . 2. On the lateral aspects of the xiphisternal junction, identify the co st al cart ilag e s of the false ribs m erging to form the co st al m arg in (FIG. 4.7).

Bo n y Pe lvis 1. In the m idline of the bony pelvis, identify the junction of the rig h t and le ft p ub ic b o n e s at the p ub ic sym p h ysis . 2. Identify the p ub ic cre st coursing laterally from the p ubic sym p hysis on the superior aspect of the pubic b ones. 3. On the lateral aspect of the pubic crest, identify the p ub ic t ub e rcle , which is the m edial attachm ent of the in g uin al lig am e n t . 4. The inguinal ligam ent courses from the pubic tubercle laterally and sup eriorly to the ASIS of the ilium . 5. Identify the ASIS and follow the bony ridge of the iliac cre st posteriorly toward the m idaxillary line and identify the iliac t ub e rcle (FIG. 4.7).

Disse ct io n In st ruct io n s Ex t e rn al Ob liq ue Muscle [G 296; L 216; N 245; R 214] 1. Clean any rem nants of the super cial fascia from the surface of the external obliq ue m uscles and p lace the fascia in the tissue container. 2. Observe the e xt e rn al o b liq ue m uscle and note that its bers course from superolateral to inferom edial (FIG. 4.8A). The investing fascia m ay be rem oved from the surface of the external oblique m uscle to b etter visualize the ber direction and extent of the m uscle, although in thinner cadavers, this m ay com p rom ise the stability of the m uscle. 3. Use blunt dissection to clean the aponeurosis of the external oblique m uscle and clearly delineate the se m ilun ar lin e (FIG. 4.8A). [G 300, 304; L 216, 220; N 245; R 221, 224] 4. Review the attachm ents and actions of the external oblique m uscle (see TABLE 4.1). 5. Clean the inferom edial portion of the external oblique aponeurosis and identify the opening of the sup e r cial in g uin al rin g form ed in the external oblique aponeurosis. Observe that the super cial inguinal ring p erm its the sp erm atic cord in the m ale, and round ligam ent of the uterus in the fem ale, to p ass from the inguinal canal into the suprapubic region (FIG. 4.8B).

Body of sternum Xiphisternal junction Costal cartilages

Xiphoid process

T11 T12

Costal margin

L1 L2

Ilium: Iliac crest Tubercle of iliac crest

L3

Iliac fossa

L4

Sacral promontory

L5

Sacrum

Anterior superior iliac spine Inguinal ligament

Iliopubic eminence

Pubic tubercle and pubic crest

FIGURE 4.7

Pubic symphysis

Skeleton of the anterior abdom inal wall.

6. At the m argins of the super cial inguinal ring, observe the thin layer of fascia that extends from the external obliq ue aponeurosis onto the sp erm atic cord. This is the ext e rn al sp erm at ic fascia , which is derived from the aponeurosis of the external oblique m uscle. 7. Identify the ilio in g uin al n erve em erging through the super cial inguinal ring, anterior to the sperm atic cord in the m ale, or the round ligam ent of the uterus in the fem ale (FIG. 4.8B). In the fem ale, the ilioinguinal nerve is a useful structure to verify the location of the sup er cial inguinal ring because the round ligam ent of the uterus m ay be quite sm all and dif cult to identify. Note that the ilioinguinal nerve supplies sensory innervation to the skin on the anterior surface of the external genitalia and the medial surface of the thigh. 8. Use a probe to identify the lat eral (in ferio r) crus dening the lateral m argin of the super cial inguinal ring (FIG. 4.8B). Observe that these bers arch around the sperm atic cord and attach to the pubic tubercle. 9. Identify the m e d ial (sup e rio r) crus de ning the m edial m argin of the super cial inguinal ring and observe that these bers attach to the pubic crest (FIG. 4.8B). 10. Identify the in t e rcrural b e rs , the delicate bers sp anning the crura superolateral to the sup er cial inguinal ring (FIG. 4.8B). Note that the intercrural bers prevent the crura from spreading apart.

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12. Insert a probe through the sup er cial inguinal ring into the inguinal canal and observe that the external oblique aponeurosis form s the anterior wall of the inguinal canal and that the inguinal ligam ent form s its oor. 13. Use an illustration to study the lacun ar lig am en t and observe that it is form ed at the m edial end of the inguinal ligam ent by bers that turn posteriorly and attach to the pecten pubis. [G 300; L 220, 221; N 254]

A

Linea alba Semilunar line External oblique m.

In t e rn al Ob liq ue Muscle [G 297; L 216; N 246; R 216]

Cut 2 Umbilicus

Cut 1 Anterior superior iliac spine

Cut 3

Inguinal ligament

Intercrural fibers

Superficial inguinal ring

B

Intercrural fibers Superficial inguinal ring Medial crus

Lateral crus Spermatic cord

Ilioinguinal n.

FIGURE 4.8 Cuts used to re ect the external obliq ue m uscle and the super cial inguinal ring.

11. Observe that the inferior bord er of the ap oneurosis of the external obliq ue m uscle curves posteriorly and thickens to form the in g uin al lig am e n t attaching from the ASIS to the pubic tubercle. Large vessels and nerves that pass between the abdom inal cavity and the lower lim b run deep to the inguinal ligam ent.

The internal oblique m uscle lies deep to the external oblique m uscle and form s the interm ediate layer of the anterolateral abdom inal wall. To exp ose the internal obliq ue m uscle, the external oblique m uscle will be partially transected and the resulting ap re ected inferiorly. 1. Make a vertical cut through the external oblique m uscle beginning at the ASIS and ending at the level of the um bilicus (FIG. 4.8A, cut 1). 2. Insert your ngers into cut 1 and carefully separate the m uscle layers. 3. Use scissors to m ake a horizontal cut across the external oblique m uscle stopping at the se m ilun ar lin e (FIG. 4.8A, cut 2). Note that your ngers cannot pass medial to the semilunar line because the external oblique aponeurosis fuses to the underlying internal oblique aponeurosis at this location. 4. Insert your ngers into cut 2 directing them inferiorly toward the inguinal ligam ent to sep arate the external oblique m uscle from the underlying internal oblique m uscle. 5. Use scissors to m ake a vertical cut through the external oblique ap oneurosis lateral to the sem ilunar line. Continue the cut inferiorly toward the sup er cial inguinal ring (FIG. 4.8A, cut 3). Make an effort to only cut the external oblique aponeurosis and none of the underlying layers. 6. Re ect the ap of external oblique m uscle inferiorly, using the inguinal ligam ent as a hinge to reveal the inguinal p ortion of the in t e rn al o b liq ue m uscle (FIG. 4.9). 7. Observe the upper portion of the internal oblique m uscle and note that its bers are arranged perpendicularly to the external oblique m uscle and course from superom edial to inferolateral (FIG. 4.9). [G 298; L 216; N 246; R 216] 8. Review the attachm ents and actions of the internal oblique m uscle (see TABLE 4.1). 9. Exam ine the exposed inferior portion of the internal oblique m uscle and observe that the lowest bers run transversely from the lateral half of the inguinal lig am ent and arch over the sperm atic cord (round ligam ent) to join with the ap oneurosis of the transversus abdom inis m uscle and attach

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105

Internal oblique m. Linea alba

Iliohypogastric n. Anterior superior iliac spine

Costal margin

Ilioinguinal n. External oblique m. (reflected)

Cut line

Deep inguinal ring (in transversalis fascia)

Internal abdominal oblique m.

Cremaster m.

External abdominal oblique m. (reflected)

Inferior epigastric vessels (deep to transversalis fascia)

Iliohypogastric n. Ilioinguinal n.

Deep inguinal ring

Inguinal ligament

Conjoint tendon

Cremaster m.

Lacunar ligament Spermatic cord (retracted) Pecten pubis Conjoint tendon

FIGURE 4.9 Exposed ing uinal canal and internal obliq ue in the inguinal region.

10.

11.

12.

13.

to the pecten pubis. Note that the arching bers of the internal oblique m uscle form part of the roof of the inguinal canal and that the aponeurotic insertion of these bers form s part of the posterior wall of the inguinal canal at the conjoint tendon (FIG. 4.9). Identify the cre m ast e r m uscle an d fascia . The crem aster is a sm all bundle of m uscle bers connecting from the internal obliq ue m uscle to the sperm atic cord in the m ale, or the round ligam ent of the uterus in the fem ale (FIG. 4.9). Identify the ilio in g uin al n e rve coursing in the interm uscular plane between the external oblique and the internal obliq ue m uscles within the inguinal canal. Observe that the ilioinguinal nerve runs p arallel and inferior to the ilio h yp o g ast ric n e rve and can be d ifferentiated from it because it em erges through the super cial inguinal ring (FIG. 4.9). The easiest point of separation of the anterolateral abdom inal wall m uscles is laterally near the m idaxillary line where the m uscles are thickest. Using the lateral vertical cut through the external oblique m uscle as a guide, continue to cut through the external oblique m uscle superiorly toward the costal m argin. Make an incision through the external oblique m uscle about 2 cm superior to the inferior edge of the costal m argin and cut m edially, keeping the cut parallel to its curvature. Continue the cut m edially through the m uscle bers stopping at the point where the m uscle becom es aponeurotic (FIG. 4.10).

Spermatic cord (retracted)

Superficial inguinal ring

FIGURE 4.10 The internal oblique m uscle shown deep to the re ected external oblique m uscle.

14. Grasp the free edge of the external oblique m uscle and use your ngers to separate it from the internal oblique m uscle to re ect the sup erior portion of the m uscle m edially (FIG. 4.10).

Tran sve rsus Ab d o m in is Muscle [G 297; L 217; N 247; R 218] The transversus abdom inis m uscle lies deep to the internal oblique m uscle and has predom inantly horizontally oriented bers in its upp er part. In the inguinal region, the transversus abdom inis m uscle has attachm ents sim ilar to the internal ob lique m uscle as the two aponeuroses fuse to form the conjoint tendon. 1. Follow the ilioinguinal nerve proxim ally to nd where the nerve pierces the internal oblique m uscle and follow it into the plane of separation between the internal oblique m uscle and the transversus abdom inis m uscles (FIG. 4.10). Gently push a probe through the opening to increase the separation of the m uscular layers at this location. 2. Make a vertical incision through the internal oblique m uscle following the path of the lateral cut through the external obliq ue m uscle (FIG. 4.10, d ashed lines), m aking an effort to spare the ilioinguinal and iliohypogastric nerves.

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3. Near the ASIS, use your ngers to separate the internal oblique m uscle from the underlying transversus abdom inis m uscle. Note that the transversus abdom inis m uscle is dif cult to separate from the internal oblique m uscle m ed ially because their tendons are fused to form the conjoint tendon near their distal attachm ents. 4. Cut through the internal oblique m uscle along the costal m argin continuing its separation from the underlying transversus abdom inis and re ect the m uscle m edially with the external oblique m uscle (FIG. 4.11). 5. Observe that, as is true of the internal oblique m uscle, the arching bers of the inferior part of the transversus abdom inis m uscle form part of the roof of the inguinal canal, and its aponeurotic insertion form s p art of the p osterior wall (FIG. 4.11). [G 298; L 216; N 247; R 218] 6. Observe that below the arching bers of the internal oblique and transversus abdom inis m uscles, the abd om inal wall is unsupp orted by m uscle, thus creating a natural weak point in the posterior wall of the ing uinal canal known as Hesselbach’s triangle, through which transversalis fascia is visible. 7. Review the attachm ents and actions of the transversus abdom inis m uscle (see TABLE 4.1).

External abdominal oblique m. (reflected)

Internal abdominal oblique m. (reflected) Transversus abdominis m.

Conjoint tendon Spermatic cord

Transversalis fascia Superficial inguinal ring

FIGURE 4.11 The transversus abdom inis m uscle shown deep to the re ected internal and external ob liq ue m uscles.

CLIN ICA L CORRELATION

In g uin al He rn ias [L 223; R 223] The inguinal canal is a weak area of the anterior abdom inal wall through which abdom inal viscera m ay protrude (inguinal hernia). An inguinal hernia is classi ed according to its position relative to the inferior epig astric vessels. An in d ire ct in g uin al h e rn ia exits the abdom inal cavity through the deep inguinal ring lateral to the inferior epigastric vessels and follows the inguinal canal (an ind irect course through the abdom inal wall) (FIG. 4.12A, B). In contrast, a d ire ct in g uin al h e rn ia exits the abdom inal cavity m edial to the inferior ep igastric vessels throug h Hesse lb ach ’s (in g uin al) t rian g le and follows a relatively direct course through the abdom inal wall (FIG. 4.12A, C). Hesselbach’s triangle is bound laterally by the inferior epig astric vessels, m edially by the lateral edge of the rectus abdom inis m uscle, and inferiorly by the inguinal ligam ent (FIG. 4.12A).

8. Carefully incise the transversus abdom inis along the sam e vertical line (FIG. 4.11, dashed lines) and use a p robe or your nger to sep arate the underlying transversalis fascia and parietal p eritoneum from the deep surface of the transversus abdom inis m uscle. Take care to not pierce the peritoneum and enter the abdom inal cavity. If done correctly, the thoracoabdom inal nerves should be p reserved. 9. Cut the transversus abdom inis along its attachm ent to the costal m argin and re ect all three anterolateral abdom inal wall m uscles m edially. 10. Repeat this process on the contralateral side, m aking a vertical incision through all three m uscular layers just anterior to the m idaxillary line.

Re ct us Ab d o m in is Muscle [G 296; L 217, 218; N 246; R 215] The rectus sheath contains the re ct us ab d o m in is m uscle , the p yram id alis m uscle , the sup e rio r and in fe rio r e p ig ast ric ve sse ls , and the term inal ends of the ventral ram i of spinal nerves T7–T12. The purpose of this dissection is rst to op en the anterior wall of the rectus sheath and observe the rectus abdom inis m uscle in situ and then transect and re ect the rectus abdom inis m uscle to expose the p osterior wall of the rectus sheath. 1. On the anterior abdom inal wall, identify the an t e rio r laye r o f t h e re ct us sh e at h . The re ct us sh eat h is form ed by the aponeuroses of the three pairs of anterolateral abdom inal wall m uscles (external obliq ue, internal oblique, and transversus abdom inis) as they fuse toward their m edial attachm ent at the lin e a alb a (FIG. 4.13).

CHAPTER 4

Hesselbach’s triangle Inferior epigastric artery

Direct inguinal hernia Indirect inguinal hernia

Site of deep inguinal ring

Deep inguinal ring

Superficial inguinal ring

Inguinal canal

Pubic tubercle

Superficial inguinal ring

A Inguinal hernias Peritoneum Extraperitoneal fat Transversalis fascia

Inferior epigastric artery

Transversus abdominis m. Internal oblique m. External oblique aponeurosis

Deep inguinal ring

Subcutaneous fat Skin

B Indirect inguinal hernia Peritoneum Extraperitoneal fat Transversalis fascia

Inferior epigastric artery

Transversus abdominis m. Internal oblique m. External oblique aponeurosis

Deep inguinal ring

Subcutaneous fat Skin C Direct inguinal hernia

FIGURE 4.12 Inguinal hernias. A. Anatom ical relationships and course through the abdom inal wall. B. An indirect inguinal hernia leaves the abdom inal cavity lateral to the inferior epigastric vessels and passes down the inguinal canal. C. A direct inguinal hernia leaves the abdom inal cavity m edial to the inferior epigastric vessels.

THE ABDOMEN

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107

2. Study an illustration to verify that in the upper threefourths of the abdomen, layers of the rectus sheath pass both anterior and posterior to the rectus abdominis muscle. However, halfway between the umbilicus and the pubic symphysis, all layers of the aponeuroses course anterior to the rectus abdominis muscle (FIG. 4.13). 3. Use scissors to m ake a transverse cut through the anterior layer of the rectus sheath beginning at the sem ilunar line laterally and ending ap proxim ately 2.5 cm lateral to the um bilicus. Use a probe to lift the free edge of the rectus sheath as you cut, ensuring you do not cut through the m uscle of the underlying re ct us ab d o m in is (FIG. 4.13, cut 1). 4. Use scissors to m ake a vertical incision through the rectus sheath extending in a superior direction along the m edial border of the rectus abdom inis m uscle. Cut sup eriorly to the costal m argin keep ing about 2.5 cm from the lin e a alb a (FIG. 4.13, cut 2). 5. Extend the vertical cut inferiorly along the m edial border of the rectus abdom inis m uscle to the level of the pubic crest (FIG. 4.13, cut 3). Again, do not disturb the linea alba. 6. Insert your ngers into the vertical cut and separate the anterior wall of the rectus sheath from the anterior surface of the rectus abdom inis m uscle. 7. Observe that the anterior wall of the rectus sheath is rm ly attached to the anterior surface of the rectus abdom inis m uscle by several t e n d in ous in t e rse ct ion s (FIG. 4.14). 8. Carefully cut through the tendinous intersections to free the rectus sheath from the rectus abdom inis m uscle and re ect the rectus sheath laterally. 9. To increase visibility of the rectus abdom inis m uscle, additional cuts m ay be m ade through the rectus sheath both superiorly and inferiorly to allow for further re ection of the sheath. 10. Observe that the subdivisions of the re ct us ab d o m in is m uscle by the tendinous intersections are responsible for the app earance of the “six p ack” (FIG. 4.14). 11. Review the attachm ents and actions of the rectus abdom inis m uscle (see TABLE 4.1). 12. Anterior to the inferior end of the rectus abdom inis m uscle, look for the p yram id alis m uscle . The pyram idalis m uscle is frequently absent. When present, it attaches to the anterior surface of the pubis and the linea alba. When the pyram idalis contracts, it puts tension on the linea alba. 13. Along the lateral side of the rectus abdom inis m uscle, observe that the branches of six nerves (T7–T12) enter the rectus sheath and penetrate the deep surface of the rectus abdom inis m uscle. The distal parts of the nerves then em erge from the sheath as an t e rio r cut an e o us b ran ch e s (FIG. 4.15). [G 297; L 171, 214; N 253; R 220]

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Internal abdominal oblique m. External abdominal oblique m.

Rectus abdominis m. Linea alba

Cut 2

Cut 1 Umbilicus

Transversus abdominis m.

Peritoneum

Transversalis fascia

Cut 3 External oblique aponeurosis

Rectus abdominis m. Linea alba

FIGURE 4.13 Cuts used to open the rectus sheath (left) and transverse sections of the rectus sheath at the two levels indicated by the blue dashed lines.

14. Use your ng ers to m obilize the m edial border of the rectus abdom inis m uscle. 15. At the level of the um bilicus, transect the rectus abdom inis m uscle on one side with scissors and re ect the two halves superiorly and inferiorly. If the nerves prevent full re ection of the rectus abdom inis m uscle, cut them where they enter the m uscle. 16. On the posterior surface of the rectus abdom inis m uscle superiorly, identify the sup e rio r e p ig ast ric art e ry an d ve in (FIG. 4.15). 17. On the posterior surface of the rectus abdom inis m uscle inferiorly, identify the m uch larger in fe rio r CLIN ICA L CORRELATION

Ep ig ast ric An ast o m o se s The superior epigastric vessels anastomose with the inferior epigastric vessels within the rectus sheath (FIG. 4.14). If the inferior vena cava becomes obstructed, the anastomosis between the inferior epigastric and superior epigastric veins provides a collateral venous channel that drains into the superior vena cava. If the aorta is occluded, collateral arterial circulation to the lower part of the body occurs through the superior and inferior epigastric arteries.

ep ig ast ric art e ry an d ve in (FIG. 4.15). [G 297; L 217, 219; N 251; R 220] 18. Exam ine the posterior wall of the rectus sheath and identify the arcuat e lin e m idway between the pubic sym p hysis and the um bilicus. 19. Observe that the inferior epigastric vessels enter the rectus sheath at the level of the arcuate line (FIG. 4.15). Note that the arcuate line is the inferior limit of the posterior wall of the rectus sheath and may be indistinct . 20. Inferior to the arcuate line, identify the thin, brous t ran sve rsalis fascia . Note that the transversalis fascia is reinforced on its deep surface by the pa rieta l peritoneum lining the abdom inal cavity.

De e p In g uin al Rin g [G 303; L 217, 219, 220; N 255; R 222] Tran sve rsalis fascia lines the inner surface of the transversus abdom inis m uscles (FIG. 4.1). The d e e p in g uin al rin g is the point at which the gubernaculum passed through the transversalis fascia during developm ent. In the adult, the deep inguinal ring is located superior to the m idp oint of the inguinal lig am ent. In the m ale, the ductus deferens passes through the deep inguinal ring. In the fem ale, the round ligam ent of the uterus passes through the deep

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109

Thoracoabdominal nerves: T7 T8

Rectus abdominis m.

Anterior rectus sheath (reflected)

T9 T10

Tendinous intersections Linea alba Internal oblique m.

Umbilicus

T11

Superior epigastric a. Transversus abdominis m.

Subcostal n. (T12) Iliohypogastric n. (L1) Ilioinguinal n. (L2)

Inferior epigastric a.

Inguinal ligament

External oblique m. (reflected)

FIGURE 4.14

Rectus abdom inis m uscle.

inguinal ring. During developm ent of the m ale, the testis and all its related vessels, nerves, and ducts passed through the deep inguinal ring on the way to the scrotum . 1. Retract the sp erm atic cord (or round ligam ent of the uterus) inferiorly (FIG. 4.9). 2. Use a probe to lift the arching bers of the internal oblique and transversus abdom inis m uscles and observe the inferior ep ig astric vessels through the transversalis fascia (FIG. 4.9). Note that the inferior epigastric vessels are located within the layer of extraperitoneal fascia. 3. Observe that the deep inguinal ring is lateral to the inferior epigastric vessels and is identi ed by the p resence of the ductus deferens (or round ligam ent of the uterus) passing through this area.

FIGURE 4.15 Nerves and arteries within the rectus sheath. The rectus abdom inis m uscle has been rem oved.

4. Use a text to illustrate the orientation and location of the inguinal canal and ap preciate that this sp ace is shaped som ewhat like a attened tube between the deep and super cial inguinal rings. 5. Use a probe to verify that the an t e rio r wall o f t h e in g uin al can al is the aponeurosis of the external oblique m uscle and the p o st e rio r wall is the transversalis fascia laterally and conjoint tendon m edially. 6. Observe that the in fe rio r wall ( oor) of the inguinal canal is the inguinal ligam ent and lacunar ligam ent and that the sup e rio r wall (roof) is the arching bers of the internal obliq ue and transversus abdom inis m uscles (FIG. 4.10).

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Replace the m uscles of the anterior abdom inal wall in their correct anatom ical positions. Review the proxim al attachm ent, distal attachm ent, and action of each m uscle. Review the structures that form the nine layers of the abdom inal wall (FIG. 4.1). Use the dissected sp ecim en to review, com pare, and contrast the rectus sheath just superior to the level of the um bilicus and just superior to the pubic sym physis (FIG. 4.15). 5. Review the blood and nerve supply to the anterior abdom inal wall.

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TABLE 4.1

GRANT’S DISSECTOR

Muscle s o f t h e An t e ro lat e ral Ab d o m in al Wall

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

External oblique

External surfaces of ribs 5–12

Linea alba, pubic crest and tubercle, and anterior half of the iliac crest

Internal oblique

Thoracolumbar fascia, iliac crest, and lateral half of inguinal ligament

Inferior borders of ribs 10–12, linea alba, pubic crest, and pecten pubis via conjoint tendon

Transversus abdominis

Internal surfaces of costal cartilages 7–12, thoracolumbar fascia, and iliac crest

Linea alba with internal oblique, pubic crest and pecten pubis via conjoint tendon

Rectus abdominis

Xiphoid process, costal cartilages 5–7

Pubic symphysis, and pubic crest

Innerva tion Thoracoabdominal nn. T7–T11 and subcostal n.

Compresses and supports abdominal viscera, exes and rotates the trunk

Flexes trunk, assists in pelvic tilt, and compresses abdominal viscera

Thoracoabdominal nn. T7–T11, subcostal n., and L1

Thoracoabdominal nn. T7–T11 and subcostal n.

Abbreviations: n., nerve; nn., nerves.

REFLECTION OF THE ABDOMINAL WALL Disse ct io n Ove rvie w As previously discussed, the ab dom inal cavity is com m only described in both quadrant and regional subdivisions. Two m ethods of abdom inal wall dissection will be described and either m ethod m ay be followed depending on the needs of the course. The rst dissection sequence subdivides the anterior abdom inal wall into q uadrants sim ilar to the quad rant lines illustrated in FIGURE 4.3. In this way, the contents of the abdom inop elvic cavity can be accessed and the abdom inal wall can be repositioned for review. Direct reference to the position of the abdom inal organs within the abdom inal quadrants will be given. The second dissection sequence involves re ecting the entire anterior abdom inal wall in one large piece. This will m aintain the anatom ical relations of the structures coursing along the inner aspect of the anterior abdom inal wall. The entire anterior abdom inal wall can be repositioned for reviewing either the quadrant or the regional approach to subdividing the abdom inal cavity and contents. The order of dissection will be as follows: The anterior abdom inal wall will be cut and opened in either the quadrant or the abdom inal wall re ection ap proach. The inner surface of the anterior abdom inal wall will be studied.

Disse ct io n In st ruct io n s Select either the four abdom inal quadrants app roach or the abdom inal wall re ection app roach for your study of the anterior abdom inal wall and disregard the dissection sequence for the other app roach. When you have nished with the selected approach, continue to the “Peritoneum and Peritoneal Cavity” section.

5.

6.

Fo ur Ab d o m in al Quad ran t s 1. Refer to FIGURE 4.16A. 2. Re ect the halves of the rectus abdom inis m uscles superiorly and inferiorly. 3. On the left side of the um bilicus, use scissors to create a sm all hole (2.5 cm ) through the posterior wall of the rectus sheath, extrap eritoneal fascia, and p arietal p eritoneum . 4. Insert your nger through the hole into the abdom inal cavity and pull the p osterior wall of the rectus

7. 8.

9.

sheath and associated extrap eritoneal fascia and peritoneum anteriorly to create a space between the anterior abdom inal wall and the abdom inal viscera. Use scissors to m ake a vertical cut throug h the linea alba to the xiphoid p rocess 1 cm to the left of the m idline to preserve the falciform ligam ent (FIG. 4.16A, cut 1). Extend the m idline cut inferiorly as far as the pubic sym physis, staying 1 cm to the left of the m idline to p reserve the m edian um bilical fold (FIG. 4.16A, cut 2). Return the rectus abdom inis m uscles to their correct anatom ical p ositions. At the level of the um bilicus, p lace one hand through the vertical cut and raise the abdom inal wall creating a space between it and the abd om inal contents. On the right side of the abdom en, use scissors to cut the p osterior wall of the rectus sheath, extrap eritoneal fascia, and peritoneum in the transum bilical p lane (FIG. 4.16A, cut 3). The scissors should p ass through

CHAPTER 4

THE ABDOMEN

Linea alba

Umbilicus Cut 3

111

Cut

Cut 1

Previous cuts

•

Costal margin

Previous cuts

Umbilicus

Cut 2

A FIGURE 4.16 system .

10.

11. 12.

13.

14.

B Cuts used to open the abdom inal cavity. A. Following the q uadrant system . B. Following the regional

the p revious transverse cut m ade in the rectus abdom inis m uscle and the external oblique m uscle. Extend the transverse incision laterally through all three anterolateral abdom inal m uscles as far as the m idaxillary line. Repeat this transverse cut on the left side of the abdom en. Open the aps of the abdom inal wall and identify the falcifo rm lig am e n t on the inner surface of the right upp er quadrant ap. Observe that the falciform ligam ent connects the anterior abdom inal wall to the anterior surface of the liver. [G 312; L 219, 224; N 249; R 301] On the inner surface of the lower abdom inal wall, identify the m e d ian um b ilical fo ld in the m idline inferior to the um bilicus (FIG. 4.17). Observe that the m edian um bilical fold is attached to the right lower q uadrant ap and contains the urachus (rem nant of the allantois). Identify the m e d ial um b ilical fo ld lateral to the m edian um bilical fold (FIG. 4.17). Note that the medial um bilical fold contains the rem nant of the umbilical artery.

15. Identify the lat e ral um b ilical fo ld lateral to the m edial um bilical fold (FIG. 4.17). Observe that the lateral um bilical fold overlies the inferior epigastric artery and vein. 16. Lateral to the lateral um bilical fold, observe a sm all depression in the peritoneum m arking the location of the d e e p in g uin al rin g in the transversalis fascia (FIG. 4.17). Note that in the m ale, this depression is m ore readily visible due to the presence of the testicular vessels and vas d eferens p assing through the deep inguinal ring to the inguinal canal. 17. Close the abdom inal wall and return the abdom inal wall m uscles to their anatom ical position.

Ab d o m in al Wall Re e ct io n 1. Refer to FIGURE 4.16B. 2. Elevate the superior portion of the rectus abdom inis m uscle using a probe and transect the m uscle bers superior to the curve of the costal m argin. 3. Continue the transverse cut laterally through the attached portions of anterolateral abdom inal wall m uscles following the curve of the costal m argin

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GRANT’S DISSECTOR

Umbilicus Median umbilical ligament (remnant of urachus)

Peritoneum Median umbilical fold Arcuate line Medial umbilical ligament (obliterated umbilical a.) Medial umbilical fold

Rectus abdominis m.

Lateral umbilical fold (inferior epigastric vessels) Inferior epigastric a. Inferior epigastric v.

Hesselbach’s (inguinal) triangle

Urinary bladder Location of deep inguinal ring

FIGURE 4.17 Posterior view of anterior ab dom inal wall displaying um bilical folds form ed b y the peritoneum . Cuts used to op en the ab dom inal cavity following the reg ional system .

4.

5.

6.

7.

8.

9.

toward the m id axillary line (FIG. 4.16B, dashed line). Note that a portion of this cut was m ade during the re ection of the abdominal oblique muscles. Cut through the p osterior rectus sheath superiorly to free the anterior abdom inal wall from the costal m argin and xiphoid process. Make an incision through the transversalis fascia and p arietal peritoneum around the circum ference of the entire cut edge of anterolateral abdom inal wall m usculature. Begin re ection of the entire anterolateral abdom inal wall in the up per right hand quadrant of the abdom en. Cut through the falciform ligam ent attaching the anterior surface of the liver to the posterior (inner) surface of the anterior abdom inal wall. Make the cut as close to the abdom inal wall as possible. [G 312; L 219, 224; N 249; R 301] Re ect the entire anterior abdom inal wall inferiorly using the distal attachm ents of the m uscles to the suprap ubic region as a hinge. On the inner surface of the lower abdom inal wall, identify three folds beginning with the m e d ian um b ilical fo ld , which lies in the m idline inferior

10.

11.

12.

13.

to the um bilicus (FIG. 4.17). Note that the median umbilical fold contains the urachus, the rem nant of the allantois from embryological developm ent. Identify the m e d ial um b ilical fo ld located lateral to the m edian um bilical fold , which angles inferolaterally away from the m edian um bilical fold (FIG. 4.17). Note that the m edial umbilical fold contains the remnant of the um bilical artery. Identify the lat e ral um b ilical fo ld located lateral to the m edial um b ilical fold (FIG. 4.17). The lateral um bilical fold overlies the inferior epigastric artery and vein. Lateral to th e lateral um b ilical fold , ob serve a sm all d ep ression in th e p eriton eum m arkin g th e location of th e d e e p in g u in a l rin g in th e tran sversalis fascia (FIG. 4.17). Note th at in th e m ale, th is d ep ression is m ore read ily visib le d ue to th e p resen ce of th e testicular vessels an d vas d eferen s p assin g th roug h th e d eep in g uin al rin g to th e in g uin al can al. To increase m obility of the ap of abdom inal wall, it m ay be helpful to m ake short lateral incisions just above the inguinal ligam ent to the lateral um bilical folds to free the m usculature and re ected wall.

CHAPTER 4

THE ABDOMEN

•

113

Disse ct io n Fo llo w-up 1. Replace the m uscles of the anterior abdom inal wall in their correct anatom ical positions. 2. Review the location of the falciform ligam ent. 3. Review the location and contents form ing each um bilical fold.

PERITONEUM AND PERITONEAL CAVITY Disse ct io n Ove rvie w All body cavities (thoracic, pericardial, abdom inal, and pelvic) are lined by regionally nam ed serous m em branes, which secrete a sm all am ount of uid to lubricate the m ovem ents of organs. In the abdom inal and pelvic cavities, this bilayer m em brane is called p e rit o n e um . The p arie t al p e rit o n e um lines the inner surfaces of the abdom inal and pelvic walls, and the visce ral p e rit o n e um covers the surfaces of the abdom inal and pelvic organs. Between the two layers of peritoneum is a potential space called the p e rit o n e al cavit y. During em bryological developm ent, som e abdom inal organs grow away from the posterior abdom inal wall and end up suspended by p eritoneum within the p eritoneal cavity. The org ans that develop in this m anner and carry their neurovascular supply with them are referred to as in t rap e rit o n e al (p e rit o n e al) o rg an s . Intraperitoneal organs include the stom ach, the rst p art of duodenum , the jejunum , the ileum , the cecum and ap pendix, the transverse colon, the sigm oid colon, the upp er one-third of the rectum , the liver, the tail of the pancreas, and the sp leen. Other abdom inal organs develop behind the peritoneum (retroperitoneal) and are not suspended in the peritoneal cavity. The organs that develop in this m anner are called re t ro p e rit o n e al (e xt rap e rit o n e al) o rg an s . Retroperitoneal organs include the kidneys, the ureters, the suprarenal glands, and the inferior two-thirds of the rectum . Som e p arts of the gastrointestinal tract begin as intraperitoneal organs in the em bryo but becom e attached to the abdom inal wall later in developm ent and thus are referred to as se co n d arily re t ro p e rit o n e al. Exam ples of secondarily retroperitoneal organs include the duodenum (second through fourth parts); the head, neck, and uncinate process of the pancreas; the ascending colon, and the descending colon. The order of d issection will be as follows: The abdom inal viscera will be identi ed in situ and localized by abdom inal quadrant. The nam ed specializations of the peritoneum will be studied. For a m ore com plete understanding, review the developm ent of the gastrointestinal tract before exam ining the peritoneal specializations.

Disse ct io n In st ruct io n s Ab d o m in al Visce ra [G 313, 322; L 224, 225; N 263; R 299, 300] 1. Re ect the anterior abdom inal wall. 2. Use your hands to inspect the abdom inal cavity observing how som e organs are susp ended within the cavity (intraperitoneal), whereas others lie further posteriorly covered by peritoneum (retroperitoneal). 3. As you perform the inspection, you m ay encounter adhesions between the ab dom inal wall and organs or between p arts of org ans. If adhesions are present, tear them gently with your ngers or cut them carefully with scissors to m obilize the organs. Do not m ake a hole in the colon. 4. As you exam ine the organs in the abdom inal cavity, particularly those related to the g ast roin t est in al t ract , relate the organs to the four abdom inal quadrants. 5. Identify the live r in the right upper q uadrant extending across the m idline into the left upper quadrant (FIG. 4.18). The liver lies against the inferior surface of the diaphragm to which it is attached by ligam ents m ade of peritoneum . The attachm ent of the falciform

6.

7.

8.

9. 10. 11.

ligam ent from the anterior abdom inal wall divides the liver into rig h t and le ft lo b e s . Identify the g allb lad d e r in the right upper q uadrant where it extends below the inferior border of the liver (FIG. 4.18). Com m only, the gallbladder is found at the tip of the right ninth costal cartilage in the m idclavicular line. Identify the st o m ach in the left upp er quadrant. Observe that the stom ach lies deep to the liver, which partially covers its anterior surface. Verify that the stom ach is continuous with the esop hagus proxim ally and the duodenum distally. Find the sp leen in the left upper quadrant posterior to the stom ach. Reach around the left side of the stom ach with your right hand and cup the spleen in your hand. Identify the g re at e r o m e n t um attached to the greater curvature of the stom ach (FIG. 4.18). Re ect the greater om entum superiorly over the costal m argin and identify the sm all in t est in e (FIG. 4.19). The sm all intestine has three parts and begins at the pyloric end of the stom ach with the d uo d e n um , followed by the je jun um , and ending as the ile um (FIGS. 4.18 and 4.19). Note that the duodenum lies

114

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GRANT’S DISSECTOR

Liver: Left lobe Right lobe Gallbladder Layers of abdominal wall: Skin Superficial fascia External abdominal oblique muscle Internal abdominal oblique muscle Transversus abdominis muscle Extraperitoneal fat and connective tissue Parietal peritoneum

Falciform ligament Round ligament of liver Stomach

Greater omentum Large intestine

Small intestine

FIGURE 4.18 The relationship of the greater om entum to the abdom inal viscera.

posterior to the other parts of the gastrointestinal tract and will be dissected and studied with the pancreas. 12. The je jun um and ile um extend from the left up per quadrant to the right lower quadrant, but due to their length and m obility, they occupy all four abdom inal quad rants. Beginning in the left upper quadrant, pass the jejunum and ileum between your hands and appreciate their length, position, com parative thickness, and term ination.

Omental apron portion of greater omentum (turned up)

13. Identify the larg e in t est in e beginning in the right lower quadrant at the ileocecal junction where it m eets the ileum (FIGS. 4.18 and 4.19). Use your hands to trace the large intestine from the right lower quadrant to the left lower quadrant noting the position (quadrant) and m obility of each of its six p arts. 14. Identify the ce cum , the rst of six portions of the large intestine, in the right lower q uadrant. Observe, on the inferior end of the cecum , the “worm -like” outgrowth of the ve rm ifo rm ap p e n d ix . Note that the appendix has a variety of orientations and m ay or m ay not be present because it com m only becom es in am ed and is rem oved surgically. 15. Follow the cecum superiorly and identify the asce n d in g co lo n , which extends from the right lower quadrant to the right upper quadrant, where it ends at the rig h t co lic (h e p at ic) e xure (FIG. 4.19). 16. At the hepatic exure, the large intestine changes direction and courses horizontally as the t ran sve rse co lo n , which extends from the right upper quadrant to the left up per q uadrant ending at the left co lic (sp le n ic) e xure (FIG. 4.19). 17. At th e sp lenic exure, th e larg e intestine curves inferiorly as the d e sce n d in g co lo n , which exten d s from the left up p er q uad rant to the left lower q uad rant. 18. The sig m o id co lo n is located in the left lower quadrant and is the portion of the large intestine coursing from the abdom inal cavity into the p elvic cavity, ending at the level of the third sacral vertebra. 19. The last portion of the large intestine, the re ct um , is located partly in the abd om en and partly in the pelvis. The superior one-third of the rectum will be dissected with the abdom inal viscera. The inferior two-thirds will be dissected with the p elvic viscera.

Re e ct io n o f t h e Diap h rag m Transverse colon (turned up) Transverse mesocolon Right colic (hepatic) flexure

Left colic (splenic) flexure

Ascending colon

Descending colon

Cecum

Sigmoid colon

Small intestine: Jejunum Ileum

FIGURE 4.19 Re ection of the greater om entum superiorly to expose the sm all intestine and large intestine.

Depending on the cadaver, som e of the structures within the abdom inal cavity m ay or m ay not be readily visible. If the thorax has p reviously been dissected but visibility of the upp er abdom inal cavity rem ains lim ited and m ob ility of the contents is dif cult, use the following dissection steps to increase visibility of the abdom inal contents. 1. On the left side only, use bone cutters to detach the costal cartilages of ribs 6 and 7 from the xiphisternal junction and lateral border of the sternum . 2. Working through the opening just created, use your hands to elevate the left side of the costal cartilage and use scissors to detach the diaphragm from its anterior attachm ent on the posterior surface of the costal cartilages. 3. Continue to re ect the left portion of the costal cartilag e laterally toward the m idaxillary line leaving the lateral aspect connected to act as a hinge.

CHAPTER 4

4. Repeat step s 2 and 3 on the right side and re ect the right costal cartilage laterally. 5. Beginning near the m idaxillary line, use scissors to m ake an incision through the m uscular portions of the left and right hem idiap hragm s arching m edially toward the central tendon of the diaphragm while sparing the central tendon and p hrenic nerves. 6. Re ect the anterior aspect of the diap hragm superiorly into the thoracic cavity using the ligam entous attachm ents to the liver as a hinge.

Pe rit o n e um [G 313; L 224–226; N 263; R 316] 1. Identify the visceral p erit o n eum on the surface of the stom ach, sm all intestine, large intestine, or liver and observe that it is sm ooth and slippery (FIG. 4.20). 2. Identify the p arie t al p e rit o n e um on the inner surface of the abdom inal wall. Observe that the parietal peritoneum is a continuous layer with the visceral peritoneum but changes nam es due to location (FIG. 4.20). 3. Identify the g re at e r o m e n t um and observe that it attaches to the greater curvature of the stom ach. The greater om entum extends out into the abdom inal cavity and then doubles back on itself and attaches

Right lobe Right triangular ligament

Aorta

Visceral peritoneum

Inferior border of liver Ascending colon

4.

Pancreas

Transverse mesocolon

Superior mesenteric artery

Transverse colon

Duodenum

Inferior recess

5. Mesentery of small intestine

Greater peritoneal sac

Rectouterine pouch

Greater omentum

6.

Small intestine Pubic symphysis

Rectum

Urinary bladder

7. Urethra

FIGURE 4.20 section.

Uterus

Vagina

Peritoneum and peritoneal cavity, m edian

Duodenum Transverse colon

FIGURE 4.21 Anterior view of the ligam ents supporting the liver and relationship s of the gallbladder.

Celiac trunk

Peritoneal cavity

Left triangular ligament

Pylorus of stomach

Right colic flexure

Lesser peritoneal sac (omental bursa)

Parietal peritoneum

Left lobe

Round ligament of the liver

Gallbladder

Superior recess

Stomach

115

•

Falciform ligament

Liver

Bare area of liver Lesser omentum

Coronary ligament

Diaphragm

Diaphragm

Liver

THE ABDOMEN

to the transverse colon. Sp read out the apron-like structure of the greater om entum to app reciate its full size. Note that the greater omentum typically lies between the intestines and the anterior abdom inal wall but may shift in location or become partially fused to surrounding structures (FIGS. 4.18 and 4.20). [G 318; L 224; N 269; R 316] Elevate the inferior border of the liver and identify the lesse r o m e n t um attaching from the inferior surface of the liver to the lesser curvature of the stom ach and rst part of the duodenum (FIG. 4.20). The p oints of attachm ent subdivide the lesser om entum into the h e p at o g ast ric lig am en t , from the liver to the lesser curvature of the stom ach, and the h ep at o d uo d e n al lig am e n t , from the liver to the rst part of the duodenum . On the anterior surface of the liver, identify the falcifo rm lig am e n t (FIG. 4.21). The falciform ligam ent passes from the parietal peritoneum on the anterior abdom inal wall to the visceral peritoneum on the surface of the liver. Identify the ro un d lig am e n t o f t h e live r (lig am e n t um t e re s h e p at is) in the inferior edge of the falciform ligam ent. The round ligam ent of the liver is the rem nant of the left um bilical vein from fetal developm ent. Follow the falciform ligam ent sup eriorly and observe that it is continuous with the co ro n ary lig am e n t attaching the liver to the inferior aspect of the diaphragm (FIG. 4.21). The coronary ligam ent bounds the reg ion of the liver known as the bare area and

116

8.

9.

10.

11.

12.

13.

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GRANT’S DISSECTOR

can be subdivided into right and left portions as well as anterior and posterior portions. The lateral aspects of the coronary ligam ents fuse as the le ft t rian g ular lig am e n t , between the left lobe of the liver and the diap hragm , and the rig h t t rian g ular lig am e n t , between the right lobe of the liver and the diaphragm (FIG. 4.21). Identify the g astrophrenic ligam ent , which connects the superior part of the greater curvature of the stomach to the inferior aspect of the diaphragm, by sliding your hand superiorly around the left side of the stomach. The g ast ro sp len ic (g ast ro lie n al) lig am e n t passes from the greater curvature of the stom ach to the sp leen, and the sp le n o re n al (lie n o ren al) lig am e n t attaches the spleen to the body wall anterior to the left kidney (FIG. 4.22). Re ect the greater om entum superiorly over the costal m argin and identify the t ran sverse m esocolon (FIGS. 4.19 and 4.20). The transverse m esocolon attaches from the transverse colon to the anterior surface of the duodenum and pancreas along the posterior abdom inal wall. At the left end of the transverse m esocolon is the p h ren icocolic lig am en t , which attaches the left colic exure to the diaphragm . [L 224; N 265; R 321] Identify the m e se n t e ry (p ro p e r) suspending the jejunum and ileum from the posterior abdom inal wall (FIG. 4.20). The root of the m esentery attaches to the p osterior abdom inal wall along an oblique line from the left upper quadrant to the right lower quadrant. Observe that the parietal p eritoneum lines the posterior abdom inal wall superior to the oblique

Greater sac Lesser sac (omental bursa) Hepatogastric ligament Parietal peritoneum Hepatoduodenal Stomach ligament with contents Omental foramen

14.

15.

16. 17.

18.

19.

20.

21.

22. Visceral peritoneum Gastrosplenic ligament

23.

Peritoneal cavity

24.

Spleen Right kidney

Inferior vena cava

Aorta

Left kidney

Splenorenal ligament

FIGURE 4.22 Schem atic drawing of the peritoneal cavity in transverse section, inferior view. The arrow p asses through the om ental foram en.

25.

attachm ent of the m esentery p roper to ll the rig h t in fram e so co lic co m p art m e n t in the region m edial to the ascending colon. On the lateral side of the ascending colon, identify the right paracolic gutter . Observe that the paracolic gutter is the point of re ection of peritoneum from the lateral wall of the abdominal cavity to the surface of the organ. Elevate the sm all intestine with the m esentery prop er and observe that the parietal peritoneum lines the posterior abdom inal wall inferior to the oblique attachm ent of the m esentery proper to ll the left in fram e so co lic co m p art m e n t in the region m edial to the descend ing colon. On the lateral side of the descending colon, identify the le ft p araco lic g ut t e r . Identify the m e soap p e n d ix , which attaches the appendix to the distal ileum and cecum and contains the ap pendicular artery. Identify the sig m o id m e so co lo n in the lower left quadrant, which suspends the sigm oid colon from the p osterior abdom inal wall. The p reviously identi ed peritoneal structures are all found in a part of the peritoneal cavity called the g reat e r p e rit o n e al sac (FIG. 4.20). Posterior to the stom ach and lesser om entum is a sm aller p art of the p eritoneal cavity called the le sse r p e rit o n e al sac (o m e n t al b ursa) (FIGS. 4.20 and 4.22). The o m e n t al fo ram e n (e p ip lo ic fo ram e n ) connects the greater and lesser p eritoneal sacs and lies posterior to the hepatoduodenal ligam ent (FIG. 4.22). [G 318; L 230; N 269; R 319] Insert your nger into the om ental foram en and review its boundaries beginning with the an t e rior b o un d ary, which is form ed by the hepatoduodenal ligam ent. The hepatoduodenal ligam ent contains the hepatic portal vein, the hepatic artery prop er, and the com m on bile duct (FIG. 4.22). Identify the p o st e rio r b o un d ary of the om ental foram en, which is the parietal peritoneum overlying the inferior vena cava and rig ht crus of the diaphragm . Identify the superior boundary of the omental foramen, which is the caudate lobe of the liver, and the in ferior boundary, which is the rst part of the duodenum, both of which are covered with visceral peritoneum. Study a diagram of the le sse r p e rit o n e al sac to appreciate that its lowest part, the in fe rio r re ce ss , extends inferiorly as far as the greater om entum (FIG. 4.20). During develop m ent, the inferior recess extended between the layers of the greater om entum (review an em bryology text). The highest part of the lesser peritoneal sac, the sup erior recess, extends superiorly between the diaphragm and the caudate lobe of the liver. Note that the posterior wall of the lesser peritoneal sac is the peritoneum overlying the pancreas. [G 314; L 230; N 266, 267; R 321]

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THE ABDOMEN

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117

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Use the cadaver specim en to review all parts of the gastrointestinal tract proxim al to distal in order. State the quadrant(s) in which each abdom inal organ is typically found. List the intraperitoneal organs and nam e the specialized peritoneal structures suspending each. Review the locations of the paracolic and m esenteric gutters and discuss how these channels can assist in the spread of infection or disease. 5. Review the list of retroperitoneal and secondarily retroperitoneal organs. 6. Review the em bryology of the gut tube and m esenteries. 7. Replace the abdom inal organs and m uscles of the anterior abdom inal wall in their correct anatom ical positions.

CELIAC TRUNK, STOMACH, SPLEEN, LIVER, AND GALLBLADDER Disse ct io n Ove rvie w The order of dissection will be as follows: The surface features of the stom ach will be studied. The vessels and ducts in the hepatoduodenal ligam ent will be dissected, and the branches of the celiac trunk that sup ply the stom ach, spleen, liver, and gallbladder will be dissected. The rem ainder of the eld of supply of the celiac trunk (to the duodenum and pancreas) will be dissected later. The hepatic portal vein will be studied. The spleen, liver, and gallbladder will be studied.

Disse ct io n In st ruct io n s 1. With the greater om entum in its correct anatom ical position, identify the g re at e r curvat ure of the stom ach on the left lateral m argin of the b o d y o f t h e st o m ach (FIG. 4.23). [G 323; L 231; N 269; R 302] 2. Observe that the body of the stom ach is inferior to the rounded superior protrusion of the fun d us . The fundus of the stom ach is delineated from the card ia of the stom ach by the card ial (card iac) n o t ch . The cardia contains the inlet of the stom ach connecting to the esophagus.

Esophagus

Cardial notch Fundus

Cardia

Body

Lesser curvature Angular incisure (notch) Duodenum

Greater curvature

Pylorus Pyloric part

FIGURE 4.23

Parts of the stom ach.

3. Identify the le sse r curvat ure of the stom ach on the right m argin and note the change of direction of the curvature at the an g ular in cisure (n o t ch ) , where the body of the stom ach transitions to the p ylo ric p art (FIG. 4.23). 4. The p yloric part of the stom ach contains the p ylo ric sp h in ct e r . Palp ate the pyloric sphincter, the circular m uscle responsible for controlling the passage of food from the stom ach to the duodenum . 5. On the anterior surface of the liver, identify the rig h t lo b e and le ft lo b e on either side of the falciform lig am ent (FIG. 4.21). [G 340; L 233; N 277; R 307] 6. Follow either lobe sup eriorly to identify the d iap h rag m at ic surface of the liver and inferiorly to identify the in fe rio r b o rd e r of the liver on the free edge of the anterior surface. 7. Use your hand to raise the inferior border of the liver and identify the visce ral surface o f t h e live r (FIG. 4.24). The visceral surface is in contact with the gallbladder and the p eritoneum covering the stom ach, duodenum , colon, right kidney, and rig ht suprarenal gland. 8. On the visceral surface of the liver, identify the p o rt a h e p at is , the ssure through which vessels, ducts, lym phatics, and nerves enter and leave the liver (FIG. 4.24). [G 341; L 233; N 277; R 308] 9. Identify the g allb lad d e r along the inferior border of the liver and observe that it is d irected posteriorly toward the p orta hep atis (FIG. 4.24). Note that the gallbladder m ay have been surgically rem oved; however, the depression m arking its location should still be visible on the visceral surface of the liver.

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Falciform ligament Gallbladder

Cystic duct

Visceral surface of liver (elevated)

Gallbladder

Right hepatic artery Right hepatic duct

Porta hepatis

Left hepatic duct Hepatic a. proper Hepatic portal v.

Paper passes through the omental foramen

Left hepatic artery

Bile duct

Common hepatic duct Cystic artery

Lesser omentum Hepatogastric ligament Hepatoduodenal ligament

Cystic duct

Hepatic portal vein Hepatic artery proper

Bile duct

FIGURE 4.24 Lesser om entum displaying the hepatogastric ligam ent and hepatod uodenal ligam ent with associated structures. Pap er shown passing through the om ental foram en.

Common hepatic artery Gastroduodenal artery

Po rt al Triad [G 324; L 231; N 284; R 323] As you d issect the branches of the celiac trunk, realize that the arteries are nam ed by their region of distribution and not by their p oint of origin or branching pattern. 1. Gently elevate the liver and diaphragm superiorly to exp ose the lesser om entum . 2. Identify the om ental foram en and grasp its anterior border form ed by the h e p at o d uo d e n al lig am e n t , which contains the b ile d uct , the h e p at ic art e ry p ro p e r , the h e p at ic p o rt al ve in , aut o n o m ic n e rve s , and lym p h at ic ve sse ls . To aid dissection, a strip of white paper m ay be placed into the om ental foram en to increase visibility of the surrounding structures (FIG. 4.25). 3. Use blunt dissection to separate the peritoneum of the hepatoduodenal ligam ent anterior to the vessels and ducts. 4. Within the hepatoduodenal ligam ent, identify contents of the p o rt al t riad : the b ile d uct laterally, the h e p at ic art e ry p ro p e r m edially, and the h e p at ic p o rt al vein posteriorly (FIG. 4.25). 5. Use blunt dissection to trace the bile duct superiorly and identify the cyst ic d uct and the co m m o n h e p at ic d uct (FIG. 4.25). 6. Follow the com m on hepatic duct superiorly until it receives its tributaries, the rig h t h e p at ic d uct and the le ft h e p at ic d uct , which exit the p o rt a h e p at is . 7. Return to the hepatoduodenal ligam ent and clean the h e p at ic art e ry p ro p e r rem oving the tough “connective tissue” around this vessel. The connective tissue is so tough because it contains an aut o n o m ic n e rve p le xus . Use the scissors technique to rem ove

Right gastric artery

FIGURE 4.25 Structures contained within the hepatoduodenal ligam ent. Trib utaries of the (com m on) bile duct and branches of the com m on hep atic artery.

8.

9.

10.

11.

the autonom ic nerve bers from the artery. [G 324; L 231; N 283; R 323] Follow the hep atic artery p rop er toward the liver until it b ranches, into the le ft h e p a t ic a rt e ry and the rig h t h e p a t ic a rt e ry near the p orta hep atis (FIG. 4.25). Identify the cyst ic art e ry arising from the right hepatic artery in the hepatoduodenal ligam ent and follow it toward the gallbladder (FIG. 4.25). Identify the rig h t g ast ric art e ry arising from the hepatic artery prop er and follow it to the lesser curvature of the stom ach. Identify and rem ove any visible lym ph nodes within the hep atoduodenal ligam ent. Note that the lymphatic vessels accompanying the lymph nodes are typically too small to see in em balm ed specim ens, and no effort should be m ade to identify them .

Ce liac Trun k [G 324; L 231; N 284; R 323] The following dissection descriptions reference a com m on pattern of branching of the celiac trunk and associated vessels. As m entioned in the clinical correlate, variations in the arteries of this region are com m on. 1. Use blunt dissection to gently split the hepatogastric ligam ent near its attachm ent to the liver. 2. Follow the hepatic artery proper inferiorly and con rm that it is the continuation of the com m o n h e p at ic art e ry (FIG. 4.26).

CHAPTER 4

Left gastric a. Celiac trunk Right gastric a. Left hepatic a. Right hepatic a.

THE ABDOMEN

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119

CLIN ICA L CORRELATION Esophageal a. Short gastric aa.

Cystic a. Hepatic a. proper Gastroduodenal a. Supraduodenal a.

Splenic a. Right gastro-omental a.

Left gastro-omental a.

An at o m ical Variat io n in Art e rie s In about 12% of cases, the right hepatic artery arises from the superior m esenteric artery. An aberrant left hepatic artery m ay arise from the left gastric artery. During surgical rem oval of the stom ach (gastrectom y), blood ow to an aberrant left hepatic artery could be interrupted, endangering the left lobe of the liver. The cystic artery usually arises from the right hepatic artery, but other origins are possible. The cystic artery m ay pass p osterior (75%) or anterior (24%) to the com m on hepatic duct (FIG. 4.27).

Superior pancreaticoduodenal a.

FIGURE 4.26 trunk.

Schematic drawing of the branches of the celiac

3. Observe that the com m on hepatic artery gives rise to the g ast ro d uo d e n al art e ry, which passes posterior to the rst part of the duodenum (FIG. 4.26). Follow the gastroduodenal artery until it divides to give rise to the rig h t g ast ro -o m e n t al (g ast ro e p ip lo ic) art e ry and the sup e rio r p an cre at ico d uo d e n al art e ry. 4. Follow the com m on hep atic artery to the left side of the body toward its origin from the ce liac t run k (FIG. 4.26). Note that the celiac trunk arises from the anterior surface of the abdom inal aorta at the level of the 12th thoracic vertebra and that it will be dif cult to see in this dissection. Verify its location by identifying the origin of the other branches of the celiac trunk. 5. Observe that the celiac trunk also gives rise to the le ft g ast ric art e ry and the sp le n ic art e ry (FIG. 4.26). 6. Use b lunt d issection to follow the le ft g ast ric art e ry toward the esophagus and stom ach (FIG. 4.26). Observe that the left gastric artery reaches the stom ach near the esophagus and then follows the lesser curvature of the stom ach within the lesser om entum . The left gastric artery forms an anastom osis with the right gastric artery along the lesser curvature of the stom ach. Branches of the gastric arteries distribute to the anterior and posterior surfaces of the stom ach. 7. Re ect the greater om entum superiorly and use blunt dissection to separate it from its attachm ent to the transverse colon while sparing its attachm ent to the greater curvature of the stom ach. 8. Re ect the stom ach superiorly and follow the sp le n ic art e ry to the left for about 5 cm and verify that it lies against the posterior abdom inal wall. Observe that the splenic artery is tortuous and courses along the sup erior border of the p ancreas where it m ay be p artially im bedded. Do not dissect the branches arising from the m iddle portion of the splenic artery at this tim e.

9. Follow the splenic artery to its distal end where it gives the sh ort g ast ric art eries to supply the fundus of the stom ach (FIG. 4.26). Observe that the short gastric arteries are em bedded in the gastrosplenic ligam ent. 10. Observe that near its distal end, the splenic artery also gives rise to the le ft g ast ro -o m e n t al (g ast ro e p ip lo ic) art e ry, which courses in the greater om entum about 2 cm away from the greater curvature of the stom ach (FIG. 4.26). 11. Find the rig h t g ast ro -o m e n t al art e ry from its origin off the com m on hepatic artery and follow it along its path within the greater om entum near the right end of the greater curvature of the stom ach. The right gastro-om ental artery anastom oses with the left gastro-om ental artery along the greater curvature of the stom ach. [G 324; L 231; N 284; R 322] 12. Return to the hep atoduodenal ligam ent and identify the h e p at ic p o rt al ve in lying posterior to both the hep atic artery p roper and the bile duct (FIG. 4.24).

Right hepatic artery and duct 24%

75%

Cystic artery Cystic duct

Cystic artery Common hepatic duct

Hepatic artery proper

FIGURE 4.27 The two m ost com m on branching patterns of the cystic artery.

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CLIN ICA L CORRELATION

Sp le e n The relationship of the spleen to ribs 9, 10, and 11 is of clinical im portance in evaluating rib fractures and penetrating wounds (FIG. 4.28). A lacerated spleen bleeds profusely into the abdom inal cavity and m ay have to be rem oved surgically (sp lenectom y). It m ust be em phasized that there is a risk of puncturing the spleen during pleural tap (thoracentesis). An enlarged spleen (splenom egaly) m ay be encountered during p hysical exam ination. The spleen is considered enlarged when it can be palp ated inferior to the costal m argin.

13. Follow the hepatic portal vein superiorly and observe that it passes into the p orta hep atis where it divid es into rig h t an d le ft p o rt al ve in s . Note that the hepatic portal vein usually receives the left an d rig h t g ast ric ve in s as tributaries. 14. Follow the hepatic portal vein inferiorly and observe that it passes posterior to the rst part of the duodenum.

Sp le e n [G 326; L 232; N 282; R 327] The spleen is the largest hem atopoietic organ in the body. Its size and weight m ay vary considerably depending on the blood volum e that it contains and the health of the individual. The spleen is covered by visceral peritoneum except at the hilum where the splenic vessels enter and leave. 1. Use your left hand to retract the fundus of the stom ach to the right and use your right hand to gently pull the spleen anteriorly. 2. Observe that the spleen has a sm ooth d iap h rag m at ic surface and sharp anterior, inferior, and sup erior borders (FIG. 4.28A). Note that the superior border of the spleen is often notched due to its pattern of em bryological development. 3. The visce ral surface o f t h e sp lee n is related to four organs: the st o m ach , the le ft kid n e y, the t ran sve rse co lo n (le ft co lic e xure ) , and the p an cre as . Note that the diaphragm atic surface of the spleen is related through the diaphragm to ribs 9 , 10 , a nd 11 (FIG. 4.28B).

Live r [G 340; L 233; N 277; R 307] The liver is the largest gland in the body, com prising about 2.5% of the body weight of an adult. To study the surface features of the liver, it m ust be detached from the diaphragm . 1. Review the location of the falciform and coronary ligam ents of the liver. 2. Use scissors to cut the falciform ligam ent between the liver and diaphragm , extending the incision superiorly to the level of the coronary ligam ent.

Lung

Parietal pleura Midaxillary line Costodiaphragmatic recess Rib 9

Spleen Diaphragm 10

Colon Parietal peritoneum

A

Stab wound 11

Spleen

B

FIGURE 4.28 Relationships of the spleen to the thoracic wall. A. Frontal section. B. Lateral view. A penetrating wound through the ninth intercostal sp ace, just p osterior to the m idaxillary line, will penetrate the p leural cavity, diaphragm , peritoneal cavity, and spleen.

3. Gently pull the liver inferiorly and extend the cut bilaterally through the coronary ligam ent toward the right and left triangular ligam ents along the inferior surface of the diap hragm . 4. Use scissors to cut the in fe rio r ven a cava between the liver and the diap hragm . 5. Insert your ngers between the liver and the diaphragm and gently tear the connective tissue attaching the liver directly to the diaphragm across the bare area of the liver. 6. On the posterior aspect of the liver, cut the posterior layer of the coronary ligam ent freeing the liver from the diap hragm . 7. Elevate the inferior border of the liver and cut the inferior vena cava again as close to the inferior surface of the liver as possible. The two cuts through the inferior vena cava will leave a short segm ent of vena cava within the liver (FIG. 4.29). 8. The liver should now be freely m obile but attached to the other abdom inal viscera by the bile duct, the hep atic artery proper, and the hep atic p ortal vein. Move the liver carefully to avoid tearing these structures. 9. Exam ine the live r and note that the rig h t lo b e is ap proxim ately six tim es larger than the le ft lo b e and that the sharp in fe rio r b o rd e r of the liver separates its visce ral surface from its d iap h rag m at ic surface . 10. Identify the b are area on the posterior aspect of the diaphragm atic surface of the liver and observe that it is bound by the cut edges of the coron ary lig am en t . Note that in this location, the liver was immediately adjacent to the diaphragm and not covered by peritoneum.

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CLIN ICA L CORRELATION

Caudate lobe Inferior vena cava Bare area

Ligamentum venosum

THE ABDOMEN

Portal triad in porta hepatis

Left lobe

Right lobe

Live r The liver m ay undergo pathologic changes that could be encountered during dissection. The liver m ay be enlarged, which happ ens in liver congestion due to cardiac insuf ciency (cardiac cirrhosis), or it m ay be sm all and have brous nodules indicating cirrhosis of the liver. Because the liver is essentially a capillary bed downstream from the gastrointestinal tract, m etastatic tum or cells are often trapped within it, resulting in secondary tum ors.

Falciform ligament Round ligament of the liver

Quadrate lobe

Gallbladder

FIGURE 4.29 Inferior view of the four anatom ic lobes of the liver (rig ht, left, q uad rate, and caudate), and the associated H-shaped ssures and sulci.

h e p at ic lym p h n o d e s , which follow lym p hatic vessels accom panying the hepatic arteries toward ce liac lym p h n o d e s located around the celiac trunk. Lym ph from the liver also drains posteriorly into p h re n ic n o d e s.

Gallb lad d e r [G 348; L 236; N 280; R 306] 11. Exam ine the visce ral surface of the liver and identify the H-shap ed set of ssures and fossae de ning its four lobes. Observe that the lig am e n t um ve n o sum and falcifo rm lig am e n t occupy the left ssure of the “H” and that the g allb lad d e r and in fe rio r ve n a cava occupy the fossae that form the right side of the “H” (FIG. 4.29). 12. Identify the p o rt a h e p at is form ing the horizontal bar of the “H.” Recall that the structures passing through the hepatoduodenal lig am ent (bile ducts, hep atic arteries, hep atic portal vein, lym p hatics, and autonom ic nerves) enter or leave the liver at the porta hepatis. 13. Identify the caud at e lo b e between the inferior vena cava and the ligam entum venosum and the q uad rat e lo b e between the round ligam ent of the liver and the g allbladder (FIG. 4.29). [G 341, 348; L 233; N 277; R 308] 14. Exam ine the sm all segm ent of the in fe rio r ve n a cava attached to the liver and rem ove any coagulated b lood from within the vessel. Observe that several h e p at ic ve in s drain directly from the liver into the inferior vena cava. 15. Two com m on conventions are used to divide the liver. The rst divides the liver into rig h t an d le ft an at o m ical lo b e s using the falciform ligam ent as a g uide. The second divides the liver by the pattern of bile drainage and vascular supply. In this schem e, right and left livers are separated by the inferior vena cava and ultim ately divided into eight hepatic segm ents. [G 344; L 234, 235; R 308] 16. The liver has a substantial lym phatic drainage. At the porta hepatis, sm all lym ph vessels drain into

Th e g allb lad d er occup ies a sh allow fossa on th e visceral surface of th e liver an d is a reservoir for th e storag e an d con cen tration of b ile. Th e g allb lad d er is usually stain ed d ark g reen b y b ile, wh ich leaks th roug h th e wall of th e g allb lad d er after d eath often stain in g th e surroun d ing tissue. 1. Replace the liver into its correct anatom ical position. 2. Con rm th at th e g allb lad d er is located n ear th e tip of th e n in th costal cartilag e in th e m id clavicular line. 3. Observe that the distal end of the gallbladder, or the fun d us , is free of the liver and directed anteriorly. The attached portion of the gallbladder is the b o d y, whereas the n e ck is the narrow p ortion leading toward the biliary tree (FIG. 4.30). 4. Lift the inferior border of the liver to exp ose the visceral surface. Use blunt dissection to carefully rem ove the gallb ladder from its fossa. 5. Review the course of the cyst ic art e ry from the hepatic vessels (FIG. 4.25). Note that the cystic artery is often stained green by bile and is often fragile m aking it dif cult to dissect. 6. Use scissors to m ake a longitudinal cut through the wall of the gallbladder, beginning at the fundus and continuing through the neck into the cystic duct. If gallstones are present, rem ove them . 7. Look for the sp iral (valve ) fo ld , which is a fold in the m ucosal lining of the neck continuing into the cyst ic d uct allowing for bidirectional ow in and out of the organ (FIG. 4.30). 8. Return the gallbladder and other abdom inal organs to their correct anatom ical p ositions.

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Liver

Gallbladder: Neck Body Fundus

Hepatic ducts: Left Right Common hepatic duct Cystic duct: Spiral fold Smooth part Bile duct

Duodenum: Superior (1st) part Descending (2nd) part

Head of pancreas Pancreatic duct Hepatopancreatic ampulla Major duodenal papilla

FIGURE 4.30

Gallbladder and extrahepatic bile ducts.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5. 6. 7.

Review the location of each organ relative to the abdom inal quadrant system . Use an illustration and the dissected specim en to trace the branches of the celiac trunk. Review the relationships of the structures in the hepatoduodenal ligam ent. Review the boundaries of the om ental foram en. Review the parts of the organs dissected and their relationships to surrounding structures. Use an em bryology textbook to review the developm ent of the liver, pancreas, and ventral m esogastrium . Review all derivatives of the em bryonic foregut.

SUPERIOR MESENTERIC ARTERY AND SMALL INTESTINE Disse ct io n Ove rvie w The superior m esenteric artery arises from the anterior surface of the abdom inal aorta about 1 cm inferior to the celiac trunk at vertebral level L1. At its origin, the sup erior m esenteric artery lies p osterior to the neck of the p ancreas. When the superior m esenteric artery em erges from posterior to the neck of the p ancreas, it passes anterior to the p ancreatic uncinate process, the third part of the duodenum , and the left renal vein. The superior m esenteric artery then enters the m esentery of the sm all intestine where it courses into the right lower q uadrant, toward the term inal end of the ileum . The superior m esenteric artery delivers the m ajority of the blood supply to both the sm all intestine and the large intestine, up to the right two-thirds of the transverse colon. The order of dissection will be as follows: The m esentery will be exam ined. The branches of the superior m esenteric artery that supp ly the jejunum , ileum , cecum , ascending colon, and transverse colon will be dissected. The rem ainder of the eld of sup ply of the sup erior m esenteric artery (to the duodenum and pancreas) will be dissected later because these structures lie deep to the attachm ent of the transverse m esocolon. The external features of the jejunum and ileum will be studied.

CHAPTER 4

Disse ct io n In st ruct io n s Sup e rio r Me se n t e ric Art e ry an d Sm all In t e st in e [G 334; L 225; N 287, 288; R 313] 1. Re ect the greater om entum and transverse colon superiorly over the costal m argin so the posterior surface of the transverse m esocolon faces anteriorly (FIG. 4.31). 2. Position th e coils of th e je ju n u m an d ile u m to th e left sid e of th e ab d om en so th e rig h t sid e of th e m esen tery faces anteriorly (FIG. 4.31). Ob serve th at th e root of th e m esen tery is attach ed to th e p osterior ab d om in al wall alon g an ob liq ue lin e from th e left up p er q uad ran t to th e rig h t lower q uad ran t. 3. Rem ove the anterior portion of the peritoneum on the right side of the m esentery to expose the branches of the superior m esenteric artery. To do this, m ake a sm all incision through the anterior layer of the peritoneum and then use forcep s to grasp it and slowly p eel it away while using a p robe to separate it from the underlying blood vessels. 4. Rem ove the parietal peritoneum from the posterior abdom inal wall on the right side of the m esentery as far laterally as the ascending colon. Note that all portions of the peritoneum on the surface of an organ are visceral, whether it is a retroperitoneal organ or an intraperitoneal organ. 5. Identify the sup e rio r m e se n t e ric art e ry (FIG. 4.31). Use blunt dissection to trace the superior m esenteric artery p roxim ally and observe that it crosses anterior to the third part of the duodenum . Note that the third

6.

7.

8.

9.

Greater omentum (reflected)

Superior mesenteric v. and a.

Middle colic a. Right colic a.

10.

Jejunum Root of mesentery

Intestinal arteries

Ileocolic a.

11.

Mesentery

Cecum

Vasa recta

Appendix Ileum

Arterial arcades

FIGURE 4.31 Sm all intestines positioned to the left for dissection of the superior m esenteric artery.

12.

THE ABDOMEN

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123

part of the duodenum and/ or the left renal vein can becom e compressed between the superior mesenteric vessels and the abdom inal aorta leading to superior mesenteric artery syndrome or nutcracker syndrom e, respectively. Use blunt dissection to clean the branches of the superior m esenteric artery, which are em bedded in a variable am ount of m esenteric fat. As you dissect, observe the sup e rio r m e se n t e ric p lexus o f n e rve s , a dense autonom ic nerve network surrounding the blood vessels. Rem ove the nerve bers as necessary to de ne the vessels. Identify the sup e rio r m e se n t e ric ve in p ositioned along the right side of the superior m esenteric artery (FIG. 4.31). The superior m esenteric vein is form ed by tributaries that correspond in nam e and position to the branches of the superior m esenteric artery. Posterior to the pancreas, the sup erior m esenteric vein joins the sp lenic vein to form the h e p at ic p o rt al vein . The m esentery m ay contain up to 200 m e se n t e ric lym p h n o d e s . Identify one or two of these lym ph nod es, if visible, along the branches of the superior m esenteric vessels. The m esenteric lym phatic channels follow the branches of the superior m esenteric artery and drain into the sup e rio r m e se n t e ric lym p h n od e s near the origin of the superior m esenteric artery from the abdom inal aorta. Lym ph nodes m ay be rem oved to clear the dissection eld. Beg in id en ti cation of th e b ra n ch e s o f t h e su p e rio r m e se n t e ric a rt e ry with the 15 to 18 in t e st in a l a rt e rie s orig in atin g from th e left sid e of the sup erior m esenteric artery and sup p lying the jejunum and ileum (FIG. 4.31). In testinal arteries end in straig h t term inal b ran ch es called va sa re ct a (straig h t arteries), which are in terconnected b y a rt e ria l a rca d e s . Note that the inferior pa ncrea ticoduodena l a rtery is usually the rst branch of the superior m esenteric artery; this vessel will be dissected with the duodenum . Observe the blood supply to the proxim al jejunum and note that only one or two arcades are found between adjacent intestinal arteries, resulting in relatively long vasa recta (FIG. 4.32A). Exam ine the distal ileum and note that four or ve arcades occur between adjacent intestinal arteries, resulting in relatively short vasa recta (FIG. 4.32B). Identify the ile o co lic art e ry arising from the rig ht side of the superior m esenteric artery and coursing toward the right lower quadrant in a retroperitoneal position to supply the cecum (FIG. 4.33). The ileocolic artery gives rise to the ap p e n d icular art e ry and anastom oses with intestinal branches and the right colic artery.

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A

14. Identify the m id d le co lic art e ry arising from the anterior surface of the sup erior m esenteric artery and coursing through the transverse m esocolon to supply the transverse colon (FIG. 4.31). Observe that the m iddle colic artery divides into a right and a left branch.

Jejunum

Circular folds Vasa recta

Sm all In t e st in e [G 330, 331; L 225, 228; N 264; R 318]

Arterial arcades

The sm all intestine consists of the d uodenum , jejunum , and ileum and is the m ajor site of digestion of food and absorption of nutrients. The sm all intestine has elaborate folds of m ucosa that increase the surface area for absorption and a rich blood sup ply to transport the absorbed nutrients. The je jun um (ap proxim ately two- fths of the sm all intestine)

B

Ileum

Circular folds

A

Vasa recta

Transverse colon

Arterial arcades

Duodenojejunal junction

Root of mesentery

FIGURE 4.32 Com parison of intestinal arteries. A. Arteries of the jejunum . B. Arteries of the ileum .

Jejunum

Ascending colon Ileocecal junction Mesentery Cecum

13. Identify the rig h t co lic art e ry arising from the right side of the sup erior m esenteric artery and p assing to the right in a retrop eritoneal position to supp ly the ascending colon (FIG. 4.31). Observe that the right colic artery often divides into a superior branch and an inferior branch.

Haustra (sacculations)

Ileum

B

Tenia coli

Right paracolic gutter

Ileocolic artery: Ascending branch Ileal branch Anterior cecal artery and fold Posterior cecal artery

Omental appendages

Cecum

Appendicular artery within mesoappendix

Appendix

Central tendon of diaphragm Esophagus in esophageal hiatus

Superior mesenteric artery

External iliac vessels (seen through peritoneum)

FIGURE 4.33

Appendix

Branches of the ileocolic artery.

Inferior vena cava in caval foramen Aorta in aortic hiatus Suspensory ligament of the duodenum Duodenojejunal junction

FIGURE 4.34 Sm all intestines positioned to the left side to disp lay the duodenojejunal junction. Inset: The duodenojejunal junction is suspended by the susp ensory m uscle (ligam ent) of the duodenum .

CHAPTER 4

and ile um (distal three- fths) will be studied together because the transition from one to the other is gradual. 1. Move the small intestine to the left side of the abdominal cavity and follow the jejunum proximally to nd the d uod enojejunal junction (FIG. 4.34A). Note that the small intestine is anchored at the duodenojejunal junction by the suspensory liga ment of the duodenum , a bromuscular band arising from the right crus of the diaphragm. The suspensory ligament passes posterior to the pancreas; thus, it cannot be seen at this time (FIG. 4.34B). 2. Palpate the sm all intestine and note that the wall of the jejunum is thicker than the wall of the

THE ABDOMEN

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125

ileum and that the overall d iam eter of the jejunum is larger. 3. Identify the term ination of the ileum where it em pties into the ce cum at the ile o ce cal jun ct io n (FIG. 4.34A). 4. Verify that the ro o t o f t h e m e se n t e ry crosses the posterior abdom inal wall from the duodenojejunal junction to the ileocecal junction and is about 15 cm long (FIG. 4.34A). Note that the in t e st in al at t ach m e n t o f t h e m e se n t e ry is nearly 6 m long. 5. Replace the sm all intestine and other displaced abdom inal contents in their correct anatom ical position.

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Review the location of the jejunum and ileum relative to the abdom inal quadrant system . Review the relationships of the jejunum and ileum to surrounding structures. Use an illustration and the dissected specim en to review the branches of the superior m esenteric artery. Use an em bryology textbook to review the derivatives of the em bryonic m idgut.

INFERIOR MESENTERIC ARTERY AND LARGE INTESTINE Disse ct io n Ove rvie w The in fe rio r m e se n t e ric art e ry arises from the anterior surface of the abdom inal aorta at vertebral level L3. The inferior m esenteric artery supplies the left third of the transverse colon, descending colon, sigm oid colon, and the superior onethird of the rectum . Excep t for the branches that pass through the sigm oid m esocolon to supp ly the sigm oid colon, the inferior m esenteric artery and its branches lie retroperitoneally. The order of dissection will be as follows: The inferior m esenteric artery and its branches will be dissected. The external features of the large intestine will be studied.

Disse ct io n In st ruct io n s In fe rio r Me se n t e ric Art e ry [G 336; L 226; N 288; R 315] 1. Re ect the transverse colon and greater om entum superiorly over the costal m argin to expose the p osterior surface of the transverse m esocolon (FIG. 4.35). 2. Move the sm all intestine to the right so the descending colon is visible from the left colic exure to the sigm oid colon (FIG. 4.35). 3. Identify the inferior m esenteric artery where it arises from the abdom inal aorta, com m only posterior to the third part of the duodenum . If you have trouble nding it, nd one of its branches in the sigm oid m esocolon and trace that branch back to the m ain vessel and then proceed with the dissection of the peripheral branches. Disse ct ion n o t e: The left ureter could be m istaken for the inferior m esenteric artery or one of its branches because the inferior m esenteric artery and vein and the ureter all lie in the retroperitoneal space. The vessels can be differentiated from the ureter because they descend in the abdom inal cavity anterior to the ureter.

Omental apron portion of greater omentum (turned up)

Transverse colon (turned up)

Transverse mesocolon Middle colic artery

Duodenojejunal junction

Superior mesenteric artery Inferior mesenteric artery Left colic artery Sigmoid arteries

Paraduodenal fold (inferior mesenteric vein) Retroduodenal fossa Descending colon Tenia coli Haustra

Superior rectal artery

Sigmoid colon

Rectum

FIGURE 4.35 Sm all intestines positioned to the right for dissection of the inferior m esenteric artery.

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4. Use a probe to clean the b ran ch e s o f t h e in ferio r m esen t eric art ery beginning with the left co lic art ery, which supplies the descending colon and the left third of the transverse colon. Note that the left colic artery anastomoses with the middle colic branch of the superior mesenteric artery and the ascending branch of the rst sigmoid artery (FIG. 4.35). 5. Identify three or four sig m o id art e rie s supp lying the sigm oid colon. Sigm oid arteries p ass through the sigm oid m esocolon and form arcades sim ilar to those of the intestinal arteries. 6. Identify the sup erio r rect al art ery descending into the pelvic cavity to supply the proxim al part of the rectum . Follow the superior rectal artery until it divides into a rig h t b ran ch and a left b ran ch , which descend into the pelvic cavity on either side of the rectum . 7. Superior to the left colic artery, identify the m arg in al art e ry o f t h e co lon coursing along the inner circum ference of the large intestine near the splenic exure. Observe that the m arginal artery reaches the m iddle colic artery to form an anastom osis between the superior and inferior m esenteric arteries. 8. Observe that the tributaries of the in ferio r m e se n t eric ve in corresp ond to the branches of the inferior m esenteric artery. The inferior m esenteric vein ascends on the left side of the inferior m esenteric artery and p asses p osterior to the pancreas where it joins either the sp le n ic ve in or the sup e rio r m e se n t e ric ve in as a tributary of the hepatic portal vein. 9. Lym p h vessels that accom pany the branches of the inferior m esenteric artery drain the descending colon and sigm oid colon. These lym phatic vessels drain into the in fe rio r m e sen t e ric n o d e s located around the origin of the inferior m esenteric artery from the abdom inal aorta. 10. Return the sm all intestine and transverse colon to their correct anatom ical positions.

64%

1% Retrocecal position

Cecum

Terminal ileum

2% 32%

FIGURE 4.36

3.

4.

5.

Larg e In t e st in e [G 330, 331; L 224, 226; N 276; R 317] The large intestine consists of the ce cum (with attached ve rm ifo rm ap p e n d ix), co lo n (ascending, transverse, descending, and sigm oid), re ct um , and an al can al. Absorption of water from fecal m aterial is a m ajor function of the large intestine. The relatively sm ooth m ucosal surface of the large intestine is well suited for this function because a sm ooth surface is less likely to im pede the m ovem ent of progressively m ore solid fecal m aterial. 1. Beginning in the right lower quadrant, identify the various com ponents of the larg e in t e st in e beginning with the ce cum (L. caecus, blind) (FIG. 4.33). The length of its m esentery and the degree of its m ob ility vary considerably from individual to individual. 2. Identify the ap p e n d ix (ve rm ifo rm ap p en d ix) (L. appendere, to hang on) attached to the end of

0.5%

6.

7.

8.

Variations in the p osition of the app end ix.

the cecum in one of several positions (FIG. 4.36). Recall that the appendix is suspended on a m esentery called the m e so ap p e n d ix and that the ap p e n d icular art ery is found within the m esoap pendix (FIG. 4.33). Identify the asce n d in g co lo n extending from the cecum to the rig h t colic e xure and the t ran sve rse co lo n from the rig h t co lic e xure to the le ft co lic e xure . Observe that the left colic exure lies at a m ore superior level than the right colic exure due to the location of the liver. Between the two exures, the transverse colon is freely m ovable and susp ended by the transverse m esocolon (FIG. 4.35). Observe the d e sce n d in g co lo n from the left colic exure to the left lower quadrant and recall that it is a secondarily retrop eritoneal organ (FIG. 4.35). In the left lower quadrant, nd the sig m o id co lo n and observe that the sigm oid colon has a m esentery (sig m o id m e so co lo n ) , is m obile, and ends in the p elvis at the level of the S3 where it is continuous with the rectum . The re ct um and an al can al are contained entirely within the pelvic cavity and will be dissected with the pelvic viscera. On the external surface of the large intestine, observe three features that distinguish it from the sm all intestine: The t e n iae co li are three narrow bands of longitudinal m uscle running the length of the large intestine (FIG. 4.35), the h aust ra are outpouchings of the wall of the colon, and the o m e n t al ap p e n d ice s (e p ip lo ic ap p e n d ag e s) are sm all accum ulations of fat covered by visceral peritoneum . Review the branches of the superior m esenteric artery and inferior m esenteric artery that supply the large intestine. [G 339; L 226; N 288; R 324]

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THE ABDOMEN

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127

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Review the location of each part of the large intestine relative to the abdom inal quadrant system . Review the relationship of each part of the large intestine to the surrounding structures. Use an illustration and the dissected specim en to trace the branches of the inferior m esenteric artery. Use an em bryology textbook to review the derivatives of the em bryonic hindgut.

DUODENUM, PANCREAS, AND HEPATIC PORTAL VEIN Disse ct io n Ove rvie w The duodenum is the part of the sm all intestine between the stom ach and the jejunum and is the recipient of the ducts of the liver and p ancreas. The p ancreas lies within the bend of the duodenum with its head directed at the descending or second portion of the duodenum . The p ancreas is both an endocrine and an exocrine organ and has a rich blood supp ly arising from the celiac trunk and the sup erior m esenteric artery. The order of dissection will be as follows: The p arts of the duodenum will be studied. The pancreas will be dissected. The form ation of the hepatic portal vein will be dem onstrated.

Disse ct io n In st ruct io n s Duo d e n um [G 327, 328; L 238, 239; N 271; R 326] 1. Re ect the transverse colon and greater om entum superiorly over the costal m argin. 2. Use blunt dissection to separate and rem ove the transverse m esocolon and connective tissue overlying the anterior surface of the duodenum and pancreas. 3. Beginning with the sup e rio r ( rst ) p art at the L1 vertebral level, identify the fo ur p art s o f t h e d uo d e n um (FIG. 4.37). Observe that the superior p art of the duod enum lies in the transverse plane and that the hepatoduodenal ligam ent is attached to it. Note that the rst part is mostly intraperitoneal and has an expanded initial part called the a mpulla which clinicians often call the duodena l ca p or duodena l bulb . 4. Identify the d e sce n d in g (seco n d ) p art of the duod enum at the L2 vertebral level and observe that it is

Gallbladder Common bile duct Main pancreatic duct

Accessory pancreatic duct Minor duodenal papilla

Neck

Spleen

Body

1

2

Sphincter of Odi Major duodenal papilla Head

4 3 Uncinate process

FIGURE 4.37

Tail Pancreas Superior mesenteric a.

Main pancreatic duct and parts of the pancreas.

positioned to the right of m idline and anterior to the hilum of the right kidney, right renal vessels, and inferior vena cava (FIG. 4.37). Note that the second part of the duodenum is retroperitoneal and receives the bile duct and the pancreatic duct. 5. Identify the horizontal (third) p art of the duodenum at the L3 vertebral level anterior to the inferior vena cava and the abdominal aorta. Observe that it is crossed anteriorly by the superior mesenteric vessels and posteriorly by the inferior mesenteric vessels and is retroperitoneal. 6. Lastly, identify the asce n d in g (fo urt h ) p art of the duodenum at the L2 vertebral level. Note that the ascending part of the duodenum is retroperitoneal throughout most of its length until it turns anteriorly to join the jejunum at the duodenojejuna l junction .

Pan cre as [G 327, 350; L 239; N 281; R 327] 1. Identify the p an cre as within the bend of the duod enum . Note that it is a secondarily retroperitoneal organ that lies across the midline and is positioned against vertebral bodies L1–L3. 2. Identify the h ead of th e p an creas adjacent to the descending duodenum (FIG. 4.37). Observe that the inferior vena cava lies posterior to the head of the pancreas. 3. At the inferior m argin of the head of the pancreas, identify the un cin at e p ro cess , a sm all projection that lies posterior to the superior m esenteric vessels. 4. Superior to the head of the pancreas, identify the an t e rio r an d p o st e rio r sup e rio r p an cre at ico d uo d e n al art erie s arising from the sup e rio r p an cre at ico d uo d e n al art e ry near the g ast ro d uo d e n al art e ry (FIG. 4.38). [G 329; L 239; N 283; R 326] 5. Identify the n eck of th e p ancreas, a short portion that lies anterior to the superior m esenteric vessels connecting the head and body of the pancreas. Observe that the b od y of t he p an creas extends from right to left and slightly superiorly as it crosses the abdom inal aorta.

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Gastroduodenal a.

Posterior superior pancreaticoduodenal a.

Hepatic a. proper Common hepatic a. Celiac trunk Splenic a.

Pylorus (cut and reflected) Anterior superior pancreaticoduodenal a. Right gastroomental a.

Greater pancreatic a.

1

2 4

Anterior inferior pancreaticoduodenal a. Posterior inferior pancreaticoduodenal a.

3 Dorsal pancreatic a. Superior mesenteric a.

Left gastroomental a.

Inferior pancreaticoduodenal a.

FIGURE 4.38

Blood supply of the duodenum and pancreas.

6. Identify the t ail o f t h e p an cre as , the narrow left end of the gland which lies in the splenorenal ligam ent and contacts the hilum of the spleen. 7. Use a probe to dissect into the anterior surface of the head of the pancreas and nd the m ain p ancreatic duct (FIG. 4.37). Follow the main pancreatic duct through the neck and into the body. Note that the a ccessory pa ncrea tic duct joins the superior side of the main pancreatic duct. 8. Follow the com m on bile duct inferiorly and observe that it joins the m ain pancreatic duct near the left side of the descending p art of the duodenum . 9. Inferior to the head of the p ancreas, identify the in fe rio r p an cre at ico d uo d e n al art e ry com m only arising as the m ost p roxim al branch of the sup erior m esenteric artery, although its origin is variable (FIG. 4.38). 10. Return to the celiac trunk and follow the splenic artery as it passes to the left along the sup erior border of the pancreas (FIG. 4.38).

11. Remove the remaining peritoneum over the anterior aspect of the pancreas and observe that up to 10 small branches of the splenic artery supply the body and tail of the pancreas although only two will be named here: the dorsal pancreatic artery entering the neck of the pancreas and the greater pancreatic (pancreatica m agna ) artery entering the pancreas about halfway between the neck and the tail. Recall that the splenic artery also gave rise to the short gastric arteries and left gastro-omental artery. 12. The veins of the pancreas correspond to the arteries and drain into the superior m esenteric and splenic veins and ultim ately are tributaries to the hepatic portal vein.

He pat ic Po rt al Ve in [G 354; L 240; N 291; R 313] The sup e rio r m e se n t e ric ve in and the sp le n ic ve in join to form the hepatic p ortal vein p osterior to the neck of the pancreas. The h ep at ic p o rt al ve in carries venous blood to the liver from the abdom inal portion of the gastrointestinal tract, the spleen, and the p ancreas. 1. Identify the sp le n ic vein where it courses posterior to the pancreas and inferior to the splenic artery. Use a probe or blunt dissection to isolate the splenic vein posterior to the body of the pancreas. Observe that the splenic vein is typically atter and straighter than the m ore tortuous thicker sp lenic artery. 2. Follow the splenic vein to the right where it is joined by the superior m esenteric vein to form the h e p at ic p o rt al ve in (FIG. 4.39). Recall that the hep atic p ortal vein ascends in the hepatoduodenal ligam ent to the porta hepatis. 3. Return to the eld of distribution of the inferior m esenteric vein and follow it superiorly. Note that the inferior m esenteric vein may join the superior m esenteric vein, the splenic vein, or the junction of the superior m esenteric and splenic veins.

CLIN ICA L CORRELATION

Po rt al Hyp e rt e n sio n The hepatic portal system of veins has no valves. When the hepatic portal vein becomes blocked, blood pressure increases in the hepatic portal system (portal hypertension) and its tributaries become engorged. Portal hypertension causes hemorrhoids and varicose gastric and esophageal veins. Bleeding from ruptured gastroesophageal varices is a dangerous complication of portal hypertension. Four portal-systemic (portal-caval) anastomoses exist within the abdomen to allow for alternative routes of venous return: the gastroesophageal (left gastric vein/ esophageal veins/azygos vein), the anorectal (superior rectal vein/middle and inferior rectal veins), the paraumbilical (paraum bilical veins/super cial epigastric veins), and the retroperitoneal (colic veins/retroperitoneal veins).

Liver Left epigastric v. Splenic v.

Hepatic portal v. Inferior mesenteric v.

Superior mesenteric v.

FIGURE 4.39

Hepatic portal vein.

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THE ABDOMEN

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129

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Review the relationship of each part of the duodenum to the surrounding structures. Review the branches of the celiac trunk and superior m esenteric artery. Use an illustration and the dissected specim en to reconstruct the blood supply to the pancreas and duodenum . Review the form ation and eld of drainage of the hepatic portal vein. Trace a drop of blood from the sm all intestine to the inferior vena cava, nam ing all veins that are encountered along the way. Rep eat this exercise beginning at the descending colon. 6. Use an em bryology textbook to review the developm ent of the liver, pancreas, and duodenum .

REMOVAL OF THE GASTROINTESTINAL TRACT Disse ct io n Ove rvie w The interior features of the various parts of the gastrointestinal tract and the posterior abdom inal wall are best dissected with the gastrointestinal tract rem oved from the abdom inal cavity. The order of dissection will be as follows: The stom ach will be opened and reviewed. The sm all and large intestine will be opened regionally and reviewed. The rectum and esophagus will be cut, using ligatures to p revent sp illing their contents. The arteries to the gastrointestinal tract (celiac trunk, sup erior m esenteric artery, and inferior m esenteric artery) will be cut close to the aorta. The gastrointestinal tract will then be rem oved en bloc and reviewed outside of the body.

Disse ct io n In st ruct io n s Op e n in g t h e St o m ach 1. Elevate the diaphragm and identify the opening of the e so p h ag e al h iat us allowing passage of the esophagus into the abdom inal cavity. Use blunt dissection to clean the anterior surface of the esophagus and cardia of the stom ach. 2. Use scissors to open the stom ach along its anterior surface. If necessary, rinse and clean the m ucosa to observe the internal structures (FIG. 4.40). [G 323; L 231; N 270; R 302] 3. On the inner surface of the stom ach, identify the g ast ric fo ld s (rug ae ) . Note that the rugae will atten

Esophagus Cardial orifice of stomach

Pyloric sphincter Pyloric orifice Duodenum

Gastric folds (rugae)

Pyloric canal Pyloric antrum

FIGURE 4.40

Internal features of the stom ach.

out with stom ach expansion and are thus not always present. 4. Observe the narrowing of the body of the stom ach inferiorly at the p ylo ric an t rum just p rior to the p ylo ric can al. 5. Insert a probe into the p yloric canal and extend the cut through the anterior surface of the stom ach into pylorus. 6. Identify the p ylo ric sp h in ct e r at the end of the pyloric canal (FIG. 4.40), which controls the passage of food into the am p ulla of t h e d uod e n um through the p ylo ric o ri ce .

Op e n in g t h e Sm all In t e st in e an d Larg e In t e st in e 1. Use scissors to extend the longitudinal cut m ade through the stom ach into the anterior wall of the duodenum following the shape of the duodenum through the four p arts. 2. Spread open the second part of the duodenum and identify the circular fold s (p licae circulare s ) (FIG. 4.41). Note that unlike the rugae of the stomach, the folds of the small intestine are transversely oriented and are always present. [G 327; L 238; N 272; R 306] 3. Identify the m ajo r (g re at e r) d uo d e n al p ap illa , an elevation of m ucosa on the posterior-m edial wall of the second part of the duodenum (FIGS. 4.37 and 4.41). Note that the m ajor duodenal papilla is the shared opening of the main pancreatic duct and bile duct. 4. Identify the m in o r (le sse r) d uo d e n al p ap illa , the site of drainage of the accessory pancreatic duct, approxim ately 2 cm superior to the m ajor duodenal papilla (if present) (FIG. 4.41).

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Hood

Ileocolic artery

Major duodenal papilla Minor duodenal papilla

Longitudinal fold

Superior Ileocecal fold Ileum Ileocecal valve: Superior lip Orifice Inferior lip

Cecum

FIGURE 4.43

5. Use scissors to m ake one 5-cm longitudinal cut in the p ro xim al je jun um and another in the d ist al ile um . Rinse the m ucosa to com pare the two regions and ob serve that the p licae circulares are larger and closer together in the jejunum than they are in the ileum (FIG. 4.42). [G 330; N 272] Circular folds

Mesoappendix Appendicular artery

Circular folds

FIGURE 4.41 Mucosal features in the descending (second) p art of the duodenum .

Inferior ileocecal fold

Opening of appendix

Appendix

Interior of the cecum . Anterior view.

6. Use scissors to m ake a cut approxim ately 7.5 cm long in the anterior wall of the ce cum . Rinse the m ucosa and identify the ile o ce cal o ri ce located between the sup e rio r an d in fe rio r lip s o f t h e ile o ce cal valve (FIG. 4.43). [G 333; L 227; N 274; R 318] 7. Identify the o p e n in g o f t h e ve rm ifo rm ap p en d ix inside the cecum , using the app endix as a landm ark for orientation. Observe the proxim ity of the op ening of the appendix to the ileocecal ori ce. 8. Use an illustration to verify that the colon consists of se m ilun ar fo ld s (p licae se m ilun are s) between adjacent h aust ra and its m ucosa is relatively sm ooth com pared to the other parts of the gastrointestinal tract. [G 331; N 276]

Re m o val o f t h e Gast ro in t e st in al Tract

Proximal jejunum

Distal ileum

FIGURE 4.42 Com parison of m ucosal features in the p roxim al jejunum and distal ileum .

1. Use your ngers to separate fascia and peritoneum surrounding the distal end of the sigm oid colon and rectum and g ently p ull them anteriorly away from the sacrum . 2. Tie two strings 4 cm apart around the distal end of the sigm oid colon, close to the rectum , or as far inferiorly as possible in the pelvic cavity. Make an effort to m ake the knots tight but do not tighten the string so m uch as to sever the colon. 3. Use scissors to cut the sigm oid colon between the strings to ensure as little rem aining fecal m atter as possible enters the dissection eld. 4. Cut the superior rectal artery distally as well as any fascia preventing the sigm oid colon from being elevated out of the pelvic cavity. 5. Inferior to the thoracic diaphragm , identify the esophagus and cut the anterior and posterior vagal trunks just below where they pass through the diaphragm . 6. Tie one string around the esophagus m aking sure to not pull the knot so tight as to sever the esophagus and cut the esophagus superior to the string. It is not necessary to tie two strings around the esop hagus because typically, the esophagus is void.

CHAPTER 4

7. Use scissors to cut the celiac trunk close to the abdom inal aorta. Depending on the length of the celiac trunk, it m ay be p ossible to leave a very short stum p. 8. Use scissors to cut the sup erior m esenteric artery near the aorta, leaving a 1-cm stum p. 9. Use scissors to cut the inferior m esenteric artery near the aorta, leaving a 1-cm stum p. 10. Free the stom ach by cutting through any peritoneal attachm ents it m ay still have to the posterior abdom inal wall. 11. Grasp the spleen and gently pull it anteriorly and medially. Insert your ngers posterior to the spleen and carefully free the splenic vessels, tail of the pancreas, and body of the pancreas from the posterior abdominal wall. 12. Use scissors to cut the suspensory ligam ent of the duodenum close to the duodenojejunal junction. 13. Insert your ngers posterior to the duodenum and free it and the head of the pancreas from the posterior abdom inal wall. 14. Use scissors to cut the parietal peritoneum lateral to the ascending colon and use your ngers to free the ascending colon from the posterior abdom inal wall. Roll the ascending colon toward the m idline and use your ngers to loosen its blood vessels from the posterior abdom inal wall. 15. Cut the parietal p eritoneum lateral to the descending colon and use your ngers to free the descending colon from the posterior abdom inal wall. Roll the descending colon toward the m idline and use your ngers to loosen its blood vessels from the posterior abdom inal wall. 16. The gastrointestinal tract, liver, pancreas, and spleen should now be free of attachm ents. Rem ove them from the abdom inal cavity en bloc (FIG. 4.44). Support the liver and be careful not to twist or tear the structures in the hep atoduodenal lig am ent. 17. Arrange the abdom inal viscera on a dissecting table or large tray in anatom ical position and study the p arts from the anterior view (FIG. 4.44).

THE ABDOMEN

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18. Trace the branches of the celiac trunk, superior m esenteric artery, and inferior m esenteric artery to their areas of distribution. 19. Observe the form ation and term ination of the hepatic portal vein, noting the differences between the branching pattern of the arteries and the veins. 20. Turn the viscera and repeat the exercise of tracing the vessels from the posterior view. 21. The viscera m ay be stored in a large plastic bag or in the abdom inal cavity. Wet these specim ens frequently with m old-inhibiting solution.

Esophagus: Thoracic part Abdominal part

Liver

Gallbladder

Spleen Stomach

Pylorus

Pancreas

Duodenum

Left colic flexure Right colic flexure Transverse colon Ascending colon Descending colon Ileum

Jejunum

Cecum Appendix Anal canal

Sigmoid colon Rectum

FIGURE 4.44 Schem atic drawing of the abdom inal organs. Part of the transverse colon and the g reater om entum have been rem oved .

Disse ct io n Fo llo w-up 1. Review the features of the gastrointestinal m ucosa. 2. Com pare the quantity and com plexity of circular folds in the proxim al and distal parts of the sm all intestine. Com pare this arrangem ent to the m ucosal features seen in the stom ach and large intestine. Correlate your ndings to the function of the organs dissected. 3. Recall the locations of valves in the gastrointestinal tract.

POSTERIOR ABDOMINAL VISCERA Disse ct io n Ove rvie w The posterior abdom inal viscera are located in an area called the re t ro p e rit o n e al sp ace . The retroperitoneal sp ace is not a real space but is the part of the body between the posterior parietal peritoneum bounding the abdom inal cavity and the m uscles and b ones of the posterior abdom inal wall. The retroperitoneal space contains the kidneys,

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ureters, sup rarenal glands, aorta, inferior vena cava, and abdom inal p ortions of the sym pathetic trunks. [G 365; L 243; N 315; R 334] The order of dissection will be as follows: The posterior abdom inal viscera will be palpated and the parietal peritoneum rem oved. The renal fascia will be opened and the kidneys and sup rarenal glands will be studied. The abdom inal aorta and the inferior vena cava will be dissected. The m uscles of the posterior abdom inal wall will be studied. The lum bar plexus of nerves will be exam ined. Finally, the diaphragm will be studied.

Disse ct io n In st ruct io n s 1. If the gastrointestinal track and associated organs were stored within the abdom inal cavity, rem ove them from the dissection eld and place them in a bag. 2. If necessary, use a sponge or paper towels to clean and dry the posterior abdom inal wall.

Diaphragm

3. Palpate the kid n eys and the sup rare n al (ad re n al) g lan d s between vertebral levels T12 and L3 where they lie lateral to the vertebral colum n. [G 357; L 242; N 308; R 341] 4. Identify and palpate the ab d om in al aort a (FIG. 4.45). Clean the abdom inal aorta inferiorly to dem onstrate that it term inates at the level of L4 where it bifurcates into right and left com m on iliac art eries .

Esophagus Left adrenal gland

Celiac trunk Left kidney Superior mesenteric a. Left renal v. Right renal v.

Inferior vena cava

Transversus abdominis m.

Quadratus lumborum m.

Left testicular v.

Right testicular v.

Inferior mesenteric a.

Psoas major m.

Abdominal aorta Lumbar a. and v.

Sympathetic trunk

Left testicular a.

Right testicular a. and v. Femoral n.

Left ureter

FIGURE 4.45

Posterior abdom inal wall and kidneys.

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Te st icular Varico ce le Testicular varicocele occurs when the pam piniform plexus of veins becom es engorged with blood due to restriction of venous return through these vessels. Testicular varicocele is m ore com m on on the left side because the left testicular vein drains into the left renal vein and the left renal vein is subject to com pression where it passes inferior to the superior m esenteric artery, thus restricting venous return.

5. To the right of the abdom inal aorta, identify and palpate the in fe rio r ven a cava (FIG. 4.45). Observe that the inferior vena cava originates at the level of L5 where the right and left co m m o n iliac ve in s join. 6. If you are d issecting a fem ale cadaver, go to step 10. 7. On a m ale cadaver, identify and clean the t est icular art e ry an d ve in beginning at the deep inguinal ring and p rogressing sup eriorly (FIG. 4.45). Observe that the testicular vessels cross anterior to the ureter and are q uite sm all and delicate. Make an effort not to dam age the ureter while following the vessels. 8. The rig h t and le ft t e st icular art e rie s branch directly from the anterolateral surface of the aorta at about vertebral level L2, inferior to the origin of the renal arteries.

Kid n e ys [G 357; L 243, 244; N 308; R 341] The kidneys p lay key roles in the proper elim ination of waste and in m aintaining hom eostasis in a variety of ways including blood volum e and pressure regulation. The kidneys are well protected by their position within the abdom en as well as by a cushioning layer of fat. The retroperitoneal p osition of the kidneys and their p rotective fatty layer is best illustrated in a transverse section (FIG. 4.46). 1. Observe that the kidneys lie against the posterior abdom inal wall and that the anterior surface of the kidneys face anterolaterally (FIG. 4.46).

Inferior vena cava Duodenum (2nd part)

Superior mesenteric vessels

Abdominal aorta Duodenum (4th part)

Peritoneum Crura of the diaphragm Three flat abdominal muscles: Transverse abdominis m. Internal oblique m. External oblique m.

Perirenal fat

Sympathetic trunks

Right kidney

Perirenal fat Quadratus lumborum m. Psoas major m.

FIGURE 4.46

133

9. Observe that the le ft t e st icular vein d rains into the left renal vein, whereas the rig h t t e st icular ve in drains directly into the inferior vena cava (FIG. 4.45). 10. In the fe m ale cad ave r , identify and clean the o varian ve sse ls . Observe that the o varian art e rie s originate from the aorta in a com parable location to that of the testicular arteries in the m ale. 11. Observe that the le ft o varian ve in drains into the left renal vein, whereas the rig h t o varian ve in drains into the inferior vena cava. 12. Follow the ovarian vessels inferiorly toward the p elvic cavity until they cross the e xt e rn al iliac ve sse ls but do not follow them into the pelvis at this tim e. Observe that the ovarian vessels cross anterior to the ureters along their descent.

CLIN ICA L CORRELATION

Retroperitoneal space and perirenal fat

THE ABDOMEN

Deep back muscles

Transverse section throug h the posterior abdom inal wall at the level of the kid neys.

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2. Use your ngers to tear through the re n al fascia and separate the kid n ey from the p e rire n al fat around the circum ference of the kid ney (FIG. 4.46). 3. Using blunt dissection, carefully rem ove portions of the perirenal fat from the dissection eld to increase visibility of the kidneys. Make an effort not to disrupt the fascia lining the p osterior abdom inal wall during the fat rem oval p rocess. 4. Observe that the sup erio r p o le of the kidney is separated from the suprarenal gland by a thin layer of renal fascia. Carefully use your ngers to identify the border between the kidney and the suprarenal gland. Be careful not to rem ove the suprarenal gland with the fat. 5. Note the size and shape of the kidney (FIG. 4.45). 6. Place the right kidney in its correct anatom ical position and verify that the suprarenal gland is superior to the kidney. Use an illustration to verify that the right kidney, through its peritoneal covering, is in contact with the right colic exure, the visceral surface of the liver, and the second p art of the duodenum . [G 356; L 241; N 308; R 328] 7. Place the left kidney in its correct anatom ical position and verify that through the peritoneum , the left kidney is in contact with the tail of the p ancreas, the left colic exure, the stom ach, and the sp leen. 8. Observe that the hilum of the kidney faces anterom edially and that the lateral border faces p osterolaterally. 9. Identify the le ft re n al ve in and use a p robe to trace it from the left kidney across the m idline to the inferior vena cava (FIG. 4.45). Observe that it lies anterior to b oth renal arteries and the aorta. 10. Identify and clean the le ft t e st icular (o r o varian ) ve in draining into the left renal vein inferiorly and the le ft sup rare n al ve in draining into the left renal vein superiorly (FIG. 4.45). 11. Identify the le ft re n al art e ry, which lies posterior to the left renal vein. Follow the left renal artery to the hilum of the kidney and observe that it usually divides into several se g m e n t al art e rie s before it enters the kidney. Note that accessory renal arteries are comm on and dem onstrate one of the important processes that take place during renal developm ent. Accessory renal arteries are an excellent exam ple of anatomical variation. 12. Identify the in fe rio r sup rare n al art e ry, branching off the left renal artery to the left suprarenal gland, and if visible, the ure t e ric b ran ch to the left ureter. 13. Using the left renal artery as a hinge, turn the left kidney toward the right and observe the posterior surface of the left kidney. 14. Identify the re n al p e lvis and its inferior continuation, the uret e r (FIG. 4.47). 15. Use blunt dissection to follow the ureter inferiorly. Observe that the abdom inal part of the ureter p asses p osterior to the testicular (or ovarian) vessels

Renal papilla

Renal medulla: Renal column Renal pyramid

Renal cortex

Minor calyces

Major calyx Renal sinus Renal pelvis

Ureter Renal capsule

FIGURE 4.47 section.

Internal features of the kidney in longitudinal

and crosses the anterior surface of the psoas m ajor m uscle. Note that before the gastrointestinal tract was removed, the left ureter passed posterior to the branches of the inferior m esenteric artery. 16. Use a scalpel to divide the left kidney into anterior and posterior halves by splitting it longitudinally along its lateral border. Open the two halves of the kidney like a book using the renal pelvis as the hinge. 17. On the internal aspect of the kidney, identify the re n al co rt e x , the outer zone of the kidney (about one-third of its depth). Observe that the cortex is surrounded by the re n al cap sule, a thin brous capsule rm ly attached to the surface of the kidney (FIG. 4.47). [G 360; L 244; N 311; R 336] 18. Deep to the renal cortex, identify the re n al m e d ulla , the inner zone of the kidney (about two-thirds of its depth). Observe that the renal m edulla consists of re n al p yram id s sep arated by re n al co lum n s (FIG. 4.47). CLIN ICA L CORRELATION

Kid n e y St o n e s Kidney stones (renal calculi) m ay form in the calyces and renal p elvis. Sm all kidney stones m ay spontaneously pass through the ureter into the bladder. Larger kidney stones m ay lodge at one of three natural constrictions of the ureter: (1) where the renal p elvis becom es constricted to form the ureter, (2) where the ureter crosses the p elvic brim , and (3) at the entrance of the ureter into the urinary bladder.

CHAPTER 4

19. At the ap ex of the renal pyram ids, identify the re n al p ap illa that projects into a m in o r calyx . Observe that the m in o r calyx is a cup-like cham ber that is the beginning of the extrarenal duct system . 20. Observe that several m inor calyces com b ine to form a m ajo r calyx , which d rains into the ren al p e lvis , the funnel-like proxim al end of the ureter that begins within the re n al sin us and em erges from the renal hilum . Note that the rena l sinus is the space within the kidney occupied by the renal pelvis, calices, vessels, nerves, and fat. 21. Follow the renal pelvis to the ure t e r , the m uscular duct that carries urine from the kidney to the urinary bladder. 22. Return the left kidney to its correct anatom ical position. 23. Clean the relatively short rig ht renal vein observing that it has no tributaries. 24. Deep to the right renal vein, expose the right renal artery by re ecting the inferior vena cava inferiorly and slightly toward the right. 25. Clean the right renal artery and observe that is longer than the left renal artery. 26. Identify the in fe rio r sup rare n al art e ry to the right suprarenal gland and the ure t e ric b ran ch to the right ureter. 27. Re ect the right kidney over the inferior vena cava and observe that the right renal pelvis lies posterior to the rig ht renal artery. 28. Follow the right ureter inferiorly from the right renal pelvis and observe that the ureter passes posterior to the right testicular (or ovarian) vessels (FIG. 4.45).

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CLIN ICA L CORRELATION

Sup rare n al Glan d s The kidneys and suprarenal glands have different em bryonic origins. If the kidney fails to ascend to its norm al p osition during develop m ent, the sup rarenal gland still develops in its norm al position lateral to the celiac trunk.

4. Use an illustration to observe that each suprarenal gland receives m ultiple arteries from various sources (FIG. 4.48). 5. Identify the in fe rio r sup rare n al art e ry arising from the renal artery. To isolate the sm all delicate arteries, gently p ush the probe through the fat parallel to the exp ected direction of the vessels. 6. Using a sim ilar technique with the probe, carefully identify the sup e rio r sup rare n al art e ry arising from the inferior phrenic artery and the m id d le sup rare n al art e ry arising from the aorta near the celiac trunk (FIG. 4.48). 7. Rem ove the rem aining perirenal fat from the region noting the presence of a vast collection of sm all nerve bers paralleling the vessels. 8. Use an illustration or the cadaver, if the veins in the region are still present, to observe that the left suprarenal vein em pties into the left renal vein and that the right suprarenal vein drains directly into the inferior vena cava. 9. The suprarenal glands receive num erous sym pathetic nerve bers from the surrounding ganglia. It is not necessary to try to identify the sym pathetic innervation of the adrenal glands.

Sup rare n al Glan d s [G 357; L 243, 244; N 310, 322; R 336] The sup rare n al (ad re n al) g lan d s are closely related to the sup erior p oles of the kidneys and are contained within their own com p artm ent of renal fascia (FIG. 4.48). Because the adrenal glands are fragile, they m ay b e easily torn, so they m ust b e dissected with a gentle hand. The suprarenal g land s are endocrine glands and have a cop ious blood sup ply from vessels that are sim ilarly delicate and easy to tear. 1. Palpate the suprarenal glands within the perirenal fat. Often, the boundaries of the glands are dif cult to d ifferentiate from the surrounding fat, therefore use the vessels in the region to help delineate the border. 2. Observe that the rig h t sup rare n al g lan d is com m only triangular in shape (FIG. 4.48) and that a part of it lies posterior to the inferior vena cava. 3. Observe that the le ft sup rare n al g lan d is com m only sem ilunar in shape (FIG. 4.48) and m ore exp osed.

THE ABDOMEN

Inferior phrenic aa. Left suprarenal gland

Right suprarenal gland

Superior suprarenal aa.

Right kidney

Middle suprarenal a. Inferior suprarenal a. Left kidney Left renal a. Left testicular a. (male) Left ovarian a. (female)

Right renal a. Right testicular a. (male) Right ovarian a. (female)

FIGURE 4.48

Abdominal aorta

Blood supply of the suprarenal glands.

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Ab d o m in al Ao rt a an d In fe rio r Ve n a Cava [G 369; L 246; N 308; R 345] 1. Use an illustration to study the abdom inal aorta and observe in the b ody that it beg ins at vertebral level T12 as the continuation of the thoracic aorta inferior to the diap hragm and ends by bifurcating at vertebral level L4 to form the right and left com m on iliac arteries. 2. Observe that the abdom inal aorta has three types of branches: unpaired visceral, paired visceral, and paired som atic. Identify the un p aire d visce ral art e rie s arising from the m idline to the gastrointestinal tract (celiac trunk, superior m esenteric artery, and inferior m esenteric artery) (FIG. 4.48). 3. Identify the p aired visce ral art e ries coursing to the three p aired abdom inal organs (m iddle sup rarenal arteries, renal arteries, and gonadal [testicular or ovarian arteries]). 4. Identify the p aired so m at ic art e rie s to the abdom inal wall (inferior phrenic arteries and lum bar arteries). 5. Identify at least one of four pairs of lum b ar art e rie s (FIG. 4.45). Observe that the right lum bar arteries cross the lum bar vertebral bodies and pass posterior to the inferior vena cava. Note that on both sides, the lumbar arteries pass deep to the psoas major muscles. 6. On the inferior surface of the diaphragm , clean the in fe rio r p h re n ic art e rie s and trace them back to their p oint of origin from the aorta near the aortic hiatus (FIG. 4.48). Recall that these arteries give rise to superior suprarenal arteries.

7. At the term ination of the abdom inal aorta, identify and clean the proxim al portion of the co m m o n iliac art e rie s at L4. The com m on iliac arteries sup ply blood to the pelvis and lower lim bs and will be dissected in m ore detail with the p elvis. 8. Observe that p re ao rt ic g an g lia surround the abdom inal aorta and its visceral branches form ing a com plex network of autonom ic nerves. The p reaortic ganglia include ce liac , sup e rio r m e se n t e ric , ao rt ico re n al, and in fe rio r m e se n t eric com p onents. Connections from the preaortic ganglia extend along the lateral aspect of the aorta inferiorly in the h yp o g ast ric p le xuse s , which carry autonom ic inform ation to and from the pelvis. 9. Identify and clean the in fe rio r ve n a cava beginning at the L5 vertebral level as well as its m ajor tributaries, the right and left com m on iliac veins. Recall that the inferior vena cava ends at the T8 vertebral level by passing through the diaphragm to em pty into the right atrium . 10. Observe that the inferior vena cava receives venous drainage from the paired abdom inal organs (renal veins, suprarenal veins, gonadal [testicular or ovarian] veins) either directly (right side) or indirectly (left side). Note that the inferior vena cava has no unpaired tributaries from the gastrointestinal tract because the hepatic portal system collects all the blood from the gastrointestinal tract and drains into the liver. From there, the hepatic veins drain the liver into the inferior vena cava. 11. Identify and clean the paired veins from the abdom inal wall (lum bar veins, inferior p hrenic veins), which drain into the inferior vena cava.

Disse ct io n Fo llo w-up 1. Replace the kidneys in their correct anatom ical positions. 2. Use an illustration and the dissected specim en to review the relationships of each kidney to the surrounding structures. 3. Trace the path taken by a drop of urine from the renal papilla through the ureter to the level of the pelvic brim , noting the points of possible constriction. 4. Review the shape, position, relationships, arterial supply, and venous drainage of each suprarenal gland. 5. Review the branches of the abdom inal aorta. 6. Review the tributaries of the inferior vena cava.

POSTERIOR ABDOMINAL WALL Disse ct io n Ove rvie w The posterior abdom inal wall is com posed of the vertebral colum n, m uscles that m ove the vertebral colum n, m uscles that m ove the lower lim bs, and the diaphragm . The nerves that supply the abdom inal wall and the lum bar plexus of nerves that innervate the lower lim b will be dissected with the posterior abdom inal wall. The order of dissection will be as follows: Muscles that form the posterior abdom inal wall will be dissected. The branches of the lum bar plexus will be studied. The abdom inal part of the sym pathetic trunk will be studied.

CHAPTER 4

Disse ct io n In st ruct io n s 1. As you dissect each side of the posterior abdominal wall, move the respective kidney and suprarenal gland toward the midline making sure you do not cut their associated vessels and use your hands to remove the remaining fat and renal fascia from the posterior abdominal wall. 2. Identify the p so as m ajo r m uscle (FIG. 4.49). While identifying the m uscles of the posterior abdominal wall, do not yet remove the overlying fascia and clean the m uscles because the nerves in the region may be dam aged. [G 366; L 245; N 258; R 341] 3. Look for the p so as m in o r m uscle , which has a long at tendon passing down the anterior surface of the p soas m ajor m uscle. Note that the psoas m inor m uscle is absent in approxim ately 40% of cases and may be present on only one side of the body. 4. Identify the iliacus m uscle (FIG. 4.49). Note that the iliacus and psoas major m uscles form a functional unit and together are called the iliopsoa s muscle. 5. Identify the q uad rat us lum b orum m uscle (FIG. 4.49). 6. Review the attachm ents, actions, and innervations of the psoas m ajor, p soas m inor, iliacus, and quadratus lum borum m uscles (see TABLE 4.2). 7. Identify the t ran sve rsus ab d o m in is m uscle and rem em ber that it is one of the anterolateral abdom inal wall m uscles that you dissected at the beginning of this unit. Observe that the transversus abdom inis m uscle lies posterior to the quadratus lum borum m uscle.

THE ABDOMEN

Lum b ar Ple x us [G 366, 367; L 250; N 262; R 345] The nerves of the posterior abdominal wall arise from the anterior rami of spinal nerves T12–L4. The lum b ar plexus (L1–L4) is formed within the psoas major muscle and its branches can be seen as they emerge from the lateral border of the psoas. The branching pattern of the nerves of the lumbar plexus varies somewhat between individuals. Use the peripheral relationships of the nerves (their region of distribution or a point of exit from the abdominal cavity) for positive identi cation. 1. Refer to FIGURE 4.49. 2. Identify the g e n it o fe m o ral n e rve on the anterior surface of the psoas m ajor m uscle. Observe that the genitofem oral nerve divides into genital and fem oral branches superior to the inguinal ligam ent. 3. Identify the g enital b ranch of the g en itofem oral n erve and observe that it passes through the deep

Subcostal nerve Iliohypogastric nerve (1) Transversus abdominis m. 1

Ilioinguinal nerve (2)

2

Quadratus lumborum m. Psoas major m. Iliacus m.

3 Lumbosacral trunk

Sympathetic trunk and ganglion

Genital br.

Anterior superior iliac spine

Femoral br.

Lateral cutaneous nerve of the thigh (3)

4

5

Genitofemoral nerve (4)

Sciatic nerve

Femoral nerve (5)

FIGURE 4.49

137

8. Use an illustration and the dissected specim en to study the relationship s between the kidneys and the posterior abdom inal wall (FIG. 4.45). Verify that the posterior surface of each kidney is related, through the renal fat and fascia, to the diaphragm , psoas m ajor m uscle, quadratus lum borum m uscle, and transversus abdom inis m uscle. 9. Observe that the superior pole of the right kidney is near the 12th rib and that the superior p ole of the left kidney is slightly higher, near the 11th rib.

Rib 12

Obturator nerve

•

Inguinal ligament

Lum bar plexus of nerves and posterior abdom inal wall m uscles.

138

4.

5.

6. 7.

8. 9.

10.

11.

12.

•

GRANT’S DISSECTOR

inguinal ring and down the inguinal canal. Note that the genital branch is the motor nerve to the cremaster muscle. Identify the fem oral b ran ch of the g enitofem oral n erve and observe that it passes under the inguinal ligam ent on the anterior surface of the external iliac artery. Note that the fem oral branch supplies a small area of skin inferior and m edial to the inguinal ligam ent. Use blunt dissection to rem ove the extraperitoneal fascia from the posterior abdom inal wall lateral to the psoas m ajor m uscle. The branches of the lum bar plexus are em bedded in the extraperitoneal fascia and care m ust be taken not to dam age them . To nd the sub costal n erve , palpate rib 12 and look for the subcostal nerve about 1 cm inferior and parallel to it. Find the ilioh yp og astric and ilioin g uin al nerves, which descend steeply across the anterior surface of the quadratus lum borum m uscle. Frequently, these two nerves arise from a com m on trunk with the iliohypogastric nerve located m ore superiorly, and do not separate until they reach the transversus abdom inis m uscle. To positively identify the ilioinguinal nerve, follow it through the inguinal canal to the super cial inguinal ring. Identify the lat e ral cut an e o us n e rve o f t h e t h ig h where it passes deep to the inguinal ligam ent near the ASIS. The lateral cutaneous nerve of the thigh sup plies the skin on the lateral asp ect of the thig h. Identify the fe m o ral n e rve on the lateral sid e of the psoas m ajor m uscle in the groove between the psoas m ajor and iliacus m uscles. The fem oral nerve innervates the iliacus m uscle and p asses deep to the inguinal ligam ent to p rovide m otor and sensory branches to the anterior thigh. To nd the o b t urat o r n e rve , insert your nger into the extraperitoneal fascia on the m edial side of the psoas m ajor m uscle and m ove your nger parallel to the m uscle, creating a gap between the p soas m ajor m uscle and the com m on iliac vessels. Identify the obturator nerve running anterior/ posterior in this gap . Note that the obturator nerve supplies m otor and sensory innervation to the m edial thigh. Identify the lum b osacral t run k m edial to the obturator nerve. The lum bosacral trunk is a large nerve form ed by contributions from the anterior ram us of L4 and all of the anterior ram us of L5. The lum bosacral trunk passes into the pelvis to join the sacral plexus and should be followed only a short distance at this tim e.

13. On the left side of the abdom inal cavity, follow each nerve of the lum bar plexus p roxim ally into the p soas m ajor m uscle and observe that each branch of the lum bar plexus passes through the psoas m ajor m uscle at a different depth. 14. Clean the posterior abdom inal wall to clearly display each nerve of the lum bar plexus as well as the superior extent of each m uscle passing deep to the diaphragm .

Ab d o m in al Part o f t h e Sym p at h e t ic Trun k [G 370; L 251–253; N 262; R 346] 1. On the left side of the posterior abdominal wall, identify and clean the sym p athetic trunk. Observe that the sympathetic trunk lies on the lum bar vertebral bodies between the crus of the diaphragm and the psoas major muscle. Study the location of the sym p athetic trunk on a transverse section of the abdomen (FIG. 4.46). 2. Identify lum b ar sp lan ch n ic n e rve s that p ass anteriorly from the lum bar sym pathetic ganglia to the aortic autonom ic nerve plexus. 3. Beginning at the genitofem oral nerve, rem ove the psoas m ajor m uscle piece by piece, on one side only, to fully expose the lum bar plexus. Pay attention not to dam age the lum bar vessels or the sym pathetic trunk. 4. Cut and rem ove the psoas m ajor m uscle to a point just p roxim al to its p assage deep to the inguinal ligam ent and place its pieces in the tissue container. 5. With the psoas m ajor m uscle rem oved, exam ine the point of exit of each spinal nerve from its intervertebral foram en and verify the spinal level contributions to each nam ed nerve (e.g., fem oral nerve—L2, L3, L4). 6. Identify ram i co m m un ican t e s that pass p osteriorly from the sym p athetic ganglia to the lum bar anterior ram i. Note that the gray ram i of the lower lum bar region are the longest in the body because the sym pathetic trunk crosses the anterolateral surface of the lum bar vertebral bodies. 7. Observe that the ram i com m unicantes lie against the lateral surface of the vertebral bodies. To assist nding the ram i com m unicantes, clean and follow the lum bar arteries from their origin off the abdom inal aorta and observe the relationship of the arteries, veins, and nerves in the lum bar region. 8. Use an illustration to review the autonom ic nerve supp ly of the abdom inal viscera.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the proxim al and distal attachm ents as well as the action of each of the m uscles of the posterior abdom inal wall. 2. Review the three m uscles that form the anterolateral abdom inal wall (external oblique, internal oblique, and transversus abdom inis). 3. Follow each branch of the lum bar plexus peripherally. Review the region of innervation of each of these nerves. 4. Use an atlas drawing to review the abdom inal part of the sym pathetic trunk, the lum bar splanchnic nerves, and ram i com m unicantes (both gray and white).

CHAPTER 4

THE ABDOMEN

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TABLE 4.2

Muscle s o f t h e Po st e rio r Ab d o m in al Wall

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Psoas major

Lumbar vertebrae (bodies, intervertebral discs, and transverse processes)

Lesser trochanter of the femur

Flexes the thigh and extends the vertebral column

L1–L4 (anterior rami)

Psoas minor

Lateral surface of T12 and L1

Iliopubic eminence and arcuate line of the ilium

Tilts pelvis posteriorly

L1–L2 (anterior rami)

Iliacus

Iliac fossa

Lesser trochanter of the femur

Flexes the thigh

Femoral n.

Quadratus lumborum

12th rib and lumbar transverse processes

Iliolumbar ligament and iliac crest

Flexes vertebral column laterally and anchors the rib cage during respiration

T12–L4 (anterior rami)

Abbreviation: n., nerve.

DIAPHRAGM Disse ct io n Ove rvie w The d iap h rag m form s the roof of the abdom inal cavity and the oor of the thoracic cavity. The diaphragm is the principal m uscle of respiration and has a right half and a left half (the h e m id iap h rag m s ). The order of dissection will be as follows: The parts of the diaphragm will be identi ed. The phrenic nerve will be reviewed. The greater splanchnic nerves that pass through the diaphragm will be studied.

Disse ct io n In st ruct io n s If the ribs were p reviously cut, separate them to either side to increase visibility and ease of access to the diaphragm . If they were not, consider sep arating them at this tim e to facilitate the following dissection sequence. 1. Use blunt dissection to strip the parietal peritoneum and connective tissue off the abdom inal surface of the diap hragm sp aring the inferior p hrenic vessels. [G 368; L 245; N 258; R 292, 293] 2. Identify the ce n t ral t en d o n o f t h e d iap h rag m , the ap oneurotic center of the diap hragm , and distal attachm ent of all of its m uscular parts (FIG. 4.50). Recall that the pericardial sac fused with the superior asp ect of the central tendon. 3. The m uscular portion of the diaphragm can be subdivided into sternal, costal, and lum bar parts. Identify the st e rn al p art of the diap hragm : two sm all b undles of m uscle bers attaching to the posterior surface of the xiphoid process. 4. Identify the co st al p art of the diaphrag m , where the m uscle bers attach to the inferior six ribs and their costal cartilages. 5. Identify the lum b ar p art of the diaphragm form ed by two crura (right and left) and the m uscle bers that arise from the m edial and lateral arcuate ligam ents. 6. Identify the rig h t crus of the diap hragm and observe that it has attachm ents to the bod ies of vertebrae L1–L3 and wraps around the esophagus to form the e so p h ag e al h iat us (FIG. 4.50).

Sternal part Costal part Median arcuate ligament Lumbar part, right crus

Central tendon Costal cartilage Inferior vena cava in vena caval foramen Esophagus in esophageal hiatus Aorta in aortic hiatus

Lumbar part, left crus Medial arcuate ligament Lateral arcuate ligament

Quadratus lumborum m.

FIGURE 4.50 Inferior view of the respiratory diaphragm and structures passing between the abdom inal and thoracic cavities.

7. Identify the le ft crus of the diap hragm and observe that it has attachm ents to the bodies of vertebrae L1 and L2 (FIG. 4.50). 8. Identify the arcuat e lig am e n t s , thickenings of transversalis fascia that serve as proxim al attachm ents for som e of the m uscle bers of the diap hragm .

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9. Identify the lat e ral arcuat e lig am e n t bridg ing the anterior surface of the quadratus lum borum m uscle, the m e d ial arcuat e lig am e n t bridging the anterior surface of the psoas m ajor m uscle, and the m e d ian arcuat e lig am e n t (unp aired) bridging the anterior surface of the aorta at the aortic hiatus. 10. Three large openings in the diaphragm allow p assage of contents between the thoracic and abdom inal cavities. Beginning superiorly, identify the ve n a caval fo ram en p assing through the central tendon at vertebral level T8 (FIG. 4.50). Observe that the caval foram en only allows p assage of the inferior vena cava through the diap hragm . 11. Identify the e so p h ag e al h iat us p assing through the right crus at vertebral level T10 and observe that the esop hagus and vagal trunks pass through this opening. 12. Lastly, identify the ao rt ic h iat us passing posterior to the diap hragm at vertebral level T12. The aortic hiatus transm its the aorta, the azygos and hem iazygos veins, and the thoracic duct. Note that the sympathetic trunk passes through the diaphragm between the m uscle bers and the posterior abdom inal wall m usculature. 13. Within the thorax, identify the rig h t and le ft p h re n ic n e rve s and recall that they p rovide m otor innervation to the right and left hem idiaphragm s, respectively, and also sup ply m ost of the sensory innervation to the diap hragm atic (p arietal) peritoneum inferiorly and diap hragm atic (parietal) pleura sup eriorly. Note that the pleural and peritoneal coverings of the p eripheral part of the diaphragm receive sensory bers from the lower intercostal nerves (T5–T11) and the subcostal nerve. 14. To increase m obility of the diaphragm , cut the right p hrenic nerve approxim ately 4 cm away from the superior surface of the diap hragm and p ush the right hem idiap hragm inferiorly. 15. Clean and follow the azygos vein and the thoracic d uct inferiorly toward where they pass through

16.

17.

18.

19.

the aortic hiatus. To verify the op ening in the diaphragm that the azygos vein and thoracic duct pass through, gently push a probe through the aortic hiatus parallel to the aorta and note the proxim ity of these structures. Identify the g re at e r sp lan ch n ic n e rve in the right thorax and observe that it arises from vertebral levels T5–T9. Follow the greater splanchnic nerve inferiorly and verify that it penetrates the crus of the diaphragm to enter the abdom inal cavity. Note that the m ain portion of the greater splanchnic nerve distributes to the celiac ganglion where its sympathetic axons will synapse. [G 370; L 251–253; N 262; R 290, 291] Inferior to the greater splanchnic nerve, m ake an effort to identify and clean the le sse r sp lan ch n ic n e rve arising from vertebral levels T10–T11. Note that the least splanchnic nerve is dif cult to identify because it arises from vertebral level T12 deep to the posterior attachments of the diaphragm. Find the celiac g an g lia , if they have not been previously rem oved, on the left and right sides of the celiac trunk near its origin from the aorta. The celiac ganglia are the largest of the sym pathetic ganglia located on the surface of the aorta. Use an illustration or textbook description to review the autonom ic nerve supply of the abdom inal viscera.

CLIN ICA L CORRELATION

Diap h rag m The phrenic nerves arise from cervical spinal cord segm ents C3–C5. Pain from the diaphragm is referred to the shoulder region (supraclavicular nerve territory) because this is area of cutaneous innervation of C3–C5. The diaphragm can be paralyzed in cases of m id-cervical spinal cord injuries, but it is spared in low-cervical spinal cord injuries. A paralyzed hem idiaphragm cannot contract (descend), so it will be positioned higher than norm al in the thorax on a chest radiograph.

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Review the attachm ents of the diaphragm to the skeleton of the thoracic wall. Trace the course of the thoracic aorta as it passes through the aortic hiatus to becom e the abdom inal aorta. Review the course of the esophagus and vagus nerve trunks through the esophageal hiatus. Recall the position of the heart on the superior surface of the diaphragm and review the course of the inferior vena cava to the right atrium through the liver and diaphragm . 5. Study an illustration and observe that the thoracic duct passes through the aortic hiatus, and that the splanchnic nerves (greater, lesser, and least) penetrate the crura.

CHAPTER 5

The Pelvis and Perineum ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

Lesser (true) pelvis Greater (false) pelvis h e p elvis is th e area of tran sition between th e tru n k an d th e lower lim bs. Th e bon y p elvis serves as th e Plane of pelvic inlet Iliac crest fou n d ation for th e p elvic region an d p rovid es p rotection for p elvic organ s as well as stron g su p p ort for th e vertebral colu m n on th e lower lim bs. Th e p elvic ca vit y is con tin u ou s with th e abdom in al cavity, with th e tran sition occu rGluteal rin g at th e p lan e of th e p elvic in let (FIG. 5.1). Th e p elvic region cavity con tain s th e rectu m , th e u rin ary blad d er, an d th e in tern al gen italia. [G 390] Th e p er in eu m is t h e regio n o f t h e t ru n k lo cat ed b et ween t h e t h igh s an d sep arat ed fro m t h e p elvic cavit y b y t h e p elv ic d ia p h r a gm (FIG. 5.1). Th e p erin eu m co n t ain s t h e an al can al, t h e u ret h ra, an d t h e ext ern al gen it alia (p en is an d scro t u m in t h e m ale, vu lva in Pelvic brim Pelvic diaphragm t h e fem ale). Perineal region Ischioanal fossa Perineal membrane Th is ch ap ter begin s with th e d issection of stru ctu res in FIGURE 5.1 The pelvis on coronal section. th e an al trian gle com m on to both sexes. Dissection of in tern al an d extern al gen italia is d ivid ed in to two section s: on e for m ale cadavers an d on e for fem ale cadavers. Stu d en ts are exp ected to learn th e an atom y of both th e m ale an d fem ale p elvis an d p erin eu m ; th erefore, each d issection team sh ou ld p artn er with an oth er team d issectin g a cad aver of th e op p osite sex.

T

ANAL TRIANGLE Disse ct io n Ove rvie w Th e p e rin e u m is a d iam on d -sh ap ed area, inferior to th e p elvic d iap h rag m , b etween th e th ig h s. The p erin eum is com m on ly d ivid ed , for d escrip tive p urp oses, in to two triang les (FIG. 5.2). Th e a n a l t ria n g le is th e p osterior p art of th e p erin eum an d con tain s th e an al canal an d an us. Th e u ro g e n it a l t ria n g le is th e an terior p art of the p erin eum an d con tain s th e ureth ra an d th e extern al g en italia. At th e outset of d issection , it is im p ortan t to un d erstan d th at th ese two trian g les are n ot in th e sam e p lan e an d th at th e pelvic diaphragm separates the pelvic cavity from the perineum (FIG. 5.1). The order of dissection will be as follows: The skeleton of the m ale and fem ale pelvis will be reviewed. The skin of the gluteal region will be rem oved, and the gluteus m axim us m uscle will be retracted. The nerves and vessels of the ischioanal fossa will be dissected. The fat will be rem oved from the ischioanal fossa to reveal the inferior surface of the pelvic diaphragm .

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Scrotum Pubic symphysis Labium minus Labium majus Ischiopubic ramus Ischial tuberosity Anus Tip of coccyx

FIGURE 5.2

Boundaries of the urogenital and anal triangles in the m ale and fem ale.

Ske le t o n o f t h e Pe lvis Refer to an articulated bony pelvis. 1. Observe that the p e lvis (L. pelvis, basin) is form ed by two h ip b o n e s (o s co xae ) joined p osteriorly to the sacrum (FIG. 5.3A). Inferior to the sacrum , identify the fused coccyg eal vertebrae m aking up the co ccyx and note that they do not articulate with the hip bones. [G 390; L 261; N 333; R 450] 2. Identify the three bones com prising the hip bone: p ub is , isch ium , and ilium . Note that the three bones fuse in the ace t ab ulum at the t rirad iat e cart ilag e , which is not present in the adult. 3. In the e re ct p o st ure (anatom ical position), the an t e rio r sup e rio r iliac sp in e s and the anterior aspect of the p ubis at the p ub ic t ub e rcle s are in the sam e coronal plane. In this p osition, the p lane of the p elvic inlet form s an angle of approxim ately 55° to the horizontal. [G 391; L 262; N 334; R 455] 4. On the anterior surface of the hip bone, identify the iliac fo ssa . Observe that the iliac fossae are directed toward one another and form the lateral boundaries of the false (g re at e r) p e lvis , the portion of the bony pelvis superior to the p e lvic (in le t ) b rim (FIG. 5.1). [G 391; L 260; N 334; R 455] 5. Observe that the pelvic inlet is form ed by the sacral p ro m o n t o ry and an t erio r b o rd e r o f t h e ala (win g ) o f t h e sacrum posteriorly, the arcuat e lin e of the ilium laterally, and the p e ct en p ub is and p ub ic cre st of the p ubic bones anteriorly, which m eet at the p ub ic sym p h ysis . [G 393; L 261; N 333; R 449] 6. Observe that the lesser p elvis is located inferior to the pelvic brim and surrounded by bone. Note that the inferior boundary of the lesser pelvis is the pelvic diaphragm . [G 390] 7. Identify the point of dem arcation between the ilium and the pubic bone at the ilio p ub ic e m in e n ce , on the lateral asp ect of the sup erio r p ub ic ram us . 8. Observe the large opening on the anterior aspect of the pelvis, the o b t urat o r fo ram e n . In anatom ical position, this foram en faces inferiorly and is bound anteriorly by the superior pubic ram us, m edially by the isch io p ub ic ram us , and laterally by the bod y of the ischium . Note that the ischiopubic ram us is form ed by the isch ial ram us and the in fe rio r p ub ic ram us , which are often not easily delineated. 9. Identify the p ub ic arch posterior to the p ubic sym p hysis b etween the inferior p ubic ram i. Note that the sub p ub ic an g le (angle of the pub ic arch) is wider in fem ales than in m ales. [G 392, 393; L 262; N 334; R 450] 10. Observe that the ischial ram us transitions to the roughened area of the isch ial t ub e ro sit y on the lowest point of the bony pelvis. Note that the ischial tuberosity is the area of attachm ent for the ham strings as well as the sacro t ub e ro us lig am e n t . 11. From a posterior perspective, identify the isch ial sp in e of the ischium and note that this bony p rojection is directed toward the sacrum . The ischial sp ine sep arates the g re at e r sciat ic n o t ch from the le sse r sciat ic n o t ch and serves as point of attachm ent for the sacro sp in o us lig am e n t . [G 395; L 263; N 334; R 460] 12. Observe that the sacrospinous ligam ent creates the inferior aspect of the g re at e r sciat ic fo ram e n and the superior aspect of the le sse r sciat ic fo ram e n and that the sacrotuberous ligam ent com pletes the lesser sciatic foram en inferiorly (FIG. 5.3A, B). 13. On the sacrum , identify the an t e rio r sacral fo ram in a and observe that these foram ina connect to the sacral can al and are continuous with the p o st e rio r sacral fo ram in a . [G 390; L 261; N 333; R 452]

CHAPTER 5 Transverse process of L5 vertebra

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143

Anterior longitudinal ligament

Iliac crest

Iliolumbar ligament

Iliac fossa

Anterior sacroiliac ligament

Ala of sacrum

Anterior sacral foramina

Sacral promontory (covered by anterior longitudinal ligament)

Greater sciatic foramen Sacrotuberous ligament

Arcuate line

Sacrospinous ligament

Iliopubic eminence Coccyx Pecten pubis Superior pubic ramus Pubic tubercle Ischiopubic ramus: Ischial ramus Inferior pubic ramus

Femur Superior margin of pubic symphysis

A

Pubic symphysis and pubic arch

Obturator foramen and membrane

Iliolumbar ligament

Supraspinous ligament

Posterior superior iliac spine

Posterior sacroiliac ligament

Posterior sacral foramina

Sacrotuberous ligament

Greater sciatic foramen

Ischial spine Sacrospinous ligament

Coccyx

Lesser sciatic foramen Ischial tuberosity

B FIGURE 5.3

Bones and ligam ents of the p elvis. A. Anterior view. B. Posterior view.

14. Observe that the sacroiliac art iculat ion is strengthened by an an t erior sacroiliac lig am en t and a p ost erior sacroiliac lig am en t (FIG. 5.3A, B). Note that the sacroiliac articulation is a synovial joint between the auricular surfaces of the sacrum and the ilium . 15. On an articulated p elvis, observe that the ilio lum b ar lig am e n t strengthens the articulation at the lum b o sacral jo in t . 16. Identify the p e lvic o ut le t and observe that it is bound anteriorly by the in fe rio r m arg in o f t h e p ub ic sym p h ysis and p osteriorly by the t ip o f t h e co ccyx . Laterally, the pelvic outlet is bound by the isch io p ub ic ram i, the isch ial t ub e ro sit ie s , and the sacro t ub e ro us lig am e n t s . [G 396; L 260, 263; N 334; R 460]

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Disse ct io n In st ruct io n s

Gluteus maximus m.

Skin an d Sup e r cial Fascia Re m o val 1. If the lower lim b has been dissected previously, re ect the gluteus m axim us m uscle laterally and m ove ahead to the dissection of the ischioanal fossa . If the lower lim b has not been dissected, continue with step 2. 2. Refer to FIGURE 5.4 . 3. With the cadaver in the p rone position, m ake an incision that follows the lateral bord er of the sacrum and the iliac crest from the tip of the coccyx (S), to the m idaxillary line (T). If the back has been skinned, this incision has been m ade previously. 4. Make a m idline skin incision from S to the posterior edge of the anus. 5. Make an incision that encircles the anus. 6. Make an incision from the anterior ed g e of the an us d own the m ed ial surface of the thig h to p oint D (ab out 7.5 cm d own the m ed ial surface of the thig h). 7. Make a skin incision from D obliq uely across the posterior surface of the thigh to point E on the lateral surface of the thigh. Point E should be app roxim ately 30 cm inferior to the iliac crest. 8. Make a skin incision along the lateral sid e of the thigh from T to E. 9. Rem ove the skin from m edial to lateral and place it in the tissue container. 10. Rem ove the sup er cial fascia from the surface of the gluteus m axim us m uscle and place it in the tissue container.

T

T S Anus

D

E

FIGURE 5.4

Skin incisions.

Posterior superior iliac spine

Gluteal aponeurosis covering gluteal medius m.

Tensor of the fascia lata

Sacrum Sacrotuberous ligament Ischial tuberosity

Inferior cluneal nn.

Iliotibial tract (IT band)

Posterior cutaneous n. of the thigh

Fascia lata

FIGURE 5.5

The gluteus m axim us m uscle.

11. Clean the inferior border of the g lut e us m axim us m uscle (FIG. 5.5). It is not necessary to save the in fe rio r clun e al n e rve s but take care not to cut the fascia lata (deep fascia) of the posterior thigh. 12. Use your hands to de ne the inferior m argin of the g luteus m axim us m uscle and separate it from the d eeper fat and connective tissue. 13. Use your ngers to retract the inferior border of the gluteus m axim us m uscle and palpate the sacro t ub e ro us lig am e n t . Note that the gluteus maxim us muscle is attached to the sa crotuberous liga ment and the sacrum . 14. Retract the gluteus m axim us m uscle superiorly to b roaden the dissection eld and expose the fat of the ischioanal fossa.

Isch io an al Fo ssa

D

E

Iliac crest

The isch io an al (isch io re ct al) fo ssa is a wedge-shaped area on either side of the anus. The apex of the wedge is directed superiorly toward the coccyx, and the base is b eneath the skin. The ischioanal fossa is lled with loose fat to accom m odate physical changes within the p elvis such as m ovem ent of the fetus during childbirth or distension of the anal canal during the passage of feces. The loose ischioanal fat is part of the super cial fascia of this

CHAPTER 5

region but is a different texture than the dense fat overlying the ischial tuberosities. The goal of this dissection is to rem ove the loose fat and identify the nerves and vessels passing through the ischioanal fossa. [G 449; L 283, 286; N 389; R 363] 1. Lateral to the anus, use scissors to perform blunt dissection in the ischioanal fossa. Begin by inserting the closed scissors into the ischioanal fat to a dep th of 3 cm and then opening the scissors in the transverse d irection to tear and p ush the fat with the blunt outer edge of the scissors (FIG. 5.6). 2. Insert your nger into this opening and m ove it back and forth (m edial to lateral) to enlarge the opening. 3. Palpate the in ferio r re ct al (an al) n e rve and vesse ls (FIG. 5.6). Preserve the branches of the inferior rectal nerve and vessels using blunt dissection to rem ove the surrounding fat and dry the area with p aper towels if necessary. Note that the inferior rectal nerve innervates the external anal sphincter m uscle and the skin around the anus. 4. Use blunt dissection to clean the e xt e rn al an al sp h in ct e r m uscle (FIG. 5.6). Note that the external anal sphincter muscle has three parts, a subcuta neous portion encircling the anus (often destroyed in dissection), a super cia l portion anchoring the anus to the perineal body and coccyx, and a deep portion form ing a ring of m uscle that is fused with the pelvic diaphragm . 5. Use blunt dissection to clean the in fe rio r surface o f t h e p e lvic d iap h rag m (m edial boundary of the ischioanal fossa). 6. Use blunt dissection to clean the fascia o f t h e o b t urat o r in t e rn us m uscle (the lateral boundary of the ischioanal fossa). 7. Laterally, observe that the inferior rectal nerve and vessels p enetrate the fascia of the obturator internus m uscle through a space known as the p ud e n d al can al. 8. Place gentle traction on the inferior rectal vessels and nerve and observe that a ridge is raised in the obturator internus fascia. The raised ridge of fascia overlies the pudendal canal.

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Initial cut Tip of coccyx Gluteus maximus m. Anococcygeal ligament Inferior rectal nerve and artery Pelvic diaphragm (inferior surface) Pudendal nerve and internal pudendal artery Perineal nerve and artery Anus Superficial part of external anal sphincter m. Scrotum (posterior view)

FIGURE 5.6 Initial incision used to begin the dissection of the ischioanal fossa.

9. Gen t ly p lace a p ro b e with in th e p u d en d al can al an d carefu lly cut t h e ob turato r fascia alon g th e raised rid g e to o p en th e can al. Take care to n ot cu t th e p u d en d al n erves an d vessels. O b serve t h at th e in ferio r rectal vessels an d n erve exit t h e in ferio r asp ect o f t h e p u d en d al can al to en ter t h e isch io an al fo ssa. N ote that the superior aspect of the canal com m unicates with the lesser scia t ic fora men . 10. Use a probe to elevate and clean the contents of the pudendal canal, nam ely the p ud en d al n e rve and the in t e rn al p ud e n d al art e ry and ve in .

Disse ct io n Fo llo w-up 1. Review the boundaries of the true pelvis and the concept that the pelvic diaphragm separates the pelvic cavity from the perineum . 2. In the dissected specim en, review the inferior surface of the pelvic diaphragm and understand that this is the “roof” of the perineum . 3. Use the dissected specim en to review the lateral and m edial walls of the ischioanal fossa. 4. Review the location of the external anal sphincter m uscle, its blood supply, and its pattern of innervation as a skeletal m uscle under voluntary control.

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MALE EXTERNAL GENITALIA AND PERINEUM Disse ct io n Ove rvie w If you are dissecting a fem ale cadaver, go to the section entitled “Fem ale External Genitalia, Urogenital Triangle, and Perineum ” and use this section for review with a m ale cadaver. In the em bryo, the scro t um form s as an outpouching of the anterior abdom inal wall; therefore, m ost layers of the abdom inal wall are represented in the scrotum (FIG. 5.7). The super cial fascia of the scrotum is represented by d art o s fascia , which contains sm ooth m uscle bers (d art o s m uscle ) and no fat. The order of dissection will be as follows: The scrotum will be opened by a vertical cut along its anterior surface. The sperm atic cord will be followed from the super cial inguinal ring into the scrotum . The testis will be rem oved from the scrotum . The sp erm atic cord will be dissected. The testis will be studied. Peritoneum Extraperitoneal fat Transversalis fascia Transversus abdominis m. Internal oblique m. External oblique m. Membranous layer Superficial (Scarpa's) Fatty layer fascia (Camper's)

Deep inguinal ring formed by transversalis fascia Obliterated processus vaginalis Parietal layer of tunica vaginalis Visceral layer of tunica vaginalis (covering testis and epididymis) Internal spermatic fascia Cremasteric fascia and muscle External spermatic fascia Dartos fascia and muscle Skin

FIGURE 5.7 Contrib utions of the anterior ab dom inal wall to the coverings of the sp erm atic cord and testis.

Disse ct io n In st ruct io n s Scro t um [G 306; L 282, 288; N 365; R 221, 224] Th e d issectio n o f th e scro tum corresp on d s to th e d issection of th e lab ium m ajus in fem ale cad avers. Partn er with a d issectio n team th at h as a fem ale cad aver fo r th e d issectio n o f th e extern al g en italia b ecau se yo u are exp ected to ob serve an d learn th e an atom y for b oth sexes.

1. Identify the sp e rm at ic co rd em erging from the sup e r cial in g uin al rin g . 2. Inferior to the sup er cial inguinal ring, insert your nger deep to the subcutaneous tissue of the lower anterior abdom inal wall and push your nger into the scrotum creating a space around the sp erm atic cord along its path of descent. 3. Make a vertical incision down the anterior surface of the scrotum , along the path m ade by your nger,

CHAPTER 5

4. 5.

6. 7.

8.

through the skin, dartos, and super cial fascia, ensuring you do not cut the sperm atic cord. Use your ngers to free the testis and sperm atic cord from the scrotum . Identify the scro t al lig am e n t (the rem nant of the g ub e rn aculum t e st is ), a band of tissue anchoring the inferior pole of the testis to the scrotum . [G 306; N 365; R 355] Use scissors to cut the scrotal ligam ent. Use your ngers to rem ove the testis from the scrotum but leave the testis attached to the sperm atic cord. Observe that the scro t al se p t um divides the scrotum into two com partm ents.

Testicular a. with pampiniform plexus of veins Cremasteric m. and fascia with genital branch of genitofemoral n. Internal spermatic fascia Lymph vessels and autonomic nerve fibers Artery of ductus deferens

FIGURE 5.8

Ductus deferens

Transverse section through the sperm atic cord.

147

Vase ct o m y The ductus deferens can be surgically interrup ted in the superior part of the scrotum (vasectom y). Sperm p roduction in the testis continues but the sperm atozoa cannot reach the urethra.

Sp e rm at ic Co rd [G 310; L 288; N 365; R 355]

External spermatic fascia

•

CLIN ICA L CORRELATION

4. The sperm atic cord contains the ductus deferens, testicular vessels, lym phatics, and nerves. The contents of the sperm atic cord are surrounded by three fascial layers, the co ve rin g s o f t h e sp e rm at ic co rd , derived from layers of the anterior abdom inal wall (FIG. 5.7). Each layer was added to the sp erm atic cord as the testis and associated structures passed through the inguinal canal during developm ent. 1. Study an illustration of a transverse section through the sperm atic cord (FIG. 5.8). 2. Palpate the sperm atic cord and identify the location of the d uct us d efe re n s (vas d e fe re n s) within the surrounding fascia. Observe that the vas deferens is the hardest and m ost “cord-like” structure in the sp erm atic cord. 3. Carefully m ake an in cision th roug h th e co ve rin g s o f t h e sp e rm a t ic co rd . Note th at th e coverin g s of th e sp erm atic cord , from sup er cial to d eep , are th e e xt e rn a l sp e rm a t ic fa scia (d erived from th e

THE PELVIS AND PERINEUM

5.

6.

7.

extern al ob liq ue ap on eurosis), th e cre m a st e ric m u scle a n d fa scia (d erived from th e in tern al ob liq ue m uscle an d ap on eurosis), an d th e in t e rn a l sp e rm a t ic fa scia (d erived from th e tran sversalis fascia) (FIGS. 5.7 an d 5.8). Use a probe to separate the ductus deferens from the p am p in ifo rm p le xus o f ve in s . Observe the art e ry o f t h e d uct us d e fe re n s , a sm all vessel located on the surface of the ductus deferens (FIG. 5.8) Follow the ductus deferens superiorly through the inguinal canal toward the d eep inguinal ring. Observe that the ductus deferens p asses through the deep inguinal ring lateral to the inferior epigastric vessels. Use a probe to sep arate the t e st icular art e ry from the pam piniform plexus of veins. The testicular artery can be d istinguished from the veins by its slightly thicker wall and its tortuous course. Note that sensory nerve bers, autonom ic nerve bers, and lym phatic vessels accompany the blood vessels in the sperm atic cord but that they are too sm all to dissect (FIG. 5.8).

Te st is [G 311; L 289; N 368; R 355] 1. The testis is covered by the t un ica vag in alis , a serous sac derived from the p arietal peritoneum (FIG. 5.7). The tunica vaginalis has a visce ral laye r on the surface of the testis and a p ariet al laye r on the wall of the sac (FIG. 5.9). Note that the ca vity of the tunica va gina lis is only a potential space containing a very small am ount of serous uid. 2. Use scissors to cut the parietal layer of the tunica vaginalis along its anterior surface and open it widely. Observe that the visceral layer of the tunica vaginalis covers the anterior, m edial, and lateral surfaces of the testis but not its posterior surface. 3. Use a prob e to follow the ductus deferens inferiorly until it joins the e p id id ym is . Identify the h e ad o f t h e e p id id ym is , the superior expanded part that receives the efferent ductules (FIG. 5.9). 4. Identify the b o d y o f t h e e p id id ym is , the m iddle part that is narrower in diam eter than the head, and the t ail o f t h e e p id id ym is , the inferior part that turns superiorly to join the ductus deferens. 5. Use a scalp el to section the testis along its anterior surface long itud inally from its sup erior p ole to

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its inferior p ole. Use the ep id id ym is as a hing e and op en the halves of the testis as you would op en a b ook. 6. Note the thickness of the t un ica alb ug in e a , which is the brous capsule of the testis. Observe the se p t a that divide the interior of the testis into lo b ule s (FIG. 5.9). 7. Use a n eed le o r fin e-tip p ed fo rcep s to tease so m e o f th e se m in ife ro u s t u b u le s o u t o f o n e lo b u le.

Ductus deferens

Spermatic cord

Testicular artery

Testicular vein (pampiniform plexus) Efferent ductules

Epididymis: Head Body

Rete testis Seminiferous tubule Septum

Tail

CLIN ICA L CO RRELATIO N

Lobules

Lym p h at ic Drain ag e o f t h e Te st is Lym p hatics from the scrotum drain to the super cial ing uinal lym p h nod es. In am m ation of the scrotum m ay cause tend er, enlarged super cial ing uinal lym ph nod es. In contrast, lym phatics from the testis follow the testicular vessels through the inguinal canal and into the abdom inal cavity, where they drain into lum bar (lateral aortic) and preaortic lym ph nodes. Testicular tum ors m ay m etastasize to lum bar and preaortic lym ph nodes, not to super cial inguinal lym p h nodes.

Visceral layer of tunica vaginalis Cavity of tunica vaginalis Parietal layer of tunica vaginalis Tunica albuginea Anterior

FIGURE 5.9 lateral view.

Parts of the testis and epididym is, right testis in

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Review the course of the ductus deferens from the abdom inal wall to the testis. Review the coverings of the sperm atic cord and review the layers of the abdom inal wall from which they are derived. Use an illustration to trace the route of sperm atozoa from their origin in the sem iniferous tubule to the ejaculatory duct. Visit a dissection table with a fem ale cadaver and com plete the “Dissection Follow-up” that follows the dissection of the labium m ajus.

MALE UROGENITAL TRIANGLE Disse ct io n Ove rvie w The order of dissection of the m ale urogenital triangle will be as follows: The skin will be rem oved from the urogenital triangle. The sup er cial perineal fascia will be rem oved, and the contents of the super cial perineal pouch will be identied. The skin will be rem oved from the penis, and its parts will be studied. The contents of the deep perineal pouch will be described but not dissected.

Disse ct io n In st ruct io n s Skin Re m o val Partner with a dissection team that has a fem ale cadaver for the dissection of the urogenital triangle. Because the space is particularly tight, usually only one student can work on the urogenital triangle at a tim e. To facilitate dissection, the student should be positioned between the thighs with the trunk of the cadaver pulled toward the end of the dissection table.

1. With the cadaver in the sup ine position, stretch the thighs widely ap art and brace them . 2. Make a skin incision that encircles the p roxim al end of the penis, m aking sure to not cut too deeply because the skin is very thin (FIG. 5.10). 3. Make a m idline skin incision p osterior to the proxim al end of the penis that splits the scrotum along the scrotal sep tum and continues p osteriorly as far as the anus (FIG. 5.10, blue dashed line).

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Cam p er’s fascia (the sup er cial fatty layer of the anterior abdom inal wall) and the fatty fasciae in the ischioanal fossa and thigh. The m e m b ran o us laye r o f t h e sup e r cial p e rin e al fascia (Co lle s’ fascia) is continuous with the m em branous layer of the sup er cial fascia of the anterior abdom inal wall (Scarpa’s fascia) and the d art o s fascia of the p enis and scrotum (FIG. 5.11A).

Shaft of penis

Peritoneum

Anus

FIGURE 5.10

Superficial abdominal fascia: Fatty layer (Camper's) Membranous layer (Scarpa's)

Rectum

Bladder

Skin incisions for the m ale perineum .

4. Make an incision in the m idline superior to the penis to the point where the skin of the abd om en was rem oved previously. 5. Re ect the skin aps from m edial to lateral. Detach the scrotum and skin aps along the m edial thigh (FIG. 5.10) and p lace them in the tissue container. 6. If the cadaver has a large am ount of fat in the supercial fascia of the m edial thighs, rem ove a portion of the sup er cial fascia starting at the ischiop ubic ram us and extending down the m edial thigh about 7 cm . Stay super cial to the fascia lata (deep fascia of the thigh) when rem oving the sup er cial fascia.

External urethral sphincter

Deep fascia of penis (Buck's)

Perineal membrane

Dartos fascia

Membranous layer of superficial perineal fascia (Colles')

A A

External oblique m. Membranous layer of superficial abdominal fascia

Male Sup e r cial Pe rin e al Po uch [G 444, 449; L 284; N 359; R 362]

Bloody extravasation

Like the lower anterior abdom en, the super cial perineal fascia has a super cial fatty layer and a deep m em branous layer. The sup er cial fatty layer is continuous with

Deep fascia of penis (Buck's) Membranous layer of superficial perineal fascia (Colles')

Dartos fascia

CLIN ICA L CORRELATION

Male Sup e r cial Pe rin e al Po uch If the urethra is injured in the perineum , urine m ay escap e into the sup er cial p erineal p ouch. The urine m ay spread into the scrotum and penis and upward into the lower abdom inal wall between the m em branous layer of the abdom inal super cial fascia (Scarpa’s fascia) and the aponeurosis of the external oblique m uscle (FIG. 5.11B). The urine would not enter the thigh because the m em branous layer of the sup er cial fascia attaches to the fascia lata, ischiopubic ram us, and p osterior edge of the perineal m em brane.

B B

Perforation of spongy urethra

Bloody extravasation

FIGURE 5.11 Fasciae of the perineum . A. The m em branous layer of the super cial perineal fascia (Colles’ fascia) is continuous with the super cial fascia (dartos fascia) of the scrotum and the penis. It is also continuous with the m em branous layer of super cial fascia of the lower ab dom inal wall (Scarpa’s fascia) and is attached to the posterior border of the p erineal m em brane. B. Following injury to the urethra in the perineum , extravasated urine is contained in the super cial perineal pouch and spreads into the lower abdom inal wall.

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1. In the m ale, three pairs of m uscles (left and right) overlie the erectile tissue of the root of the p enis and contribute to the co n t e n t s o f t h e sup e r cial p e rin e al p o uch along with the erectile tissues and the accom panying art e rie s , ve in s , an d n e rve s that supp ly the structures (FIG. 5.12A, B). 2. The three m uscles are the isch io cave rn o sus m uscle , b ulb o sp o n g io sus m uscle , and the sup e r cial t ran sve rse p e rin e al m uscle . 3. Identify the p o st e rio r scro t al n e rve an d ve sse ls and observe that they are term inal branches of the sup e r cial b ran ch o f t h e p erin e al art e ry an d n e rve and supp ly the posterior part of the scrotum . Note that the super cial branch of the perineal artery and nerve enter the urogenital triangle by passing lateral to the external anal sphincter muscle (FIG. 5.12A). 4. It is not necessary to identify the m e m b ran o us laye r o f t h e sup e r cial p e rin e al fascia (Co lles’ fascia) to com plete the dissection. Rather, review the attachm ents of Colles’ fascia by palpating the isch io p ub ic ram us and isch ial t ub e ro sit y as well as the posterior

A

5.

6. 7.

8.

edge of the p e rin e al m e m b ran e . Note that Colles’ fascia form s the super cial boundary of the super cia l perinea l pouch (space). Use b lunt d issection to nd the b ulb o sp o n g io sus m uscle in the m id line of the urogenital triangle (FIG. 5.12A). Observe that the bulbosp ong iosus m uscle covers the surface of the b ulb o f t h e p e n is and lies anterior to the thick fascia of the p e rin e al b o d y. Review the attachm ents and actions of the b ulb o sp o n g io sus m uscle (see TABLE 5.1). Lateral to the bulbospongiosus m uscle, clean the surface of the isch io cave rn o sus m uscle overlying the surface of the crus o f t h e p e n is (FIG. 5.12A). Using blunt dissection, attem p t to nd the sup e rcial t ran sve rse p e rin e al m uscle at the posterior border of the urogenital triangle (FIG. 5.12A). Observe that the super cial transverse perineal m uscle help s to sup port the p e rin e al b o d y, a brom uscular m ass located anterior to the anal canal and posterior to the perineal m em brane. Note that the super cial

Glans penis Corona penis Scrotum (lifted) Dartos fascia

B

Glans penis Navicular fossa Penile (spongy) urethra

Corpus cavernosum penis Corpus spongiosum penis

Corpus cavernosum penis

Posterior scrotal a. and n. (cut) Bulbospongiosus m. Ischiocavernosus m. Perineal body Perineal membrane Superficial transverse perineal m. Superficial branch of perineal a. and n. Internal pudendal a. and pudendal n. Inferior rectal nerve and artery Anus

Corpus spongiosum penis Bulbospongiosus m. (cut) Crus of penis Bulb of penis Perineal membrane Superficial branch of perineal n. and a. (cut) Superficial transverse perineal m. Internal pudendal a. and pudendal n.

Pelvic diaphragm

Inferior rectal n. and a.

Anococcygeal ligament

Gluteus maximus m.

Gluteus maximus m. Superficial fatty layer of perineal fascia

FIGURE 5.12 Contents of the super cial p erineal p ouch in the m ale. A. Sup er cial dissection. Skin has been rem oved on left side of gure to reveal fatty layer of super cial perineal fascia. Skin, fatty layer of super cial perineal fascia, and the m em branous layer of super cial p erineal fascia (Colles’ fascia) have been rem oved on the right side of the gure to show the m uscles, vessels, and nerves. B. Deep dissection. Bulbospongiosus and ischiocavernosus m uscles, vessels, and nerves have been rem oved to show the erectile tissues.

CHAPTER 5

9.

10.

11.

12. 13.

14.

transverse perineal muscle may be delicate and dif cult to nd. Lim it the time you spend looking for it. Use blunt dissection to clean between the m uscles of the sup er cial perineal pouch until a sm all triangular op ening is created (FIG. 5.12A). Within the triangular opening, identify the p erin e al m e m b ran e . The perineal m em brane is the deep boundary of the super cial perineal pouch. Use a scalp el to m ake a shallow incision along the m idline raphe of the bulbospongiosus m uscles. Take care because this is a thin m uscle and effort m ust be taken to not cut too d eep ly. Rem ove the bulbospongiosus m uscle on the left side of the cadaver. Identify the b ulb o f t h e p e n is and use an illustration to observe that it is continuous with the corpus spongiosum p enis and contains a portion of the spongy urethra (FIG. 5.12B). On the left side of the cadaver, use blunt dissection to rem ove the ischiocavernosus m uscle from the crus of th e p en is (FIG. 5.12B) (L. crus, a leg-like part; pl. crura). Use an illustration and the cadaver to verify that the crus of the penis attaches to the ischiopubic ramus and is continuous with the corpus cavernosum penis.

Penis [G 453; L 288, 289; N 359, 360; R 349, 351] In the anatom ical position, the penis is erect, thus m aking the surface of the penis closest to the anterior abdom inal wall the d o rsal surface o f t h e p e n is . Study a drawing of a transverse section of the p e n is (L. penis, tail) and observe that the sup e r cial fascia o f t h e p e n is (d art o s fascia) has no fat, and contains the sup e r cial d o rsal ve in o f t h e p e n is (FIG. 5.13). Study a drawing of a sagittal section of the penis and observe that the d e ep fascia o f t h e p e n is (Buck’s fascia) is an investing fascia and surrounds the co rp us sp o n g io sum

Superficial dorsal v. of penis

Dorsal a. of penis

Deep dorsal v. of penis

Dorsal n. of penis Skin

Septum penis Deep a. of penis

Superficial fascia of the penis (dartos fascia)

Corpora cavernosa penis

Deep fascia of the penis (Buck’s fascia)

Spongy urethra Corpus spongiosum penis

FIGURE 5.13 penis.

Tunica albuginea: of corpora cavernosa of corpus spongiosum

Transverse section through the body of the

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p e n is (unpaired), the co rp us cave rn o sum p e n is (paired), the d e e p d o rsal vein o f t h e p e n is (unpaired), the d o rsal art e ry o f t h e p en is (paired), and the d o rsal n e rve o f t h e p e n is (paired). 1. Id en tify th e ro o t o f t h e p e n is , th e p art o f th e p en is attach ed to th e isch iop ub ic ram i (b ulb an d crura). 2. Identify the b o d y (sh aft ) o f t h e p e n is , the part of the penis that is pendant (corp ora cavernosa and corpus spong iosum p enis). 3. Identify the g lan s p e n is at the distal end of the penis. Use an illustration to observe that it is continuous with the corpus spongiosum penis and thus contains the urethra, which term inates at the e xt e rn al ure t h ral o ri ce , and erectile tissue. 4. Around the circum ference of the g lans, identify the co ro n a o f t h e g lan s . In an uncircum cised sp ecim en, identify the p re p uce (foreskin). Ob serve the m id line location of the fre n ulum on the ventral surface of the glans connecting along the distal shaft of the penis. 5. Use a scalp el to m ake a shallow m idline skin incision through the skin down the ventral surface of the penis. Using a probe, gently elevate the skin from around the body of the penis and detach it b y cutting it just p roxim al to the corona of the glans. Do not skin the glans. 6. On the dorsal surface of the penis, identify and clean the sup e r cial d o rsal ve in . The super cial dorsal vein of the penis drains into the sup e r cial ext e rn al p ud e n d al ve in , which drains into the great sap henous vein. 7. On th e d orsum of th e p en is, use a p rob e to d issect th roug h the d e e p fa scia o f t h e p e n is an d id en tify th e d e e p d o rsa l ve in o f t h e p e n is (un p aired ) in th e m id line. Note that m ost of the blood from the penis drains through the deep dorsal vein into the prosta tic venous plexus (FIG. 5.14). [G 4 5 2 ; L 2 8 8 ; R 353] 8. Identify and clean the d o rsal art e ry o f t h e p e n is (paired) on each side of the deep dorsal vein. The dorsal artery of the penis is a term inal branch of the internal pudendal artery. 9. Identify and clean the d o rsal n e rve o f t h e p e n is (paired) on each side of the m idline lateral to the deep dorsal artery. Note that the dorsal nerve of the penis is a branch of the pudendal nerve. 10. Use a p rob e to trace the vessels and nerves of the p enis proxim ally. Use an atlas illustration to study the course of the p ud endal nerve and the internal p udendal artery [G 455; L 286; N 361; R 364]. Observe that the dorsal artery and nerve of the penis course deep to the p erineal m em brane b efore they em erg e onto the d orsum of the p enis. The d eep dorsal vein p asses between the p ubic arch and the

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Superficial external pudendal vein and artery

Suspensory ligament of penis Deep dorsal vein of penis

3.

Dorsal artery of penis Dorsal nerve of penis

Superficial dorsal artery and vein of penis

Tunical albuginea

4.

Deep fascia of penis (Buck’s fascia, cut)

5.

Corona

6.

Glans penis

7. FIGURE 5.14 Arteries and nerves of the penis. Skin has been rem oved on the left sid e of the illustration. Skin and super cial fascia have b een rem oved on the rig ht side of the illustration.

anterior ed g e of the perineal m em brane to enter the p elvis. Note that the deep d orsal vein d oes not accom pany the deep dorsal artery and dorsal nerve p roxim al to the bod y of the p enis. [G 452, 455; N 381, 390; R 352]

Sp o n g y ( Pe n ile ) Ure t h ra [G 453; L 266; N 363; R 350, 351] The m ale ureth ra is d escrib ed as having four reg ions: the p re p ro st a t ic u re t h ra , the p ro st a t ic ure t h ra , the m e m b ra n o u s u re t h ra , and the sp o n g y (p e n ile ) ure t h ra (FIG. 5.15). The sp ong y ureth ra is th e p ortion located within th e corp us sp ong iosum p en is. To exam in e the in tern al features of th e sp on g y ureth ra, th e g lan s an d shaft of the p enis will b e cut long itud inally along the m id lin e. 1. Identify the e xt e rn al ure t h ral o ri ce at the tip of the glans penis. Gently insert a probe into the external urethral ori ce and use a scalp el to cut down to the probe from both the dorsal and ventral surfaces of the penis in the m edian plane of the penis. Note that the pathway of the spongy urethra may not be a straight line, or m ay be slightly off center. 2. Advance the probe proxim ally and continue to divide the penis until you reach a point inferior to the pubic sym p hysis where the two corpora cavernosa sep arate from the bulb of the penis. Dorsal to the probe, the cut should p ass between the corp ora cavernosa

8.

9.

10.

and possibly sp lit the deep dorsal vein longitudinally. Ventral to the probe, the cut should divide the corpus sp ongiosum into eq ual halves. Carefully continue the cut through the bulb of the penis posterior to the urethra but do not cut through the perineal m em brane. Note that the urethra bends at a sharp angle and passes through the perineal m embrane (FIG. 5.15). Observe the sagittal section of the penis and identify the g lan s p e n is (L. glans, acorn), the d istal expansion of the corpus spongiosum . Note that it caps the two corpora cavernosa p enis. Identify the sp ongy urethra and observe that it term inates by passing through the glans to the external urethral ori ce. Exam ine the interior of the sp ongy urethra at the glans penis and identify the n avicular fo ssa , a widening of the urethra. In the proxim al part of the spongy urethra (in the bulb), look for the openings of the ducts of the b ulb o ure t h ral g lan d s . Note that the opening of the ducts may be too small to see. On the left side of the penis, m ake a transverse cut through the body of the penis about m idway d own its length. On the dorsal aspect of the transversely cut surface, identify the co rp us cave rn o sum p e n is and ob serve that it is surrounded by the thick fascia of the t un ica alb ug in ea o f t h e co rp us cave rn o sum p e n is . Note that the bisection of the p enis likely cut through the se p t um p e n is , which separates the corpora cavernosa of the penis. On the ventral aspect of the transversely cut surface, identify the co rp us sp o n g io sum p e n is and observe that it is surrounded by the t un ica alb ug in e a o f

Rectum Bladder

Preprostatic urethra

Ejaculatory duct

Perineal membrane Corpus cavernosum penis Glans penis Navicular fossa External urethral orifice

FIGURE 5.15

Prostatic urethra within prostate Membranous urethra within deep perineal pouch Spongy urethra within corpus spongiosum penis

Parts of the m ale urethra.

CHAPTER 5

t h e co rp us sp o n g io sum p e n is (FIG. 5.13). [G 455; L 289; N 359; R 351] 11. Study the erectile tissue within the corpus sp ongiosum p enis and con rm that the corpus sp ongiosum penis surrounds the spongy urethra. 12. Study the erectile tissue within the corpus cavernosum p enis and identify the d e e p art e ry o f t h e p en is near the center of the erectile tissue (FIG. 5.13). Note that the origin of the deep artery of the penis is the internal pudendal artery.

THE PELVIS AND PERINEUM

Deep dorsal vein of penis

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153

Inferior pubic ligament

Membranous urethra Dorsal nerve of penis

Anterior edge of perineal membrane

Dorsal artery of penis External urethral sphincter muscle

Male De e p Pe rin e al Po uch The deep perineal pouch lies superior (deep) to the perineal m em brane (FIG. 5.15). The deep perineal p ouch (sp ace) will not be dissected because few of the structures are easily identi able. 1. Refer to FIGURE 5.16 to study the contents of the deep p erineal p ouch in the m ale . [G 444; L 285; N 361] 2. Identify the m e m b ran o us ure t h ra in the m idsagittal plane and observe that it pierces the p e rin e al m e m b ran e . 3. The m e m b ran o us ure t h ra extends from the perineal m em brane to the prostate gland and is the shortest (about 1 cm ), thinnest, narrowest, and least distensible part of the urethra (FIG. 5.15). 4. Surrounding the m em branous urethra, identify the e xt ern al ure t h ral sp h in ct e r m uscle (sp h in ct er ure t h rae ) (FIG. 5.16). The external urethral sp hincter m uscle is a voluntary m uscle that when contracted acts to com press the m em branous urethra and stop the ow of urine. 5. Posterolateral to the urethra, identify the b ulb o ure t h ral g lan d s . The b ulb o ure t h ral g lan d (paired) is located in the deep perineal pouch but its duct passes through the perineal m em brane and drains into the p roxim al p ortion of the spongy urethra in the super cial perineal p ouch. 6. Identify the d e e p t ran sve rse p e rin e al m uscle (paired) along the posterior m argin of the deep

Perineal membrane

FIGURE 5.16 m ale.

Location of bulbourethral gland Deep transverse perineal m.

Contents of the deep perineal pouch in the

perineal pouch (FIG. 5.16). Note that its ber direction and function are identical to those of the super cial transverse perineal m uscle, which is in the super cial perineal pouch. 7. Collectively, the m uscles within the deep p erineal pouch plus the perineal m em brane are known as the uro g e n it al d iap h rag m . 8. Review the attachm ents and actions of the e xt e rn al ure t h ral sp h in ct e r and the d e e p t ran sve rse p e rin e al m uscle (see TABLE 5.1). 9. Coursin g an teriorly alon g th e lateral m arg in of the d eep p erin eal p ouch , id en tify th e b ra n ch e s o f t h e in t e rn a l p u d e n d a l a rt e ry a n d ve in (m ost notab ly, the d orsal artery of the p en is) and the b ra n ch e s o f t h e p u d e n d a l n e rve (m ost notab ly, the d orsal n erve of the p enis). Th ese structures sup p ly th e external ureth ral sp h in cter m uscle, th e d eep transverse p erineal m uscle, and the p enis (FIG. 5.16).

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5. 6. 7. 8.

Return the m uscles of the urogenital triangle to their correct anatom ical positions. Review the contents of the m ale super cial perineal pouch. Visit a dissection table with a fem ale cadaver and view the contents of the super cial perineal pouch. Use an atlas illustration to review the course of the internal pudendal artery from its origin in the pelvis to the dorsum of the penis. Use an atlas illustration to review the course and branches of the pudendal nerve. Study an atlas illustration showing the course of the deep dorsal vein of the penis into the pelvis to join the prostatic venous plexus. Draw a cross section of th e p en is sh owin g th e erectile b od ies, sup erficial fascia, d eep fascia, vessels, an d n erves. Review the parts of the m ale urethra.

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TABLE 5.1

Male Sup e r cial an d De e p Pe rin e al Po uch e s

SUPERFICIAL GROUP OF MUSCLES Muscle

Anterior Atta chments

Posterior Atta chments

Actions

Innerva tion

Bulbospongiosus

Contralateral bulbospongiosus muscle at the midline raphe

Perineal body

Compress the bulb of the penis to expel urine or semen

Ischiocavernosus

Crus of the penis

Ischial tuberosity and ischiopubic ramus

Forces blood from the crus of the penis into the distal part of the corpus cavernosum penis

Super cial transverse perineal

Perineal body (medial attachment)

Ischial tuberosity (lateral attachment)

Provides support to the perineal body

Perineal n. (branch of pudendal n.)

Muscle

Anterior Atta chments

Posterior Atta chments

Actions

Innerva tion

Deep transverse perineal

Perineal body (medial attachment)

Ischial tuberosity (lateral attachment)

Provides support to the perineal body

Perineal n. (branch of pudendal n.)

External urethral sphincter

Attaches to itself around the urethra

Compresses the membranous urethra and stops the ow of urine

Deep branch of the perineal n. (branch of pudendal n.)

Deep branch of the perineal n. (branch of pudendal n.)

DEEP GROUP OF MUSCLES

Abbreviation: n., nerve.

MALE PELVIC CAVITY Disse ct io n Ove rvie w The m ale pelvic cavity contains the urinary bladder, m ale internal genitalia, and the rectum (FIG. 5.17). The order of dissection will be as follows: The p eritoneum will b e studied in the m ale pelvic cavity. The p elvis will be sectioned in the m idline, and the cut surface of the sectioned pelvis will be studied. The ductus deferens will be traced from the anterior abdom inal wall to the region between the urinary bladder and rectum . The sem inal vesicles and prostate gland will be studied.

Disse ct io n In st ruct io n s Male Pe rit o n e um [G 403, 409; L 265; N 344; R 349] Using FIGURE 5.17 as a reference, exam ine the p e rit o n e um in the m ale pelvis. 1. Identify the peritoneum on the posterior aspect of the anterior abdom inal wall superior to the pubis. 2. Observe that the peritoneum re ects from the anterior abdom inal wall inferiorly across the apex of the urinary bladder. 3. Th e p eriton eum courses alon g th e sup erior surface of th e urin ary b lad d er. Id en tify th e p a ra ve sica l fo ssa (p aired ), th e sh allow d ep ression in th e p eriton eal cavity on th e lateral sid es of th e urin ary b lad d er. 4. Observe that the peritoneum descends posterior to the bladder in close p roxim ity to the superior ends of the sem inal vesicles. 5. Use a probe to follow the peritoneum posterior to the bladder and identify the re ct o ve sical p o uch , the re ection point between the urinary bladder and the rectum . Note that the rectovesical pouch is the lowest point in the m ale abdom inopelvic cavity.

6. Follow the peritoneum sup eriorly along the posterior aspect of the pelvic cavity and observe that it contacts the anterior surface and sides of the rectum and form s the sigm oid m esocolon at the level of the third sacral vertebra.

1 2

3

4 56 7

8

Bladder Retropubic space

Rectum

Anal canal Puboprostatic ligament

FIGURE 5.17 Peritoneum in the m ale pelvis. The num bered features in the gure correlate to the m ale peritoneum dissection instruction step s.

CHAPTER 5

CLIN ICA L CORRELATION

Pe lvic Pe rit o n e um As the urinary bladder lls, the p eritoneal re ection from the anterior body wall to the urinary bladder is elevated above the level of the pubis (FIG. 5.17). A needle inserted just sup erior to the pubis can penetrate a lled urinary bladder without entering the p eritoneal cavity.

7. The peritoneum covers the anterior surface of the inferior rectum . 8. Identify the p arare ct al fo ssa (paired), the shallow depression in the peritoneal cavity on the lateral side of the rectum .

Se ct io n o f t h e Male Pe lvis Th e p elvis will b e d ivid ed in th e m id lin e. First, th e p elvic viscera an d th e soft tissues of th e p erin eum will b e cut in th e m id lin e with a scalp el. Th e p ub ic sym p h ysis an d verteb ral colum n (up to verteb ral level L3) will b e cut in th e m id lin e with a saw. Sub seq uen tly, th e left sid e of th e b od y will b e tran sected at verteb ral level L3. Th e rig h t lower lim b an d rig h t sid e of th e p elvis will rem ain attach ed to th e trun k. 1. In the pelvic cavity, m ake a m idline cut beginning posterior to the pubic sym physis. Carry this m idline cut through the superior surface of the urinary bladder and spread open the bladder. Sponge the interior if necessary. 2. Identify the internal urethral ori ce in the bladder and insert a probe into it. Use the probe as a guide to continue the m idline cut inferior to the urinary bladder to divide the prostatic urethra and the prostate g land. 3. Exten d th e m id lin e cut in th e p osterior d irection cuttin g th roug h th e an terior an d p osterior walls of th e rectum an d th e d istal p art of th e sig m oid colon . 4. Clean the internal aspect of the rectum and anal canal. Use caution when cleaning and moving fecal matter. Refer to your instructor for proper safety techniques. 5. In the perineum , insert the scalpel blade inferior to the pubic sym physis with the cutting ed ge directed posteriorly between the halves of the bulb of the penis and m ake a cut in the m idline from the pubic sym p hysis to the coccyx p assing through the perineal m em brane, perineal body, and anal canal. 6. Use a scalpel to cut the left com m on iliac vein, left com m on iliac artery, left testicular vessels, and left ureter about 1 cm distal to their respective p oints of origin.

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7. Cut through the left lum bar arteries at vertebral levels L4 and L5 and re ect the ab dom inal aorta to the right side of the abdom inal cavity. 8. Use a scalp el to m ake an incision through the m uscles of the left lateral abdom inal wall about 2 cm superior to the iliac crest and cut m edially to the vertebral colum n 9. Cut through the nerves of the left lum bar p lexus at the point they cross the horizontal incision and use the scalp el to cut through any rem aining bers of the left p soas m ajor and q uadratus lum borum m uscles at vertebral level L3. 10. With the cadaver in the supine position, use a saw to cut through the pubic sym physis in the m idline from anterior to posterior, stopping at the inferior border of the pubic sym physis. 11. Turn the cadaver 90° to the right, so it is lying on its right side. Prop the cadaver or have your lab partners hold the body so it does not fall or rotate. 12. Have your lab partners abduct the left lower lim b to facilitate the sectioning of the sacrum . 13. Cut through the sacrum from posterior to anterior, m aking an effort not to allow the saw to pass between the soft tissue structures that were cut with the scalp el, retracting them out of the path of the blade if necessary. 14. Forcibly spread apart the lower lim bs to expand the opening division of the sacrum and extend the m idline cut as far superiorly as the body of the third lum bar vertebra. 15. Adduct the left lower lim b and use the saw to cut horizontally through the left half of the intervertebral disc between L3 and L4, sparing the inferior aspect of the abdom inal aorta. 16. Once the horizontal and vertical cuts are connected, return the cadaver to the supine position. 17. Cut any rem aining p ieces of tissue preventing the left lower lim b from being rem oved and p ull the left lower lim b away from the rest of the cadaver. 18. Clean the rectum and anal canal on both sides of the bisected pelvic specim en.

Male In t e rn al Ge n it alia [G 403; L 270; N 344; R 349] 1. Study the cut surface of the sectioned m ale pelvis (FIG. 5.18). 2. Identify the p e rin e al m e m b ran e deep to the bulb of the penis. Note that the perineal m embrane can be identi ed as a thin line at the deep edge of the bulb (FIG. 5.18). 3. Superior (deep) to the perineal m em brane, identify the e xt e rn al ure t h ral sp h in ct er m uscle surrounding the m e m b ran o us ure t h ra . Note that the external urethral sphincter m uscle m ay be dif cult to see in the sectioned specim en.

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Ductus deferens

Rectum

Bladder

Transverse rectal fold

Prostate

Rectovesical pouch

Deep dorsal vein of penis

Rectovesical septum

Corpus cavernosum

Ampulla of rectum

Corpus spongiosum

Anal sphincters: External Internal

Testis

Anal canal

Bulb of penis and bulbospongiosus m.

Perineal membrane

FIGURE 5.18

External urethral sphincter m.

Perineal body

Sagittal section of the m ale pelvis.

4. On the sectioned pelvis, identify the four parts of the urethra: p re p ro st at ic ure t h ra , p ro st at ic uret h ra , m e m b ran o us ure t h ra , and sp o n g y ure t h ra (FIG. 5.16). 5. Exam ine the in t e rio r o f t h e p ro st at ic ure t h ra and observe that it is about 3 cm in length and passes through the prostate gland.

6. Use an illustration to identify the longitudinal ridge of the ure t h ral cre st on the posterior wall of the prostatic urethra in the m idline (FIG. 5.19). [G 413; L 267; N 363; R 350] 7. On the illustration, identify the se m in al co lliculus , an enlargem ent of the urethral crest, and observe the presence of the p ro st at ic sin use s on either side.

Detrusor muscle Orifices of the ureters

Trigone of bladder Uvula of bladder Internal urethral orifice Prostate Prostatic sinus Seminal colliculus: Prostatic utricle Ejaculatory duct orifice Levator ani muscle External urethral sphincter muscle Dorsal nerve and artery of penis Perineal membrane Deep artery of penis Tunica albuginea Bulb of penis (corpus spongiosum) Bulbospongiosus muscle

FIGURE 5.19

Interureteric crest Prostatic venous plexus Urethral crest Crus of corpus cavernosum (crus of penis) Ischiocavernosus muscle Superficial perineal fascia

Urinary bladder and proxim al portion of the m ale urethra seen in coronal section.

CHAPTER 5

8.

9.

10.

11.

On the surface of the sem inal colliculus, identify the p ro st at ic ut ricle , the sm all opening in the m idline. On either side of the prostatic utricle, identify the o p e n in g s o f t h e e jaculat o ry d uct s . In the cadaver, near the inner surface of the anterior ab dom inal wall, nd the d uct us d e fe re n s where it p asses through the d ee p in g uin al rin g lateral to the inferior epigastric vessels (FIG. 5.18). Use blunt dissection to break through the peritoneum near the deep inguinal ring and peel the peritoneum off the lateral wall of the pelvic cavity from lateral to m edial. Detach the peritoneum at the point of re ection between the rectum and urinary bladder and p lace it in the tissue container. Use blunt dissection to trace the ductus deferens from the deep inguinal ring toward the m idline of the p elvis. Observe that the ductus deferens passes superior and then m edial to the branches of the internal iliac artery and sup erior to the ureter. [L 270; N 345; R 348] Trace the ductus deferens into the re ct o ve sical se p t um , the endopelvic fascia between the rectum and

12.

13.

14.

15.

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157

the urinary bladder, and observe that the ductus deferens is in contact with the fundus (posterior surface) of the urinary bladder (FIG. 5.18). Identify the am p ulla o f t h e d uct us d e fe re n s , the enlarged portion just before its term ination (FIG. 5.20). [G 412; L 270; N 362; R 351] Identify the se m in al ve sicle located inferolateral to the am pulla of the ductus deferens in the rectovesical septum posterior to the bladder. Note that the duct of the sem inal vesicle joins the ductus deferens to form the eja cula tory duct close to the prostate. Use blunt dissection to release the sem inal vesicle from the rectovesical septum . Pay attention because the ejaculatory duct is delicate and easily torn where it enters the p rostate (FIG. 5.20). Note that the ejaculatory ducts em pty into the prostatic urethra from their openings on the sem inal colliculus. Inferior to the urinary bladder, identify the p rost at e (FIG. 5.18). Note that the ap ex of the prostate is directed inferiorly and the b ase of the prostate is located superiorly against the neck of the urinary bladder. Use an atlas illustration to study the lob es o f t h e p ro st at e .

Transversalis fascia (peritoneum removed) Inferior epigastric vein and artery Deep inguinal ring Testicular vessels External iliac vessels

Peritoneum (cut)

Femoral ring

Left ureter (cut)

Umbilical artery

Urinary bladder

Obturator vessels and nerve

Seminal vesicle Prostate: Base Apex Perineal membrane

Obturator canal Obturator internus muscle Ampulla of ductus deferens

Ductus deferens

FIGURE 5.20 Posterior view of the urinary bladder and the m ale internal genitalia. Peritoneum has been rem oved from the inner surface of the abdom inal wall on the right side of the gure.

Disse ct io n Fo llo w-up 1. Review the position of the m ale pelvic viscera within the lesser pelvis and com pare it to the position of the viscera in the fem ale cadaver. 2. Review the peritoneum in the pelvic cavity and describe the differences in the m ale and fem ale peritoneum (FIGS. 5.17 and 5.32). 3. Follow the ductus deferens from the epididym is to the ejaculatory duct, recalling its relationships to vessels, nerves, the ureter, and the sem inal vesicle along this p ath. 4. Visit a dissection table with a fem ale cadaver and follow the round ligam ent of the uterus from the labium m ajus to the uterus and com p are this route to the course of the ductus deferens in the m ale p elvis.

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MALE URINARY BLADDER, RECTUM, AND ANAL CANAL Disse ct io n Ove rvie w The urinary bladder is a reservoir for the urine produced in the kidneys. When em pty, the urinary bladder lies within the pelvic cavity. When full, the urinary bladder extends superiorly into the abdom inal cavity. Organs located inferior to the peritoneum are classi ed as sub p erit on eal org an s and are surrounded by en d o p elvic fascia . The urinary bladder and lower two-thirds of the rectum are subperitoneal, whereas the upper third of the rectum is partially covered by peritoneum (FIG. 5.17). Between the pubic sym physis and the urinary bladder is a potential space called the re t ro p ub ic sp ace (p re ve sical sp ace ) (FIG. 5.17). The retrop ubic space is lled with fat and loose connective tissue to accom m odate the expansion of the urinary b ladder. The inferior lim it of the retrop ubic sp ace is de ned by the p ub o p ro st at ic lig am e n t , a cond ensation of fascia that ties the prostate to the inner surface of the pubis (FIG. 5.17). The order of dissection will be as follows: The p arts of the urinary bladder will be studied. The interior of the urinary bladder will be studied. The interior of the rectum and anal canal will be studied.

Disse ct io n In st ruct io n s Male Urinary Bladde r [G 413; L 266, 267; N 348; R 349] 1. Begin the identi cation of the p art s o f t h e urin ary b lad d e r with the ap e x, the pointed part directed toward the anterior abdom inal wall and identi ed by the attachm ent of the urachus (FIG. 5.21). 2. The b o d y o f t h e urin ary b lad d e r is located between the apex and the fun d us . The fundus of the bladder is the inferior p art of the p osterior wall, also called the b ase o f t h e urin ary b lad d e r . Observe that in the m ale the fundus is related to the ductus deferens, sem inal vesicles, and rectum . 3. Use an illustration to identify the n e ck o f t h e urin ary b lad d e r , the portion where the urethra exits the urinary bladder and the wall thickens to form the in t e rn al ure t h ral sp h in ct e r . Note that the internal urethral sphincter is positioned at the junction of the urinary bladder and the urethra and is an involuntary m uscle controlled by the autonom ic nervous system . 4. Observe that the sup e rio r surface o f t h e urin ary b lad d e r is covered by peritoneum , whereas the

5.

6.

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9.

Urachus Superior surface

10. Ureter

p o st e rio r surface is covered by peritoneum on its superior p art and by the endop elvic fascia of the rectovesical septum on its inferior p art (FIG. 5.21). Verify that the in fe ro lat e ral (paired) surface of the urinary bladder is covered by endopelvic fascia and lies deep to the re ection p oint of the p eritoneum . Exam ine the wall o f t h e urin ary b lad d e r noting its thickness and observe that it consists of bundles of sm ooth m uscle called d e t ruso r m uscle (L. detrudere, to thrust out). Note that the m ucous m embrane lining the m ajority of the inner surface of the urinary bladder lies in folds when the bladder is empty but will atten out to accomm odate expansion. Use an illustration to study the inner surface of the fundus and identify the t rig o n e o f t h e urin ary b lad d e r (urin ary t rig o n e ) (FIG. 5.19). The trigone of the bladder is a sm ooth, triangular region of m ucous m em brane de ned by lines between the in t e rn al ure t h ral o ri ce and the two ure t e ric o ri ce s . In the cadaver, identify a half of the urinary trig one de ned by one of the ureteric ori ces, and the now bisected internal urethral ori ce. Observe that the internal urethral ori ce is located at the m ost inferior point in the urinary bladder at the inferior aspect of the trigone. Identify the in t e rure t e ric cre st , a visible horizontal ridge extending between the ori ces of the ureters. [G 413; L 267; N 348; R 350] Insert the tip of a probe into the ori ce of the ureter and observe that the ureter passes through the

Apex Peritoneum Inferolateral surface

Urethra

FIGURE 5.21

Fundus (posterior surface) Ejaculatory duct Prostate gland

Parts of the urinary bladder in the m ale.

CLIN ICA L CORRELATION

Kid n e y St o n e s Kidney stones pass through the ureter to the urinary bladder and m ay becom e lodged in the ureter. The point where the ureter passes through the wall of the urinary bladder is a relatively narrow passage. If a kidney stone becom es lodged, severe colicky pain results. The pain stops suddenly once the stone passes into the bladder.

CHAPTER 5

m uscular wall of the urinary bladder in an oblique direction. When the urinary bladder is full (distended), the pressure of the accum ulated urine attens the part of the ureter within the wall of the bladder and thus prevents re ux of urine into the ureter. 11. Find the ureter where it crosses the external iliac artery, or the bifurcation of the com m on iliac artery, and use b lunt dissection to follow the ureter to the fundus of the urinary bladder.

Male Re ct um an d An al Can al [G 403, 405; L 272, 273; N 344, 371; R 348] 1. Identify the re ct um at its p oint of origin at the level of the third sacral vertebra. On the sectioned pelvis, observe that the rectum follows the curvature of the sacrum (FIG. 5.18). 2. Identify the am p ulla o f t h e re ct um , the dilated portion of the rectum just proxim al to the p oint where the rectum bends ap proxim ately 80° p osteriorly (an o re ct al e xure ) . Observe that the am pulla is continuous with the anal canal (FIGS. 5.18 and 5.22). 3. Identify the prostate gland and sem inal vesicles and observe that they are located adjacent to the anterior wall of the rectum (FIG. 5.18). 4. Exam ine the inner surface of the rectum and observe that the mucous membrane is smooth except for the presence of transverse rectal fold s (FIG. 5.18). There is usually one transverse rectal fold on the right side of the rectum and two on the left side. Note that the transverse rectal folds may be dif cult to identify in some cadavers. 5. Observe that the an al can al is only 2.5 to 3.5 cm in length and p asses out of the pelvic cavity and into the anal triangle of the p erineum (FIG. 5.22).

Circular muscle Longitudinal m. Transverse rectal fold (valve of houston)

Puborectalis m. Anterior

Levator ani m. and fascia Parts of external anal sphincter m. Deep* Superficial Subcutaneous

Ampulla of rectum Anal sinus

Anal canal

Internal anal sphincter m. Anal column Anal valve

FIGURE 5.22

*Blended with puborectalis m.

Rectum , anal canal, and anal sphincter muscles.

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CLIN ICA L CORRELATION

Re ct al Ex am in at io n Digital rectal exam ination is part of the physical exam ination. The size and consistency of the prostate gland can be assessed by palpation through the anterior wall of the rectum . As the prostate continues to grow throughout life, it is com m on in elderly m ales to have partial or even com plete obstruction of the rectum and/ or the prostatic urethra with an enlarged prostate, and thus, regular rectal exam inations are strongly recom m ended. 6. Examine the inner surface of the anal canal and identify the anal colum ns, 5 to 10 longitudinal ridges of mucosa in the proximal part of the anal canal. The anal columns contain branches of the sup erior rectal artery and vein (FIG. 5.22). Note that the mucosal features of the anal canal may be dif cult to identify in older individuals. 7. Identify the sem ilunar folds of m ucosa form ing the an al valves , which unite the distal ends of the anal colum ns. Between the anal valve and the wall of the anal canal is a sm all pocket called an an al sin us . 8. Identify the p e ct in at e lin e , the irregular line form ed by the contour of the collective anal valves. 9. Identify the ext ern al an al sp h in ct er m uscle in the sectioned specim en surrounding the anal canal. Note that the external anal sphincter is composed of skeletal muscle and is under voluntary control (FIGS. 5.18 and 5.22). 10. Identify the in t e rn al an al sp h in ct e r m uscle in the sectioned specim en surrounding the anal canal (FIGS. 5.18 and 5.22). Note that the internal anal sphincter is composed of sm ooth muscle and is under involuntary control. 11. Observe that the longitudinal m uscle of the anal canal separates the two sphincter m uscles. If you have dif culty identifying the anal sp hincters, use a scalpel to cut another section through the wall of the anal canal to im prove the clarity of the dissection. CLIN ICA L CORRELATION

He m o rrh o id s In the anal colum ns, the superior rectal veins of the hepatic portal system anastom ose with m iddle and inferior rectal veins of the inferior vena caval system . An abnorm al increase in blood pressure in the hepatic portal system causes engorgem ent of the veins contained in the anal colum ns and results in in t ern al h em orrh oid s. Internal hem orrhoids are covered by m ucous m em brane and are relatively insensitive to painful stim uli because the m ucous m em brane is innervated by autonom ic nerves. Ext ern al h em orrh oid s are enlargem ents of the tributaries of the inferior rectal veins, are covered by skin, and are very sensitive to painful stim uli because they are innervated by som atic nerves (inferior rectal nerves).

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Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the features of the urinary bladder, rectum , and anal canal. 2. Review the relationships of the sem inal vesicles, am pulla of the ductus deferens, and ureters to the rectum and fundus of the urinary bladder. 3. Visit a dissection table with a fem ale cadaver and review the relationships of the uterus, vagina, and ureters to the rectum and fundus of the urinary bladder. 4. Review the kidney, the abdom inal course of the ureter, the pelvic course of the ureter, and the function of the urinary b ladder as a storage organ. 5. Review the m ale urethra and com pare it with the fem ale urethra. 6. Review all parts of the large intestine and recall its function in absorption of water and in com paction and elim ination of fecal m aterial. 7. Com pare m uscle type and innervation of the external and internal anal sphincters.

MALE INTERNAL ILIAC ARTERY AND SACRAL PLEXUS Disse ct io n Ove rvie w Anterior to the sacroiliac articulation, the co m m o n iliac art ery divides to form the e xt ern al and in t e rn al iliac art e rie s (FIG. 5.23). The external iliac artery distributes to the lower lim b, and the internal iliac artery distributes to the pelvis. The internal iliac artery has one of the m ost variable branching patterns of any artery, and it is worth noting at the outset of this d issection that you m ust use the target distribution of the branches to identify them , not their p attern of b ranching or p oint of origin. The internal iliac artery com m only divides into an anterior division and a p osterior division. Branches arising from the anterior division are m ainly visceral and supply the urinary bladder, internal genitalia, external genitalia, rectum , and gluteal region. Branches arising from the p osterior division are parietal and sup ply the p elvic walls and gluteal region. The order of d issection will be as follows: The branches of the posterior division of the internal iliac artery will be identied. The branches of the anterior division of the internal iliac artery will be identi ed. The nerves of the sacral plexus will be dissected. Subsequently, the pelvic portion of the sym pathetic trunk will be dissected.

Disse ct io n In st ruct io n s Blo o d Ve sse ls [G 417; L 274; N 380, 381; R 359] The dissection of the p elvic vasculature m ay be perform ed on both the right and left sides of the hem isected pelvis; however, it is recom m ended to focus the dissection on just the right side because a deeper dissection will be perform ed on the left side with the detached lower lim b. 1. Identify the in t e rn al iliac ve in and ob serve that its tributaries largely p arallel the nearby arteries but are p lexiform in nature. To clear the dissection eld, rem ove all trib utaries to the internal iliac vein as each correlating artery is identi ed and cleaned. 2. Use an atlas illustration to study the p ro st at ic ve n o us p le xus , ve sical ven o us p le xus , and re ct al ve n o us p le xus , all of which drain into the internal iliac vein. 3. On the dissected specim en, identify the d e e p d o rsal ve in o f t h e p e n is just inferior to the pubic sym physis and verify that it em pties into the prostatic venous plexus. 4. Identify and clean the co m m o n iliac art e ry and follow it distally until it bifurcates into the e xt e rn al iliac art e ry and the in t e rn al iliac art e ry.

5. Use b lunt d issection to follow the internal iliac artery into the pelvis and observe that it gives num erous sm aller vessels from two m ajor divisions, anterior and posterior (FIG. 5.23). 6. Begin identi cation of the branches of the posterior division of the internal iliac artery by nding the m ost posterior and superior branch, the ilio lum b ar art e ry (FIG. 5.23). Observe that the ilio lum b ar art e ry p asses p osteriorly from the posterior division and then ascends lateral to the sacral p ro m o n t o ry, lum bar vertebrae, lum bosacral trunk, and the obturator nerve. 7. Identify the lat e ral sacral art e ry, which gives rise to a superior b ranch and an inferior branch. Observe that the inferior branch p asses anterior to the sacral ventral ram i. Note that the lateral sacral artery m ay arise from a com mon trunk with the iliolumbar artery. 8. Identify the last and typically largest branch of the posterior division, the sup erio r g lut e al art e ry, which exits the p elvic cavity through the greater sciatic foram en superior to the p irifo rm is m uscle . 9. Identify the branches of the an terior d ivision of t h e in ternal iliac art ery beginning with the um b ilical artery.

CHAPTER 5

External iliac artery

Deep circumflex iliac artery

Anterior rami: S1 S2 S3 S4

Inferior epigastric artery

Superior gluteal artery Inferior gluteal artery

Medial umbilical ligament (obliterated umbilical artery)

Pudendal nerve Inferior vesical artery

Superior vesical arteries

Internal pudendal artery

Umbilical artery Obturator artery

Urinary bladder

Middle rectal artery Prostatic branch of inferior vesical artery

Prostate

FIGURE 5.23

12.

13.

161

Lumbosacral trunk Lateral sacral artery

Internal iliac artery

11.

•

Iliolumbar artery

Common iliac artery

10.

THE PELVIS AND PERINEUM

Branches of the internal iliac artery in the m ale.

In the m edial um bilical fold, nd the m ed ial um b ilical lig am en t (the rem nant of the um bilical artery) and use blunt dissection to trace it posteriorly to the um bilical artery. Identify and clean several sup e rio r ve sical art e rie s , which arise from the inferior surface of the um bilical artery and descend to the superolateral part of the urinary b ladder. Inferior to the um bilical artery, identify the ob t urat or art ery, which passes into the obturator canal along with the ob t urat or n erve . Find the obturator artery where it enters the obturator canal in the lateral wall of the pelvis and follow the artery posteriorly to its origin. Note that in about 20% of cases, the obturator artery arises from the external iliac or inferior epigastric arteries. This a berra nt obtura tor a rtery crosses the pelvic brim to enter the obturator canal and is particularly at risk of injury during surgical repair of a femoral hernia. Follow the anterior division of the internal iliac artery toward the pelvic oor and identify the in ferior g lut eal artery. Observe that the inferior gluteal artery com m only passes out of the pelvic cavity into the gluteal region through the greater sciatic foram en inferior to the piriform is m uscle. Note that the inferior gluteal artery may share a common trunk with the internal pudendal artery, or less commonly, with the superior gluteal artery. Identify the in ferio r vesical art e ry off the anterior aspect of the anterior division of the internal iliac artery. Observe that the inferior vesical artery courses toward the fundus of the urinary bladder to supply the bladder, sem inal vesicle, and prostate. Note that the inferior vesical artery is a named branch only in the male, in the female, it is an unnamed branch of the vaginal artery.

14. Identify the m id d le re ct al art e ry coursing m edially toward the rectum . The m iddle rectal artery often arises from a com m on trunk with the inferior vesical artery, m aking p ositive identi cation dif cult. Note that the middle rectal artery, like the inferior vesical artery, sends branches to the sem inal vesicle and prostate. 15. Identify the in t e rn al p ud e n d al art e ry anterior to the inferior gluteal artery. Observe that the internal pudendal artery exits the pelvic cavity by passing out of the greater sciatic foram en. Note that the internal pudendal artery stays m ore m edial than the inferior gluteal artery because it will enter the lesser sciatic foram en to reach the perineum . Note that the internal pudendal artery often arises from a comm on trunk with the inferior gluteal artery.

Ne rve s [G 400, 420; L 275, 276; N 388, 486; R 487] The som atic plexuses of the pelvic cavity, the sacral p le xus and the co ccyg e al p le xus , are located between the pelvic viscera and the lateral p elvic wall em b edded in the endopelvic fascia. These som atic nerve plexuses are form ed by contributions from anterior ram i of spinal nerves L4–Co1. The prim ary visceral nerve plexus of the pelvic cavity is the in ferio r h yp o g ast ric p le xus (p e lvic p le xus ), form ed by contributions from the hypogastric nerves, sacral splanchnic nerves (sym pathetic), and pelvic sp lanchnic nerves (parasym pathetic). 1. Use your ngers to free the rectum from the anterior surface of the sacrum and coccyx. 2. Retract the rectum m edially and identify the sacral p lexus of nerves. Observe that the sacral plexus is

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Lumbosacral trunk

Superior gluteal a.

Anterior rami: S1 S2 S3 S4

Inferior gluteal a.

Pelvic splanchnic nerves Pudendal nerve Sciatic nerve Rectum (cut)

FIGURE 5.24

3.

4.

5.

6.

7.

8.

9.

Sacral p lexus of nerves in the m ale.

closely related to the anterior surface of the piriform is m uscle. Just lateral to the sacral prom ontory, identify and clean the lum b o sacral t run k (anterior ram i of L4 and L5) and verify that it joins the sacral plexus (FIG. 5.24). Inferior to the lum bosacral trunk, identify the anterior ram i of S2 and S3, which em erge between the proxim al attachm ents of the piriform is m uscle. Identify the sciat ic n erve and observe that it is form ed by the anterior ram i of spinal nerves L4 through S3. The sciatic nerve exits the pelvis by passing through the greater sciatic foram en to enter the gluteal region, usually inferior to the piriform is m uscle. Observe that the sup e rio r g lut e al art e ry usually passes between the lum b o sacral t run k and the an t e rio r ram us o f sp in al n e rve S1 and exits the pelvis through the greater sciatic foram en, passing sup erior to the piriform is m uscle. Observe that the in ferior g luteal artery usually passes between the anterior rami of spinal nerves S2 and S3, but may pass between the anterior ram i S1 and S2, to exit the pelvis inferior to the piriform is muscle. Identify the p ud e n d al n e rve and observe that it is form ed by contributions from the anterior ram i of spinal nerves S2, S3, and S4. Note that the pudendal nerve exits the pelvis by passing inferior to the piriform is muscle, through the greater sciatic foram en. The pudendal nerve then enters the perineum by passing through the lesser sciatic foramen. Identify the p elvic sp lan chnic nerves (nervi erig entes) . Observe that pelvic splanchnic nerves arise from the anterior rami of spinal nerves S2, S3, and S4 (FIG. 5.24). Note that pelvic splanchnic nerves carry presynaptic parasympathetic axons for innervation of pelvic organs and the distal gastrointestinal tract from the left colic exure to the anal canal. [G 400; L 276; N 388; R 361]

10. Identify the sacral p o rt io n o f t h e sym p at h e t ic t run k located on the anterior surface of the sacrum , m edial to the ventral sacral foram ina. Observe that the sym p at h e t ic t run k continues from the abdom inal region into the pelvis and that the two sides join in the m idline near the level of the coccyx to form the g an g lio n im p ar . 11. Identify the g ray ram i co m m un ican t e s , which connect the sym pathetic ganglia to the sacral anterior ram i. Note that each gray ramus comm unicans carries postsynaptic sym pathetic bers to an anterior ram us for distribution to the lower extrem ity and perineum. 12. Identify the sacral sp lan ch n ic n e rve s arising from two or three of the sacral sym p athetic ganglia and observe that they p ass directly to the in fe rio r h yp o g ast ric p le xus . Note that sacral splanchnic nerves carry sym pathetic bers that distribute to the pelvic viscera. 13. On one side of the pelvic cavity, m ake an effort to follow the hypogastric plexus superiorly toward the condensation of the plexus into the rig h t or le ft h yp o g ast ric n e rve . Use an illustration to identify the sup e rio r h yp o g ast ric p le xus and review the origins of the autonom ics in b oth the superior and inferior hypogastric plexuses. CLIN ICA L CORRELATION

Pe lvic Ne rve Ple x use s The inferior hypogastric plexus is located in the endopelvic fascia lateral to the rectum , bladder, sem inal vesicles, and prostate. The inferior hyp ogastric p lexus, as well as its sup erior contribution of the hyp ogastric nerve, could be injured during p elvic surgery. Dam age to the autonom ic p lexus could cause loss of bladder control and erectile dysfunction.

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Disse ct io n Fo llo w-up 1. Review the abdom inal aorta and its term inal branches. 2. Use the dissected specim en to review the branches of the internal iliac artery and the region supplied by each branch. 3. Visit a dissection table with a fem ale cadaver and review the arteries unique to the fem ale (uterine artery and vaginal artery) and note their relationship to the ureter. 4. Review the form ation of the sacral plexus and the branches dissected in the pelvis. 5. Use the dissected specim en and an atlas illustration to review the course of the pudendal nerve from the pelvic cavity to the urogenital triangle.

MALE PELVIC DIAPHRAGM Disse ct io n Ove rvie w The p e lvic d iap h rag m is the m uscular oor of the pelvic cavity and is form ed by the le vat o r an i m uscle and co ccyg e us m uscle as well as the fasciae covering their sup erior and inferior surfaces (FIG. 5.25A, B). The pelvic diap hragm extends from the pubic sym physis anteriorly to the coccyx posteriorly. Laterally, the pelvic diaphragm is attached to the fascia covering the o b t urat o r in t e rn us m uscle . The urethra and anal canal pass through m idline openings in the pelvic diaphragm called the uro g e n it al h iat us and an al h iat us , respectively. The order of dissection will b e as follows: The pelvic viscera will be retracted m edially. The obturator internus, tendinous arch of the levator ani, and the levator ani will be identi ed. The vas deferens, prostate, and anal canal will be cut and the pelvic viscera re ected.

Disse ct io n In st ruct io n s Perform the following dissection sequence on only one side of the cadaver. If the left lower lim b was rem oved d uring the bisection of the pelvis, it is recom m ended that this dissection be perform ed on the left side to p reserve the continuity of the vasculature into the abdom inal cavity on the right side. [G 396–398; L 278, 279; N 338, 339] 1. Retract the rectum , urinary bladder, prostate, and sem inal vesicles m edially and identify the p e lvic d iap h rag m . 2. Use blunt dissection to rem ove any rem aining fat and connective tissue from the superior surface of the p elvic diaphragm . 3. Locate the o b t urat o r can al piercing the obturator internus by identifying and following the obturator artery and nerve. 4. Palpate the m edial surface of the ischial spine through the levator ani and identify the t e n d in o us arch o f t h e le vat o r an i m uscle (FIG. 5.25A). Observe that the tendinous arch lies just inferior to a line connecting the ischial spine and the obturator canal. Note that the tendinous arch is the origin of part of the levator ani m uscle. Identify the three com ponents of the levat o r an i m uscle by their anterolateral attachm ents. Learn, b ut do not dissect, their posterior attachm ents. 5. Identify the p ub orect alis m uscle attaching anteriorly to the body of the pubis and posteriorly to the

6.

7.

8.

9.

10.

puborectalis m uscle of the opposite side (in a m idline raphe). The puborectalis m uscles form the m argin of the urogenital hiatus, and a “puborectal sling,” which m aintains the an orect al exure of the rectum (FIGS. 5.22 and 5.25B). Note that during defecation, the puborectalis muscles relax, the anorectal exure straightens, and the elimination of fecal matter is facilitated. Identify the p ub o co ccyg e us m uscle attaching from the body of the pubis anteriorly to the coccyx and the an o co ccyg e al rap h e (lig am e n t ) p osteriorly. Identify the ilio co ccyg e us m uscle attaching from the tend inous arch anterolaterally to the coccyx and the anococcygeal raphe posteriorly. Note that the levator ani m uscle supports the pelvic viscera and resists increases in intra-abdominal pressure. Identify the co ccyg eus m uscle , which com pletes the pelvic diaphragm posteriorly. Observe that the anterior attachm ent of the coccygeus m uscle is the ischial spine and that its posterior attachm ent is the lateral border of the coccyx and the lowest part of the sacrum (FIG. 5.25A). Place the ng ers of one hand in the ischioanal fossa inferior to the p elvic d iap hrag m an d the n g ers of the oth er han d on the sup erior surface of the p elvic d iap hrag m . Palp ate the p elvic d iap hrag m b etween b oth hand s and ap p reciate its thinness. Turn the left lower lim b and observe that the o b t urat o r in t e rn us m uscle form s the lateral wall of the ischioanal fossa and p erineum inferior to the p elvic

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A

Obturator internus muscle and fascia Piriformis muscle

Tendinous arch of levator ani muscle

Ischial spine Obturator canal Coccygeus muscle

Levator ani muscle: Iliococcygeus muscle Pubococcygeus muscle Puborectalis muscle

Arcuate pubic ligament

B

Urogenital hiatus Ischiopubic ramus Anal hiatus

Pelvic diaphragm: Levator ani muscle: Puborectalis muscle Pubococcygeus muscle Iliococcygeus muscle Coccygeus muscle

Anococcygeal raphe Ischial tuberosity

Obturator internus muscle and tendon

Ischial spine

Piriformis muscle Sacrotuberous ligament

FIGURE 5.25

Sacrospinous ligament (cut)

Pelvic diaphragm in the m ale. A. Left lateral view. B. Inferior view

diaphragm and the lateral wall of the pelvic cavity superior to the pelvic diaphragm . 11. The m edial attachm ent of the obturator internus m uscle is the m argin of the obturator foram en and inner surface of the obturator m em brane. The lateral attachm ent of the obturator internus m uscle is the

greater trochanter of the fem ur and will be studied when the gluteal region is dissected. 12. Observe that the urethra and anal canal p ass throug h m idline op ening s in the pelvic diap hrag m called the uro g e n it a l h ia t us and a n a l h ia t u s , resp ectively.

CHAPTER 5

13. To increase the visibility of the pelvic diaphragm , cut the vas d e fe re n s a few centim eters away from the deep inguinal ring and re ect it along with the pelvic viscera m edially. 14. If the m uscles form ing the pelvic diaphragm rem ain dif cult to see, m ake an incision through the inferior asp ect of the prostate and anal canal and detach the viscera from the pelvic oor. Leave the viscera

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attached to the neurovascular structures so the relationships are m aintained for later review. 15. Use your textbook to learn the general pattern of lym phatic drainage of the pelvis and the location of the co m m o n iliac nodes, the e xt e rn al iliac n o d e s , the in t e rn al iliac n o d e s , the sacral n o d e s , and the lum b ar n o d e s . [G 407, 418, 420; L 291; N 386]

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5. 6.

7. 8.

Use the dissected specim en to review the proxim al attachm ent and action of each m uscle of the pelvic diaphragm . Review the relationship of the branches of the internal iliac artery to the pelvic diaphragm . Review the relationship of the sacral plexus to the pelvic diaphragm . Use an atlas illustration to review the role played by the pelvic diaphragm in form ing the boundary between the pelvic cavity and the perineum . Review the function of the pelvic diaphragm and perineal body in supporting the pelvic and abdom inal viscera. Use an atlas illustration to review lym phatic drainage in the perineum . Note that perineal structures (including the scrotum and the lower part of the anal canal) d rain into sup er cial inguinal lym p h nod es and that the lym p hatic drainage of the testis follows the testicular vessels to the lum bar chain of nodes, thereby bypassing the perineal and pelvic drainage system s. Review the form ation of the thoracic duct to com plete your understanding of the lym phatic drainage from this region. Visit a dissection table with a fem ale cadaver and perform a com plete review of the dissected fem ale pelvis.

FEMALE EXTERNAL GENITALIA, UROGENITAL TRIANGLE, AND PERINEUM Disse ct io n Ove rvie w If you dissected a m ale cadaver, use the rem ainder of this chapter for review with a fem ale cadaver. In the em bryo, the m ale and fem ale external genitalia have sim ilar origins and rem ain m orphologically sim ilar until a certain stage in developm ent. Thus, m any of the structures of the external genitalia have a hom ologous counterpart in the op posite sex. The labium m ajus in the fem ale is the hom ologue of the scrotum in the m ale. However, the labium m ajus contains both Cam p er’s fascia and d art o s fascia , unlike the scrotum , which only contains dartos. The order of dissection of the fem ale urogenital triangle will be as follows: The round ligam ent of the uterus will be followed from the super cial inguinal ring for a short distance into the superior part of the labium m ajus. The external genitalia will be exam ined. The skin will be rem oved from the labia m ajora. The super cial perineal fascia will be rem oved, and the contents of the super cial perineal pouch will be identi ed. The contents of the deep perineal pouch will be described but not dissected.

Disse ct io n In st ruct io n s Lab ium Majus ( p l. Lab ia Majo ra) [G 304; L 221; R 224] The d issection of the lab ium m ajus corresp ond s to the d issection of the scrotum in m ale cadavers. The labium m ajus, however, does not have the layer of d artos m uscle as seen in the scrotum but rather contains a layer of Cam p er’s fascia. Partner with a d issection team that has a m ale cadaver for the dissection of the external genitalia. You are expected to observe and learn the anatom y for b oth sexes. 1. At the sup e r cial in g uin al rin g , identify the ro un d lig am e n t o f t h e ut e rus .

2. Use b lunt d issection to d em onstrate that the round lig am ent of the uterus em erg es from the sup er cial inguinal ring and sp read s out into the fatty tissue of the lab ium m ajus. Note that the round ligam ent is a delicate structure that can be dem onstrated for

CLIN ICA L CORRELATION

Lym p h at ic Drain ag e o f t h e Lab ium Majus Lym phatics from the labium m ajus drain to the super cial inguinal lym ph nodes. In am m ation of the labium m ajus m ay cause tender, enlarged super cial inguinal lym ph nodes.

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only 1 to 2 cm distal to the super cial inguinal ring. [G 3 5; R 224, 362]

Fe m ale Ext e rn al Ge n it alia [G 443; L 282; N 354; R 373] Partner with a dissection team that has a m ale cadaver for the dissection of the urogenital triangle. Usually, only one student can work on the urogenital triangle at a tim e. The student should be p ositioned between the thighs with the trunk of the cadaver pulled toward the end of the d issection table. 1. Place the cadaver in the supine position. Stretch the thighs widely ap art and brace them . 2. Exam ine the vulva (fem ale external genitalia) inferior to the reg ion of the m o n s p ub is (FIG. 5.26). Observe that the m ons p ubis is the reg ion of the fem ale external genitalia anterior to the pubic sym physis lled with fat and covered with pubic hair. 3. Identify the lab ium m ajus ( p l. lab ia m ajo ra) and observe that the right and left sides m eet anteriorly at the an t e rio r lab ial co m m issure and p osteriorly at the p o st e rio r lab ial co m m issure just anterior to the fre n ulum o f lab ia m in o ra . Note that the labia m ajora are covered in hair and lled with fat. 4. Just p osterior to th e an terior lab ial com m issure, id entify the clit o ris . Ob serve th at th e g la n s of th e clitoris is covered b y th e p re p u ce on its d orsal surface, wh ereas th e fre n u lu m o f t h e clit o ris curves p osteriorly for a sh ort d istan ce along the

ven tral surface. Note that the glans, prepuce, and frenulum of the clitoris are analogous to the m ale counterparts on the penis except that they do not carry the urethra. 5. Medial to the labia m ajora, identify the lab ia m in o ra (sing. lab ium m in us) and observe that unlike the labia m ajora, they are not covered with hair. The labia m inora have num erous sebaceous glands and lie super cial to the bulbs of the vestibule. 6. Identify the region of the ve st ib ule o f t h e vag in a between the labia m inora. 7. Within the vestibule, identify the sm all anteriorly located e xt e rn al ure t h ral o ri ce and the larger and m ore posteriorly located vag in al o ri ce . Note that within the vestibule, the o p e n in g s o f t h e p araure t h ral d uct s are p resent on each side of the external urethral ori ce, although it is unlikely they will be visible in the cadaveric specim en.

Skin Re m o val 1. Refer to FIGURE 5.27. 2. Make a skin incision in the m idline from the anterior m argin of the anus to the posterior labial com m issure (FIG. 5.27, red dashed line). 3. Make a skin incision that follows the m edial surface of the labium m ajus on each side beginning at the posterior labial com m issure, passing lateral to the labium m inus, and ending at the anterior lab ial com m issure.

Anterior labial commissure Labium majus (plural: Labia majora)

Prepuce of clitoris Glans of clitoris

Labium minus (plural: Labia minora)

Frenulum of clitoris External urethral orifice

Vestibule of vagina Vaginal orifice Frenulum of labia minora

Opening of greater vestibular gland (Bartholin's gland)

Posterior labial commissure

FIGURE 5.26

Fem ale external genitalia.

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surface of the thigh and p lace it in the tissue container (FIG. 5.27, blue dashed lines). 7. If the cadaver has a large am ount of fat in the sup ercial fascia of the m edial thighs, rem ove a portion of the sup er cial fascia corresponding to the areas of rem oved skin.

Mons pubis

Fe m ale Supe r cial Pe rine al Po uch and Clit o ris [G 443, 458 – 461; L 283, 284; N 355, 356; R 375, 376] Anus

FIGURE 5.27

Skin incisions for the fem ale perineum .

4. Make a skin incision in the m idline from the anterior labial com m issure to the m ons pubis (FIG. 5.27, red dashed lines). 5. Make a transverse incision across the m ons pubis from the right thigh to the left thigh (FIG. 5.27, blue dashed lines). 6. Rem ove the skin from the labium m ajus from m edial to lateral. Detach each skin ap along the m edial

The sup er cial p erineal fascia has a sup er cial fatty layer and a d eep m em b ran ous layer. In th e fem ale, the sup ercial fatty layer p rovid es th e sh ap e of th e lab ium m ajus and is continuous with the fat of the lower ab d om inal wall (Cam p er’s fascia), ischioanal fossa, and thig h. The m e m b ra n o u s la ye r o f t h e su p e r cia l p e rin e a l fa scia (Co lle s’ fa scia ) is attached to th e ischiop ub ic ram us as far p osteriorly as th e isch ial tub erosity an d to th e p osterior ed g e of the p e rin e a l m e m b ra n e (FIG. 5.28). The m em b ran ous layer of th e sup er cial p erin eal fascia form s the sup er cial b ound ary of the su p e r cia l p e rin e a l p o u ch (sp a ce ) . The m em branous layer of super cial perineal fascia (Colles’ fascia) is continuous with the m em b ranous layer of sup er cial fascia of the lower ab dom inal wall (Scarpa’s fascia). The m em branous layer of the super cial perineal

Sacrum Rectum Superficial abdominal fascia: Fatty layer (Camper's) Membranous layer (Scarpa's)

Uterus (cervix)

Pubic symphysis

Vaginal canal

Bladder Perineal body Urethra

Anus

Membranous layer of superficial perineal fascia (Colles' fascia)

FIGURE 5.28

Deep perineal pouch Superficial perineal pouch Perineal membrane

Peritoneal fascia in the fem ale p elvis in sagittal plane.

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fascia is attached along the posterior border of the perineal m em brane. 1. In th e fem ale, th ree p airs of m uscles (left an d rig h t) o verlay th e erectile tissu e o f th e clitoris an d con trib ute to th e co n t e n t s o f t h e su p e r ficia l p e rin e a l p o u ch with th e acco m p an yin g a rt e rie s , ve in s , a n d n e r ve s th at sup p ly th e structu res ( FIG. 5.12A, B). 2. The three m uscles are the isch io cave rn o sus m uscle , b ulb o sp o n g io sus m uscle , and the sup e r cial t ran sve rse p e rin e al m uscle (FIG. 5.29). 3. Id en tify th e p o st e rio r la b ia l n e r ve a n d ve sse ls an d ob serve th at th ey are term in al b ran ch es of th e su p e r cia l b ra n ch o f t h e p e rin e a l a rt e r y a n d n e r ve an d sup p ly th e p osterior p art of th e lab ium m ajus. Note that the super cial branch of the perineal artery and nerve enter the urogenital triangle by passing lateral to the external anal sphincter m uscle (FIG. 5.30). 4. It is not necessary to identify the m e m b ran o us laye r o f t h e sup e r cial p e rin e al fascia (Co lle s’ fascia) to com plete the dissection. Rather, review the attachm ents of the Colles’ fascia by palpating the isch io p ub ic ram us and isch ial t ub e ro sit y as well as the p osterior edge of the p e rin e al m e m b ran e . Note that the Colles’ fascia forms the super cial boundary of the super cia l perinea l pouch (space).

Ischiopubic ramus External urethral orifice Ischiocavernosus m.

Mons pubis Anterior labial commissure Prepuce of clitoris External urethral orifice

Glans of clitoris Frenulum of clitoris

Ischiocavernosus m.

Labium majus Vestibule of vagina

Hymenal caruncle

Labium minus

Bulbospongiosus m.

Vaginal orifice Opening of greater vestibular gland

Perineal membrane

Frenulum of labia minora

Superficial transverse perineal m.

Posterior labial commissure Perineal body Anus Anococcygeal ligament

FIGURE 5.29 Contents of the super cial perineal p ouch in the fem ale. Super cial dissection. Skin, super cial fascia, and the m em branous layer of super cial perineal fascia (Colles’ fascia) have been rem oved on the right side of the gure to show the m uscles and p erineal m em brane.

Dorsal nerve and artery of clitoris Body of clitoris Glans of clitoris Crus of clitoris

Vaginal orifice Posterior labial nerve and artery

Bulb of vestibule

Bulbospongiosus m.

Opening of greater vestibular gland

Perineal membrane Superficial transverse perineal m. Deep branch of perineal nerve and artery Superficial branch of perineal nerve and artery Perineal nerve and artery Pudendal nerve and internal pudendal artery

Greater vestibular gland Perineal body External anal sphincter m. Anus Pelvic diaphragm

Inferior rectal artery and nerve

FIGURE 5.30 Contents of the super cial perineal pouch in the fem ale. Deep dissection. Bulbospongiosus and ischiocavernosus m uscles have been rem oved on the right side of the illustration to show the erectile tissues.

CHAPTER 5

5. Use a probe to dissect through the super cial perineal fascia about 2 cm lateral to the labium m inus. Rem ove the m ass of fat contained in the labium m ajus and place it in the tissue container. 6. Use blunt dissection to nd the b ulb o sp o n g io sus m uscle deep to the labium m inus overlying the bulb of the vestibule (FIG. 5.30). Observe that the bulbospongiosus m uscle covers the surface of the b ulb o f t h e ve st ib ule and lies anterior to the dense fascia of the p e rin e al b o d y. Note that the bulbospongiosus m uscle in the fem ale does not join the bulbospongiosus m uscle of the opposite side across the midline as it does in the m ale. 7. Review the attachm ents and actions of the b ulb o sp o n g io sus m uscle (see TABLE 5.2). 8. Lateral to the bulbospongiosus m uscle, use a probe to clean the surface of the isch io cave rn o sus m uscle overlying the super cial surface of the crus o f t h e clit o ris (FIG. 5.30). 9. Using b lunt d issection, attem p t to nd the sup e rcia l t ra n sve rse p e rin e a l m uscle at the p osterior b ord er of the urog enital triang le (FIG. 5.30). Ob serve that the sup er cial transverse p erineal m uscle help s to sup p ort the p e rin e a l b o d y , a b rom uscular m ass located anterior to th e anal canal and p osterior to the p erineal m em b rane. Note that the super cial transverse perineal m uscle m ay be delicate and dif cult to nd. Lim it the tim e you spend looking for it. 10. Use blunt dissection to clean between the three m uscles of the super cial perineal pouch until a sm all triangular op ening is created (FIG. 30). 11. With in th e t rian g ular o p en in g , id en tify th e p e rin e a l m e m b ra n e . Th e p erin eal m em b ran e is th e d eep b o u n d ary o f t h e su p erficial p erin eal p ouch . 12. O n th e left sid e of th e cad aver, use b lun t d issection to rem ove th e b ulb osp on g iosus m uscle an d id en tify th e b u lb o f t h e ve st ib u le ( FIG. 5.3 0). O b serve th at th e b u lb o f th e vestib u le is an elo n g ated m ass o f erectile tissu e th at lies lateral to th e vag in al o rifice. Th e g re a t e r ve st ib u la r g la n d is fo un d in th e su p erficial p erin eal p o u ch im m ed iately p osterior to th e b ulb of th e vestib ule. N ote that in the cadaver, the greater vestibular gland is difficult to find. 13. Anteriorly, the bulbs of the two sides are joined at the co m m issure o f t h e b ulb s, which is continuous with the g lan s o f t h e clit o ris . Do not attem pt to nd the com m issure of the bulbs. 14. On the left side of the cadaver, use blunt dissection to rem ove the ischiocavernosus m uscle from the

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crus o f t h e clit o ris (L. crus, a leg-like part; pl. crura ) (FIG. 5.30). The crus of the clitoris attaches to the ischiop ubic ram us and is continuous with the corpus cavernosum clitoris. 15. Use an atlas illustration to study the erectile bodies of the clitoris and observe that the two corpora cavernosa form the body of the clitoris and that the glans clitoris caps the two corpora cavernosa. [G 461; L 284; N 356; R 373, 375]

Fe m ale De e p Pe rin e al Po uch The deep perineal pouch lies superior (deep) to the perineal m em brane (FIG. 5.28). The deep perineal p ouch (sp ace) will not be dissected because few of the structures are easily identi able. 1. Refer to FIGURE 5.31 to stud y the con t e n t s of t h e d e e p p e rin e al p o uch in t h e fe m ale . [G 444; L 285; N 361] 2. Id en tify the u re t h ra in th e m id sag ittal p lan e an d ob serve th at it p ierces th e p e rin e a l m e m b ra n e . Th e fem ale ureth ra exten d s from th e in tern al ureth ral ori ce in th e urin ary b lad d er to th e extern al ureth ral ori ce in th e vestib ule of th e vag in a (ab out 4 cm ). 3. Observe that the e xt e rn al ure t h ral sp h in ct e r (sp h in ct er ure t h rae ) m uscle surrounds the m em branous urethra. The external urethral sphincter m uscle is a voluntary m uscle that when contracted com presses the m em branous urethra and stop s the ow of urine.

Deep dorsal vein of clitoris

Inferior pubic ligament Urethra

Dorsal nerve of clitoris

Anterior edge of perineal membrane

Dorsal artery of clitoris External urethral sphincter muscle

Perineal membrane

FIGURE 5.31 fem ale.

Deep transverse perineal m.

Contents of the deep perineal pouch in the

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4. Posterior to the opening of the urethra, identify the vaginal opening. 5. Identify the d eep t ran sverse p erin eal m uscle (paired) along the posterior m argin of the deep perineal pouch (FIG. 5.31). Note that its ber direction and function are identical to those of the super cial transverse perineal muscle, which is located in the super cial perineal pouch. 6. Collectively, the m uscles within the deep perineal p ouch plus the perineal m em brane are known as the uro g e n it al d iap h rag m . 7. Review the attachm ents and actions of the e xt e rn al ure t h ral sp h in ct e r and the d e e p t ran sve rse p e rin e al m uscle (see TABLE 5.2). 8. Coursing anterior along the lateral m argin of the d eep p erineal pouch, identify the b ran ch e s o f t h e in t e rn al p ud e n d al art e ry an d ve in (m ost notably, the dorsal artery of the clitoris) and the b ran ch es o f t h e p ud e n d al n e rve (m ost notably, the dorsal nerve of the clitoris). These structures supply the external urethral sphincter m uscle, the deep transverse perineal m uscle, and the clitoris (FIG. 5.31).

CLIN ICA L CORRELATION

Ob st e t ric Co n sid e rat io n s To alleviate the p ain of child b irth, a p u d e n d a l n e rve b lo ck is p erform ed b y injecting a local anesthetic around the p ud end al nerve near the ischial sp ine. To p erform the injection, the ischial sp ine is p alp ated throug h the vag ina, and the need le is d irected throug h the wall of the vag inal canal toward the ischial sp ine. As the head of the baby passes through the vagina during childbirth, the anus and the levator ani m uscles are forced posteriorly toward the sacrum and coccyx. The urethra is forced anteriorly toward the pubic sym physis. Perineal lacerations during childbirth are com m on, and it m ay be necessary to surgically widen the vaginal ori ce (ep isiotom y). If the p erineal body is lacerated, it m ust be repaired to p revent weakness of the pelvic oor; otherwise, it could result in prolapse of the urinary b ladder, uterus, or rectum .

Disse ct io n Fo llo w-up 1. Replace the m uscles of the urogenital triangle in their correct anatom ical positions. 2. Review the contents of the fem ale super cial perineal pouch. Visit a dissection table with a m ale cadaver and view the contents of the sup er cial p erineal pouch. 3. Use an atlas illustration to review the course of the internal pudendal artery from its origin in the pelvis. 4. Use an atlas illustration to review the course and branches of the pudendal nerve. 5. Review an atlas illustration that shows the fem ale urethra and note its course from the urinary bladder to the perineum .

TABLE 5.2

Fe m ale Sup e r cial Pe rin e al Po uch

SUPERFICIAL GROUP OF MUSCLES Muscle

Anterior Atta chments

Posterior Atta chments

Actions

Innerva tion

Bulbospongiosus

Corpus cavernosum clitoris

Perineal body

Compress the bulb of the clitoris

Ischiocavernosus

Crus of the clitoris

Ischial tuberosity and ischiopubic ramus

Forces blood from the crus of the clitoris into the distal part of the corpus cavernosum clitoris

Deep branch of the perineal n. (branch of pudendal n.)

Super cial transverse perineal

Perineal body (medial attachment)

Ischial tuberosity (lateral attachment)

Provides support to the perineal body

Perineal n. (branch of pudendal n.)

Muscle

Anterior Atta chments

Posterior Atta chments

Actions

Innerva tion

Deep transverse perineal

Perineal body (medial attachment)

Ischial tuberosity (lateral attachment)

Provides support to the perineal body

Perineal n. (branch of pudendal n.)

External urethral sphincter

Attaches to itself around the urethra

Compresses the membranous urethra and stops the ow of urine

Deep branch of the perineal n. (branch of pudendal n.)

DEEP GROUP OF MUSCLES

Abbreviation: n., nerve.

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FEMALE PELVIC CAVITY Disse ct io n Ove rvie w The fem ale pelvic cavity contains the urinary bladder anteriorly, the fem ale internal genitalia, and the rectum posteriorly (FIG. 5.32). The term ad n exa (L. adnexa , adjacent parts) refers to the ovaries, uterine tubes, and ligam ents of the uterus. Rem oval of the uterus (hysterectom y), with or without the ovaries, is a com m on surgical procedure. If the uterus has been surgically rem oved from your cadaver, exam ine it in other cad avers. The order of dissection will be as follows: The peritoneum will be studied in the fem ale pelvic cavity. The pelvis will be sectioned in the m idline, and the cut surface of the sectioned pelvis will be studied . The uterus and vagina will be studied. The uterine tube will be traced from the uterus to the ovary. The ovary will be studied.

Disse ct io n In st ruct io n s

CLIN ICA L CORRELATION

Fe m ale Pe rit o n e um [G 422, 423; L 265; N 340; R 366] Using FIGURE 5.32 as a reference, exam ine the p e rit o n e um in the fem ale p elvis. 1. Identify the peritoneum on the posterior aspect of the anterior abdom inal wall superior to the pubis. 2. Observe that the peritoneum re ects from the anterior abdom inal wall inferiorly across the apex of the urinary bladder. 3. The peritoneum courses along the superior surface of the urinary bladder. Identify the p arave sical fo ssa (paired), the shallow depression in the peritoneal cavity on the lateral sides of the urinary bladder. 4. Follow the lining of the peritoneum posteriorly and observe that it passes from the superior surface of the urinary bladder to the uterus. The peritoneal re ection from bladder to uterus form s the vesicout erin e p ouch . 5. Observe that the peritoneum in the fem ale additionally covers the fundus and body of the uterus and contacts the wall of the posterior part of the vaginal fornix.

Pe lvic Pe rit o n e um As the urinary bladder lls, the peritoneal re ection from the anterior abdom inal wall to the bladder is elevated above the level of the pubis (FIG. 5.32). A lled urinary bladder can be penetrated by a needle inserted superior to the pubis without entering the peritoneal cavity.

6. Observe that posteriorly, the p eritoneum covers a depression, the re ct o ut e rin e p o uch , between the uterus and the rectum . Note that the rectouterine pouch (the pouch of Douglas) is the lowest point in the fem ale abdom inop elvic cavity. 7. Follow the peritoneum sup eriorly along the posterior aspect of the pelvic cavity and observe that it contacts the anterior surface and sides of the rectum and form s the sigm oid m esocolon at the level of the third sacral vertebra. 8. Identify the p arare ct al fo ssa (paired), the shallow depression in the peritoneal cavity on the lateral sides of the rectum .

Bro ad Lig am e n t [G 426; L 269; N 350; R 369] 5 1 2

4

6

3

7

8

Bladder Retropubic space Vagina

Pubovesical ligament

FIGURE 5.32 Peritoneum in the fem ale pelvis. The num bered features in the gure correlate to the fem ale peritoneum dissection instruction step s.

1. Identify the b ro ad lig am e n t o f t h e ut e rus . The broad ligam ent of the uterus is form ed by two layers of peritoneum , which extend bilaterally from the lateral side of the uterus to the lateral pelvic wall. Note that the connective tissue enclosed between the two layers of the broad ligament is called pa ra metrium (Gr. para , beside; m etra , wom b, uterus). 2. Observe that the ut erin e t ub e is contained within the superior m argin of the broad ligam ent. The portion of the broad ligam ent surrounding the uterine tube is called the m e so salp in x (Gr. salpinx, tube) (FIG. 5.33). 3. The portion of the broad ligam ent that suspends the ovaries is the m eso varium . The portion of the broad ligam ent that is adjacent to the body of the uterus is the m e so m e t rium . 4. Identify the ro un d lig am en t o f t h e ut erus (paired), visible through the anterior layer of the broad

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Parietal peritoneum

Uterus

Inferior epigastric vein and artery

Transversalis fascia (peritoneum removed)

Deep inguinal ring External iliac vessels Parts of broad ligament: Mesosalpinx Mesovarium Mesometrium

Femoral ring Round ligament of uterus Uterine tube (cut) Ovarian ligament within mesovarium (cut)

Broad ligament

Perineal membrane

Ureter (cut) Perineal body

Vagina

Rectouterine fold

FIGURE 5.33 Posterior view of the broad ligam ent of the uterus. Peritoneum has been rem oved from the inner surface of the ab dom inal wall on the right side of the illustration.

5.

6.

7.

8.

ligam ent (FIG. 5.33). Observe that the round ligam ent of the uterus passes over the pelvic brim and exits the abdom inal cavity by passing through the deep inguinal ring lateral to the inferior epigastric vessels. The round ligam ent of the uterus passes through the inguinal canal and ends in the labium m ajus. Identify the o varian lig am e n t (p aired), a brous cord within the broad ligam ent that connects the ovary to the uterus. Identify the susp e n so ry lig am e n t o f t h e o vary (p aired), a peritoneal fold that covers the ovarian vessels. Observe that the suspensory ligam ent of the ovary extends into the greater pelvis from the posterior abdom inal wall. Study an atlas illustration and note that the en d op elvic fascia (extraperitoneal fascia) contains condensations of connective tissue that passively support the uterus. [G 441; L 270; N 343] The endopelvic fascia includes distinct condensations of tissue: the ut e ro sacral (sacro g e n it al) lig am e n t (p aired), which extends from the cervix to the sacrum underlying the ut e ro sacral fo ld ; the t ran sve rse ce rvical lig am e n t (card in al lig am e n t ) (paired), which extends from the cervix to the lateral wall of the p elvis; and the p ub o ce rvical (p ub o ve sical) (p aired) ligam ent, which extends from the pubis to the cervix.

Se ct io n o f t h e Fe m ale Pe lvis The pelvis will be divided in the m idline. First, the pelvic viscera and the soft tissues of the perineum will be cut in the m idline with a scalpel. The pubic sym physis and vertebral

colum n (up to vertebral level L3) will be cut in the m idline with a saw. Subsequently, the left side of the body will be transected at vertebral level L3. The right lower lim b and right side of the pelvis will rem ain attached to the trunk. The pelvic viscera, pelvic vasculature, and nerves of the p elvis will be dissected in both halves of the pelvis. Onehalf of the p elvis will be used to dem onstrate the m uscles of the pelvic diaphragm . 1. Make a m idline cut, beginning posterior to the p ubic sym p hysis, and carry this m idline cut through the superior surface of the urinary bladder. Spread op en the bladder and sponge the interior if necessary. 2. Position the uterus in the m idline and use a scalpel to divide the uterus in its m edian p lane, which m ay or m ay not align with the m idline of the pelvis. Note that female cadavers m ay or may not have an intact uterus or other internal pelvic organs following hysterectom y procedures. 3. Extend the cut through the m idline of the cervix inferiorly and into the fornix of the vaginal canal. 4. Extend the m idline cut in the posterior direction cutting through the anterior and posterior walls of the rectum and the distal part of the sigm oid colon. 5. Clean the internal aspect of the rectum and anal canal. Use caution when cleaning and moving fecal matter. Refer to your instructor for proper safety techniques. 6. Identify the internal urethral ori ce in the bladder and insert a probe into it. Using the probe as a guide, cut through the inferior part of the bladder, dividing the urethra. 7. In the p erineum , insert the tip of a p robe into the external urethral ori ce. Use the p robe as a guide to

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8.

9.

10.

11.

12.

13.

14.

15. 16.

m ake a m idline cut through the clitoris, dividing it into right and left sides. Extend this cut posteriorly, dividing the urethra and vagina into right and left sides. In the m idline, extend the cut to the tip of the coccyx cutting through the perineal m em brane, perineal body, and anal canal. Use a scalpel to cut the left com m on iliac vein, left com m on iliac artery, left ovarian vessels, and left ureter about 1 cm distal to their respective points of origin. Cut through the left lum bar arteries at vertebral levels L4 and L5 and re ect the abdom inal aorta to the right side of the abdom inal cavity. Use a scalp el to m ake an incision through the m uscles of the lateral abdom inal wall about 2 cm superior to the iliac crest and cut m edially to the vertebral colum n. Cut through the nerves of the left lum bar plexus at the point they cross the horizontal incision, and use the scalpel to cut through any rem aining bers of the left psoas m ajor and quadratus lum borum m uscles at vertebral level L3. With the cad aver in the supine position, use a saw to cut through the pubic sym physis in the m idline from anterior to p osterior, stopp ing at the inferior border of the pubic sym physis. Turn the cadaver 90° to the right, so it is lying on its right side. Prop the cadaver or have your lab p artners hold the body so it does not fall or rotate. Have your lab p artners abduct the left lower lim b to facilitate sectioning of the sacrum . Cut through the sacrum from posterior to anterior. Make an effort to not allow the saw to contact the

17.

18.

19. 20.

21.

THE PELVIS AND PERINEUM

Fe m ale In t e rn al Ge n it alia [G 422; L 268, 269; N 340, 346; R 366] 1. Study the cut surface of the sectioned fem ale pelvis (FIG. 5.34). 2. Trace the sectioned urethra anteroinferiorly from the urinary bladder to the e xt e rn al ure t h ral o ri ce and attem pt to identify the e xt e rn al ure t h ral sp h in ct e r m uscle . Note that the external urethral sphincter m uscle m ay be dif cult to see. 3. In the sectioned specim en, identify the vag in a (FIG. 5.34). Observe that the anterior vaginal wall is shorter than the posterior vaginal wall.

Uterus: Fundus Body Isthmus Cervix Vaginal fornices: Posterior part Anterior part

Bladder Urethra

Transverse rectal fold

External urethral sphincter m.

Rectouterine pouch

Perineal membrane

Rectum Ampulla of rectum

External urethral orifice Labium minus

FIGURE 5.34

Perineal body

173

soft tissue structures that were cut with the scalp el. Retract the soft tissue structures out of the path of the blade if necessary. Forcibly spread apart the lower lim bs to expand the opening division of the sacrum , and extend the m idline cut as far superiorly as the body of the third lum bar vertebra. Adduct the left lower lim b and use the saw to cut horizontally through the left half of the intervertebral disc between L3 and L4, sparing the inferior aspect of the abdom inal aorta. Once the horizontal and vertical cuts are connected, return the cadaver to the supine position. Cut any rem aining p ieces of tissue preventing the left lower lim b from being rem oved and p ull the left lower lim b away from the rest of the cadaver. Clean the rectum and anal canal on both sides of the bisected pelvic specim en.

Vesicouterine pouch

Vaginal canal and orifice

•

Anal canal

Anal sphincters: External Internal

Sagittal section of the fem ale pelvis.

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Suspensory ligament of ovary (containing ovarian vessels)

Fundus of uterus

Round ligament of uterus

Uterine tube (retracted): Isthmus Ampulla Infundibulum Fimbriae

Peritoneum (cut)

Broad ligament: Mesosalpinx Mesovarium Mesometrium

Ovarian artery and vein Ovary Ovarian ligament Uterine cavity Internal os Cervical canal

Body of uterus Cervix of uterus

Fornix of vagina (lateral part) External os Vagina

FIGURE 5.35

Uterus, uterine tubes, ovaries, and broad ligam ent. Posterior view.

4. Within the vaginal canal, identify the vag in al fo rn ix surrounding the inferior m ost aspect of the uterus, the ce rvix . Observe that the vaginal fornix has an an t e rio r p art , a p o st e rio r p art , and a lat e ral p art (p aired : right and left) (FIGS. 5.34 and 5.35). 5. Observe that the posterior wall of the vagina (near the posterior part of the vaginal fornix) is in contact with the peritoneum that lines the rectouterine pouch. 6. Study the ut e rus (FIGS. 5.34 and 5.35) and observe that it is tilted approxim ately 90° anterior to the axis of the vagina (anteverted). Note that the position of the uterus changes as the bladder lls, and during pregnancy. [G 427, 428; L 270; N 352; R 368, 369] 7. Identify the fun d us o f t h e ut e rus , the rounded p ortion that lies superior to the attachm ents of the uterine tubes. 8. Inferior to the fundus, identify the b o d y o f t h e ut e rus . Observe that the ve sical surface of the body of the uterus faces the vesicouterine pouch and the in t e st in al surface faces the rectouterine pouch (FIG. 5.35). Note that the broad ligam ent is attached to the lateral surface of the body of the uterus. 9. Identify the ist h m us o f t h e ut e rus , the narrowed p ortion of the body superior to the ce rvix . The ce rvix is the thick-walled portion of the uterus that protrudes into the vaginal canal. 10. Identify the ut e rin e cavit y. Observe that in a sagittal section, it is a slit (FIG. 5.34), whereas in a coronal section, it is triangular (FIG. 5.35).

11. The uterine wall contains three distinct layers. The bulk of the wall of the uterus is com posed of the thick m uscular wall called m yo m e t rium . The e n d o m e t rium is the innerm ost aspect of the uterine wall form ed by uterine m ucosa, and the p e rim e t rium (Gr. peri, around) covers the external surface of the uterus. Note that the tissues within the broad ligam ent are called pa ra metrium (Gr. para, beyond). 12. Identify the ut e rin e t ub e (FIG. 5.35). Use your ngers to follow the uterine tube as it passes laterally within the m esosalpinx beginning at the ist h m us , the narrow m edial one-third of the uterine tube. 13. Continue to palpate laterally along the length of the uterine tube and identify the am p ulla , the widest and longest part of the uterine tube. The am pulla transitions to the in fun d ib ulum , the funnel-like end of the uterine tube. 14. Identify the m b riae , the nger-like processes that surround the distal m argin of the infundibulum . 15. Identify the ovary. Observe that the ovary is ovoid, with a tub al (d istal) extrem ity where the ovarian vessels enter the ovary, and a uterine (p roxim al) extrem ity attached to the ligam ent of the ovary. 16. The ovary sits in the o varian fo ssa , a shallow depression in the lateral pelvic wall bounded by the ureter, external iliac vein, and uterine tube. 17. Review the abdom inal origin and course of the ovarian vessels and note that they p ass through the susp e n so ry lig am e n t o f t h e o vary (FIG. 5.35).

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Disse ct io n Fo llo w-up 1. Review the position of the fem ale pelvic viscera within the pelvic cavity. 2. Visit a dissection table with a m ale cadaver and observe the position of the m ale pelvic viscera. 3. Review the peritoneum in the fem ale pelvic cavity. Visit a dissection table with a m ale cadaver and com pare differences in the fem ale and m ale peritoneum (FIGS. 5.17 and 5.34). 4. Trace the round ligam ent of the uterus from the super cial inguinal ring to the uterus. 5. Com pare the pelvic course of the ductus deferens with the pelvic course of the round ligam ent of the uterus. 6. Review the parts of the broad ligam ent and review the function of the endopelvic fascia in passive support of the uterus.

FEMALE URINARY BLADDER, RECTUM, AND ANAL CANAL Disse ct io n Ove rvie w The urinary bladder is a reservoir for urine. When em pty, it is located within the pelvic cavity. When lled, it extends into the ab dom inal cavity. The urinary bladder is a retroperitoneal organ that is surrounded by e n d o p e lvic fascia . Between the pubic sym physis and the urinary bladder, there is a potential space called the re t ro p ub ic sp ace (p re ve sical sp ace ) (FIG. 5.32). The retrop ubic sp ace is lled with fat and loose connective tissue that accom m odates the expansion of the urinary bladd er. The p ub o ve sical lig am e n t is a condensation of fascia that ties the neck of the urinary bladder to the pubis across the retrop ubic space. The pubovesical ligam ent de nes the inferior lim it of the retropubic space (FIG. 5.32). The lower two-thirds of the rectum is surrounded by endopelvic fascia. The upper one-third of the rectum is partially covered by peritoneum (FIG. 5.32). The order of dissection will be as follows: The parts of the urinary bladder will be studied. The interior of the urinary bladder will be studied. The interior of the rectum and anal canal will be studied.

Disse ct io n In st ruct io n s Fe m ale Urin ary Blad d e r [L 266, 267; N 348] 1. Begin identi cation of the p art s o f t h e urin ary b lad d e r with the ap ex , the pointed p art directed toward the anterior abdom inal wall and identi ed by the attachm ent of the urachus (FIG. 5.36). 2. The b o d y o f t h e urin ary b lad d e r is located between the apex and the fun d us . The fundus of the bladder is the inferior p art of the p osterior wall, also called the b ase o f t h e urin ary b lad d e r . 3. Observe the proxim ity of the fundus of the bladder to the vagina and uterus. Note that in the m ale, the fund us is related to the ductus deferens, sem inal vesicles, and rectum . 4. Use an illustration to identify the n e ck o f t h e urin ary b lad d e r , the portion where the urethra exits the urinary bladder and the wall thickens to form the in t e rn al ure t h ral sp h in ct e r . Note that the internal urethral sphincter is positioned at the junction of the urinary bladder and the urethra and is an involuntary m uscle controlled by the autonom ic nervous system . 5. Observe that the sup e rio r surface o f t h e urin ary b lad d e r is covered by peritoneum , whereas the p o st e rio r surface lies im m ediately adjacent to the anterior cervix and anterior wall of the vagina, separated from them by a thin layer of endopelvic fascia (FIG. 5.36).

6. Verify that the in fe ro lat e ral (paired) surface of the urinary bladder is covered by endopelvic fascia and lies below the re ection point of the p eritoneum . 7. Exam ine the wall o f t h e urin ary b lad d e r noting its thickness and observe that it consists of bundles of sm ooth m uscle called d e t ruso r m uscle (L. detrudere, to thrust out). Note that the m ucous m embrane lining the m ajority of the inner surface of the urinary bladder lies in folds when the bladder is em pty but will atten out to accomm odate expansion.

Urachus

Vesicouterine pouch Superior surface

Ureter Apex Fundus (posterior surface)

Peritoneum Inferolateral surface

Neck

Urethra

FIGURE 5.36

Parts of the urinary bladder in the fem ale.

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CLIN ICA L CO RRELATIO N

Kid n e y St o n e s Kidney stones pass through the ureter to the urinary bladder and m ay becom e lodged in the ureter. The point where the ureter passes through the wall of the urinary bladder is a relatively narrow passage. If a kidney stone becom es lodged, severe colicky pain results. The pain stops suddenly once the stone passes into the bladder.

8. Use an illustration to study the inner surface of the fundus and identify the t rig o n e o f t h e urin ary b lad d e r (urin ary t rig o n e ) (FIG. 5.37). The trigone of the bladder is a sm ooth, triangular region of m ucous m em brane de ned by lines between the in t e rn al ure t h ral o ri ce and the two ure t e ric o ri ce s . Identify the in t e rure t e ric cre st , a visible ridge extending between the ori ces of the ureters. [G 413; L 267; N 348; R 350] 9. On the inner surface of the bisected fundus of the cadaver, identify one-half of the t rig o n e o f t h e urin ary b lad d er (FIG. 5.37). Observe that the internal urethral ori ce is located at the m ost inferior point in the urinary bladder. [L 267; N 348; R 350] 10. Insert the tip of a probe into the ori ce of the ureter and observe that the ureter passes through the m uscular wall of the urinary bladder in an oblique

direction. When the urinary bladder is full (distended), the pressure of the accum ulated urine attens the part of the ureter within the wall of the bladder and thus prevents re ux of urine into the ureter. 11. Find the ureter where it crosses the external iliac artery, or the bifurcation of the com m on iliac artery, and use blunt dissection to follow the ureter to the fundus of the urinary bladder. Observe that the ureter crosses inferior to the ut e rin e art e ry and superior to the vag in al art e ry. [G 424; L 268; N 378; R 340]

Fe m ale Re ct um an d An al Can al [G 405, 422; L 272; N 340, 371; R 366] 1. Identify the re ct um at its p oint of origin at the level of the third sacral vertebra. On the sectioned pelvis, observe that the rectum follows the curvature of the sacrum (FIG. 5.34). 2. Identify the am p ulla o f t h e re ct um , the dilated portion of the rectum p roxim al to the point where the rectum bends approxim ately 80° posteriorly (an o re ct al e xure) . Observe that the am pulla of the rectum is continuous with the anal canal (FIGS. 5.34 and 5.38). 3. Exam ine the inner surface of the rectum and observe that the m ucous m em brane is sm ooth except for the presence of t ran sve rse re ct al fo ld s (FIG. 5.34). There is usually one transverse rectal fold on the right side of the rectum and two on the left side. Note that

Detrusor muscle

Orifices of the ureters

Trigone of bladder Internal urethral orifice Interureteric crest

Levator ani muscle Urethra External urethral sphincter muscle Perineal membrane

Dorsal nerve and artery of clitoris

Deep artery of clitoris Crus of corpus cavernosum (crus of clitoris) Ischiocavernosus muscle Tunica albuginea Bulbospongiosus muscle Bulb of vestibule

FIGURE 5.37

Superficial perineal fascia External urethral orifice Vestibule of vagina

Urinary bladder and urethra in the fem ale seen in coronal section.

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the transverse rectal folds m ay be dif cult to identify in som e cadavers. 4. Observe that the an al can al is only 2.5 to 3.5 cm in length and passes out of the pelvic cavity and into the anal triangle of the p erineum (FIG. 5.38). 5. Exam ine the inner surface of the anal canal and identify the an al co lum n s , 5 to 10 longitudinal ridges of m ucosa in the proxim al part of the anal canal. The anal colum ns contain branches of the sup e rio r re ct al art e ry and vein . Note that the mucosal features of the anal canal may be dif cult to identify in older individuals. 6. Identify the sem ilunar folds of m ucosa form ing the an al valve s , which unite the distal ends of the anal colum ns. Between the anal valve and the wall of the anal canal is a sm all pocket called an an al sin us .

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CLIN ICA L CORRELATION

He m o rrh o id s In the anal colum ns, the sup erior rectal veins of the hepatic p ortal system anastom ose with m iddle and inferior rectal veins of the inferior vena caval system . An abnorm al increase in blood pressure in the hepatic portal system causes engorgem ent of the veins contained in the anal colum ns, resulting in in t e rn al h e m o rrh o id s. Internal hem orrhoids are covered b y m ucous m em brane, which is innervated by autonom ic nerve bers. They m ay not exp erience pain or the pain m ay be poorly localized. Ext e rn al h e m o rrh o id s are enlargem ents of the tributaries of the inferior rectal veins. External hem orrhoids are covered by skin, which is innervated by som atic nerves (inferior rectal nerves). External hem orrhoids exp erience hig hly sp eci c, som atic p ain.

Circular muscle Longitudinal m. Transverse rectal fold (valve of houston)

Puborectalis m. Anterior

Levator ani m. and fascia Parts of external anal sphincter m. Deep* Superficial Subcutaneous

Ampulla of rectum Anal sinus

Internal anal sphincter m.

Anal canal

Anal column Anal valve

FIGURE 5.38

*Blended with puborectalis m.

Rectum , anal canal, and anal sphincter muscles.

7. Identify the p e ct in at e lin e , the irregular line form ed by the contour of the collective anal valves. 8. Identify the e xt e rn al an al sp h in ct e r m uscle in the sectioned specim en surrounding the anal canal. Note that the external anal sphincter is com posed of skeletal muscle and is under voluntary control (FIGS. 5.34 and 5.38). 9. Identify the in t e rn al an al sp h in ct e r m uscle in the sectioned specim en surrounding the anal canal (FIGS. 5.34 and 5.38). Note that the internal anal sphincter is composed of sm ooth muscle and is under involuntary control. 10. Observe that the long itud inal m uscle of the anal canal sep arates the two sp hincter m uscles. If you have d if culty id entifying the anal sp hincters, use a scalp el to cut another section throug h the wall of the anal canal to im p rove the clarity of the d issection.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the features of the urinary bladder, rectum , and anal canal. 2. Review the relationships of the uterus, vagina, and ureters to the rectum and fundus of the urinary bladder. 3. Visit a dissection table with a m ale cadaver and review the relationships of the sem inal vesicles, am pulla of the ductus deferens, and ureters to the rectum and fundus of the urinary bladder. 4. Review the kidney, the abdom inal course of the ureter, the pelvic course of the ureter, and the function of the urinary bladder as a storage organ. 5. Review the fem ale urethra. Visit a table with a m ale cadaver and review the parts of the m ale urethra. 6. Review all parts of the large intestine and recall its function in absorption of water and in com paction and elim ination of fecal m aterial. 7. Recall that the external anal sphincter m uscle is com posed of skeletal m uscle and is under voluntary control, whereas the internal anal sp hincter m uscle is com posed of sm ooth m uscle and is involuntary.

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FEMALE INTERNAL ILIAC ARTERY AND SACRAL PLEXUS Disse ct io n Ove rvie w Anterior to the sacroiliac articulation, the co m m o n iliac art ery divides to form the e xt ern al and in t e rn al iliac art e rie s (FIG. 5.39). The external iliac artery distributes to the lower lim b and the internal iliac artery d istributes to the pelvis. The internal iliac artery has the most variable branching pattern of any artery, and it is worth noting at the outset of this dissection that you m ust use the distribution of the branches to identify them , not their pattern of branching or origin . The internal iliac artery com m only divides into an anterior division and a posterior d ivision. Branches arising from the anterior division are m ainly visceral (branches to the urinary bladder, internal g enitalia, external genitalia, rectum , and gluteal region). Parietal branches arise from the posterior division (branches to the pelvic walls and gluteal region). The order of dissection will be as follows: The branches of the posterior division of the internal iliac artery will be identied. The branches of the anterior division of the internal iliac artery will be identi ed. The nerves of the sacral plexus will be dissected. Finally, the pelvic portion of the sym pathetic trunk will be dissected.

Disse ct io n In st ruct io n s Blo o d Ve sse ls [G 433; L 274; N 378, 380] The dissection of the p elvic vasculature m ay be perform ed on both the right and left sides of the hem isected pelvis; however, it is recom m ended to focus the dissection on just the right side because a deeper dissection will be perform ed on the left side with the detached lower lim b. 1. Identify the in t e rn al iliac ve in and ob serve that its tributaries largely p arallel the nearby arteries but are plexiform in nature. To clear the dissection eld, rem ove all tributaries to the internal iliac vein as each correlating artery is identi ed and cleaned. 2. Use an atlas illustration to study the ve sical ve n o us p le xus , ut e rin e ve n o us p le xus , vag in al ve n ous p le xus , and re ct al ve n o us p le xus . All of these plexuses drain into the internal iliac vein.

3. Identify and clean the co m m o n iliac art e ry and follow it distally until it bifurcates into the e xt e rn al iliac art e ry and in t e rn al iliac art e ry. 4. Use blunt dissection to follow the internal iliac artery into the p elvis and observe that it gives num erous sm aller vessels from two m ajor divisions, anterior and posterior (FIG. 5.39). 5. Begin identi cation of the branches of the posterior division of the internal iliac artery by nding the m ost posterior and superior branch, the ilio lum b ar art e ry (FIG. 5.39). Observe that the ilio lum b ar art e ry branches posteriorly from the posterior division and then ascends lateral to the sacral p ro m o n t o ry, lum bar vertebrae, lum bosacral trunk, and the obturator nerve. 6. Identify the lat e ral sacral art e ry, which gives rise to a superior branch and an inferior branch. Observe

Iliolumbar artery

Common iliac artery

Lumbosacral trunk Lateral sacral artery

Internal iliac artery External iliac artery

Anterior rami: S1 S2 S3 S4

Umbilical artery Obturator artery Deep circumflex iliac artery Inferior epigastric artery

Superior gluteal artery Inferior gluteal artery

Medial umbilical ligament (obliterated umbilical artery)

Pudendal nerve Internal pudendal artery

Superior vesical arteries

Uterine artery Middle rectal artery

Urinary bladder Vagina

FIGURE 5.39

Rectum

Branches of the internal iliac artery in the fem ale.

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7.

8.

9.

10.

11.

12.

that the inferior branch passes anterior to the sacral ventral ram i. Note that the lateral sacral artery m ay arise from a com m on trunk with the iliolumbar artery. Identify the last and typically larg est branch of the posterior division, the sup e rio r g lut e al art e ry, which exits the p elvic cavity through the greater sciatic foram en superior to the p irifo rm is m uscle . Identify the branches of the an t e rio r d ivisio n o f t h e in t e rn al iliac art e ry beginning with the um b ilical artery. In the m edial um bilical fold, nd the m ed ial um b ilical lig am e n t (the rem nant of the um bilical artery) and use blunt dissection to trace it posteriorly to the um bilical artery. Identify and clean several sup e rio r ve sical art e ries , which arise from the inferior surface of the um bilical artery and descend to the superolateral part of the urinary bladder. Inferior to the um bilical artery, identify the o b t urat o r art e ry, which passes into the obturator canal along with the o b t urat o r n e rve . Find the obturator artery where it enters the obturator canal in the lateral wall of the pelvis and follow the artery posteriorly to its origin. Note that in about 20% of cases, the obturator artery arises from the external iliac or inferior epigastric arteries. This a berra nt obtura tor a rtery crosses the pelvic brim to enter the obturator canal. The aberrant obturator artery is particularly at risk of injury during surgical repair of a fem oral hernia. Follow the anterior division of the internal iliac artery toward the p elvic oor and identify the in fe rio r g lut e al art e ry. Observe that the inferior gluteal artery com m only passes out of the pelvic cavity into the gluteal region through the greater sciatic foram en inferior to the piriform is m uscle. Note that the inferior gluteal artery m ay share a comm on trunk with the internal pudendal artery, or less com m only, with the superior gluteal artery. Identify the ut e rin e art e ry coursing along the inferior attachm ent of the broad ligam ent. Use blunt dissection to trace the uterine artery to the lateral aspect of the uterus and observe that it passes sup erior to the

CLIN ICA L CORRELATION

Ut e rin e Art e ry The close proxim ity of the ureter and the uterine artery near the lateral fornix of the vagina is of clinical im portance. During hysterectom y, the uterine artery is tied off and cut. The ureter m ay be unintentionally clam ped, tied off, and cut where it crosses the uterine artery. This would have serious consequences for the corresponding kidney. To recall this relationship, use the m nem onic device “water under the bridge.” The “water” is urine; the “bridge” is the uterine artery.

13.

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15. 16.

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ureter. Com m only, the uterine artery divides into a large superior branch to the body and fundus of the uterus and a sm aller b ranch to the cervix and vagina (FIG. 5.39). Observe the close relationship of the lateral part of the vaginal fornix to the uterine artery. Note that in a living person, the pulsations of the uterine artery m ay be felt through the lateral part of the vaginal fornix. Identify the vag in al art e ry and observe that it p asses across the oor of the pelvis, inferior to the ureter, to supp ly the vagina and the urinary bladder. Note that the m ale cadaver does not have a vaginal or uterine artery but rather has an inferior vesical artery. Identify the ureter and observe that it passes between the vaginal artery and the uterine artery. Identify the in t e rn al p ud e n d al art e ry anterior to the inferior gluteal artery. Observe that the internal pudendal artery exits the pelvic cavity through the greater sciatic foram en but stays m ore m edial than the inferior gluteal artery because it will enter the lesser sciatic foram en to reach the p erineum . Note that the internal pudendal artery often arises from a com mon trunk with the inferior gluteal artery.

Ne rve s [G 400, 433; L 275; N 390, 486; R 487] The som atic plexuses of the pelvic cavity are the sacral p le xus and coccyg e al p le xus . These plexuses are located between the pelvic viscera and the lateral pelvic wall, within the endopelvic fascia. These som atic nerve plexuses are form ed by contributions from anterior ram i of spinal nerves L4–Co1. The prim ary visceral nerve plexus of the p elvic cavity is the in fe rio r h yp o g ast ric p le xus (also called p e lvic p lexus ). It is form ed by contributions from the hypogastric nerves, sacral splanchnic nerves (sym p athetic), and p elvic splanchnic nerves (parasym pathetic). 1. Use your ngers to free the rectum from the anterior surface of the sacrum and coccyx. 2. Retract the rectum m edially and identify the sacral p le xus of nerves. Observe that the sacral p lexus is closely related to the anterior surface of the piriform is m uscle. 3. Just lateral to the sacral prom ontory, identify and clean the lum b o sacral t run k (anterior ram i of L4 and L5) and verify that it joins the sacral plexus (FIG. 5.40). 4. Inferior to the lum bosacral trunk, identify the anterior ram i of S2 and S3, which em erge between the proxim al attachm ents of the piriform is m uscle. 5. Identify the sciat ic n erve and observe that it is form ed by the anterior ram i of spinal nerves L4 through S3. The sciatic nerve exits the pelvis by passing through the greater sciatic foram en to enter the gluteal region, usually inferior to the piriform is m uscle.

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Lumbosacral trunk

Superior gluteal a.

Anterior rami: S1 S2 S3 S4

Inferior gluteal a.

Pelvic splanchnic nerves

10.

11.

Pudendal nerve Sciatic nerve Rectum Vagina

FIGURE 5.40

12.

Sacral p lexus of nerves in the fem ale.

6. Observe that the sup erio r g lut e al art e ry usually passes between the lum b o sacral t run k and the an t e rio r ram us o f sp in al n e rve S1 and exits the p elvis by passing superior to the piriform is m uscle. 7. Observe that the in ferio r g lut eal art ery usually passes between the anterior ram i of spinal nerves S2 and S3, but m ay pass between the anterior ram i S1 and S2, to exit the pelvis inferior to the piriform is m uscle. 8. Identify the p ud en d al n erve and observe that it is formed by contributions from the anterior rami of spinal nerves S2, S3, and S4. Note that the pudendal nerve exits the pelvis by passing inferior to the piriformis muscle, through the greater sciatic foramen, where it then enters the perineum by passing through the lesser sciatic foramen. 9. Identify the p e lvic sp lan ch n ic n e rve s (n e rvi e rig e n t e s) . Observe that pelvic sp lanchnic nerves are b ranches of the anterior ram i of sp inal nerves S2, S3, and S4 (FIG. 5.24). Note that pelvic splanchnic nerves

13.

carry presynaptic parasym pathetic axons for innervation of pelvic organs and the distal gastrointestinal tract from the left colic exure to the anal canal. [G 437; L 275, 276; N 390] Identify the sacral p ortion of the sym p ath etic trunk located on the anterior surface of the sacrum, m edial to the ventral sacral foram ina. Observe that the sym p athetic trunk continues from the abdom inal region into the pelvis and that the two sides join in the m idline near the level of the coccyx to form the g an g lion im p ar . Identify the g ray ram i co m m un ican t e s , which connect the sym pathetic ganglia to the sacral anterior ram i. Note that each gray ramus comm unicans carries postsynaptic sympathetic bers to an anterior ram us for distribution to the lower extrem ity and perineum. Identify the sacral sp lan ch n ic n e rve s arising from two or three of the sacral sym p athetic ganglia, and observe that they pass directly to the in ferio r h yp o g ast ric p le xus . Note that sacral splanchnic nerves carry sym pathetic bers that distribute to the pelvic viscera. On the right side of the pelvic cavity, m ake an effort to follow the hypogastric plexus superiorly toward the condensation of the plexus into the rig ht h yp og astric n erve . Use an illustration to identify the sup erior h yp og astric p lexus and review the origins of the autonomics in both the superior and inferior hypogastric plexuses.

CLIN ICA L CORRELATION

Pe lvic Ne rve Ple x use s The inferior hypogastric plexus is located in the endopelvic fascia lateral to the bladder, uterus, vagina, and rectum . The inferior hypogastric plexus, as well as its superior contribution of the hypogastric nerve, could be injured during pelvic surgery, leading to loss of bladd er control.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Review the abdom inal aorta and its term inal branches. Use the dissected specim en to review the branches of the internal iliac artery. Review the region supplied by each branch. Review the relationship of the uterine and vaginal arteries to the ureter. Review the form ation of the sacral plexus and the branches that were dissected in the pelvis. Use the dissected specim en and an atlas illustration to review the course of the pudendal nerve from the pelvic cavity to the urogenital triangle.

FEMALE PELVIC DIAPHRAGM Disse ct io n Ove rvie w The p e lvic d iap h rag m is the m uscular oor of the pelvic cavity and is form ed by the le vat o r an i m uscle and co ccyg e us m uscle , plus the fasciae covering their superior and inferior surfaces (FIG. 5.41A, B). The pelvic diap hragm extends from

CHAPTER 5

THE PELVIS AND PERINEUM

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181

the pubic sym p hysis to the coccyx p osteriorly. Laterally, the pelvic diaphragm is attached to the fascia covering the o b t urat o r in t e rn us m uscle . The urethra and vagina and the anal canal pass through m idline openings in the pelvic diaphragm called the uro g e n it al h iat us and an al h iat us , respectively. The order of dissection will be as follows: The p elvic viscera will be retracted m edially. The obturator internus, tendinous arch of the levator ani, and the levator ani will b e identi ed. The urethra, vaginal canal, and anal canal will be cut and the pelvic viscera re ected.

Obturator internus muscle and fascia Piriformis muscle

Tendinous arch of levator ani muscle

Ischial spine Obturator canal Coccygeus muscle

Levator ani muscle: Iliococcygeus muscle Pubococcygeus muscle Puborectalis muscle

A Arcuate pubic ligament Urogenital hiatus Ischiopubic ramus Anal hiatus

Pelvic diaphragm: Levator ani muscle: Puborectalis muscle Pubococcygeus muscle Iliococcygeus muscle Coccygeus muscle

Anococcygeal raphe Ischial tuberosity

Obturator internus muscle and tendon

Ischial spine

Piriformis muscle

B Sacrotuberous ligament

FIGURE 5.41

Sacrospinous ligament (cut)

Pelvic diaphragm in the fem ale. A. Left lateral view. B. Inferior view.

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Disse ct io n In st ruct io n s Perform the following dissection sequence on only one side of the cadaver. If the left lower lim b was rem oved d uring the bisection of the p elvis, it is recom m ended that the deep dissection be perform ed on the left side to preserve the continuity of the vasculature into the abdom inal cavity on the right side. [G 396, 399; L 278, 279; N 335–337] 1. Retract the rectum , vagina and uterus, and urinary bladder m edially and identify the p e lvic d iap h rag m . 2. Use blunt dissection to rem ove any rem aining fat and connective tissue from the superior surface of the pelvic diaphragm . 3. Locate the o b t urat o r can al piercing the obturator internus by identifying and following the obturator artery and nerve. 4. Palpate the m edial surface of the ischial spine through the levator ani and identify the t e n d in o us arch o f t h e le vat o r an i m uscle (FIG. 5.41A). Observe that the tendinous arch lies just inferior to a line connecting the ischial spine and the obturator canal. Note that the tendinous arch is a thickening in the obturator fascia and the origin of part of the levator ani muscle. Identify the three com ponents of the levat o r an i m uscle by their anterior attachm ents. Learn, but do not dissect, their posterior attachm ents. 5. Identify the p ub orect alis m uscle (paired) attaching anteriorly to the body of the pubis and posteriorly to the puborectalis m uscle of the opposite side (in a m idline raphe). The puborectalis m uscles form the m argin of the urogenital hiatus and a “puborectal sling,” which m aintains the an orectal exure of the rectum (FIGS. 5.38 and 5.41B). Note that during defecation, the puborectalis muscles relax, the anorectal exure straightens, and the elimination of fecal matter is facilitated. 6. Identify the p ub ococcyg eus m uscle (paired) attaching from the body of the pubis anteriorly to the coccyx and the an ococcyg eal rap h e (lig am en t ) posteriorly. 7. Identify the ilio co ccyg e us m uscle (p aired) attaching from the tend inous arch anterolaterally to the coccyx

8.

9.

10.

11.

12.

13.

14.

and the anococcygeal raphe p osteriorly. Note that the levator ani muscle supports the pelvic viscera and resists increases in intra-abdom inal pressure. Identify the co ccyg e us m uscle (paired), which com pletes the pelvic diaphragm posteriorly. Observe that the anterior attachm ent of the coccygeus m uscle is the ischial sp ine and that its posterior attachm ent is the lateral border of the coccyx and the lowest part of the sacrum (FIG. 5.41A). Place the ngers of one hand in the ischioanal fossa inferior to the pelvic diap hragm and the ngers of the other hand on the superior surface of the pelvic diaphragm . Palpate the pelvic diaphragm between both hands and app reciate its thinness. Turn the left lower lim b and observe that the o b t urat o r in t e rn us m uscle form s the lateral wall of the ischioanal fossa and p erineum inferior to the p elvic diaphragm and the lateral wall of the pelvic cavity superior to the pelvic diap hragm . The m edial attachm ent of the ob turator internus m uscle is the m argin of the obturator foram en and inner surface of the obturator m em brane. The lateral attachm ent of the obturator internus m uscle is the greater trochanter of the fem ur and will be studied when the gluteal region is dissected. Observe that the urethra and vagina and the anal canal pass through m idline openings in the p elvic diaphragm called the uro g e n it al h iat us and an al h iat us , respectively. If the m uscles form ing the pelvic diaphragm remain dif cult to see, m ake an incision through the inferior aspect of the urinary bladder, vaginal canal, and anal canal and detach the viscera from the pelvic oor. Leave the viscera attached to the neurovascular structures so the relationships are m aintained for later review. Use your textbook to learn the general pattern of lym phatic drainage of the pelvis and the location of the co m m o n iliac nodes, the e xt ern al iliac n o d e s , the in t e rn al iliac n o d es , the sacral n o d es , and the lum b ar n o d e s . [G 407, 434, 435; L 290; N 384; R 372]

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Use the dissected specim en to review the proxim al attachm ent and action of each m uscle of the pelvic diaphragm . Review the relationship of the branches of the internal iliac artery to the pelvic diaphragm . Review the relationship of the sacral plexus to the pelvic diaphragm . Use an atlas illustration to review the role played by the pelvic diaphragm in form ing the b oundary between the pelvic cavity and the perineum . Review the function of the p elvic diaphragm and perineal body in supp orting the pelvic and abdom inal viscera. 5. Use an atlas illustration to review lym phatic drainage in the perineum . Note that perineal structures (including the labia m ajora and the lower part of the anal canal) drain into super cial inguinal lym ph nodes, whereas the lym phatic drainage of the ovary follows the ovarian vessels to the lum bar chain of nodes, bypassing the pelvic drainage system s. 6. Review the form ation of the thoracic duct to com plete your understanding of the lym ph drainage from this region. 7. Visit a dissection table with a m ale cadaver and perform a com plete review of the dissected m ale pelvis.

CHAPTER 6

The Lower Lim b ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

h e fu n ction al req u irem en ts of th e lower lim b are weigh t bearin g, locom otion , an d m ain ten an ce of eq u ilibriu m . Alth ou gh th e u p p er an d lower lim bs d evelop with a sim ilar p attern of organ ization , th e lower lim b is con stru cted for stren gth at th e cost of m obility. Th e lower

T

lim b is d ivid ed in to fou r p arts: h ip , t h igh , leg, an d fo o t (FIG. 6.1). It is worth n otin g th at th e term leg refers on ly to th e p ortion of th e lower lim b between th e kn ee an d an kle, n ot to th e en tire lower lim b.

SUPERFICIAL VEINS AND CUTANEOUS NERVES Disse ct io n Ove rvie w Iliac crest

i

p

Anterior superior iliac spine H

Th e order of d issection will be as follows: Th e en tire lower lim b will be skin n ed . Th e su p er cial vein s an d cu tan eou s n erves will be d issected . Th e su bcu tan eou s con n ective tissu e an d fat will be rem oved leavin g selected su p er cial vein s an d cu tan eou s n erves in tact. Th e deep fascia of th e th igh will be stu d ied .

Inguinal ligament Pubic tubercle

g i h T

Lateral femoral epicondyle Medial femoral epicondyle Patella

L

e

g

Tibial tuberosity Anterior border of tibia

Lateral malleolus

o

o

t

Medial malleolus

F

The surface anatom y of the lower lim b can be studied on a living subject or on the cadaver. [G 481; L 87; N 468; R 488, 489] 1. Place the cadaver in the supine position. 2. Beginning on the lateral aspect of the hip, palpate the iliac cre st (FIG. 6.1). 3. Follow the path of the iliac crest anteriorly and identify the an t e rio r sup e rio r iliac sp in e on the anterior asp ect of the hip. Note that the anterior superior iliac spine should be palpable even in larger cadavers because little Camper’s fascia develops at this location. 4. Move your ngers inferomedially from the anterior superior iliac spine to the pubic region following the path of the inguinal ligament and palpate the p ub ic tub ercle. 5. In the m idline of the lower lim b, between the thigh and leg, palpate the “knee cap” or p at e lla. Observe that the patella has a relatively sm all degree of m obility in the xed tissue of the em balm ed cadaver com pared to a living individual.

h

Surface An at o m y

FIGURE 6.1

Surface anatom y of the lower lim b.

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6. At the knee, palpate the m e d ial fe m o ral e p ico n d yle and lat e ral fe m o ral e p ico n d yle on the m edial and lateral aspects of the knee, respectively. 7. On the anterior aspect of the leg beginning just below the knee, palpate the t ib ial t ub e ro sit y and then, continuing inferiorly toward the ankle, palpate the an t e rio r b ord e r o f t h e t ib ia. 8. At the ankle, palpate the m e d ial m alle o lus and the lat e ral m alle o lus on the m edial and lateral aspects of the ankle, respectively.

Ske le t o n o f t h e An t e rio r Th ig h Refer to a skeleton or bone box to identify the following skeletal features using FIG 6.2: [G 498; L 92; N 473; R 450]

Pe lvis 1. On the anterior aspect of the pelvis, identify both the an t e rio r sup e rior iliac sp in e and the an t e rio r in fe rio r iliac sp in e of the ilium . 2. Follow the curve of the pelvic inlet along the p e ct e n p ub is to the p ub ic t ub e rcle . 3. Align the pelvis in anatom ical position and verify that the pubic tubercle and anterior superior iliac spine are aligned in a coronal plane. 4. Identify the o b t urat o r fo ram e n and observe that it is bounded superiorly by the sup e rio r p ub ic ram us and inferom edially by the isch io p ub ic ram us.

Fe m ur [G 498; L 92; N 476; R 455]

Anterior superior iliac spine

Superior pubic ramus Pecten pubis

Anterior inferior iliac spine

Pubic tubercle

Greater trochanter Intertrochanteric line

Ischiopubic ramus Lesser trochanter

1. On the superolateral aspect of the fem ur, identify the g re at e r t ro ch an t e r. 2. On the anterior aspect of the proxim al fem ur, follow the in t ert ro ch an t e ric lin e inferom edially from the greater trochanter to the le sse r t ro ch an t e r. 3. On the distal fem ur laterally, identify the lat e ral e p ico n d yle superior to the lat e ral co n d yle . 4. On the distal fem ur m edially, identify the ad d uct o r t ub e rcle on the m e d ial e p ico n d yle superior to the m e d ial co n d yle .

Tib ia, Fib ula, an d Pat e lla [G 498; L 94; N 500; R 456] 1. On the proxim al tibia, identify the m e d ial and lat e ral co n d yle s. 2. Observe that the b ular h ead articulates with the tibia inferior to the lateral condyle but does not articulate with the fem ur. 3. On the anterior surface of the proxim al tibia, identify the t ib ial t ub e ro sit y. 4. On the p at e lla, identify both the an t e rio r surface and the art icular surface (p o st e rior).

Disse ct io n In st ruct io n s Skin In cisio n s The objective is to rem ove the skin from the lower lim b, leaving the super cial fascia, super cial veins, and cutaneous nerves undisturbed. If the lower lim b will not be dissected

Shaft (body) of femur

Patella Adductor tubercle Lateral epicondyle

Medial epicondyle

Lateral condyle

Medial condyle

Head Neck

Tuberosity

Fibula

Tibia

FIGURE 6.2

Bones of the thigh, anterior view.

in a short period, the skin m ay be rem oved at the beginning of each region to better preserve the underlying tissue. 1. With the cadaver in the sup ine position, refer to FIGURE 6.3A. 2. Make a cut from the anterior superior iliac spine (D) along the inguinal ligam ent to the p ubic tubercle.

CHAPTER 6

D F J E E

K

A

H P P P P P

FIGURE 6.3

3.

4.

5.

6.

7.

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185

8. If the toes will b e dissected, m ake one cut along the dorsal m idline of each toe to the proxim al end of the nail (H to P) and rem ove the skin from the dorsal surface of the digits. 9. Rem ove the skin from the thigh and leg as far laterally and m edially as possible. Make as m any transverse skin incisions as are needed to sp eed up the skinning process by dividing the regions into sm aller portions. 10. Turn the cadaver to the prone position and refer to FIGURE 6.3B. 11. Make a m idline incision down the sacrum to a point just superior to the anal canal (J). Note that if the pelvis has previously been dissected, this incision has been made. 12. If the skin of the gluteal region has not previously been rem oved, work from m edial to lateral and detach the skin from the gluteal region and lateral side of the hip along line J to K and place it in the tissue container. 13. Make an incision along the posterior m idline of the thigh and leg from the gluteal fold to the heel (E to I). 14. Extend the previous transverse skin incisions around the lim b to join incision E to I. 15. Begin at line E to I and work both m edially and laterally to rem ove the skin com pletely from the thig h and leg and p lace it in the tissue container.

Sup e r cial Fascia o f t h e Po st e rio r Lo w e r Lim b [G 474, 480; L 89; N 471; R 498, 501]

G H

THE LOWER LIMB

B I

Skin incisions. A. Anterior view. B. Posterior view.

Note that if the abdom en has previously been dissected, this incision has been made. Extend the cut from the pubic tubercle around the m edial side of the thigh to the posterior surface of the thigh (E). Note that if the perineum has previously been dissected, this incision has been m ade. Elevate the skin super cial to the inguinal ligam ent to verify the depth of the skin and subcutaneous tissue and m ake a vertical cut from the m idpoint of the inguinal ligam ent (F) to a point just over the patella m aking an effort to preserve the underlying super cial veins. Extend the vertical incision from the patella to the dorsum of the foot following the path of the anterior border of the tibia (G). Carefully m ake a transverse incision across the dorsum of the foot just proxim al to the webs of the toes (H to H). Note that the skin is very thin on the dorsum of the foot, and care m ust be taken to not cut too deeply. Rem ove the skin from the dorsum of the foot by m aking incisions from the heel to H along the m edial and lateral aspects of the foot.

1. With the cadaver in the prone position, exam ine the structures contained in the sup e r cial fascia of the posterior lower lim b (FIG. 6.4B). 2. Identify and clean the sm all (le sse r) sap h e n o us ve in where it passes posterior to the lateral m alleolus at the ankle (FIG. 6.4B). Note that the small saphenous vein arises from the lateral end of the dorsa l venous a rch of the foot. 3. Use blunt dissection to follow the sm all saphenous vein superiorly and observe that it pierces the deep fascia in the popliteal fossa and drains into the popliteal vein. 4. Identify the sural n e rve (L. sura, calf of the leg) on the posterior aspect of the leg. Observe that the sural nerve pierces the deep fascia halfway down the posterior aspect of the leg and courses p arallel to the sm all saphenous vein. Note that the sural nerve innervates the skin of the lateral aspect of the ankle and foot. 5. Identify the p o st e rio r cut an e o us n e rve o f t h e t h ig h on the posterior aspect of the popliteal fossa. Observe that the posterior cutaneous nerve of the thigh is difcult to follow superiorly because it lies deep to the deep fascia (FIG. 6.4B). Note that branches of this nerve pierce the deep fascia to supply the skin on the posterior surface of the thigh and popliteal fossa. 6. If they have not already been cut with rem oval of the skin, identify the clun e al n e rve s (L. clunis, buttock), which innervate the skin of the gluteal region.

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Superficial circumflex iliac v.

Superior cluneal nerves

Saphenous opening

Middle cluneal nerves

Femoral a.

Superficial epigastric v. Femoral v. Superficial external pudendal vein Lateral femoral cutaneous n. Inferior cluneal nerves Accessory saphenous v. Cutaneous branches of obturator n. Anterior cutaneous branches of the femoral n. Great saphenous v.

Posterior cutaneous nerve of the thigh Saphenous n. Small saphenous v.

Sural n. Great saphenous v.

Superficial fibular n.

Dorsal venous arch of foot

Dorsal digital branches of the deep fibular n.

B

A Dorsal digital nerves

Medial calcaneal n.

FIGURE 6.4 Cutaneous nerves and super cial veins of the lower lim b. A. Anterior view. B. Posterior view.

CHAPTER 6

7. Use an illustration (FIG. 6.4B) or the cadaver to study the cutaneous innervation of the posterior surface of the gluteal region. 8. Observe that the sup e rio r clun e al n e rve s (p osterior ram i of L1–L3) innervate the upper buttock. 9. Observe that the m id d le clun e al n e rve s (p osterior ram i of S1–S3) innervate the m iddle part of the buttock. 10. Observe that the in fe rio r clun e al n e rve s (p osterior ram i of S2–S3) and branches of the p o st e rio r cut an e o us n e rve o f t h e t h ig h (posterior ram i of S1–S3) wrap around the inferior border of the gluteus m axim us m uscle and innervate the skin over the lower p art of the buttock. 11. Rem ove all rem nants of sup e r cial fascia from the p osterior asp ect of the gluteal region, thigh, and leg while preserving the deep fascia, cutaneous nerves, and super cial veins that have been dissected.

8.

9. 10.

11.

12.

Sup e r cial Fascia o f t h e An t e rio r Lo w e r Lim b [G 474, 480; L 88; N 470; R 490, 504, 505] 1. Turn the cadaver to the supine position and refer to FIGURE 6.4A. 2. Identify and clean the g re at sap h e n o us ve in (Gr. saphenous, m anifest; obvious) at the ankle where it courses anterior to the m edial m alleolus (FIG. 6.4A). Observe that the great sap henous vein arises from the m edial end of the d o rsal ve n o us arch o f t h e fo o t . 3. Use blunt dissection to follow the great saphenous vein proxim ally and observe that at the knee, it passes p osterior to the m edial epicondyle of the fem ur. Note that the location of the great saphenous vein posterior to the knee reduces tension on the vessel when the knee is exed. 4. Continue to follow the great saphenous vein superiorly and observe that b eginning at the level of the knee, it courses anterolaterally to eventually lie on the anterior surface of the proxim al thigh. 5. Along the course of the great saphenous vein, identify the m any unnam ed super cial veins, which drain into it, as well as the p e rfo rat in g ve in s, which connect the great saphenous vein to the deep venous system . 6. On the m edial aspect of the thigh, identify the acce sso ry sap h e n o us ve in , a nam ed tributary that drains the super cial fascia and skin of the m edial side of the thigh (FIG. 6.4A). 7. About 4 cm inferior to the inguinal ligam ent, observe that the great sap henous vein p ierces the sap h e n o us o p e n in g (sap h e n o us h iat us) and drains into the fem oral vein. The saphenous opening, a thinning

13.

14.

15.

THE LOWER LIMB

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187

in the deep fascia of the thigh (fascia lata), will be dissected later. At the sap henous opening, observe that three sm all super cial veins (sup e r cial e xt e rn al p ud e n d al, sup e r cial e p ig ast ric, and sup e r cial circum e x iliac) join the great saphenous vein (FIG. 6.4A). Use an illustration to study the cutaneous innervation of the anterior surface of the lower lim b (FIG. 6.4A). In the proxim al thigh, identify the lat e ral fe m o ral cut an e o us n e rve where it passes deep to the lateral end of the inguinal ligam ent to innervate the skin of the lateral thigh. Identify the an t e rio r cut an e o us b ran ch e s o f t h e fe m o ral n e rve , which innervate the skin of the anterior thigh. Observe that these branches of the fem oral nerve enter the sup er cial fascia lateral to the great saphenous vein. On the m edial side of the knee, identify the sap h e n o us n e rve where it p ierces the deep fascia to accom pany the great sap henous vein into the leg. Note that the saphenous nerve is a branch of the fem oral nerve and innervates the skin on the anterior and m edial sides of the leg and the m edial side of the ankle and foot. Medial to the great saphenous vein, identify the cut an e o us b ran ch e s o f t h e o b t urat o r n e rve, which innervate the skin of the m edial thigh. In th e d istal th ird of th e leg , id en tify th e su p e r ficia l fib u la r n e r ve wh ere it p ierces th e d eep fascia sup erior to th e lateral m alleolus an d follow it on to th e d orsum of th e foot. Note that the superficial fibular nerve innervates the dorsum of the foot and sends dorsa l digita l nerves to the skin of the toes. Use an illustration to observe that the d o rsal d ig it al b ran ch e s o f t h e d e e p b ular n e rve innervate the skin between the rst toe and the second toe. Note that the innervation pattern between the toes is used for the assessm ent of deep bular nerve function.

CLIN ICA L CORRELATION

Gre at Sap h e n o us Ve in Super cial veins and perforating veins have valves that p revent the back ow of blood. If these valves becom e incom petent, the veins becom e distended and tortuous—a condition known as varicose veins. Portions of the great saphenous vein m ay be rem oved and used as graft vessels in coronary byp ass surgery. The d istal end of the vein is sutured to the aorta so that the valves do not im pede the ow of blood.

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16. In the proxim al thigh, m ake an effort to identify the sup e r cial in g uin al lym p h n o d e s. 17. Use an illustration to review the distribution of the h o rizo n t al g ro up , located about 2 cm inferior to the inguinal ligam ent, and the ve rt ical g ro up around the proxim al end of the great saphenous vein (FIG. 6.5). Note that the super cial inguinal lym ph nodes collect lym p h from the lower lim b, inferior part of the anterior abdom inal wall, gluteal region, perineum , and external genitalia, and drain into the d e e p in g uin al lym p h n o d e s. 18. Rem ove the rem nants of super cial fascia from the anterior thigh, leg, and foot m aking an effort to preserve the super cial veins, cutaneous nerves, and deep fascia. 19. Exam ine the deep fascia of the lower lim b beginning with the fascia lat a (L. latus, broad) in the thigh. Observe that the fascia lata thickens laterally to form the ilio t ib ial t ract . 20. Identify the crural fascia, the deep fascia of the leg, and t h e p e d al fascia, the deep fascia of the foot.

Inguinal ligament Horizontal group of superficial inguinal lymph nodes

Margin of saphenous opening Femoral vein (seen though cribriform fascia) Fascia lata Great saphenous vein Deep inguinal lymph nodes

FIGURE 6.5 lym ph nodes.

Vertical group of superficial inguinal lymph nodes

Saphenous opening and super cial inguinal

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Trace the course of the super cial veins from distal to proxim al and note where perforating veins drain deeply. Review the location and pattern of distribution of each cutaneous nerve you have dissected in the lower lim b. Review the extent and bony attachm ents of the deep fascia and nam e its parts. Use an illustration to review the lym phatic drainage of the lower lim b.

ANTERIOR COMPARTMENT OF THE THIGH

Adductor canal

RF S VI

VM

m p t

r

a

G

o

c

l

a

i

d

e

M

AL

Femur

AM

e

m

VL

n

Th e fascia lata is con n ected to th e fem ur b y in term uscular sep ta to form the three fascial com p artm ents of the thig h: a n t e rio r (e xt e n so r), m e d ia l (a d d u ct o r), an d p o st e rio r ( e xo r) (FIG. 6.6). Th e m uscles found within each com p artm ent receive m otor innervation p rim arily throug h one nerve. Thus, the anterior com p artm ent is related to th e fem oral n erve, th e m ed ial com p artm en t to the ob turator nerve, and the p osterior com p artm ent to the b ranches of the sciatic nerve. The m uscles located on th e b ord ers of two com p artm en ts receive d ual in n ervation an d th us are often categ orized d ifferently in various texts. The anterior com p artm ent of the thigh contains the ilio p so as, the sa rt o rius, and the q uad rice p s fe m o ris m uscle (re ct u s fe m o ris, vast u s la t e ra lis, va st u s in t e rm e d ius, and vast us m e d ialis). For ease of dissection, the p e ct in e u s m uscle and the t e n so r o f t h e fascia lat a m uscle will be dissected along with the other m uscles of the anterior com p artm ent of the thig h. The fem oral artery, the m ajor blood sup p ly to the lower lim b, and the fem oral nerve, along with m any of their branches, p ass through the anterior com p artm ent of the thig h. [G 484, 485; L 101; N 49 2; R 4 71]

Anterior compartment

t

Disse ct io n Ove rvie w

BF ST

Lateral intermuscular septum

SM

Posterior compartment

FIGURE 6.6 Com partm ents of the right thigh. Inferior view. AL, adductor long us; AM, adductor m agnus; BF, biceps fem oris; G, gracilis; RF, rectus fem oris; S, sartorius; SM, sem im em b ranosus; ST, sem itendinosus; VI, vastus interm edius; VL, vastus lateralis; VM, vastus m edialis.

CHAPTER 6

THE LOWER LIMB

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189

The order of dissection will be as follows: The fascia lata of the thigh will be reviewed, and the saphenous opening will be studied. The anterior surface of the superior part of the fascia lata will be opened to expose the fem oral triangle. The fem oral triangle will be dissected, and its vascular contents will be followed distally. The sartorius m uscle will be identi ed, and the adductor canal will be dissected. The anterior surface of the inferior part of the fascia lata will be opened, and the rem aining anterior thigh m uscles will be studied.

Disse ct io n In st ruct io n s Sap h e n o us Op e n in g [G 486, 487; L 88; N 470; R 490] 1. Rem ove any rem nants of super cial fascia on the anterior surface of the fascia lata. 2. Rem ove the super cial inguinal lym ph nodes around the saphenous opening while preserving the great sap henous vein. 3. Follow the great saphenous vein superiorly and observe that it p asses through the sap h e n o us o p e n in g approxim ately 4 cm inferior to the inguinal ligam ent. 4. Use a probe to dissect the connective tissue around the great saphenous vein where it penetrates the fascia lata and de ne the m argin of the sap h e n o us o p e n in g (FIG. 6.7). Observe that the saphenous op ening is a natural d efect in the fascia lata that is covered with a relatively thin layer of fascia. 5. Trace the great saphenous vein through the saphenous op ening and observe that it d rains into the anterior asp ect of the fe m o ral ve in . 6. Insert your nger into the saphenous opening inferior to the great sap henous vein and p ush inferiorly, deep to the fascia lata, until your ngertip reaches the level of the sartorius m uscle. 7. Use scissors to m ake a vertical incision through the fascia lata from the sap henous opening to the sartorius m uscle (FIG. 6.7, cut 1).

Inguinal ligament

Anterior superior iliac spine

Cut 2

8. Use scissors to m ake a horizontal cut through the fascia lata parallel to the inguinal ligam ent from the superior m argin of the saphenous op ening to a point directly inferior to the anterior superior iliac spine (ASIS) (FIG. 6.7, cut 2). 9. Use scissors to m ake a second horizontal cut through the fascia lata inferior to the inguinal ligam ent from the superior m argin of the saphenous opening to a point directly inferior to the p ubic tubercle (FIG. 6.7, cut 3). 10. Use your ngers and blunt dissection to separate the fascia lata from deeper structures.

Fe m o ral Trian g le [G 488, 489; L 103, 104; N 487; R 491–493] 1. Re ect the aps of fascia lata m edially and laterally to op en the super cial boundary, or “roof” of the fe m o ral t rian g le . 2. Use scissors to rem ove the aps of fascia lata overlying the fem oral triangle and the anterior surface of the proxim al thigh. 3. Observe that the fem oral triangle is oriented in such a way that the base of the triangle (sup e rio r b o rd e r), form ed by the in g uin al lig am e n t , is located superiorly, whereas its ap ex is directed inferiorly (FIG. 6.8). 4. Identify and clean the proxim al portion of the sart o rius m uscle , which form s the lat e ral b o un d ary o f t h e fe m o ral t rian g le . 5. Identify and clean the proxim al portion of the ad d uct o r lo n g us m uscle , which form s the m e d ial b o un d ary o f t h e fe m o ral t rian g le. 6. From lateral to m edial, the m ajor co n t e n t s o f t h e fe m o ral t rian g le are the fe m o ral n e rve , the fe m o ral

Cut 3 Pubic tubercle

Margin of saphenous opening

Femoral vein

Fascia lata

Great saphenous vein Deep inguinal lymph nodes

Cut 1

FIGURE 6.7 Cuts used to open the fascia lata over the fem oral triangle.

CLIN ICA L CORRELATION

Fe m o ral Trian g le Within the fem oral triangle, the fem oral vessels are accessed for diagnostic purposes. The pulse of the fem oral artery can be p alpated about 3 cm inferior to the m idpoint of the inguinal ligam ent. The fem oral vein lies im m ediately m edial to the fem oral artery. A catheter introduced into the fem oral artery can be advanced superiorly into the aorta and its branches. A catheter introduced into the fem oral vein can be advanced superiorly into the inferior vena cava and the right atrium of the heart.

190

7.

8.

9.

10.

11.

12.

13.

•

GRANT’S DISSECTOR

art e ry, and the fe m o ral ve in (FIG. 6.8). Note that the fem oral triangle also contains fat, fascia, lymphatics, branches of the femoral artery and nerve, and tributaries of the vein including the great saphenous vein. Retract the fem oral artery, vein, and nerve and identify the two m uscles form ing the o o r o f t h e fe m o ral t rian g le , the ilio p so as m uscle laterally and the p e ct in e us m uscle m edially. Note that the iliacus and psoas m ajor m uscles collectively are nam ed the ilio p so as m uscle inferior to the inguinal ligam ent. Identify the fem o ral sh e at h , an extension of transversalis fascia that continues into the thigh and surrounds the fem oral vessels. Use an illustration and the cadaver to observe that the fem oral sheath is divided into three com partm ents (FIG. 6.8). Identify the fem oral artery in the lat e ral co m p art m e n t and the fem oral vein in the in t e rm e d iat e co m p art m e n t of the fem oral sheath. The m edial com partm ent of the fem oral sheath is also called the fe m o ral can al, and its p roxim al opening into the abdom inal cavity is called the fe m o ral rin g . The fem oral canal and fem oral ring are m ore readily seen from the abdom inal side of the ing uinal ligam ent. Note that the fem oral canal contains lym phatic vessels and lym ph nodes. Observe that the lateral-to-m edial arrangem ent of structures that pass under the inguinal ligam ent (including the contents of the fem oral sheath) can be identi ed by use of the m nem onic device NAVL (p ronounced navel): fem oral Nerve, fem oral Artery, fem oral Vein, Lym phatics. Identify the fe m o ral n e rve , which lies on the oor of the fem oral triangle, external to the fem oral sheath, lateral to the fem oral artery (FIG. 6.8). Follow the

14.

15. 16.

17.

18.

19.

20.

21.

External iliac artery and vein Inguinal ligament

Femoral nerve Femoral sheath: Lateral compartment Intermediate compartment Medial compartment Deep external pudendal vessels

Sartorius muscle

23.

24.

Adductor longus m. Femoral artery and vein Great saphenous vein

FIGURE 6.8

22.

Boundaries and contents of the fem oral triangle.

25.

fem oral nerve inferiorly and observe that it divides into num erous branches that will be identi ed later. Note that the femoral nerve innervates the anterior thigh m uscles and the skin of the anterior thigh. Verify that the an t e rio r cut an e o us b ran ch e s o f t h e fe m o ral n e rve enter the super cial fascia by penetrating the fascia lata along the anterior surface of the sartorius m uscle (FIG. 6.4A). Use blunt dissection to clean the fe m o ral art e ry and fe m o ral ve in within the fem oral triangle. Observe that inferior to the apex of the fem oral triangle, the fe m o ral art e ry an d ve in course between the sartorius m uscle and the adductor longus m uscle (FIG. 6.9A). Just distal to the inguinal ligam ent, identify and clean the sup e r cial e p ig ast ric art e ry coursing superiorly and super cially. Coursing m ore deeply from the fem oral artery, identify and clean the laterally oriented sup e r cial circum e x iliac art e ry and the m edially oriented sup e r cial e xt e rn al p ud e n d al art e ry (FIG. 6.9B). Gently retract the fem oral artery m edially and identify the d e e p art ery (p ro fun d a fe m o ris) o f t h e t h ig h . Observe that the deep artery of the thigh courses p arallel to the fem oral artery but posterior to the adductor longus m uscle (FIG. 6.9B). Note that the deep artery of the thigh supplies the m edial and posterior compartm ents of the thigh. Identify and clean the lat e ral circum e x fe m o ral art e ry (FIG. 6.9B). Note that the lateral circum ex fem oral artery usually arises from the deep artery of the thigh very close to the femoral artery but may arise directly from the femoral artery. Follow the lateral circum ex fem oral artery laterally, d eep to th e sup erior en d of th e rectus fem oris m uscle, an d ob serve th at it sup p lies th e m uscles an d soft tissues of th e lateral p art of th e th ig h b y th ree m ain b ran ch es: ascen d in g , tran sverse, an d d escen d in g . Identify the asce n d in g branch, which p asses sup eriorly deep to the tensor of the fascia lata m uscle to anastom ose with the superior gluteal artery. Identify the t ran sve rse branch, which p asses deep to the rectus fem oris m uscle to anastom ose with the m edial circum ex fem oral artery. Identify the d e sce n d in g b ran ch , which also p asses deep to the rectus fem oris m uscle and then courses inferiorly on the anterior surface of the vastus interm edius m uscle to anastom ose with the genicular arteries at the knee. Identify the m e d ial circum e x fe m o ral art e ry (FIG. 6.9B, C). Note that the medial circum ex femoral artery typically arises from the deep artery of the thigh close to the fem oral artery but m ay arise directly from the femoral artery.

CHAPTER 6

A

B

THE LOWER LIMB

Superficial circumflex iliac a. Superficial epigastric a.

191

C

Superficial external pudendal a.

Femoral a. Medial circumflex femoral a.

Medial circumflex femoral a. Deep artery of thigh

Lateral circumflex femoral a.: Ascending branch Transverse branch

Adductor canal

•

Descending branch Adductor longus Adductor longus

Sartorius

Femoral a.

Perforating arteries

Adductor hiatus Popliteal a.

A

B Anterior views

C Posterior view

FIGURE 6.9 Arteries of the thigh. A. Anterior view. Adductor canal is indicated with a green dashed line. B. Anterior view. Adductor long us lies b etween the fem oral artery and the deep artery of the thigh. C. Posterior view showing the course of the deep artery of the thig h and the m edial circum ex fem oral artery.

26. Follow the m edial circum ex fem oral artery directly posteriorly between the pectineus and iliopsoas m uscles. Note that in addition to supplying the soft tissues of the region, the medial circum ex fem oral artery provides an im portant blood supply to the neck of the femur. 27. Make an effort to clean the surface of the iliopsoas m uscle and the pectineus m uscle that lie posterior to the vessels. 28. Review the attachm ents and actions of the iliopsoas and p ectineus m uscles (see TABLE 6.1).

CLIN ICA L CORRELATIO N

Fe m o ral He rn ia The fem oral ring is a site of potential herniation. A fem oral hernia is a protrusion of abdom inal viscera through the fem oral ring into the fem oral canal. A fem oral hernia m ay becom e strangulated due to the in exibility of the surrounding structures.

Ad d uct o r Can al an d Sart o rius Muscle [G 496; L 102, 103; N 487; R 492] 1. Identify the ad d uct o r can al, a fascial com partm ent located deep to the sartorius m uscle. 2. Use an illustration and the cadaver to observe that the adductor canal begins at the ap e x o f t h e fe m o ral t rian g le and ends at the ad d uct o r h iat us just above the knee (FIG. 6.9A, C). Note that the adductor canal contains the fem oral artery and vein, which pass through the adductor hiatus to reach the popliteal fossa, and two branches of the femoral nerve. 3. Use scissors to cut the fascia lata along the super cial surface of the sartorius m uscle from the ASIS to the m edial epicondyle of the fem ur. 4. Use a probe and your ngers to separate the sart o rius m uscle from the deep fascia that encloses it and observe that the sartorius m uscle crosses both the hip and the knee joints. 5. Retract the sartorius m uscle laterally so its superior and inferior attachm ents can be de ned and its blood and nerve supplies can be identi ed.

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6. Review the attachm ents and actions of the sartorius m uscle (see TABLE 6.1). 7. Pull the sartorius laterally and observe the ad d uct o r can al, a sheath of dense connective tissue enclosing the fem oral vessels. 8. Use scissors to open the adductor canal and exam ine the fem oral vessels. Observe that the fe m o ral vein now lies p osterior to the fe m o ral art e ry. Recall that in the fem oral triangle, they were side by side. 9. Use blunt dissection to follow the fem oral artery distally through the ad d uct o r h iat us, where its nam e changes to p o p lit e al art e ry (FIG. 6.9C). 10. Within the adductor canal, identify the n e rve t o vast us m e d ialis and the sap h e n o us n e rve . Note that the nerve to vastus m edialis is the motor nerve to the vastus m edialis muscle and the saphenous nerve is a cutaneous nerve that innervates the skin on the m edial side of the leg, ankle, and foot. 11. If the contents of the adductor canal are dif cult to identify and clean, cut the sartorius m uscle on one side of the cadaver midway down its length and re ect the component parts of the m uscle superiorly and inferiorly.

Quad rice p s Fe m o ris Muscle [G 493, 496; L 103; N 488; R 493] 1. Use scissors to m ake a vertical cut through the fascia lata beginning at the apex of the fem oral triangle and ending at the superior border of the patella. 2. Make a transverse incision in the fascia lata above the patella extending from the m edial fem oral epicondyle to the lateral fem oral ep icondyle. 3. Use blunt dissection to open the fascia lata widely and follow the inner surface laterally with your ngers to verify that it is attached to the lat e ral in t e rm uscular se p t um (FIG. 6.10). Note that the lateral intermuscular septum is attached to the linea a spera on the posterior aspect of the fem ur. 4. Identify the q uad rice p s fe m o ris m uscle (the rectus fem oris, vastus lateralis, vastus interm edius, and vastus m edialis) and observe that it occupies m ost of the anterior com partm ent of the thigh (FIG. 6.10). 5. Observe that the tendons of all four quadriceps m uscles unite to form the q uad rice p s fe m o ris t e n d o n superior to the patella. 6. Inferior to the patella, identify the p at e llar (t e n d o n ) lig am e n t attaching to the tibial tuberosity (FIG. 6.10). Note that the patella is a sesam oid bone, m eaning it formed within the tendon, therefore the inferior attachm ent of the quadriceps fem oris m uscle is ultim ately on the tibial tuberosity. 7. Identify and clean the surface of the rectus fem oris m uscle in the m idline of the anterior thigh and observe that it crosses both the hip and knee joints (FIG. 6.10).

Iliacus

Psoas major Anterior superior iliac spine Iliopsoas Tensor of fascia lata

Inguinal ligament

Sartorius

Iliotibial tract

Rectus femoris Vastus lateralis

Quadriceps tendon

Optional cuts

Vastus medialis

Patella

Patellar tendon

FIGURE 6.10 the thigh.

Contents of the anterior com p artm ent of

8. Identify and clean the surface of the vast us lat e ralis m uscle on the lateral side of the anterior thigh (FIG. 6.11). 9. Identify and clean the surface of the vast us m e d ialis m uscle on the m edial side of the anterior thigh (FIG. 6.11). 10. Retract the rectus fem oris m uscle and identify the vast us in t e rm e d ius m uscle , which lies deep to the rectus fem oris, between the vastus lateralis and vastus m edialis m uscles (FIG. 6.11). If the vastus interm edius m uscle is not visible, transect the rectus fem oris

CHAPTER 6

Anterior cutaneous branch of femoral n. (retracted)

Rectus femoris (cut and reflected) Pectineus

Vastus lateralis

Sartorius (cut and reflected)

Vastus intermedius Rectus femoris tendon (cut)

Vastus medialis

Quadriceps femoris tendon

Saphenous n. Patellar ligament

FIGURE 6.11

•

193

Te n so r o f Fascia Lat a Muscle [G 493, 496; L 103; N 488; R 493]

Femoral n.

Sartorius (cut and reflected)

THE LOWER LIMB

Tibial tuberosity

Branches of the fem oral nerve.

on one side of the cadaver and re ect its com ponent parts superiorly and inferiorly to expose the deep m uscle. 11. Review the attachm ents and actions of the com ponent p arts of the quadriceps m uscle (see TABLE 6.1). 12. Observe the d esce n d in g b ran ch o f t h e lat e ral circum e x fe m o ral art e ry, which can be seen on the anterior surface of the vastus interm edius m uscle, deep to the rectus fem oris m uscle. 13. Identify the m o t o r b ran ch e s o f t h e fe m o ral n e rve to the anterior thigh m uscles between the rectus fem oris m uscle and the three vastus m uscles (FIG. 6.11). Note that the fem oral nerve innervates the sartorius muscle and the pectineus muscle in addition to innervating the quadriceps fem oris m uscle.

1. On the lateral aspect of the thigh, identify the ilio t ib ial t ract (IT) b an d , a thickening of the fascia lata (FIG. 6.10). 2. Elevate the remaining fascia lata from the anterior aspect of the thigh and cut through the fascia along a line from the ASIS proximally to a point just lateral to the lateral femoral condyle distally. Leave the majority of the fascia undisturbed along the lateral aspect of the thigh and just de ne the anterior edge of the iliotibial tract at this time. 3. Within the iliotibial tract proxim ally, identify the t e n so r o f t h e fascia lat a (t e n so r fasciae lat ae ) (TFL) m uscle (FIG. 6.10). Note that the TFL is often categorized with the g luteal m uscles despite its location on the anterior aspect of the hip due to its m otor innervation by the sup erior gluteal nerve. 4. Observe that the TFL is enclosed within the fascia lata inferior to the ASIS and connects to the iliotibial tract distally. The iliotibial tract serves to strengthen the lateral asp ect of the knee and is an insertion point for both the TFL and the gluteus m axim us m uscles. 5. Make a short incision through the facia lata paralleling the anterior aspect of the TFL. 6. Use blunt dissection to separate the m edial and lateral surfaces of the TFL away from the fascia lata. 7. Rem ove a sm all portion of the fascia lata to expose the anterior and lateral surfaces of the TFL but do not disrupt the iliotibial tract or the attachm ents of the m uscle. 8. Review the attachm ents and actions of the TFL (see TABLE 6.1). CLIN ICA L CORRELATIO N

Pat e llar Te n d o n ( Quad rice p s) Re e x Tapp ing the patellar tendon stim ulates the patellar reex (quadriceps re ex; knee jerk). Tapping activates m uscle spindles in the quadriceps fem oris m uscle and afferent im pulses travel in the fem oral nerve to spinal cord segm ents L2, L3, and L4. Efferent im pulses are then carried by the fem oral nerve to the quadriceps fem oris m uscle, resulting in a brief contraction. The patellar tendon re ex tests the function of the fem oral nerve and sp inal cord segm ents L2–L4.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the boundaries and contents of the fem oral triangle. 2. Review the origin and course of the fem oral artery and its branches in the thigh. 3. Use the dissected specim en to review the attachm ents and actions of the m uscles of the anterior com partm ent of the thigh. 4. Review the pattern of m otor innervation to the m uscles in the anterior com partm ent of the thigh. [L 149] 5. Recall that the pectineus m uscle is innervated by both the fem oral and obturator nerves and that the TFL is innervated by the superior gluteal nerve.

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TABLE 6.1

Muscle s o f t h e An t e rio r Th ig h

ANTERIOR THIGH Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Pectineus

Pecten pubis and superior ramus of the pubis

Pectineal line of the femur

Adducts and exes the thigh

Femoral n. and obturator n.

Iliopsoas

Iliac fossa (iliacus) and TP and bodies of vertebrae T12–L5 (psoas major)

Lesser trochanter of the femur

Flexes the thigh

Sartorius

Anterior superior iliac spine

Medial surface of the proximal tibia

Flexes and laterally rotates the thigh, exes and medially rotates the leg

Tensor fasciae lata (TFL)

Anterior superior iliac spine

Iliotibial tract

Abducts, medially rotates, and exes the thigh

Superior gluteal n.

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Rectus femoris

Anterior inferior iliac spine

Vastus medialis

Lateral lip of the linea aspera and greater trochanter

Femoral n.

QUADRICEPS

Vastus lateralis

Medial lip of the linea aspera and intertrochanteric line

Vastus intermedius

Anterior and lateral surfaces of the femur

Flexes the thigh and extends the leg

Tibial tuberosity

Extends the leg

Femoral n.

Abbreviations: n., nerve; TP, transverse process.

MEDIAL COMPARTMENT OF THE THIGH Disse ct io n Ove rvie w The m edial com partm ent of the thigh contains six m uscles: g racilis, ad d uct o r lo n g us, ad d uct o r b re vis, p e ct in e us, ad d uct o r m ag n us, and o b t urat o r e xt e rn us. The shared function of the m edial com partm ent of the thigh is to adduct the thigh, thus this group of m uscles is also known as the adductor group of thigh m uscles. [G 494; L 105–107; N 488; R 493] The order of dissection will be as follows: The fascia lata will be rem oved from the m edial thigh. The gracilis m uscle will be studied. The adductor m uscles will be separated from each other by following the m edial circum ex fem oral artery, the deep artery of the thigh, and the branches of the obturator nerve. Note: The anterior and posterior branches of the obturator nerve pass anterior and posterior, resp ectively, to the adductor brevis m uscle. The branches of the deep artery of the thigh and the obturator nerve are excellent aids to help you de ne the planes of separation between the m uscles of the m edial com partment of the thigh.

Disse ct io n In st ruct io n s 1. On the m edial aspect of the thigh, use your hands to separate the fascia lata from the m uscles of the m edial com partm ent beginning at the m edial border of the fem oral triangle and working m edially. 2. Elevate the fascia lata on the m edial aspect of the thigh and identify the g racilis m uscle (FIG. 6.12). 3. Use scissors to cut the fascia lata from its attachm ents to the pelvis superiorly and along the m edial interm uscular septum , paying attention not to rem ove the gracilis m uscle in the process. 4. Rem ove the cut portion of the fascia lata and place it in the tissue container.

5. Use your ngers to de ne the borders of the gracilis m uscle. Observe that the gracilis m uscle crosses both the hip and knee joints and thus will assist in m ovem ent at both joints. 6. Review the attachm ents, actions, and innervation of the gracilis m uscle (see TABLE 6.2). 7. Lateral to the gracilis, identify the ad d uct o r lo n g us m uscle and p e ct in e us m uscle (FIG. 6.12). Recall that the pectineus m uscle form s p art of the oor of the fem oral triangle. 8. Use an illustration to observe the sup erior attachm ents of the g racilis m uscle, p e ct in e us m uscle , and ad d uct o r lo n g us m uscle on the pubic bone. [G 498; L 98; N 477; R 469]

CHAPTER 6

Inguinal ligament

Pectineus m. Optional cuts

Adductor brevis Adductor longus Gracilis

Sartorius

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16. Clean the deep artery of the thigh and identify one or two p e rfo rat in g art e rie s. Note that the perforating arteries penetrate the adductor brevis and adductor magnus muscles, encircle the femur, and supply the m uscles of the posterior com partment of the thigh. 17. Observe that the o b t urat o r n erve splits into anterior and posterior branches in the m edial com p artm ent of the thigh (FIG. 6.13). 18. On the anterior surface of the adductor brevis m uscle, identify the an t e rio r b ran ch o f t h e o b t urat o r n e rve (FIG. 6.13). 19. Follow the anterior branch of the obturator nerve superiorly deep to the pectineus m uscle and use the nerve as a landm ark to separate the pectineus m uscle from the adductor brevis m uscle. Note that the superior border of the adductor brevis m uscle is deep to the pectineus muscle. 20. Use blunt dissection to clean the adductor brevis, paying attention not to dam age the anterior branches of the obturator nerve.

Adductor magnus Obturator n.

Pectineus (reflected)

FIGURE 6.12 the thigh.

Contents of the m ed ial com p artm ent of

9. Identify the d e e p art e ry o f t h e t h ig h where it branches from the fem oral artery (FIG. 6.9). 10. Follow the deep artery of the thigh inferiorly and ob serve that it p asses anterior to the pectineus and posterior to the adductor longus m uscle. 11. Use blunt dissection to de ne the borders of the pectineus and adductor longus m uscles while preserving the deep artery of the thigh. 12. Review the attachm ents, actions, and innervation of the adductor longus and p ectineus m uscles (see TABLE 6.2). 13. Gently pull the adductor longus m uscle m edially and the p ectineus m uscle laterally and identify the m ore deeply located ad d uct o r b re vis m uscle . 14. Continue to follow the deep artery of the thigh posterior to the adductor longus m uscle and ob serve that it courses inferiorly between the adductor longus m uscle and the adductor brevis m uscle. Use the artery as a landm ark to sep arate the adductor longus m uscle from the adductor brevis m uscle. 15. On one side of the cadaver, transect the adductor longus m uscle 5 cm inferior to its superior attachm ent and re ect it to expose the ad d uct o r b re vis m uscle (FIG. 6.12).

Obturator externus Adductor magnus

Pectineus (reflected)

Adductor brevis

Adductor longus (cut) Obturator n.: Anterior branch Posterior branch

Adductor magnus Gracilis

Adductor longus (reflected)

Cutaneous branch of obturator n. Adductor hiatus

Adductor tubercle

FIGURE 6.13 Branches of the obturator nerve. The anterior and p osterior branches of the obturator nerve are used to de ne the borders of the adductor brevis m uscle.

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21. Gently elevate the adductor brevis m uscle and identify the ad d uct o r m ag n us m uscle deep to the adductor longus m uscle and m edial to the gracilis m uscle. Note that the adductor magnus m uscle has both a ham string (ischiocondylar) portion and an adductor portion and thus shares actions and innervations with both groups of m uscles. 22. Id entify the p o st e rio r b ran ch o f t h e o b t urat o r n e rve where it lies b etween the ad d uctor b revis m uscle and the add uctor m ag nus m uscle (FIG. 6.13). 23. Use blunt dissection to follow the posterior branch of the obturator nerve sup eriorly and use the nerve as a landm ark to separate the adductor brevis m uscle from the adductor m agnus m uscle. 24. Review the attachm ents, actions, and innervation of the adductor brevis and adductor m agnus m uscles (see TABLE 6.2).

25. Trace the tendon of the ham string (ischiocondylar) part of the adductor m agnus m uscle inferiorly to its attachm ent on the ad d uct o r t ub e rcle . 26. On the lateral side of the tendon, observe the ad d uct o r h iat us, an opening in the adductor m agnus m uscle (FIG. 6.13). 27. Observe that the fem oral artery and vein pass from the anterior com partm ent of the thigh into the p osterior com p artm ent of the thigh by p assing through the adductor hiatus. Note that the adductor hiatus is the landm ark where the femoral artery and vein change names to popliteal artery and vein. 28. Study an illustration of the o b t urat o r e xt e rn us m uscle but d o not attem p t to dissect this m uscle because it lies deep to the p ectineus m uscle and iliop soas tendon. [G 510; L 107; N 488; R 469] 29. Review the attachm ents, actions, and innervation of the obturator externus m uscle.

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Replace the m edial thigh m uscles in their correct anatom ical positions. Use the dissected specim en to review the attachm ents and actions of each m uscle dissected. Trace the deep artery of the thigh from its origin to its term ination as the fourth perforating artery. Trace the m edial circum ex fem oral artery from its origin to where it passes between the iliopsoas and pectineus m uscles. 5. Trace the course of the anterior and posterior branches of the obturator nerve superiorly as far as the superior border of the adductor brevis m uscle. 6. Recall that the obturator nerve innervates the m uscles of the m edial com partm ent of the thigh. Note that the pectineus m uscle receives m otor innervation from both the fem oral and obturator nerves and the adductor m agnus receives m otor innervation from both the obturator nerve and the tibial division of the sciatic nerve. [L 150]

TABLE 6.2

Muscle s o f t h e Me d ial Th ig h ( Ad d uct o rs)

MEDIAL THIGH Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Gracilis

Body of pubis and inferior pubic ramus

Superior part of medial surface of tibia

Adducts the thigh; exes and internally rotates the leg

Obturator n.

Pectineus

Superior pubic ramus

Pectineal line

Adductor longus

Body of pubis inferior to pubic crest

Middle third of linea aspera

Adductor brevis

Body of pubis and inferior pubic ramus

Pectineal line and proximal part of linea aspera

Adductor magnus

Ischiopubic ramus and ischial tuberosity

Gluteal tuberosity, linea aspera, medial supracondylar line (adductor part); adductor tubercle of the femur (hamstring part)

Adducts and extends the thigh

Obturator n. (adductor part), tibial division of the sciatic n. (hamstring part)

Obturator externus

External margins of obturator foramen and obturator membrane (medial attachment)

Trochanteric fossa of femur (lateral attachment)

Laterally rotates the thigh

Obturator n.

Abbreviation: n., nerve.

Obturator n. and femoral n. Adducts the thigh

Obturator n.

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GLUTEAL REGION Disse ct io n Ove rvie w The gluteal region (Gr. gloutos, buttock) lies on the p osterior aspect of the p elvis and is the m ost superior part of the lower lim b. The gluteal region contains m uscles that extend, abduct, and laterally rotate the thigh. The order of dissection will be as follows: The super cial fascia will be rem oved from the gluteal region. The borders of the g luteus m axim us m uscle will be de ned , and it will be re ected laterally to exp ose the m uscles that lie deep to it. Muscles that lie deep to the gluteus m axim us m uscle will be studied. Arteries and nerves in the region will be studied. Note that the piriform is m uscle will be a key landm ark in understanding the relationships of this region.

Ske le t o n o f t h e Glut e al Re g io n Refer to a skeleton and an illustration of an articulated pelvis with intact ligam ents to identify the following skeletal features (FIG. 6.14):

Ilium [G 499; L 93; N 473; R 451] 1. Identify the iliac cre st on the sup erior aspect of the ilium . 2. On the lateral (external) surface of the ilium , identify the g lut e al lin e s (p o st e rio r, an t e rio r, in fe rio r). 3. On the posterior aspect of the ilium , identify the g re at e r sciat ic n o t ch . Observe that the greater sciatic notch is located superior to the isch ial sp in e and is p art of the ilium , whereas the le sse r sciat ic n o t ch is located inferior to the ischial spine and is part of the isch ium . 4. On an articulated pelvis, or in an illustration, identify the sacro sp in o us lig am e n t connecting from the sacrum to the ischial spine. Observe that the greater sciatic notch form s part of the m argin of the g re at e r sciat ic fo ram e n along with the sacrospinous ligam ent. 5. On an articulated pelvis, or in an illustration, identify the sacro t ub e ro us lig am e n t connecting from the sacrum to the isch ial t ub e ro sit y. Observe that the lesser sciatic notch form s part of the m argin of the le sse r sciat ic fo ram e n along with the sacrotuberous and sacrospinous ligam ents.

Iliac crest

Gluteal lines: Posterior Anterior Inferior

Greater sciatic foramen Greater sciatic notch

Margin of acetabulum

Sacrospinous ligament

Neck of femur

Head of femur

Sacrotuberous ligament

Greater trochanter Trochanteric fossa

Ischial spine

Quadrate tubercle

Lesser sciatic notch Lesser sciatic foramen

Intertrochanteric crest

Ischiopubic ramus Ischial tuberosity

Lesser trochanter

Gluteal tuberosity

Pectineal line

FIGURE 6.14

Skeleton of the gluteal region, posterior view.

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Fe m ur [G 499; L 93; N 476; R 455] 1. On the proxim al fem ur, identify the g re at e r t ro ch an t e r p osteriorly and laterally. 2. Identify the depression of the t ro ch an t e ric fo ssa on the m edial aspect of the greater trochanter posteriorly. 3. On the posterior aspect of the proxim al fem ur, identify the in t e rt ro ch an t e ric cre st between the greater trochanter and le sse r t ro ch an t e r. 4. Approxim ately m idway down the length of the intertrochanteric crest, identify the q uad rat e t ub e rcle . 5. Identify the roughened area of the g lut e al t ub e ro sit y on the p osterior asp ect of the proxim al fem ur inferior to the intertrochanteric crest.

Disse ct io n In st ruct io n s Glut e us Max im us Muscle [G 500; L 112; N 482; R 471] 1. Place the cadaver in the prone position. 2. If not done previously, rem ove the super cial fascia from the surface of the fascia lata in the gluteal region to exp ose the gluteal ap oneurosis before you proceed to step 3. 3. Identify the g lut e us m axim us m uscle (FIG. 6.15). 4. Observe that the gluteus maximus muscle attaches to the iliotibial tract, and through it, the lateral condyle of the tibia. Note that because the gluteus maximus attaches to both the gluteal tuberosity of the femur directly, and the fascia lata, which connects to the lateral intermuscular septum, it effectively attaches to the entire length of the femur and therefore acts as a powerful extensor of the thigh.

Insert fingers here Iliac crest Line of detachment of muscle

Gluteal aponeurosis covering gluteus medius

Sacrum

Tensor of the fascia lata

Sacrotuberous ligament

Gluteus maximus

Ischial tuberosity

Inferior cluneal nn.

Iliotibial tract (IT band)

Posterior cutaneous n. of the thigh

Fascia lata

FIGURE 6.15 dissection.

Muscles of the gluteal region, sup er cial

5. Identify and clean the entire length of the inferior border of the gluteus m axim us m uscle beginning m edially near its attachm ent on the sacrum and coccyx (FIG. 6.15). 6. Along the inferior border of the gluteus m axim us m uscle, identify the inferior cluneal nerves if not done previously but do not spend considerable tim e doing so. 7. Use your ngers or a p robe to de ne the superior border of the gluteus m axim us m uscle. 8. Rem ove the fascia lata from the p osterior surface of the gluteus m axim us m uscle and clean the entire expanse of the m uscle (FIG. 6.15). 9. Observe that the fascia lata is relatively thin over the surface of the gluteus m axim us m uscle but superior to the m uscle it becom es thicker and form s the g lut e al ap o n e uro sis. Observe that the gluteal ap oneurosis spans from the superior border of the gluteus m axim us m uscle up to the iliac crest and overlies the gluteus m edius m uscle. 10. Insert your ngers deep to the superior border of the gluteus maximus muscle and separate it from the gluteal aponeurosis (FIG. 6.15, arrow). Note that the aponeurosis may be strongly connected to fascia lata, and it may be necessary to use scissors to cut through the connection. 11. Near the inferior border of the gluteus maximus, palpate the sacrotuberous ligament through the muscular belly of the gluteus maximus and observe its orientation. 12. Detach the gluteus m axim us from its m edial attachm ent beginning superiorly at the superior border of the m uscle and re ect the m uscle from its attachm ent to the ilium , sacrum (FIG. 6.15, dashed line), and sacrotuberous ligam ent. Note that the gluteus maximus muscle is often tightly adhered along the length of the sacrotuberous ligament, and care must be taken not to cut through the ligament while re ecting the muscle laterally. 13. While re ecting the gluteus m axim us m uscle, push your ngers deep to the m uscle and palpate the in ferior g lut eal art ery, vein , and n erve, which are located near the center of the m uscle. Note that the inferior gluteal nerve is the only nerve supply to the gluteus maximus muscle, but the muscle receives blood from both the superior gluteal artery and the inferior gluteal artery. 14. Use scissors to cut the inferior gluteal vessels and nerve. 15. Use your ngers to loosen the gluteus m axim us m uscle from the rem aining deeper structures and re ect it laterally so it is only attached along its

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Gluteus medius m. (reflected) Anterior superior iliac spine Gluteus minimus m. Superior gluteal artery and nerve Gluteus maximus m. (cut)

Tensor of the fascia lata Gluteus medius m. (reflected) Superior gemellus m. Greater trochanter Inferior gemellus m.

Inferior gluteal artery and nerve

Trochanteric bursa

Pudendal nerve Piriformis m. N. to obturator internus

Gluteus maximus m. (reflected) Quadrate tubercle

Obturator internus m.

Quadratus femoris m.

Posterior thigh muscles

Sciatic nerve Adductor magnus m.

Posterior cutaneous nerve of the thigh

FIGURE 6.16 Muscles of the gluteal region, deep dissection. The gluteus m axim us and gluteus m edius m uscles have been re ected .

lateral attachm ents to the iliotibial tract and gluteal tuberosity (FIG. 6.16). 16. Review the attachm ents and actions of the gluteus m axim us m uscle (see TABLE 6.3).

Glut e us Me d ius an d Min im us Muscle s [G 500; L 112; N 482; R 471] 1. Use a scalpel to cut the gluteal aponeurosis along the iliac crest and use skinning motions to remove the gluteal aponeurosis to expose the gluteus medius muscle, Note that the aponeurosis is rmly attached to the gluteus medius muscle and that it serves as an attachment for the muscle. 2. Identify the g lut e us m e d ius m uscle and use your ngers or a probe to de ne its borders. Observe that the gluteus m edius attaches m ore superiorly than the gluteus m axim us and is visible even with the gluteus m axim us in its anatom ical location. 3. Review the attachm ents, actions, and innervation of the gluteus m edius m uscle (see TABLE 6.3).

4. Inferior and m edial to the gluteus m edius m uscle, identify the p irifo rm is m uscle and observe its location ap proxim ately in the m iddle of the gluteal region. Note that the superior border of the piriform is lies adjacent to the inferior border of the gluteus m edius m uscle (FIG. 6.16). 5. Insert your nger or a probe between the gluteus m edius and piriform is m uscles to open the interval between them and palpate the underlying sup e rio r g lut e al ve ssels. 6. To identify the gluteus m inim us m uscle, you m ust reect the superior part of the gluteus m edius m uscle. Insert your nger along the course of the superior gluteal vessels, deep to the gluteus m edius m uscle, and push your nger superiorly along the course of the vessels within the fascial plane between the gluteal m uscles. 7. Use scissors to transect the gluteus m edius m uscle following the course of the sup erior gluteal vessels. 8. Gently re ect the p ortions of the gluteus m edius m uscle superiorly and inferiorly and observe the

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g lut e us m in im us m uscle and sup e rio r g lut e al n e rve . Note that gluteus minim us muscle cannot be seen without transection of the gluteus medius m uscle. 9. Follow the branches of the sup erior gluteal nerve to both the gluteus m edius and m inim us. Note that branches of the superior gluteal nerve course laterally around the hip to innervate the TFL (t e n so r fasciae lat ae ) m uscle . Recall that the tensor fasciae latae m uscle was located on the anterior aspect of the hip and that it was enclosed within the fascia lata inferior to the ASIS (FIG. 6.16). 10. Review the attachm ents, actions, and innervation of the g luteus m inim us and TFL m uscles (see TABLE 6.3).

Ex t e rn al Ro t at o rs o f t h e Hip [G 500; L 112; N 482; R 471] 1. Use blunt dissection to clean the superior border of the piriform is m uscle and observe that the sup e rio r g lut e al art e ry, ve in , and n e rve exit the p elvic cavity and enter the gluteal region by p assing superior to the sup erior border of the p iriform is m uscle. 2. Use blunt dissection to clean the inferior border of the piriform is m uscle and observe that it lies superior to the cut edge of the in fe rio r g lut e al art e ry and ve in . 3. Insert your ngers in the interval inferior to the piriform is m uscle and identify the sup e rio r g e m e llus m uscle. Observe that the piriform is m uscle p asses through the greater sciatic foram en nearly lling it, whereas the superior gem ellus m uscle originates from the ischial spine. 4. Inferior to the piriform is m uscle, identify the sciat ic n e rve the largest nerve in the body (FIG. 6.16). The sciatic nerve has a t ib ial d ivision and a com m o n b ular d ivisio n . In about 12% of sp ecim ens, the divisions m ay em erge from the pelvis separately with the com m on bular division p assing over the sup erior border of the piriform is m uscle or through the center of the piriform is m uscle. 5. Make a vertical cut through the fascia lata posterior to the sciatic nerve and follow the sciatic nerve inferiorly for 6 or 7 cm into the thigh. 6. On the m edial side of the sciatic nerve, identify the p o st e rio r cut an eo us n erve o f t h e t h ig h (FIG. 6.16).

7. Follow the posterior cutaneous nerve of the thigh superiorly and observe that it lies lateral to the in fe rio r g lut e al ve sse ls and n e rve (FIG. 6.16). 8. Identify the n e rve t o o b t urat o r in t e rn us, in t e rn al p ud e n d al art e ry and ve in , and p ud e n d al n e rve near the m edial end of the inferior border of the piriform is m uscle (FIG. 6.16). 9. Observe that the pudendal nerve and internal pudendal vessels exit the pelvis by passing through the greater sciatic foram en, between the p iriform is and superior g em ellus m uscles, then enter the perineum by passing through the lesser sciatic foram en. Note that the pudendal nerve and internal pudendal vessels supply the anal and urogenital triangles. 10. Identify the tendon of the o b t urat o r in t e rn us m uscle between the g e m e llus m uscle s (L. gem ellus, twin). Observe that the tendon of the obturator internus m uscle courses inferior to the superior gem ellus m uscle and superior to the in fe rio r g e m e llus m uscle (FIG. 6.15). Note that the two gemellus m uscles attach to the obturator internus tendon and m ight obscure it. 11. Use a probe to verify that the obturator internus m uscle exits the lesser pelvis by p assing through the lesser sciatic foram en. 12. Inferior to the inferior gem ellus m uscle, identify and clean the q uad rat us fe m o ris m uscle (FIG. 6.16). 13. Review the attachm ents, actions, and innervation of the obturator internus; the sup erior gem ellus; the inferior gem ellus; and the quadratus fem oris m uscles (see TABLE 6.3). CLIN ICA L CORRELATION

In t rag lut e al In je ct io n s The gluteal region is commonly used for intramuscular injections in its sup erior lateral q uad rant. Injections into the two inferior quadrants of the gluteal region would endanger the sciatic nerve or the nerves and vessels that pass inferior to the piriformis muscle. Injections into the superior m edial quadrant could injure the superior gluteal nerve and vessels. Intragluteal injections into the superior lateral quadrant are relatively safe because the superior gluteal nerve and vessels are well branched in this region.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Replace the m uscles of the gluteal region in their correct anatom ical positions. Review the attachm ents and innervation of each m uscle. Study the functions of the m uscles in the gluteal region including extension, abduction, and lateral rotation of the thigh. Review the clinical anatom y of the gluteal region and the site where a safe intragluteal injection m ay be perform ed. If you have com pleted the dissection of the pelvis and perineum prior to dissection of the lower lim b, identify the obturator internus m uscle within the p erineum and follow the m uscle posteriorly into the gluteal region. 6. Identify the piriform is m uscle and follow it laterally to its attachm ent on the greater trochanter of the fem ur. 7. Study the gluteal vessels and their relationship to the piriform is m uscle. 8. Review the sacral plexus and its contributions to the sciatic nerve and note that branches of the sacral plexus innervate the m uscles of the gluteal region. [L 111]

CHAPTER 6

TABLE 6.3

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Muscle s o f t h e Glut e al Re g io n

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Gluteus maximus

Ilium posterior to posterior gluteal line, dorsal surface of the sacrum and coccyx, and sacrotuberous ligament

Iliotibial tract and gluteal tuberosity

Extends and laterally rotates the thigh

Inferior gluteal n.

Gluteus medius

External surface of ilium between anterior and posterior gluteal lines and gluteal fascia

Lateral surface of greater trochanter of the femur

Gluteus minimus

Lateral surface of the ilium between the anterior gluteal and inferior gluteal lines

Anterior surface of greater trochanter of the femur

Tensor of fasciae lata (TFL)

Anterior superior iliac spine

Iliotibial tract

Piriformis

Anterior surface of the sacrum

Obturator internus

Internal margin of the obturator foramen and inner surface of the obturator membrane

Superior gemellus

Ischial spine (medial)

Inferior gemellus

Ischial tuberosity (medial)

Quadratus femoris

Ischial tuberosity (medial)

Abducts and medially rotates the thigh

Superior gluteal n.

Abducts, medially rotates and exes the thigh Anterior rami of S1 and S2

Greater trochanter of the femur (lateral)

Nerve to obturator internus

Laterally rotates the thigh

Greater trochanter of the femur (lateral) and obturator internus tendon

Nerve to quadratus femoris

Quadrate tubercle (lateral)

Abbreviation: n., nerve.

POSTERIOR COMPARTMENT OF THE THIGH AND POPLITEAL FOSSA Disse ct io n Ove rvie w The p osterior com p artm ent of the thigh contains the p osterior thig h m uscles: b ice p s fe m o ris, se m im e m b ran o sus, and se m it e n d in o sus. The m uscles of the p osterior g roup extend the thigh and ex the leg . The p osterior thig h m uscles are com m only known as the “ham string ” m uscles. The order of dissection will be as follows: The m uscles of the posterior com p artm ent of the thigh will be studied. The course and branches of the sciatic nerve will be studied. The dissection will be extended inferiorly to include the popliteal fossa. The m uscular boundaries of the popliteal fossa will be identi ed and the contents of the popliteal fossa will be studied.

Ske le t o n o f t h e Po st e rio r Th ig h Refer to a skeleton or iso lated p elvis, fem ur, fib ula, an d tib ia to id en tify th e follo win g skeletal features usin g FIG. 6.17 :

Ischial tuberosity Lesser trochanter

1. Identify the roughened area of the isch ial t ub e ro sit y on the inferior asp ect of the ischium .

Medial lip Lateral lip

Pectineal line

Medial supracondylar line Popliteal surface

Lateral supracondylar line

Adductor tubercle Medial epicondyle

Pe lvis [G 499; L 93; N 473; R 454]

Linea aspera:

Medial condyle of femur Medial condyle of tibia

Lateral epicondyle Lateral condyle of femur Apex Head Neck

of fibula

Fe m ur [G 499; L 93; N 476; R 455] 1. On the posterior aspect of the fem ur, identify the m e d ial lip and lat e ral lip o f t h e lin e a asp e ra.

Soleal line

FIGURE 6.17

Skeleton of the thigh, posterior view.

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GRANT’S DISSECTOR

2. Observe that the linea aspera widens inferiorly into the m ed ial and lat e ral sup raco n d ylar lin e s to either side of the p o p lit e al surface . 3. Inferiorly on the fem ur, identify the m e d ial co n d yle and the lat e ral co n d yle .

Fib ula an d Tib ia [G 499; L 95; N 500; R 456, 457] 1. On the proxim al end of the bula, identify the h e ad of the bula and observe that it narrows toward the ap e x. 2. Just inferior to the head of the bula, identify the narrowed region of the n e ck of the bula. 3. On the proxim al tibia, identify the m ed ial con d yle and the lateral con d yle. Observe on an articulated skeleton that the condyles of the fem ur and tibia align and form the articular surfaces for the weight-bearing portion of the knee joint. 4. On the proxim al tibia posteriorly, identify the obliquely oriented so le al lin e .

Disse ct io n In st ruct io n s

CLIN ICA L CORRELATION

Po st e rio r Th ig h [G 501, 503; L 115; N 482; R 496, 497]

Sciat ic Ne rve The sciatic nerve and its branches innervate the posterior muscles of the thigh and the muscles of the leg (which act on the foot). The cutaneous branches of the sciatic nerve innervate a large area of the lower limb. When the sciatic nerve is injured, signi cant peripheral neurologic de cits may occur including paralysis of the exors of the knee and all muscles below the knee and widespread numbness of the skin on the posterior aspect of the lower limb.

1. Place the cadaver in the prone position. 2. Use scissors to continue the vertical incision m ade through the fascia lata to exp ose the sciat ic n e rve and extend the incision from the level of the gluteus m axim us m uscle to the knee. 3. Spread open the fascia lata m edially and laterally and follow the sciat ic n e rve until it branches into the tibial and com m on bular nerves. 4. Clean the fascia off the sciatic nerve and observe that it passes deep (anterior) to the long head of the biceps fem oris m uscle and courses inferiorly to the area posterior to the knee, the p o p lit e al fo ssa (FIG. 6.18). Note that the sciatic nerve m ay split into the tibial and com mon bular divisions in the gluteal region, at any level in the posterior thigh, or in the popliteal fossa. 5. Identify the p o st e rio r cut an eo us n e rve o f t h e t h ig h in the gluteal region, follow it inferiorly where it courses deep to the fascial lata, and observe that it sends cutaneous branches through the fascia lata to the p osterior surface of the thigh. 6. On the lateral aspect of the posterior thigh, identify and clean the long head of the b icep s fem oris m uscle. 7. Retract the long head of the biceps fem oris m uscle and identify the sh o rt h e ad o f t h e b ice p s fe m o ris m uscle (FIG. 6.18). 8. Follow the branches of the sciatic nerve and observe that it supplies unnam ed m uscular branches to the posterior thigh m uscles and that its nam ed branches (tibial and com m on bular nerves) usually arise just superior to the popliteal fossa. Note that the tibial division innervates the long head of the biceps femoris, whereas the common bular division innervates the short head. 9. Review the attachm ents and actions of the biceps fem oris m uscle (see TABLE 6.4). 10. On the m edial side of the thigh, identify the se m it e n d in o sus m uscle (FIG. 6.18). Note that the sem itendinosus (“half tendon”) m uscle is named for the long, cord-like tendon at its inferior end. 11. Use your ngers to isolate the semitendinosus muscle and identify the sem im em branosus m uscle. Note that

the semimembranosus (“half membrane”) muscle is named for the broad, membrane-like tendon at its superior end. 12. Verify that the ham string p art of the ad d uctor m ag n us m uscle arises from the ischial tuberosity deep to the superior attachm ents of the posterior thigh muscles. 13. Recall that the adductor m agnus m uscle is in the m edial com partm ent of the thigh and observe that it form s the anterior boundary of the p osterior com p artm ent of the thigh (FIG. 6.18).

Po p lit e al Fo ssa [G 516–518; L 117; N 489; R 499, 500] 1. Identify the borders of the diam ond-shaped p o p lit e al fo ssa (L. poples, ham ) beginning with the sup e ro lat e ral b o rd e r, form ed by the biceps fem oris m uscle, and the sup e ro m e d ial b o rd e r, form ed by the sem itendinosus and sem im em branosus m uscles. 2. Use an illustration to observe that the in fe ro lat e ral border of the popliteal fossa is form ed by the lateral head of the gastrocnem ius m uscle and the plantaris m uscle and the in fe ro m e d ial b o rd e r is form ed b y the m edial head of the gastrocnem ius m uscle. 3. Use an illustration to observe that the popliteal fossa is bounded posteriorly by the skin and deep (popliteal) fascia. Anteriorly, the popliteal fossa is lim ited by the popliteal surface of the fem ur, the posterior surface of the knee joint capsule, and the popliteus m uscle. 4. Observe that at the superior apex of the popliteal fossa, the sciatic nerve divides into the t ib ial and co m m o n b ular n e rve s (FIG. 6.19).

CHAPTER 6

THE LOWER LIMB

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203

Inferior gluteal artery and nerve Gluteus maximus m. (retracted) Posterior cutaneous nerve of the thigh (cut) Sacrotuberous ligament

Gluteus maximus m. (cut)

Ischial tuberosity Adductor magnus m. Gracilis m.

Adductor magnus m.

Sciatic nerve Semitendinosus m. (retracted) Perforated branches of the deep artery of the thigh

Semimembranosus m. Sciatic nerve

Long head (retracted) Short head

Adductor hiatus Popliteal artery and vein Superior medial genicular artery

Biceps femoris m.

Superior lateral genicular artery Common fibular nerve

Medial epicondyle of femur Tibial nerve

Plantaris m. Gastrocnemius m. (lateral head)

Gastrocnemius m. (medial head) Small saphenous vein

FIGURE 6.18

Contents of the posterior com p artm ent of the thigh and p opliteal fossa.

5. Use blunt dissection to follow the com m on bular nerve laterally along the sup erolateral border of the p opliteal fossa. Observe that the com m on bular nerve p arallels the biceps fem oris tendon and passes super cial to the lateral head of the gastrocnem ius m uscle and the plantaris m uscle. 6. Use your ngers to separate the t ib ial n erve from the loose connective tissue that surrounds it and follow the nerve inferiorly. Observe that the tibial nerve passes deep to the plantaris and gastrocnem ius m uscles at the inferior apex of the popliteal fossa (FIG. 6.19). 7. Rem ove the rem nants of the deep fascia (pop liteal fascia) to expose the m edial and lateral heads of the gastrocnem ius m uscle while sparing the branches of the tibial nerve. 8. At the inferior apex of the pop liteal fossa, insert your index ngers between the two bellies of the gastrocnem ius m uscle and gently pull the m uscle bellies ap art for a distance of 5 to 10 cm .

9. Identify the p op lit eal art ery and vein deep to the tibial nerve and observe that the popliteal artery and vein are enclosed by a connective tissue sheath. Use scissors to cut the sheath of connective and spread it open. 10. Use a probe and blunt dissection to separate the popliteal artery from the m ore super cially located popliteal vein. 11. Make an effort to preserve the popliteal vein, as well as the sm all (lesser) saphenous vein, but rem ove the other venous tributaries to clear the dissection eld. 12. Use an illustration to study the branches of the popliteal artery that participate in the arterial anastom oses around the knee joint (g en icular an ast o m o sis) (FIG. 6.19). 13. Identify and clean the sup erior lateral g enicular artery and the sup erior m ed ial g enicular artery deep in the popliteal fossa. Observe that the superior genicular arteries course proximal to the attachments of the gastrocnemius muscle. [G 530; L 117, 124; N 505; R 500]

204

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14. Follow the popliteal artery distally and observe that it passes deep to the plantaris and gastrocnem ius m uscles (FIG. 6.19). 15. Retract the popliteal artery posteriorly and identify the in fe rio r lat e ral g e n icular art e ry and the in fe rio r m e d ial g e n icular art e ry. Observe that the inferior g enicular arteries pass deep to the m edial and lateral heads of the gastrocnem ius m uscle. 16. Use an illustration [G 530; L 148; N 517; R 482] to observe that the genicular anastom osis receives contributions from the fem oral artery, lateral circum ex fem oral artery, and anterior tibial artery.

17. Retract the inferior end of the popliteal artery and vein and identify the p o p lit e us m uscle (FIG. 6.19). Observe that the oor of the popliteal fossa is partially form ed by the popliteus m uscle, which will be seen better when the posterior m uscles of the leg are dissected. 18. At the m edial side of the knee, observe that the sart o rius, g racilis, and sem it en d in o sus t e n d o n s converge on the proxim al end of the tibia in an arrangem ent that is nam ed the p e s an serin us (L., goose’s foot). Note that one muscle from each of the three compartment of the thigh is involved in the pes anserinus.

Adductor hiatus (deep to muscles) Sartorius muscle

Sciatic nerve

Gracilis muscle

Common fibular nerve

Semitendinosus muscle

Tibial nerve

Popliteal artery and vein

Superior lateral genicular artery

Superior medial genicular artery

Medial and lateral sural cutaneous nerves (cut)

Semimembranosus tendon Biceps femoris tendon Gastrocnemius muscle (lateral head)

Gastrocnemius muscle (medial head)

Plantaris muscle (ghosted)

Inferior medial genicular artery

Inferior lateral genicular artery Common fibular nerve

Popliteus muscle Tendinous arch of soleus muscle Soleus muscle Plantaris tendon

FIGURE 6.19

Contents of the p opliteal fossa.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

6. 7. 8.

Replace the m uscles of the posterior com partm ent of the thigh into their correct anatom ical positions. Using the dissected specim en, review the attachm ents and actions of the posterior thigh m uscles. Trace the course of the sciatic nerve from the pelvis to the knee and review its term inal branches. Trace the fem oral artery and vein from the level of the inguinal ligam ent to the popliteal fossa through the adductor hiatus, nam ing its branches. Review the course of the deep artery of the thigh through the m edial com partm ent of the thigh and review the course of its perforating vessels, which pass through the adductor m agnus and brevis m uscles to reach the posterior com partm ent of the thigh. Review the genicular anastom osis around the knee, nam ing the branches of the popliteal artery, fem oral artery, anterior tibial artery, and lateral circum ex fem oral artery that participate. Review the principal m uscle groups of the thigh, the group functions, and the innervation of each m uscle group. [L 152] Recall that the pectineus m uscle receives m otor innervation from both the fem oral nerve and the obturator nerve and that the adductor m agnus m uscle is innervated by both the obturator nerve and the tibial division of the sciatic nerve.

CHAPTER 6

TABLE 6.4

THE LOWER LIMB

•

205

Muscle s o f t h e Po st e rio r Th ig h an d Po p lit e al Fo ssa

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Biceps femoris

Ischial tuberosity (long head) Lateral lip of the linea aspera of femur (short head)

Head of the bula

Extends the thigh (only long head) and exes the leg

Tibial division of the sciatic n. (long head) and common bular division of the sciatic n. (short head)

Semitendinosus Semimembranosus Popliteus

Ischial tuberosity

Lateral surface of lateral condyle of femur and lateral meniscus

Medial surface of the superior part of the tibia Posterior part of the medial condyle of the tibia Posterior surface of tibia superior to soleal line

Extends the thigh and exes and medially rotates the leg Unlocks fully extended leg, weak exor of leg

Tibial division of the sciatic n.

Tibial n.

Abbreviation: n., nerve.

POSTERIOR COMPARTMENT OF THE LEG Disse ct io n Ove rvie w

S

u

p

e

r

L

f

i

a

t

c

i

e

a

r

l

a

f

l

i

b

c

u

o

l

a

r

m

n

pa

e

r

r

t

v

e

m

t

e

e

r

nt

r

i

t

o

r

y

The two bones of the leg are uneq ual in size. The larger t ib ia is the weight-bearing bone of the leg. The b ula is surround ed b y m uscles excep t at its p roxim al and distal ends. The tibia and bula are joined by an in t e ro sse o us m e m b ran e (FIG. 6.20). The crura l fascia is attached to the b ula by two in t e rm uscular se p t a: a n t e rio r and p o st e rio r. The tibia, bula, interosseous m em brane, and interm uscular septa divide the leg into t h re e co m p art m e n t s: p o st e rio r, lat e ral ( b ula r), and a n t e rio r (FIG. 6.20). [G 485; Anterior compartment L 118; N 510; R 514] Deep fibular nerve territory The p o st e rio r co m p a rt m e n t o f t h e le g lies p osterior to the tib ia, interosseous m em b rane, and b ula (FIG. 6.20). A t ra n sve rse in t e rm u scu la r se p t um d ivid es the m uscles of the p osterior com p artm ent into sup er cial and d eep g roup s. The sup er cial p osterior g roup contains three m uscles: g a st ro cn e m ius, so le us, and p la n t a ris. Tibia The com b ined action of the sup er cial p osterior m uscle g roup is exion of the knee and p lantar exion of the foot. The d eep p osterior g roup con tains four m uscles: p o p lit e us, t ib ia lis p o st e rio r, e xo r d ig it o ru m lo n g us, and e xo r h a llu cis lo n g us. The shared actions of the d eep Deep p osterior m uscle g roup are inversion of the foot, p lantar Fibula exion of the foot, and exion of the toes. The tib ial nerve innervates b oth the sup er cial and d eep p osterior m uscle g roup s. Th e ord er of d issection will b e as follows: Th e sup ercial veins an d cutan eous nerves of the p osterior sid e of Superficial th e leg will b e reviewed . The crural fascia of the p osterior sid e of the leg will b e op ened , and the sup er cial p osterior g roup of leg m uscles will b e exam ined . The m uscles in the sup er cial p osterior g roup will b e re ected to exp ose the m uscles of the d eep p osterior g roup . The Posterior compartment vessels and n erves of the p osterior com p artm ent will b e Tibial nerve territory d issected . Th e m uscles of the d eep p osterior g roup will b e id enti ed . FIGURE 6.20 Com p artm ents of the right leg, inferior view.

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Ske le t o n o f t h e Le g

Anterior view

Refer to a skeleton or isolated tibia and bula and identify the following skeletal features (FIG. 6.21):

Posterior view

Intercondylar eminence

Tib ia [G 537; L 94, 95; N 500; R 456] 1. On the p roxim al asp ect of the t ib ia m ed ially an d laterally, id en tify th e atten ed articular surfaces of th e m e d ia l co n d yle an d la t e ra l co n d yle , resp ectively. 2. Between the m ed ial and lateral cond yles, id entify the in t e rco n d yla r e m in e n ce , the roug hened p rocess for attachm ent of the cruciate lig am ents of the knee. 3. On the posterior aspect of the proxim al tibia, identify the obliq uely oriented so le al lin e . 4. On the inferior aspect of the tibia m edially, identify the large p rotrusion of the m e d ial m alle o lus.

Medial condyle Lateral condyle Head of fibula Neck of fibula Soleal line Interosseous membrane Shaft Anterior border of tibia

Fib ula 1. On the proxim al aspect of the b ula, identify the boxlike h e ad of the bula sup erior to the narrowed region of the n e ck. 2. Follow the length of the bula inferiorly along the sh aft (b o d y) to the triangular-shap ed lat e ral m alle o lus. 3. Place the tibia and bula side by side in anatom ical position and observe that the bula does not align with the superior surface of the tibia and extends further inferiorly than the tibia, does not articulate at the knee, and functions as a non-weight-bearing bone at both the ankle and the knee.

Ske le t o n o f t h e Fo o t

Tibia Fibula

Lateral malleolus Medial malleolus

A FIGURE 6.21 terior view.

B Skeleton of the leg. A. Anterior view. B. Pos-

Refer to a skeleton or articu lated foot an d id en tify th e followin g skeletal featu res u sin g FIG. 6.22: [G 545, 558; L 94; N 511; R 458] 1. In the articulated foot, identify the seven tarsal bones beginning with the “heel bone,” the calcan e us. 2. On the posterior superior surface of the calcaneus, identify the roughened region of the calcan e al t ub e ro sit y. From the calcaneal tuberosity, p alpate m edially and anteriorly to the shel ike projection of the sust en t aculum t ali. 3. Superior to the calcaneus, identify the t alus. On an articulated skeleton, observe that the superior asp ect of the talus articulates with the inferior aspect of the tibia. 4. Anterior to the talus m edially, identify the “boat-shaped” n avicular bone. 5. Observe that on the m edial aspect of the foot, the navicular articulates on its anterior surface with the t h re e cun eifo rm b o n e s: rst (m edial), second (interm ed iate, m iddle), and third (lateral). 6. On the lateral aspect of the foot, lateral to the lateral cuneiform and navicular, identify the last of the tarsal bones, the cub o id . Observe that the cuboid also articulates with the anterior aspect of the calcaneus on the lateral asp ect of the foot. 7. Distal to the tarsal bones, identify the ve m e t at arsal b o n e s b eginning with the rst m etatarsal on the m edial asp ect of the foot and ending with the fth m etatarsal on the lateral aspect of the foot. 8. Identify the t ub e ro sit y o f t h e ft h m e t at arsal b o n e and observe that it extends laterally past the cuboid and serves as a site of m uscle attachm ent. 9. Distal to the m etatarsals, identify 14 p h alan g e s. Observe that the rst toe has only two phalanges, whereas the other toes each have three phalanges.

CHAPTER 6 Phalanges

THE LOWER LIMB

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207

Tarsals (7 bones)

Metatarsals

Sustentaculum tali 1 2 3 4 5

A

Plantar view Tuberosity of the 5th metatarsal

Cuboid

Calcaneus

5 4 3

3

2

2

1

1 Talus

B

Cuneiform bones

Dorsal view

Navicular

1st metatarsal

1 1 1st cuneiform Sustentaculum tali

C

Calcaneal tuberosity

Medial view

FIGURE 6.22

Skeleton of the foot. A. Plantar view. B. Dorsal view. C. Medial view.

Disse ct io n In st ruct io n s Sup e r cial Co m p art m e n t o f Po st e rio r Le g 1. With the cadaver in the prone position, use scissors to m ake a vertical cut through the crural fascia from the popliteal fossa to the calcaneal tuberosity. 2. Use blunt dissection to spread the crural fascia and exp ose the posterior com p artm ent of the leg. 3. Id entify and clean the g ast ro cn e m ius m u scle , the m ost sup er cial m uscle in the p osterior com partm ent of the leg (FIG. 6.23). [G 548; L 119; N 503; R 47 3 ] 4. Follow the two heads of the gastrocnem ius superiorly into the popliteal fossa and rem ove any overlying fat or fascia.

5. On one lower lim b, place a probe deep to the two heads of the gastrocnem ius m uscle just superior to the point where they join (FIG. 6.23). 6. Use scissors to transect both the m ed ial and lateral heads of the m uscle while sparing the branches of the t ib ial n e rve and p o p lit e al art e ry. 7. Use b lun t d issectio n to reflect th e two h ead s sup eriorly an d th e b ulk of th e m uscle b elly in ferio rly. 8. Identify the so le us m uscle deep to the gastrocnem ius m uscle. [G 549; L 120; N 504; R 473] 9. Identify the tend on of the p lan t aris m uscle between the lateral head of the gastrocnem ius and the soleus (FIG. 6.23). Follow the tendon of the p lantaris m uscle superiorly and observe that the m uscle belly lies in

208

•

GRANT’S DISSECTOR

Common fibular nerve Popliteal artery and vein Tibial nerve

Sural vessels (some cut)

Plantaris m. Inferior medial genicular artery Inferior lateral genicular artery Tendinous arch of soleus muscle Popliteus m. Level of transection Soleus m.

Gastrocnemius m. (cut and reflected)

Tendon of plantaris m.

Tibialis posterior tendon Flexor digitorum longus tendon Posterior tibial artery and vein Tibial nerve

Calcaneal tendon

Level of transection

Flexor hallucis longus tendon Flexor retinaculum

FIGURE 6.23

Contents of the super cial posterior com partm ent of the leg.

the pop liteal fossa. Note that the plantaris muscle may be absent in a small percentage of cases. 10. Follow th e p lan taris ten d on in feriorly an d ob serve th at it courses m ed ial to th e ten d on of th e g astrocn em ius m uscle in th e leg . Ob serve th at th e p lantaris ten d on eith er join s th e calcan eal ten d on or attach es to th e calcan eal tub erosity in d ep en d en tly. 11. Review the attachm ents and actions of the super cial posterior group of leg m uscles (see TABLE 6.5).

De e p Co m p art m e n t o f Po st e rio r Le g 1. Follow the t ib ial n e rve and p o st erio r t ib ial ve sse ls from where they exit the popliteal fossa and observe that they pass deep (anterior) to the tendinous arch of the soleus m uscle (FIG. 6.23). 2. Observe that the t ib ial n e rve and p o st e rio r t ib ial ve sse ls course distally within the t ran sve rse in t e rm uscular se p t um that sep arates the sup er cial

CHAPTER 6

posterior m uscle group from the deep posterior m uscle group (FIG. 6.19). 3. To better see the deep m uscle layer, the soleus m uscle m ust be re ected. 4. On th e con tralateral sid e of th e b od y wh ere th e g astrocn em ius was tran sected , use scissors to cut th e calcan eal ten d on ab out 5 cm sup erior to th e tub erosity of th e calcan eus (FIG. 6.23, d ash ed lin e). 5. Elevate the calcaneal tendon superiorly and use your ngers to separate the calcaneal tendon from the

Superior medial genicular artery

THE LOWER LIMB

Plantaris m. (cut) Gastrocnemius m. (lateral head) (cut)

Sural (muscular) branches

Fibular collateral ligament

Popliteal artery and tibial nerve

Biceps femoris tendon (cut)

Tibial collateral ligament

Inferior lateral genicular artery

Semimembranosus tendon (cut)

Head of fibula

Inferior medial genicular artery

Common fibular nerve (cut)

Popliteus m. Posterior tibial artery

Soleus m. (cut and reflected) Anterior tibial artery

Flexor digitorum longus m. Fibular artery

Tibial nerve Tibialis posterior m.

Flexor hallucis longus m. (retracted)

Fibular artery

Interosseous membrane Tibialis posterior tendon Flexor digitorum longus tendon

Perforating branch of fibular artery

Posterior tibial artery Tibial nerve

Calcaneal (Achilles) tendon (cut)

Flexor hallucis longus tendon

Superior fibular retinaculum

Flexor retinaculum

Inferior fibular retinaculum

Medial plantar artery and nerve Lateral plantar artery and nerve Flexor hallucis longus tendon

5th metatarsal bone

1st metatarsal bone

FIGURE 6.24

209

m uscles that lie deep to it. Follow the m ajority of the dissection sequence on this side without further transection of m uscles by sim p ly retracting the m uscles to either side as needed. 6. On the ipsilateral side of the body where the gastrocnem ius was transected, use scissors to cut the soleus m uscle beginning at its tibial (m edial) attachm ent. Extend the cut across the leg to its bular attachm ent (FIG. 6.23, dashed line). This cut should pass 2 cm inferior to the tendinous arch of the soleus m uscle (FIG. 6.24).

Superior lateral genicular artery

Gastrocnemius m. (medial head) (cut)

•

Contents of the deep p osterior com partm ent of the leg.

210

•

GRANT’S DISSECTOR

7. Leave th e soleus attach ed to b oth th e calcan eal ten d on an d th e b ula an d re ect th e soleus m uscle an d th e d istal p art of th e g astrocn em ius m uscle laterally to exp ose th e transverse in term uscular sep tum . 8. Id en tify th e p o st e rio r t ib ia l a rt e r y a n d ve in an d th e t ib ia l n e r ve wit h in t h e tran sverse in t erm u scu lar sep tu m ( FIG. 6 .2 4 ) . O b serve th at th e p o sterio r t ib ial artery is u su ally acco m p an ied b y t wo vein s, th e ven ae co m itan tes, an d th us can b e d istin g u ish ed fro m th e n erve. Rem o ve t h e vein s to clear th e d issection field . [G 5 5 0 ; L 1 2 1 ; N 5 0 5 ; R 502] 9. Use b lun t d issect io n to fo llow th e p osterior t ib ial artery an d th e t ib ial n erve p ro xim ally. O b serve th at th e p o p liteal art ery b ifu rcates at th e in ferio r b o rd er o f th e p o p liteu s m u scle to fo rm t h e p o st e rio r t ib ia l a rt e r y an d t h e a n t e rio r t ib ia l a rt e r y. 10. Superior to the superior extent of the soleus, identify the p o p lit e us m uscle (FIG. 6.24). 11. To better visualize the p op liteus m uscle, g ently retract the contents of the p op liteal fossa laterally [G 5 5 1 ; L 1 2 1 ; N 5 0 5 ; R 4 7 3 ]. Ob serve that the p op liteus m uscle b ers course throug h the p op liteal fossa at an ob liq ue ang le from inferom ed ial to sup erolateral. 12. Deep to the soleus m uscle, identify the t ib ialis p o st e rio r m uscle directly posterior to the tibia. 13. Medial to the tibialis posterior m uscle, identify the e xo r d ig it o rum lo n g us m uscle . 14. Lateral to th e tib ialis p osterior m uscle, id en tify th e e xo r h a llu cis lo n g u s m u scle (L. hallux, g reat toe; g en itive, hallucis). Ob serve th at th e b ulk of th e m uscle b elly of th e exor h allucis long us lies d eep to th e soleus on th e lateral sid e of th e leg b ut its ten d on crosses th e an kle to th e m ed ial sid e with th e ten d on s of th e oth er d eep p osterior g roup m uscles.

15. Review the attachm ents and actions of the deep posterior group of leg m uscles (see TABLE 6.5). 16. Posterior to the m edial m alleolus and deep to the exor retinaculum , observe that the p o st e rio r t ib ial art e ry and the t ib ial n e rve lie between the tendons of the exor digitorum longus and exor hallucis longus m uscles (FIG. 6.24). 17. Posterior to the m edial m alleolus, the following m nem onic device m ay be used to identify the tend ons and vessels in anterior to posterior order: Tom , Dick and A Very Nervous Harry (Tibialis posterior, exor Digitorum longus, posterior tibial Artery, posterior tibial Vein, tibial Nerve, exor Hallucis long us) [G 552; L 120, 121; N 503; R 502]. Note that the tibialis p osterior m uscle tendon crossed under the exor digitorum longus m uscle tendon m aking the order of tendons from m edial to lateral: tibialis p osterior, exor digitorum longus, exor hallucis longus. 18. In the upp er p art of the posterior leg, between the tibialis posterior m uscle and the exor hallucis longus m uscle, identify the b ular a rt e ry. Observe that the bular artery arises from the p osterior tib ial artery about 2 or 3 cm d istal to the inferior bord er of the p op liteus m uscle. Note that the bular artery supplies blood to the m uscles of the lateral com p artm ent of the leg and lateral sid e of the p osterior com p artm ent of the leg by m eans of several sm all branches. 19. Use an illustration and the cadaver to review the neurovascular distribution in the posterior com partm ent of the leg (FIG. 6.24). 20. Identify the p e rfo rat in g b ran ch o f t h e b ular art e ry just above the ankle joint where it perforates the interosseous m em brane (FIG 6.24). Note that the perforating branch of the bular artery anastom oses with a branch of the anterior tibial artery. Occasionally, the p erforating branch of the bular artery will give rise to the dorsalis pedis artery.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5. 6.

Replace the m uscles of the posterior com partm ent of the leg into their correct anatom ical positions. Use the dissected specim en to review the attachm ents and actions of each m uscle dissected. Follow the popliteal artery into the posterior com partm ent of the leg and identify its branches. Follow the posterior tibial artery distally and identify the origin of the bular artery. Review the distribution of the arteries of the posterior com partm ent of the leg. Follow the tibial nerve through the popliteal fossa and posterior com partm ent of the leg, observing that it gives num erous m uscular branches. 7. Review the relationships of the nerve, tendons, and vessels posterior to the m edial m alleolus and use this pattern to org anize the contents of the d eep p osterior com p artm ent of the leg . 8. Review the pattern of innervation of the posterior com partm ent of the leg.

CHAPTER 6

TABLE 6.5

THE LOWER LIMB

•

211

Muscle s o f t h e Po st e rio r Le g

SUPERFICIAL GROUP Muscle

Proxima l Atta chments

Gastrocnemius

Superior to the lateral and medial femoral condyles

Plantaris

Lateral supracondylar line of the femur

Soleus

Soleal line of the tibia and head of the bula

Dista l Atta chments

Actions

Innerva tion

Plantar exes the foot and exes the knee Posterior surface of calcaneus via calcaneal tendon

Tibial n. Plantar exes the foot

DEEP GROUP Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Popliteus

Lateral surface of lateral condyle of femur and lateral meniscus

Posterior surface of tibia superior to soleal line

Unlocks fully extended leg, weakly exes the knee

Tibialis posterior

Tibia, bula, and interosseous membrane

Navicular, cuneiform, cuboid, and bases of metatarsals 2–4

Inverts and plantar exes the foot

Flexor digitorum longus

Medial part of posterior surface of tibia inferior to the soleal line

Bases of the distal phalanges of the lateral four toes

Flexes toes 2–5 and plantar exes the foot

Flexor hallucis longus

Inferior two-thirds of the bula and interosseous membrane

Base of the distal phalanx of the great toe

Flexes the great toe and plantar exes the foot

Innerva tion

Tibial n.

Abbreviation: n., nerve.

LATERAL COMPARTMENT OF THE LEG Disse ct io n Ove rvie w The lateral com partm ent of the leg contains two m uscles: b ularis b re vis and b ularis lo n g us. The nerve of the lateral com partm ent is the super cial bular nerve. The group action of the m uscles in the lateral com partm ent of the leg is to evert and plantar ex the foot. [G 542, 543; L 122; N 506; R 475] Depending on the orientation of the foot, the lateral com partm ent of the leg m ay be easier to access with the body either p rone or supine. Turn the cadaver to whichever orientation facilitates the dissection.

Disse ct io n In st ruct io n s 1. Exam ine the crural fascia on the lateral side of the leg and identify the sup e rio r b ular re t in aculum , a thickening of the crural fascia found on the lateral side of the ankle posterior to the lateral m alleolus (FIG. 6.25). 2. About two-thirds of the way d own the leg, id entify the sup e r cial b ular n e rve where it p enetrates the crural fascia (FIG. 6.3A). Recall that the sup er cial b ular nerve is a b ranch of the com m on b ular nerve. 3. Follow the super cial bular nerve distally to the d orsum of the foot and observe that it gives rise to several d o rsal d ig it al b ran ch e s. Note that the

4.

5.

6.

7.

super cial bular nerve is the p rim ary cutaneous nerve of the dorsum of the foot. Use scissors to cut the crural fascia overlying the lateral com partm ent of the leg as far inferiorly as the superior bular retinaculum . In the sup erior leg, observe that the b ularis lo n g us m uscle is attached to the inner surface of the crural fascia. Use a scalp el to carefully detach the bularis longus m uscle from the crural fascia using a sim ilar techniq ue to skinning. Use blunt dissection to follow and sep arate the tendons of the b ularis b re vis and b ularis lo n g us m uscle s distally. Ob serve th at th e fib ularis m u scle ten d o n s p ass p o sterior to th e lateral m alleo lus, d eep

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to th e sup erio r an d in ferior fib ular retin acula (FIG. 6.25). No te th at th e ten d o n o f th e fib u laris b revis is an terior to th e ten d on of th e fib ularis lon g us wh ere th ey p ass p osterior to th e lateral m alleolus. 8. Follow the tendon of the bularis brevis m uscle inferiorly to its distal attachm ent on the tub erosity of the fth m etatarsal bone (FIG. 6.25).

Gastrocnemius muscle (lateral head)

9. Follow the tendon of the bularis longus m uscle inferiorly to the point where it turns around the lateral side of the cuboid bone to enter the sole of the foot. The tendon of the bularis longus m uscle attaches to the p lantar surface of the m edial cuneiform and rst m etatarsal bones. 10. Review the attachm ents and actions of the lateral group of leg m uscles (see TABLE 6.6).

Tibialis anterior muscle

Soleus muscle Extensor digitorum longus muscle

Fibularis longus muscle

Fibularis brevis muscle

Extensor hallucis longus tendon

Fibularis longus tendon

Extensor retinacula: Superior Inferior

Lateral malleolus

Extensor digitorum brevis muscle

Fibular retinacula: Superior Inferior Fibularis tertius tendon Fibularis brevis tendon Tuberosity of fifth metatarsal bone

FIGURE 6.25

Contents of the lateral com partm ent of the leg.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the attachm ents and actions of the m uscles in the lateral com partm ent of the leg. 2. Understand that the bular artery supplies the m uscles of the lateral com partm ent of the leg by contributing several sm all branches that penetrate the posterior interm uscular sep tum . 3. Review the pattern of innervation for the lateral com partm ent of the leg. [L 151]

CHAPTER 6

TABLE 6.6

THE LOWER LIMB

•

213

Muscle s o f t h e Lat e ral Le g

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Fibularis longus

Head and superior two-thirds of lateral surface of bula

Base of rst metatarsal and medial cuneiform

Evert and plantar ex the foot

Super cial bular n.

Fibularis brevis

Inferior two-thirds of lateral surface of bula

Tuberosity of the fth metatarsal bone

Abbreviation: n., nerve.

ANTERIOR COMPARTMENT OF THE LEG AND DORSUM OF THE FOOT Disse ct io n Ove rvie w The an t e rio r co m p art m en t of the leg contains four m uscles: t ib ialis an t e rio r, e xt e n so r h allucis lo n g us, e xt e n so r d ig it o rum lo n g us, and b ularis t e rt ius. The deep bular nerve innervates the m uscles of the anterior com p artm ent. The group actions of the m uscles in the anterior com partm ent are dorsi exion of the foot, inversion of the foot, and extension of the toes. [G 536, 537; L 123, 131; N 507, 508; R 478, 506] The order of dissection will be as follows: The distribution of cutaneous nerves over the lower anterior surface of the leg and dorsal surface of the foot will be reviewed. The anterior asp ect of the deep fascia of the leg and foot will be exam ined and the extensor retinacula will be identi ed. The anterior com partm ent of the leg will be opened and the relationships of tendons, vessels, and nerves will be exam ined on the anterior surface of the ankle. The tendon of each m uscle of the anterior com partm ent will be followed into the foot. The intrinsic m uscles of the dorsum of the foot will be identi ed. The deep vessels and deep nerve of the leg and dorsum of the foot will be dissected.

Disse ct io n In st ruct io n s 1. Place the cadaver in the supine position. 2. Rem ove the remnants of super cial fascia on the anterior surface of the leg and dorsum of the foot so the crural fascia and deep fascia of the foot are clearly exposed. Preserve the branches of the super cial bular nerve. 3. Recall that the super cial bular nerve provides m ost of the cutaneous innervation to the anterior surface of the ankle and dorsum of the foot (FIG. 6.3A). 4. Observe the crural fascia and note that it is rm ly attached to the anterior border of the tibia. 5. Identify the sup erio r and in ferio r ext en so r ret in acula on the anterior surface of the ankle (FIGS. 6.25 and 6.26). The retinacula are transverse thickenings of the crural fascia that hold tendons in place. The superior extensor retinaculum extends across the tendons superior to the ankle joint. The inferior extensor retinaculum is at the level of the ankle joint and is Y-shaped. Observe that the stem of the “Y” is directed laterally and is attached to the calcaneus (FIG. 6.25). 6. Make a vertical cut through the crural fascia just below the lateral condyle of the tibia along the anterior tibial border. Use forceps to lift the edges of the crural fascia and observe that the m uscles of the anterior com p artm ent are attached to its d eep surface. Extend the vertical cut distally through the crural fascia while sparing the extensor retinacula. 7. Re ect and rem ove the crural fascia by peeling it away from the m uscles of the anterior com partm ent.

Note that the superior attachm ents of the anterior m uscles of the leg are on the proxim al tibia, bula, and interosseous m em brane. Do not attem pt to dissect the superior attachm ents.

An t e rio r Le g Muscle s [G 538; L 132; N 507; R 506] 1. Use your ngers to separate the vessels, nerves, and tendons of the anterior m uscles of the leg where they pass deep to the inferior extensor retinaculum . 2. Identify the t ib ialis an t e rio r t e n d o n anterior to the m edial m alleolus (FIG. 6.26). Observe that the tibialis anterior tendon and the tibialis p osterior tendon are the two tendons closest to the m edial m alleolus, and they are nam ed according to their location relative to the bone. 3. Follow the tendon of the t ib ialis an t e rio r m uscle into the foot toward its attachm ent to the rst cuneiform bone and the base of the rst m etatarsal bone. 4. Lateral to the tibialis anterior, identify the e xt e n so r h allucis lo n g us t e n d o n (FIG. 6.26). Follow the tendon of the e xt e n so r h allucis lo n g us m uscle into the foot toward its attachm ent to the base of the distal phalanx of the great toe. 5. At the level of the superior extensor retinaculum , identify the an t e rio r t ib ial art e ry deep to the extensor hallucis longus tendon (FIG. 6.26). Follow the anterior tibial artery proxim ally. Use your ngers to separate the extensor digitorum longus m uscle and

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Patellar ligament

Head of fibula Common fibular nerve Deep fibular nerve Superficial fibular nerve Fibularis longus m. (cut and retracted) Anterior tibial artery

Extensor digitorum longus m. (cut)

Fibularis brevis m. and tendon

Interosseous membrane Tibialis anterior m. (cut and retracted) Superficial fibular nerve (cut)

Deep fibular nerve and anterior tibial artery

Extensor hallucis longus m. and tendon Tibialis anterior tendon

Fibularis longus tendon Superior extensor retinaculum Synovial sheath of extensor digitorum longus tendon Lateral malleolus Inferior extensor retinaculum Lateral tarsal artery Fibularis tertius tendon Tuberosity of 5th metatarsal bone Extensor digitorum brevis and extensor hallucis brevis mm. Extensor digitorum longus tendons Dorsal metatarsal arteries Dorsal digital arteries

FIGURE 6.26 of the foot.

Tibia Medial malleolus

Cut lines Dorsalis pedis artery Deep fibular nerve Arcuate artery Deep plantar artery Extensor hallucis longus tendon Extensor expansions Dorsal digital branches of deep fibular nerve Dorsal digital branches of superficial fibular nerve

Contents of the anterior com partm ent of the leg and dorsum

the tibialis anterior m uscle and follow the anterior tibial artery p roxim ally. 6. Use b lun t d issectio n to clean th e an terio r tib ial artery. No te th at it p asses p o sterio rly o ver th e sup erior b o rd er of th e in tero sseo us m em b ran e (FIG. 6.26). 7. Observe that the d e e p b ular n e rve travels with the anterior tibial artery just below the knee (FIG. 6.26).

Recall that the deep bular nerve is the m otor nerve of the anterior com partm ent of the leg and the m uscles in the dorsum of the foot. Trace the deep bular nerve p roxim ally and con rm that it is a branch of the co m m on b ular n e rve . 8. Lateral to the extensor hallucis longus tendon, identify the tendons of the e xt e n so r d ig it o rum lo n g us m uscle. Follow these tendons distally and con rm

CHAPTER 6

that they attach to the e xt e n so r e xp an sio n s of the lateral four toes (FIG. 6.26). 9. On the lateral aspect of the extensor digitorum longus muscle, identify the tendon of the b ularis tertius m uscle. Follow the tendon of the bularis tertius to its inferior attachment on the dorsal surface of the shaft of the fth metatarsal bone (FIG. 6.26). Note that the bularis tertius muscle is absent in about 5% of specimens. 10. If the neurovascular structures and tendons of the anterior com partm ent are not clearly visible, use scissors to cut the superior and inferior extensor retinacula between the extensor digitorum longus and extensor hallucis longus tendons (FIG. 6.26, dashed lines). Retract the tendons of the extensor digitorum longus m uscle in the lateral direction. 11. Review the attachm ents and actions of the anterior group of leg m uscles (see TABLE 6.7).

7.

8.

9.

Do rsum o f t h e Fo o t 1. On the d orsum of the foot deep to the tendons of the extensor digitorum longus m uscle, identify the e xt e n so r d ig it o rum b re vis m uscle and the ext e n so r h allucis b re vis m uscle (FIG. 6.26). Observe that the extensor digitorum brevis and extensor hallucis brevis m uscles share a com m on m uscle belly that attaches to the calcaneus. 2. Identify the four tendons arising from this com m on m uscle belly to attach to the extensor expansions of toes 2 to 5. Note that the portion of this m uscle that attaches on the great toe is called the extensor hallucis brevis m uscle. 3. Review the attachm ents, and actions, of the m uscles on the dorsum of the foot (see TABLE 6.7). 4. Return to the ankle and trace the anterior tibial artery deep to the inferior extensor retinaculum . As the anterior tibial artery crosses the ankle joint, its nam e changes to d o rsalis p ed is art e ry (L. pes, pedis, foot). [G 540; L 133; N 508; R 509] 5. Follow the dorsalis pedis artery onto the dorsum of the foot and observe that it lies on the lateral side of the extensor hallucis longus tendon at the ankle. Note that in the living person, the pulse of the dorsalis pedis artery can be palpated between the tendons of the extensor hallucis longus muscle and the extensor digitorum longus muscle. 6. Deep to the tendons on the dorsum of the foot, identify the arcuat e art e ry. The arcuate artery is a branch

10.

THE LOWER LIMB

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215

of the dorsalis pedis artery that crosses the proxim al ends of the m etatarsal bones. The lateral three d o rsal m e t at arsal art e rie s are branches of the arcuate artery. [G 541; L 133; N 508; R 509] Identify the lat e ral t arsal art e ry. The lateral tarsal artery arises from the dorsalis pedis artery near the ankle joint and passes deep to the extensor digitorum brevis and extensor hallucis brevis m uscles. The lateral tarsal artery joins the lateral end of the arcuate artery to com plete an arterial arch. Identify the d e e p p lan t ar art ery. The deep plantar artery arises from the dorsalis pedis artery near the origin of the arcuate artery. The deep plantar artery passes between the rst and second m etatarsal bones to enter the sole of the foot. In the sole of the foot, the deep plantar artery anastom oses with the plantar arch. At the level of the ankle, identify the d eep b ular n e rve between the tendons of the extensor hallucis longus and extensor digitorum longus m uscles (FIG. 6.26). Use blunt dissection to follow the deep bular nerve onto the dorsum of the foot. Note that the deep bular nerve innervates the extensor digitorum brevis m uscle and extensor hallucis brevis m uscle. Trace the cutaneous branch of the deep bular nerve to the region of skin between the great toe and the second toe and id entify the two d o rsal d ig it al b ran ch e s (FIG. 6.26). Understand that the skin between the great toe and the second toe is the only skin on the dorsum of the foot that is innervated by the deep bular nerve.

CLIN ICA L CORRELATION

Co m m o n Fib ular Ne rve The com m on bular nerve is one of the m ost frequently injured nerves in the body because of its super cial position and relationship to the head and neck of the bula. When the com m on bular nerve is injured, there is im pairm ent of eversion of the foot, dorsi exion of the foot, and extension of the toes in a condition called “foot drop.” In foot drop, or steppage gait, the advancing foot hangs with the toes pointed toward the ground while the knee is lifted high enough so that the toes m ay clear the ground. Foot drop is also accom panied by sensory loss on the dorsum of the foot and toes.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to review the attachm ents and actions of the m uscles in the anterior compartment of the leg. 2. Trace the anterior tibial artery through the anterior com partm ent of the leg to the foot and identify where its nam e changes to the dorsalis pedis artery. Review the branches of this arterial system . 3. Review the pattern of innervation for the anterior com partm ent of the leg and the dorsum of the foot. 4. Review the principal m uscle groups of the leg, the group functions, and the innervation of each m uscle group.

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TABLE 6.7

Muscle s o f t h e An t e rio r Le g an d Do rsum o f Fo o t

ANTERIOR LEG Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Tibialis anterior

Lateral condyle and superior half of lateral surface of tibia

Base of rst metatarsal and medial and inferior surfaces of medial cuneiform

Dorsi exes and inverts the foot

Extensor hallucis longus

Middle part of anterior surface of bula and interosseous membrane

Dorsal aspect of base of distal phalanx of great toe

Extends great toe and dorsiexes foot

Extensor digitorum longus

Lateral condyle of tibia and superior three-fourths of anterior surface of interosseous membrane

Extensor expansion to distal phalanges of lateral four digits

Extends lateral four digits and dorsi exes foot

Fibularis tertius

Inferior third of anterior surface of bula and interosseous membrane

Dorsum of base of fth metatarsal

Dorsi exes and everts foot

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Extensor digitorum brevis

Calcaneus, oor of the tarsal sinus

Extensor expansions of digits 2–5

Extends digits

Extensor hallucis brevis

Calcaneus, oor of the tarsal sinus

Extensor expansion of digit 1

Extends great toe

Deep bular n.

Deep bular n.

DORSUM OF FOOT

Abbreviation: n., nerve.

SOLE OF THE FOOT Disse ct io n Ove rvie w The fo o t is arch e d lo n g it ud in ally (FIG. 6.22, m edial view). The weight-bearing points of the foot are the calcaneus posteriorly and the heads of the ve m etatarsal bones anteriorly. The p lan t ar ap o n e uro sis supports the longitudinal arch. Deep to the plantar aponeurosis are four layers of intrinsic foot m uscles, tendons, vessels, and nerves. The order of dissection will be as follows: The skin and fat pad on the sole of the foot will be rem oved. The plantar aponeurosis will be cleaned of super cial fascia, studied, and re ected to expose the rst m uscle layer of the sole. The dissection will proceed from sup er cial (inferior) to deep (superior) and each of the four layers of the sole will be dissected. Note that abduction and adduction m ovem ents of the toes are described around an axis that passes through the second digit (second toe), which differs from the hand, where the axis of reference p asses through the third digit.

Disse ct io n In st ruct io n s Plan t ar Ap o n e uro sis an d Cut an e o us Ne rve s [G 557; L 134; N 519; R 479] 1. Place the cadaver in the prone position. 2. Refer to FIGURE 6.27 and rem ove the skin from the sole of the foot beginning with a m idline incision extending from the heel to the base of the second digit. 3. Make a horizontal incision arching from the base of the rst digit to the base of the fth digit. 4. Rem ove the skin beginning at the m idline incision and working toward the edges of the foot. Observe that the skin is thick over the heel and over the heads of the m etatarsal bones but is thinner on the toes and the instep . 5. Rem ove the skin on the plantar surface of the toes on at least two digits. 6. Observe that the plantar fascia over the m edial and lateral sides of the sole of the foot is thin, whereas

7.

8.

9.

10.

in the center, it is thickened to form the p lan t ar ap o n e uro sis (FIG. 6.28A). Use a scalp el blade to scrap e the super cial fascia off the plantar aponeurosis. Observe that the plantar aponeurosis is attached to the calcaneus posteriorly and that it divides distally into ve bands, one to each toe. Note that the ve bands are joined by the supercial transverse m etatarsal ligam ents (FIG. 6.28). Use a probe to elevate the plantar aponeurosis longitudinally. Note that the plantar aponeurosis is approximately 4 mm thick in the midline. To fully elevate the plantar aponeurosis, it may be necessary to carefully cut along its lateral edges with a scalpel. Do not cut too deeply. Make a transverse cut through the p lantar ap oneurosis distally in the anterior one-third of the foot (FIG. 6.28B, dashed line). Re ect the plantar aponeurosis proximally toward the calcaneus. Observe that tough bands of connective tissue attach the plantar aponeurosis to the metatarsal bones.

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217

Use a scalpel to cut these bands and release the plantar aponeurosis from the underlying structures.

O O O O O

First Laye r o f t h e So le [G 446; L 135; N 520; R 479]

M

L

FIGURE 6.27

Skin incisions of the sole of the foot, inferior view.

1. Identify the exor d ig it orum b revis m uscle, which lies in the center of the foot im m ediately deep to the plantar aponeurosis (FIG. 6.29). Trace the exor digitorum brevis tendons to their distal attachm ents. Rem ove rem nants of the plantar aponeurosis as necessary. 2. Identify the ab d uct o r h allucis m uscle on the m edial side of the exor digitorum brevis m uscle (FIG. 6.29). Use blunt dissection to follow the tendon toward its distal attachm ent on the great toe. 3. Identify the ab d uct o r d ig it i m in im i m uscle on the lateral side of the exor digitorum brevis m uscle (FIG. 6.29). Follow the tendon to its distal attachm ent on the fth (sm all) toe. 4. In the distal one-third of the sole of the foot, look for com m on and p ro p er p lan t ar d ig it al n erves, which are branches of the m ed ial and lat eral p lan t ar n erves (FIG. 6.29). Observe that the com m on and proper digital nerves lie between the tendons just identi ed.

Superficial transverse metatarsal ligaments Digital slips of plantar aponeurosis

Medial plantar fascia

Lateral plantar fascia

Plantar aponeurosis

Cut 1

Calcaneus

A Cut 2

B FIGURE 6.28

Sole of the foot. A. Plantar aponeurosis. B. Cuts used to open the plantar aponeurosis.

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Proper plantar digital arteries and nerves

Plantar metatarsal arteries Proper plantar digital branch of medial plantar artery

Synovial sheaths (opened) Fibrous digital sheaths (some opened)

Flexor digitorum longus tendons Flexor digitorum brevis tendons

Medial plantar nerve and artery Lateral plantar artery and nerve

Abductor hallucis muscle

Abductor digiti minimi muscle

Flexor digitorum brevis muscle Level of cuts

Posterior tibial artery and tibial nerve

Plantar aponeurosis (cut) Tuberosity of calcaneus

FIGURE 6.29

Sole of the foot. First layer of m uscles.

5. Review the attachm ents, actions, and innervation of the m uscles of the rst layer of the foot (see TABLE 6.8).

Se co n d Laye r o f t h e So le [G 559; L 136; N 521; R 480] Perform the following deep dissection steps on only one foot. 1. Rem ove the plantar aponeurosis from the sole of one foot by m aking a horizontal incision near its attachm ent to the calcaneus. 2. Use scissors to transect the exor digitorum brevis m uscle close to the calcaneus (FIG. 6.29, dashed line). Re ect the m uscle distally. 3. Push a probe deep to the abductor hallucis m uscle along the course of the posterior tibial artery and tibial nerve. Cut the abductor m uscle over the probe (FIG. 6.29, dashed line). 4. Use blunt dissection to follow the posterior tibial artery and tibial nerve into the sole of the foot. Identify the m ed ial and lateral p lantar nerves and arteries (FIG. 6.30). 5. Identify the q uad rat us p lan t ae m uscle , which lies deep to the exor digitorum brevis m uscle (FIG. 6.30). 6. Use a probe to dissect the e xo r d ig it o rum lo n g us t e n d o n s in the sole of the foot. Ob serve that its four tendons p ass through the tendons of the exor

digitorum brevis m uscle near the p roxim al interphalangeal joints (FIG. 6.30). 7. Observe that four lum b rical m uscle s arise from the tend ons of the exor d igitorum longus m uscle. 8. Review the attachm ents, actions, and innervation of the m uscles of the second layer of the foot (see TABLE 6.8).

Th ird Laye r o f t h e So le [G 560; L 137; N 522; R 481] 1. Use scissors to transect the exor digitorum longus tendon where it is joined by the q uadratus plantae m uscle (FIG. 6.30, dashed line). Re ect the tendons distally, along with the lum brical m uscles. 2. Identify the exor h allucis b revis m uscle (FIG. 6.31). The exor hallucis brevis muscle has a m ed ial head and a lateral head and each head has its own tendon. Note that a sesam oid b on e is found in each of the tendons. 3. Observe that the t en d o n o f t h e e xo r h allucis lon g us m uscle lies sup er cial to the exor hallucis brevis and is positioned between the sesam oid bones that are located in the two exor hallucis brevis tendons. Verify that the tendon of the exor hallucis longus is attached to the base of the distal phalanx of the great toe (FIG. 6.31).

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THE LOWER LIMB

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219

Proper plantar digital arteries and nerves

Flexor digitorum longus tendons Flexor digitorum brevis tendons Common plantar digital arteries and nerves Lumbrical muscles Flexor hallucis longus tendon Flexor digitorum longus tendon Lateral plantar nerve: Superficial branch Deep branch

Abductor hallucis muscle (cut)

Level of cut

Medial plantar artery and nerve

Abductor digiti minimi muscle Lateral plantar artery and nerve

Quadratus plantae muscle Flexor digitorum brevis muscle (cut)

Posterior tibial artery and tibial nerve

Plantar aponeurosis (cut) Tuberosity of calcaneus

FIGURE 6.30

Sole of the foot. Second layer of m uscles, plantar arteries, and nerves.

4. In the central com partm ent of the foot, identify the ad d uct o r h allucis m uscle . The adductor hallucis m uscle has a t ran sve rse h e ad and an o b liq ue h e ad (FIG. 6.31). Observe that both heads attach to the lateral side of the base of the proxim al phalanx of the great toe. 5. On the lateral aspect of the foot, identify the e xo r d ig it i m in im i b re vis m uscle . 6. Review the attachm ents, actions, and innervation of the m uscles of the third layer of the foot (see TABLE 6.8).

3.

4.

Fo urt h Laye r o f t h e So le [G 561; L 138; N 523; R 481] 1. Use blunt dissection to trace the lateral plantar artery distally. At the level of the base of the m etatarsal bones, the lateral p lantar artery turns deeply to form the p lan t ar arch (FIG. 6.31). Follow the p lantar arch m edially until it passes deep to the oblique head of the adductor hallucis m uscle. 2. The m edial end of the plantar arch is form ed by the d e e p p lan t ar art e ry, a branch of the d o rsalis p e d is art e ry (FIG. 6.26). Use an illustration to study the p attern of distribution of the p lan t ar m e t at arsal

5.

6.

art e rie s that arise from the p lantar arch. [G 560; L 139; N 523; R 512] The in t e ro sse o us m uscle s are located superior (deep) to the plantar arch. Use an illustration to study the in t e ro sse o us m uscle s (FIG. 6.32) [G 561; L 138; N 524; R 481, 512]. The four Dorsal interosseous m uscles are ABductors (DAB), and the three Plantar interosseous m uscles are ADductors (PAD) of the toes. Recall that the reference axis for abduction and adduction of the foot passes through the second m etatarsal and toe. Locate the b ularis lon g us t en d on posterior to the lateral m alleolus (FIG. 6.31). Insert a probe along its super cial surface, deep to the exor digiti m inim i brevis and abductor digiti m inim i m uscles. Use scissors to transect the m uscles over the probe and re ect them . Follow the bularis longus tendon into the sole of the foot and note that it turns deeply around the lateral surface of the cuboid bone. In the sole, insert the probe along the super cial surface of the bularis longus tendon (into its tendon sheath) and gently push the probe m edially across the sole of the foot. Wiggle the probe so that you can see where the tip is and note that the bularis longus tendon crosses the sole of the foot at its deepest plane.

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Proper plantar digital arteries and nerves Flexor digitorum longus tendons (cut) Flexor digitorum brevis tendons (cut) Perforating arteries (to dorsal metatarsal arteries) Tendons of lumbrical muscles (cut) Adductor hallucis muscle: Transverse head Oblique head Common plantar digital arteries and nerves (cut)

Flexor hallucis brevis muscle: Lateral head Medial head

Plantar metatarsal arteries Plantar arch Lateral plantar nerve: Superficial branch Deep branch

Flexor hallucis longus tendon Abductor hallucis muscle (cut)

Flexor digiti minimi brevis muscle

Tibialis posterior tendon

Tuberosity of 5th metatarsal bone

Quadratus plantae muscle (cut) Sustentaculum tali Medial plantar artery and nerve (cut)

Fibularis brevis tendon Fibularis longus tendon

Lateral plantar artery and nerve

Abductor digiti minimi muscle (cut)

Posterior tibial artery and tibial nerve

Flexor digitorum brevis muscle (cut) Plantar aponeurosis (cut) Tuberosity of calcaneus

FIGURE 6.31

A

B

Axial line

Sole of the foot. Third layer of m uscles.

Axial line

Plantar interosseous muscles Dorsal interosseous muscles

FIGURE 6.32 Interosseous m uscles. A. Plantar view. B. Dorsal view. The three unipennate Plantar interosseous m uscles ADduct the toes ( PAD) in relation to the axial line through the second toe (arrows). The four bipennate Dorsal interosseous m uscles ABduct the toes ( DAB) relative to the axial line (arrows).

7. To better visualize the path of the bularis longus tendon, cut a sm all window into the tendon sheath and then gently pull on the tendon near the ankle to view it m oving through the cut window. 8. On the m edial side of the foot, follow the t ib ialis p o st e rio r t e n d o n d istally and verify that it has a broad distal attachm ent on the navicular bone; all three cuneiform bones; and the bases of the second, third, and fourth m etatarsal bones (FIG. 6.30). 9. Identify the e xo r h allucis lo n g us m uscle in the posterior com p artm ent of the leg. Follow its tendon distally until it disappears into an osseo brous tunnel at the m edial side of the ankle. Push a probe into the tunnel and then op en the tunnel by cutting down to the probe with a scalpel. 10. Lift the tendon of the exor hallucis longus m uscle with a probe and verify that it crosses the inferior surface of the sust e n t aculum t ali. Note that the sustentaculum tali acts as a pulley to change the direction of force of the exor hallucis longus m uscle. 11. Review the attachm ents, actions, and innervation of the m uscles of the fourth layer of the foot (see TABLE 6.8).

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221

Disse ct io n Fo llo w-up 1. Replace the structures of the four layers of the sole of the foot into their correct anatom ical positions reviewing the attachm ents and action of each m uscle in each layer as you go. 2. Follow the posterior tibial artery from its origin in the leg to its bifurcation in the sole of the foot. Use an illustration and the dissected specim en to review the distribution of the m edial and lateral p lantar arteries. 3. Review the connection between the deep plantar arch and the deep plantar branch of the dorsalis pedis artery. 4. Trace the course of the tibial nerve from the popliteal fossa to the m edial side of the ankle. Follow its two branches in the sole of the foot (m edial and lateral plantar nerves). 5. Trace the pathway of the m edial and lateral plantar nerves in your dissected cadaver and review their m otor and sensory functions. [L 153]

TABLE 6.8

Muscle s o f t h e So le o f Fo o t

FIRST LAYER Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Flexor digitorum brevis

Calcaneal tuberosity and plantar aponeurosis

Middle phalanges of the lateral four toes

Flexes toes 2–5

Medial plantar n.

Abductor hallucis

Medial process of tuberosity of calcaneus, exor retinaculum, and plantar aponeurosis

Medial side of base of proximal phalanx of rst digit

Abducts and exes rst digit

Abductor digiti minimi

Medial and lateral processes of tuberosity of calcaneus, plantar aponeurosis, and intermuscular septa

Lateral side of base of proximal phalanx of fth digit

Abducts and exes fth digit

Lateral plantar n.

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Quadratus plantae

Medial surface and lateral margin of plantar surface of calcaneus

Posterolateral margin of tendon of exor digitorum longus

Flexes lateral four digits

Lateral plantar n.

Lumbricals

Tendons of exor digitorum longus

Medial aspect of extensor expansion of lateral four digits

Flexes proximal phalanges and extends middle and distal phalanges of digits 2–4

Medial plantar n. ( rst) Lateral plantar n. (second to fourth)

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Flexor hallucis brevis

Plantar surfaces of cuboid and lateral cuneiforms

Both sides of base of proximal phalanx of rst digit

Flexes proximal phalanx of rst digit

Medial plantar n.

Adductor hallucis

Bases of metatarsals 2–4 (oblique head), plantar ligaments of MTP (transverse head)

Lateral side of base of proximal phalanx of rst digit

Adducts rst digit

Deep branch of lateral plantar n.

Flexor digit minimi

Base of fth metatarsal

Base of proximal phalanx of fth digit

Flexes proximal phalanx of fth digit

Super cial branch of lateral plantar n.

Muscle

Proxima l Atta chments

Dista l Atta chments

Actions

Innerva tion

Plantar interossei

Plantar surface of metatarsals 3–5

Medial sides of bases of phalanges of digits 3–5

Adducts digits 3–5 and exes MTP joints

Lateral plantar n.

Dorsal interossei

Adjacent sides of metatarsals 1–5

Medial side of proximal phalanx of second digit ( rst), lateral sides of proximal phalanx of digits 2–4 (second to fourth)

Abducts digits 2–4 and exes MTP joints

SECOND LAYER

THIRD LAYER

FOURTH LAYER

Abbreviations: MTP, metatarsophalangeal joint; n., nerve.

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JOINTS OF THE LOWER LIMB Disse ct io n Ove rvie w In order to dissect the joints in the lower lim b, it will be necessary to re ect or rem ove a m ajority of the surrounding m uscles. Because the joint dissections will m ake it dif cult to review key m uscular relationships later, it is recom m ended to lim it the joint dissections to one lower lim b and to keep the soft tissue structures of the other lim b intact for review purposes. For ease of rotation of the lower lim b, p erform the joint dissections on the side of the bod y where the lower lim b was rem oved from the pelvis. Alternatively, if enough cadaveric sp ecim ens are available in the lab, perform only select d issections on each lim b and alternate the dissections perform ed on each cad aver. While rem oving the m uscles of the selected lower lim b, take advantage of this opportunity to review the attachm ents, actions, and innervation of each m uscle as it is rem oved. The order of dissection will be as follows: The hip will be dissected. The knee joint will be dissected. The ankle joint will be dissected. The interm etatarsal joints, which are responsible for inversion and eversion, will be studied.

Disse ct io n In st ruct io n s Hip Jo in t Use an articulated skeleton to review the bony features of the hip joint. 1. Identify the three bones that form the acetabulum : the ilium , isch ium , and p ub is. 2. Review the proxim al end of the fem ur and identify the following: h e ad , fo ve a fo r t h e lig am e n t o f t h e h e ad , n e ck, and in t e rt ro ch an t e ric lin e. 3. In the cadaver, on one side, detach the sartorius m uscle from its superior attachm ent to the ASIS and re ect the m uscle inferiorly. 4. Detach the rectus fem oris m uscle from its superior attachm ent to the anterior inferior iliac spine (AIIS) and re ect the m uscle inferiorly. 5. Rem ove the pectineus m uscle. 6. Identify the ilio p so as m uscle . Trace its tendon to the lesser trochanter. Sever the tendon of the iliopsoas m uscle close to the lesser trochanter and re ect the m uscle superiorly. 7. Use an illustration to identify the ligam ents that contribute to the form ation of the b ro us jo in t cap sule : ilio fe m o ral lig am e n t , isch io fe m o ral lig am e n t , and p ub o fe m o ral lig am e n t (FIGS. 6.33 and 6.34). [G 510, 511; L 140; N 474; R 460, 461] 8. Exam ine the ilio fe m o ral lig am e n t . Verify that the distal end of the iliofem oral ligam ent is attached to the intertrochanteric line of the fem ur and that the proxim al end is attached to the AIIS and the m argin of the acetabulum . 9. Flex and extend the fem ur. Observe that the iliofem oral ligam ent becom es lax in exion and taut in extension. Note that the iliofem oral ligam ent p revents overextension of the hip joint. 10. Use a scalpel to open the anterior aspect of the jo in t cap sule as illustrated in FIGURE 6.33. 11. Inside the joint capsule, observe the cart ilag e o n t h e art icular surface o f t h e h e ad o f t h e fe m ur.

12. 13.

14. 15. 16.

Rotate the fem ur laterally and note that you can see m ore of the articular surface of the head. Rotate the fem ur m edially and observe that the articular surface disappears into the acetabulum . [G 510; L 141; N 474; R 460] Abduct and laterally rotate the fem ur and identify the lig am e n t o f t h e h e ad o f t h e fe m ur (FIG. 6.33). Identify the o b t urat o r e xt e rn us m uscle . Note that the obturator externus m uscle p asses inferior to the neck of the fem ur. Rem ove the obturator externus m uscle to expose the p ub o fe m o ral lig am e n t . Turn the cadaver to the prone position. Re ect the gluteus m axim us m uscle laterally.

Anterior inferior iliac spine Tendon of rectus femoris m.

Articular surface

Iliofemoral ligament Iliofemoral ligament (cut)

Pubofemoral ligament Probe positioned under ligament of the head of the femur

FIGURE 6.33 How to open the anterior surface of the hip joint cap sule. Right hip, anterior view.

CHAPTER 6

THE LOWER LIMB

Lunate surface

Iliofemoral ligament

Femur: Head Neck

Articular surface

Ligament of the head of the femur

Sacrotuberous ligament

Ischiofemoral ligament

FIGURE 6.35

•

223

Tendon of rectus femoris Iliofemoral ligament (cut) Acetabular notch Acetabular labrum

Transverse acetabular ligament

Disarticulated hip joint. Right hip, anterior view.

Synovial membrane

FIGURE 6.34 How to open the posterior surface of the hip joint capsule. Right hip, posterior view.

17. Re ect the gluteus m edius and gluteus m inim us m uscles laterally. 18. Detach the piriform is, superior gem ellus, obturator internus, inferior gem ellus, and q uadratus fem oris from their lateral attachm ents to the fem ur and re ect the m uscles m edially. To increase visibility of the hip joint posteriorly, com pletely rem ove the lateral rotators of the hip from the dissection eld. 19. Use a scalpel and scraping m otions to clean the posterior surface of the jo in t cap sule (FIG. 6.34). 20. Identify the isch io fe m o ral lig am e n t coursing from the acetabular m argin to the neck of the fem ur. Note that the ischiofem oral ligam ent does not attach to the intertrochanteric crest, which leaves an area where the synovial m em brane of the hip joint is exposed. 21. Extend the fem ur. Observe that the ischiofem oral ligam ent becom es taut and lim its extension of the hip joint.

22. Open the posterior wall of the joint cavity by incising the cap sule as shown in FIGURE 6.34. Observe the thickness of the joint cap sule. 23. In order to disarticulate the hip joint, return the specim en to the supine position. 24. Insert a probe under the ligam ent of the head of the fem ur (FIG. 6.33) and cut the ligam ent with a scalpel. Rotate the fem ur laterally until the head of the fem ur com es out of the acetabulum . 25. Exam ine the head and neck of the fem ur (FIG. 6.35). Identify the a rt icu la r su rfa ce of the head of the fem ur. Observe the cut end of the lig a m e n t o f t h e h e a d o f t h e fe m u r and id entify the art e ry o f t h e lig a m e n t o f t h e h e a d o f t h e fe m u r in the center of the lig am ent. Use an illustration to review the b lood sup p ly to the head and neck of the fem ur. 26. Identify the lun at e surface in the acetabulum (FIG. 6.35). Note that the lig am e n t o f t h e h e ad o f t h e fe m ur lies in the ace t ab ular n o t ch . [G 512; L 141; N 474; R 461] 27. Identify the t ran sve rse acet ab ular lig am e n t that bridges the acetabular notch and the ace t ab ular lab rum that surrounds the rim of the acetabulum .

Kn e e Jo in t Po st e rio r Ap p ro ach CLIN ICA L CO RRELATIO N

Ne ck o f t h e Fe m ur A fracture of the neck of the fem ur disrupts the blood supp ly to the head of the fem ur. If the blood supp ly (via the artery of the ligam ent of the head) is insuf cient, the head of the fem ur will b ecom e necrotic and need replacing. Necrosis of the fem oral head is a com m on com plication in fem oral neck fractures in the elderly.

Use an articulated skeleton to review the skeleton of the knee. 1. On the distal end of the fem ur, identify the m e d ial co n d yle , lat e ral co n d yle , and in t e rco n d ylar fo ssa. 2. On the proxim al end of the tibia, identify the sup e rio r art icular surface , m e d ial co n d yle , lat e ral co n d yle , and in t e rco n d ylar e m in e n ce. 3. On the patella, identify the art icular surface and an t e rio r surface .

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4. In th e cad aver, id en tify th e ten d on s of th e sartorius, g racilis, an d sem iten d in osus m uscles attach ing at th eir d istal attach m en ts (p es an serin us) on th e m ed ial sid e of th e kn ee. Recall th at th ese th ree m uscles all arise from d ifferen t com p artm en ts of th e th ig h an d th us h ave d ifferen t m otor in n ervation s, yet all work tog eth er to ex th e kn ee an d m ed ially rotate th e tib ia. [G 5 2 6 ; L 1 4 2 , 1 4 3 ; N 493; R 463] 5. Elevate the m uscles attaching to the pes anserinus and identify the t ib ial (m e d ial) co llat e ral lig am e n t (MCL) of the knee (FIG. 6.36). Note that the tibial collateral ligam ent is attached to the m edial m eniscus through the joint capsule. 6. On the lateral side of the knee, identify the tendon of the biceps fem oris m uscle close to its distal attachm ent on the head of the bula. 7. Identify the b ular (lat e ral) co llat e ral lig am en t (LCL) of the knee and observe that it is not attached to the external surface of the joint cap sule (FIG. 6.36). 8. On the posterior aspect of the knee, observe that the p opliteus tend on passes between the bular collateral ligam ent and the joint capsule. [G 526; L 145; N 493; R 463] 9. On the posterior aspect of the knee, identify the o b liq ue p o p lit eal lig am e n t that sweep s superiorly and laterally from the tendon of the sem im em branosus m uscle. Note that the ob lique popliteal ligam ent

10.

11.

12.

13.

14.

15.

16.

reinforces the posterior surface of the knee joint capsule. If th e ob liq ue p op liteal ten d on is n ot clearly visib le, rem o ve th e p op liteal vessels, th e tib ial n erve, an d th e co m m o n fib ular n erve from th e p o p liteal fo ssa. Identify the popliteus m uscle and observe the p resence of the arcuat e p o p lit e al lig am e n t that spans the super cial surface of the p op liteus tendon. Note that the pop liteus m uscle reinforces the p osterior wall of the joint capsule. Cut the popliteus tendon and re ect the m uscle inferiorly to expose the posterior surface of the capsule enclosing the knee. Use scissors to m ake a horizontal incision through the joint capsule and rem ove the posterior aspect of the joint capsule from the dissection eld. From a posterior perspective, identify the cruciate ligam ents, which cross each other within the joint capsule (FIG. 6.36C). Observe that the p o st e rio r cruciat e lig am e n t (PCL) attaches to the tibia posteriorly and note that the an t e rio r cruciat e lig am e n t (ACL) attaches to the tib ia anteriorly. [G 524; L 145; N 496; R 463] Identify the m e d ial and lat e ral m e n isci (FIG. 6.36C). Observe that the m e d ial m e n iscus is rm ly attached to the tibial collateral ligam ent. In contrast, the lat e ral m e n iscus is not attached to the bular collateral ligam ent.

Posterior cruciate ligament Anterior cruciate ligament

Lateral meniscus

Posterior cruciate ligament Fibular (lateral) collateral ligament

Lateral meniscus

Medial meniscus

Fibular (lateral) collateral ligament

Tibial (medial) collateral ligament Anterior cruciate ligament

Patellar ligament Patella

A

B FIGURE 6.36

Tibial (medial) Medial collateral ligament meniscus

C

Right knee joint. A. Posterior view. B. Anterior view. C. Superior view.

CHAPTER 6

Kn e e Jo in t An t e rio r Ap p ro ach 1. On the anterior surface of the knee, identify the tendon of the quadriceps fem oris m uscle. Observe that the tendon has p at e llar re t in acula that help keep the patella centered. Inferior to the patella, identify the p at e llar lig am e n t . 2. Make a transverse incision superior to the patella through the quadriceps fem oris tendon. Carry the incision around the sides of the knee, stopping short of the collateral ligam ents. 3. Re ect the patella and patellar ligam ent inferiorly and expose the joint cavity anteriorly (FIG. 6.36B). Con rm that the fem ur and the tibia rem ain attached to each other by t wo co llat e ral lig am en t s and t wo cruciat e lig am e n t s as well the obliq ue and arcuate p opliteal ligam ents. 4. Use an illustration or the cadaver to verify that the cruciate ligam ents are located outside of the synovial cavity but are inside the joint cap sule. [G 523; L 145; N 494; R 464] 5. Verify from an anterior perspective that the cruciate ligam ents cross each other (FIG. 6.36C). 6. Flex the knee and observe that the ACL attaches to the tibia anteriorly and note that the PCL attaches to the tibia posteriorly. 7. Extend the leg and observe that the articular surfaces of the fem ur and tibia are in m axim um contact. When the knee is fully extended, the joint is “locked” in its m ost stable position, and the ACL is taut and p rohibits further extension. 8. Flex the leg and observe that there is less contact between the articular surfaces of the fem ur and tibia. Observe that when the knee is exed, som e rotation occurs in the knee joint. 9. With th e knee exed , p ull the tib ia forward (anterior d rawer test) and ob serve th at the ACL p revents the tib ia from b ein g p ulled anteriorly. If th e tib ia h as a larg e d eg ree of forward m ovem en t,

CLIN ICA L CORRELATION

Kn e e In jurie s The m edial m eniscus is injured six to seven tim es m ore often than the lateral m eniscus because the m edial m eniscus is rm ly attached to the tibial collateral ligam ent. Forced abduction and lateral rotation of the leg m ay result in the sim ultaneous injury of the tibial collateral ligam ent, m edial m eniscus, and ACL. The injury of these three structures has been nam ed the “unhapp y triad.” Typ ically, this injury is caused by a blow to the lateral side of the knee and is a com m on injury in contact sp orts.

THE LOWER LIMB

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225

CLIN ICA L CORRELATION

An kle In jurie s Th e ankle joint is th e m ost freq uently in jured m ajor joint in th e b od y. The lateral lig am en t of the an kle is injured when the foot is forcefully inverted resulting in an ankle sp rain with swelling aroun d th e lateral m alleolus. In severe cases, the calcan eo b ular and anterior talo b ular lig am en ts are torn an d the inferior tip of th e lateral m alleolus m ay b e avulsed (p ulled off).

it m ay in d icate a rup tured ACL and is an im p ortan t clinical sig n. 10. In the sam e position, push on the tibia (posterior drawer test) and observe that the PCL prevents the tibia from being pushed posteriorly. 11. Observe from an anterosuperior view that the m e d ial m e n iscus is m ore “C” shap ed, whereas the lat e ral m e n iscus is m ore rounded (FIG. 6.36C).

An kle Jo in t [G 566; L 146; N 514; R 467] Use an articulated skeleton to review the bony landm arks related to the ankle joint. 1. On the distal end of the bula, identify the lat eral m alle o lus. 2. On the distal end of the tibia, identify the m e d ial m alle o lus. 3. Review the location of the tarsal bones and, on the talus, identify the t ro ch le a. 4. In the cadaver, cut and re ect the tendons, vessels, and nerves that cross the anterior aspect of one ankle joint. Leave approxim ately 2 cm of each tendon attached to their respective distal attachm ents on the skeleton of the foot and re ect the rem aining p ortion of the tendon and m uscle away from the ankle. 5. On the m edial aspect of the ankle joint, cut and reect the exor digitorum longus m uscle. 6. Retract the tendon of the tibialis posterior m uscle anteriorly. Do not cut it. 7. On the m edial side of the ankle, clean and dene the m e d ial (d e lt o id ) lig am e n t o f t h e an kle (FIG. 6.37A). Observe that the deltoid ligam ent has four parts that are nam ed according to their skeletal attachm ents. From anterior to posterior, identify the an t e rio r t ib io t alar lig am e n t , the t ib io n avicular lig am e n t , the t ib io calcan e al lig am e n t , and the p o st e rio r t ib io t alar lig am e n t . 8. On the lateral side of the ankle, m ake a vertical incision through the superior and inferior bular retinacula and retract the tendons of the bularis longus and bularis brevis m uscles anteriorly.

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Tibia Medial (deltoid) ligament of ankle

Posterior tibiotalar ligament Tibiocalcaneal ligament Tibionavicular ligament Anterior tibiotalar ligament

1st metatarsal bone

A

Short plantar ligament

Tibialis anterior tendon Tibialis posterior tendon

Long plantar ligament

Plantar calcaneonavicular (spring) ligament Tibia Fibula

Posterior talofibular ligament Calcaneofibular ligament Anterior talofibular ligament

Anterior and posterior tibiofibular ligaments

Lateral ligament of ankle

Superior fibular retinaculum Inferior fibular retinaculum Long plantar ligament

B FIGURE 6.37

Fibularis longus tendon

Fibularis brevis tendon

Right ankle joint. A. Medial view. B. Lateral view.

9. Clean and de ne the lat e ral lig am e n t o f t h e an kle (FIG. 6.37B). Observe that the lateral ligam ent of the ankle has three parts that are nam ed according to their skeletal attachm ents. From anterior to p osterior, identify the an t e rio r t alo b ular lig am e n t , the calcan e o b ular lig am e n t , and the p o st e rio r t alo b ular lig am e n t . 10. Dorsi ex and p lantar ex the ankle joint. Observe that these are the prim ary actions of the ankle joint.

Jo in t s o f In ve rsio n an d Eve rsio n On an articulated skeleton , stud y th e m ovem en ts of in version an d eversion of th e foot (use caution wh ile

d o in g so b ecause wired lab o ratory skeleto n s can b e d am ag ed ). 1. With one hand, im m obilize the ankle joint by holding the talus stationary between the tibia and bula. With the other hand, invert and evert the foot. Observe that the talus rem ains xed in the ankle joint and that the foot rotates about the inferior surface of the talus (subtalar joint) and anterior surface of the talus (talonavicular and talocuboid joints). 2. In the cadaver, produce e ve rsio n by pulling on the tendons of the bularis longus and bularis brevis m uscles. Produce in versio n by sim ultaneously pulling on the tendons of the tibialis anterior and tibialis posterior m uscles.

CHAPTER 6

THE LOWER LIMB

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227

Cuneiform bones Cuboid

Navicular

Short plantar ligament

Plantar calcaneonavicular (spring) ligament

Long plantar ligament Talus

Deltoid ligament Sustentaculum tali

A

B Calcaneal tuberosity

FIGURE 6.38

Plantar ligam ents. A. Long plantar ligam ent. B. Short plantar and Spring ligam ents.

3. Observe that these m ovem ents occur at the t ran sve rse t arsal jo in t (calcaneocuboid and talonavicular joints) and the sub t alar jo in t . 4. Use an illustration to observe that the longitudinal arch of the foot is supported by ligam ents that span the tarsal bones. 5. In the sole of the foot where the deep dissection was perform ed, rem ove the exor digitorum brevis and quadratus plantae m uscles. Observe the lo n g

p lan t ar lig am e n t and the sh o rt p lan t ar lig am e n t (FIG. 6.38). [G 574; L 147; N 515; R 466] 6. Rem ove the tendon of the tibialis posterior m uscle where it crosses inferior to the talus. 7. Id en tify th e p la n t a r ca lca n e o n a vicu la r (sp rin g ) lig a m e n t (FIG. 6.38). Note that the sp rin g lig am en t an d th e tib ialis p osterior ten d on sup p ort th e h ead of th e talus an d th e lon g itud in al arch of th e foot.

Disse ct io n Fo llo w-up 1. Review the nam es of the bones articulating at each joint of the lower lim b. 2. Review the m ovem ents perm itted at each joint of the lower lim b. 3. Use the dissected specim en to identify the key ligam ents associated with each joint and review their respective points of attachm ent. 4. Return the re ected m uscles of the lower lim b back to their anatom ical positions.

CHAPTER 7

The Head and Neck ATLAS REFERENCES G = Gra n t ’s, 14t h ed ., p a ge

N = Net t er, 6t h ed ., p la t e

L = Lip p in co t t , 1st ed ., p a ge

R = Ro h en , 8t h ed ., p a ge

h e stu d y of h ead an d n eck an atom y p rovid es a con sid erable in tellectu al ch allen ge becau se th e region is p acked with sm all, im p ortan t stru ctu res associated with th e proxim al en d s of th e resp iratory an d gastroin testin al system s, th e cran ial n erves, an d th e organ s of sp ecial sen se. Dissection of th e h ead an d n eck p rovid es a sp ecial p roblem in th at p erip h eral stru ctu res m u st be d issected lon g before th eir p aren t stru ctu re can be id en ti ed . Th u s, a fu ll u n d erstan d in g of th e region can n ot be gain ed u n til th e n al d issection is com p leted . Th e n eck is a region of tran sition between th e h ead an d th e th orax. Th e m ajor vessels th at su p p ly th e h ead an d th e n erves th at in n ervate th e organ s with in th e th orax an d abdom en p ass th rou gh th e n eck. Portion s of several system s are located in th e n eck: gastroin testin al system (p h aryn x an d esop h agu s), resp iratory system (laryn x an d trach ea), card iovascu lar system (m ajor vessels to

T

th e h ead an d u p p er lim bs), cen tral n ervou s system (sp in al cord ), an d en d ocrin e system (th yroid an d p arath yroid glan d s). Fin ally, n erves an d vessels to th e u p p er lim bs also p ass th rou gh th e in ferior p art of th e n eck. Th e su p er cial asp ects of th e n eck (su p er cial fascia, su p er cial vein s, an d cu tan eou s n erves) will be dissected rst. Th en th e n eck will be d ivid ed in to region s d e n ed as trian gles. Th e bou n d aries of th e trian gles will be d escribed an d th e an atom y d iscu ssed with in th ese bou n d aries. It is im p ortan t to n ote th at th e trian gles are m erely organ ization al aid s an d th at th eir bou n d aries m u st n ot be allowed to in terfere with u n d erstan d in g th e n eck as an in tegrated wh ole. Th e vascu lar stru ctu res th at go to th e h ead as well as th e en d ocrin e glan d s in th e n eck will be d issected . Th e p h aryn x an d laryn x will be d issected after th e h ead becau se th ey can n ot be m obilized u n til after th e h ead is d issected .

SUPERFICIAL NECK Disse ct io n Ove rvie w Th e ord er of d issection will b e as follows: Th e skin will b e rem oved from th e an terior an d lateral surfaces of th e neck. Th e p latysm a m uscle will b e stud ied an d re ected . Th e extern al jug ular vein will b e id en ti ed . Several cutan eous b ran ch es of th e cervical p lexus (g reat auricular n erve, lesser occip ital n erve, tran sverse cervical n erve, an d sup raclavicular n erves) will b e d issected . Th e accessory n erve (CN XI) will b e id en ti ed an d followed from th e sternocleidom astoid m uscle (SCM) to th e trap ezius m uscle.

Ske le t o n o f t h e Ne ck Refer to a skeleton or disarticulated cervical vertebrae to identify the following skeletal features (FIG. 7.1) : [G 8; L 7, 8; N 19, 22; R 194]

Ce rvical Ve rt e b rae 1. The bones of the neck were rst studied in Chapter 1, The Back. Recall that in general, cervical vertebrae have sm all bodies, relatively large vertebral foram ina, bi d spinous processes, and transverse processes that contain a transverse foram en (foram en transversarium ). 2. On the isolated at las (C1) , identify the an t e rior arch an d t ub e rcle . Recall that C1 does not have a body.

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3. Observe that C1 has a p o st e rio r t ub e rcle at the m idpoint of the posterior arch rather than a spinous process. 4. On the superior aspect of the transverse process of C1, identify the g ro o ve fo r t h e ve rt e b ral art e ry, a sm ooth depression directed posterom edially along the p o st e rio r arch . 5. On the isolated axis (C2) , identify the d e n s , a “toothlike” process extending sup eriorly from the b o d y. 6. On the p osterior aspect of C2, identify the bi d sp in o us p ro ce ss between the two lam in a . 7. On ve rt e b rae C3–C7 , identify the b o d y, the t ran sve rse p ro ce ss wit h t ran sve rse fo ram e n , the lam in a , the g ro o ve fo r a sp in al n e rve , and the sp in o us p ro ce ss of each vertebra. 8. On the articulated skeleton, observe that C7 has the longest cervical spinous process (verteb ra p rom inens) .

Dens Mastoid process

Atlas (C1)

External occipital protuberance

Axis (C2)

Cervical curvature

Hyoid bone Transverse foramen

Vertebra prominens C7 T1

FIGURE 7.1

Cervical vertebrae. Lateral view.

Org an izat io n o f t h e Ne ck To better understand the organization and com partm ents of the neck, study a transverse section through the neck (FIG. 7.2) . 1. Observe that the posterior part of the neck contains the cervical vertebral colum n and the m uscles that m ove it and is surrounded by p re ve rt e b ral fascia . 2. Observe that the anterior part of the neck houses the cervical viscera surrounded by p re t rach e al fascia . 3. Identify the re t ro p h aryn g e al sp ace , the point of sep aration between the p revertebral fascia and p retracheal fascia. The retropharyngeal space is a potential space often referred to as the “danger space” because infections from the head and neck can sp read into this sp ace and pass inferiorly into the p osterior m ediastinum . 4. The cervical viscera include the t h yro id g lan d an d p arat h yro id g lan d s , the laryn x an d t rach e a (the superior parts of the respiratory tract), and the p h aryn x an d e so p h ag us (the superior p arts of the digestive tract). [G 723; L 305; N 26; R 159] Investing (superficial) layer of deep cervical fascia Trachea

Pretracheal fascia

Thyroid gland

Sternohyoid m.

Platysma m.

Sternothyroid m.

Esophagus

Sternocleidomastoid m.

Common carotid artery

Omohyoid m.

Internal jugular vein

Sympathetic trunk

Vagus nerve Carotid sheath Retropharyngeal space Skin Prevertebral fascia

Trapezius m. Cervical vertebra

Superficial fascia

Posterior

FIGURE 7.2 cartilages.

Transverse section through the neck at the level of the second and third tracheal

CHAPTER 7

5. The visceral part of the neck has a p o st e rio r b o un d ary form ed by the cervical vertebrae and an an t e rio r b o un d ary form ed by the thin infrahyoid m uscles (FIG. 7.2) . 6. Th e visceral p art of th e n eck h as a la t e ra l b o u n d a ry form ed b y th e b ilateral SCMs an d a p o st e ro la t e ra l b o u n d a ry form ed b y th e scalen e m uscles b ilaterally. 7. In the cross sectional im age, observe that large vessels and nerves lie lateral to the cervical viscera within the caro t id sh e at h (FIG. 7.2) . Observe that the carotid sheath contains the caro t id art e ry (in t e rn al caro t id art e ry at m ore superior levels), the in t e rn al jug ular vein , and the vag us n e rve . 8. For descriptive purposes, the neck is divided into an anterior triangle and a posterior triangle (FIG. 7.3) . Observe that the p o st e rio r t rian g le o f t h e n e ck is bounded an t e rio rly by the p osterior border of the SCM, p o st e rio rly by the sup erior border of the trapezius m uscle, and in fe rio rly by the m iddle one-third of the clavicle. 9. The posterior triangle has a sup e r cial b o un d ary (ro o f) form ed by the investing layer of the deep cervical fascia and a d e e p b o un d ary ( o o r) form ed b y the m uscles of the neck covered by p revertebral fascia.

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231

Sternocleidomastoid m. Digastric m. Carotid triangle

Submental triangle

Posterior cervical triangle

Submandibular triangle

Trapezius m.

Muscular triangle

Clavicle Omohyoid m.

FIGURE 7.3

Bound aries of the cervical triangles.

Disse ct io n In st ruct io n s Skin Re m o val The skin is thin on the neck and care m ust be taken when rem oving it. 1. Refer to FIGURE 7.4 . 2. Make an anterior m idline skin incision from the chin (F) to the jugular notch of the sternum (E). 3. Make a second skin incision beginning 1 cm superior to the body of the m andible from point F that arches superiorly along the jaw line to a point just anterior to the ear lobe (G). 4. Make a skin incision in the transverse plane from p oint G to the external occip ital p rotuberance (H). If the back has been dissected, part of this incision has been made previously. 5. If the back has not been dissected, m ake a skin incision along the superior border of the trap ezius m uscle from point H to the acrom ion (I). 6. If th e th o rax h as n o t b een d issected , m ake an in cisio n alo n g t h e an t erio r su rface o f th e clavicle fro m p o in t I to th e ju g u lar n o tch o f th e stern u m (E). 7. Beginning at the anterior m idline, re ect the skin in the lateral direction as far as the anterior border of the trapezius m uscle. Detach the skin and place it in the tissue container.

H

G F

E

FIGURE 7.4

I

Skin incisions.

Po st e rio r Trian g le o f t h e Ne ck [G 728; L 297; N 25, 29; R 180] The cutaneous nerves for the shoulder and anterior neck pass to the surface through the posterior triangle of the neck. Therefore, these structures are dissected with the posterior cervical triangle even though they m ay distribute

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Skin Superficial fascia

Platysma m.

FIGURE 7.5

The platysm a m uscle.

over the shoulder or anterior triangle. Note that the structures identi ed in dissection step s 1 through 10 lie within the sup er cial fascia of the neck. The accessory nerve identi ed in step 11 lies deep to the investing layer of the deep cervical fascia. 1. Identify the p lat ysm a m uscle in the super cial fascia of the neck (FIG. 7.5) . Observe that the p latysm a m uscle is very thin and that it covers the lower part of the posterior triangle. 2. Observe that the platysm a passes super cial to the clavicle as it descends toward its inferior attachm ent in the super cial fascia of the thorax. Note that som e of the structures to be dissected in steps 4 and 5 are in contact with the deep surface of the platysma muscle and care m ust be taken to preserve them (supraclavicular nerves, transverse cervical nerve, external jugular vein).

3. Near the clavicle, raise the m edial inferior border of the platysm a m uscle (FIG. 7.5) . Carefully use sharp dissection to free the platysm a m uscle from the vessels and nerves on its deep surface and re ect the m uscle superiorly as far as the m andible. Leave the platysm a m uscle attached along the body of the m andible. 4. Identify and clean the e xt e rn al jug ular ve in in the sup er cial fascia deep to the platysm a m uscle (FIG. 7.6) . The external jugular vein begins posterior to the angle of the m andible and crosses the super cial surface of the SCM. 5. Follow the external jugular vein inferiorly and observe that about 3 cm superior to the clavicle, it pierces the investing layer of deep cervical fascia (roof of the posterior triangle) to drain into the subclavian vein [G 730; L 306; N 31; R 180]. The external jugular vein will be followed superiorly during the anterior triangle of the neck dissection. 6. Along the posterior border of the SCM, identify the n e rve p o in t o f t h e n e ck, which contains cutaneous nerve branches of the ce rvical p le xus . The cutaneous nerves enter the sup er cial fascia near the m idp oint of the SCM to innervate the skin of the neck and part of the posterior head (FIG. 7.6) . 7. Four cutaneous branches of the cervical plexus will be identi ed beginning with the le sser o ccip it al n e rve (C2) , which parallels the posterior border of the SCM as it passes superiorly. The lesser occipital nerve supplies the part of the scalp that is im m ediately posterior to the ear. 8. Identify and clean the g re at auricular n erve (C2, C3) , which crosses the super cial surface of the SCM parallel to the external jugular vein. The great auricular nerve supplies the skin of the lower part of the ear, the skin over the parotid gland, and an area of skin

Greater occipital n.

Parotid gland

Occipital v. &a.

Posterior division, retromandibular v.

Posterior auricular v. Lesser occipital n. Great auricular n. Investing (superficial) layer of deep cervical fascia

Common facial v. seen through investing layer of fascia Platysma m. (cut) Communicating vein

Accessory n. (XI)

Anterior jugular v.

Transverse cervical n. Supraclavicular nn.

External jugular v. penetrating investing layer of fascia

Trapezius m.

Sternocleidomastoid m.

FIGURE 7.6 Posterior triangle of the neck. The accessory nerve lies deep to the investing layer of deep cervical fascia.

CHAPTER 7

extend ing from the angle of the m andible to the m astoid process. 9. Identify and clean the transverse cervical nerve (C2, C3) , which passes transversely across the SCM and neck. The transverse cervical nerve supplies the skin of the anterior triangle of the neck. If you have trouble nding the transverse cervical nerve, it may have been removed with the platysma muscle. 10. Lastly, identify and clean the sup raclavicular n erves (C3, C4) , which pass inferiorly to innervate the skin over the shoulder. Observe m edial, interm ediate, and lateral branches. 11. Identify the acce sso ry n e rve (CN XI) , which crosses the posterior cervical triangle deep to the investing layer of deep cervical fascia from slightly superior to the m idpoint of the posterior border of the SCM to the superior border of the trapezius m uscle (FIG. 7.6) . The accessory nerve innervates the SCM and the trap ezius m uscle. Note that the accessory nerve is a cranial nerve and thus does not originate from the cervical plexus.

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12. Use blunt dissection to free the accessory nerve from the surrounding connective tissue. Note that branches of spinal nerves C3 and C4 join the accessory nerve in the posterior cervical triangle and these branches provide proprioceptive sensory innervation. If the back has been dissected, con rm that the accessory nerve m ay be found on the deep surface of the trapezius m uscle. 13. The inferior portion of the posterior triangle will be dissected with the root of the neck. CLIN ICA L CORRELATION

Diap h rag m at ic Pain Re fe rre d t o t h e Sh o uld e r The supraclavicular nerves and the phrenic nerve share a com m on origin from spinal cord segm ents C3 and C4. Irritation of the parietal pleura or parietal peritoneum covering the diap hragm p roduces p ain that is carried by the phrenic nerve and referred to the area sup plied by the supraclavicular nerves (shoulder region).

Disse ct io n Fo llo w-up 1. Review FIGURE 7.2 and note that the p latysm a m uscle, external jug ular vein, and cutaneous nerves of the neck are em bedded in the super cial fascia. 2. Recall that the accessory nerve is located deep to the investing layer of deep cervical fascia. 3. Use an atlas illustration to review the relationship of the platysm a m uscle to the cutaneous branches of the cervical p lexus. Note that the transverse cervical nerve crosses the neck deep to the platysm a m uscle but that its branches p ass through the m uscle to reach the skin of the anterior neck. 4. Review the area of distribution of all cutaneous branches of the cervical plexus. 5. Review the course of the accessory nerve. Note that the accessory nerve is super cial in the neck where it is vulnerable to injury by laceration or blunt traum a. 6. Review the course of the occipital artery at the apex of the posterior triangle.

TABLE 7.1

Muscle s o f t h e Po st e rio r Trian g le o f t h e Ne ck

Muscle

Superior Atta chments

Inferior Atta chments

Actions

Innerva tion

Trapezius

Superior nuchal line, external occipital protuberance, ligamentum nuchae, SP C7–T12

Lateral one-third of the clavicle and acromion and spine of scapula

Rotates, elevates (superior part), retracts (middle part), and depresses (inferior part) the scapula

Motor: spinal accessory n. (CN XI) Proprioception: C3–C4

Sternocleidomastoid (SCM)

Mastoid process, lateral half of superior nuchal line

Anterior surface of manubrium of sternum (sternal head), superior surface of medial one-third of clavicle (clavicular head)

Laterally exes the head and rotates face to opposite side (unilateral), extends head (bilateral)

Spinal accessory n. (CN XI)

Platysma

Mandible, skin of the cheek, angle of the mouth, and orbicularis oris muscle

Super cial fascia of the deltoid and pectoral regions

Tenses the skin of the neck, depresses the mandible

Cervical branch of the facial nerve (CN VII)

Abbreviations: C, cervical vertebrae; CN, cranial nerve; n., nerve; SP, spinous process.

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ANTERIOR TRIANGLE OF THE NECK Disse ct io n Ove rvie w The order of dissection will be as follows: The super cial veins of the anterior triangle will be studied. The contents of each subdivision of the anterior triangle will be d issected in the following order: m uscular triangle, subm andibular triangle, subm ental triangle, and carotid triangle. 1. Using FIGURE 7.3 , observe that the an t e rio r t rian g le o f t h e n e ck is bounded m e d ially by the m edian plane of the neck, lat e rally by the anterior border of the SCM, and sup e rio rly by the inferior border of the m andible. [G 739; L 297; N 27; R 177] 2. The anterior triangle has a sup e r cial b o un d ary (ro o f) form ed by the investing layer of the deep cervical fascia and a d ee p b o un d ary ( o o r) form ed by the larynx and pharynx. 3. For descriptive purposes, the anterior triangle is divided by the digastric and om ohyoid m uscles into sm aller triang les: m uscular , caro t id , sub m an d ib ular , and sub m e n t al (FIG. 7.3) .

Bo n e s an d Cart ilag e s o f t h e Ne ck Use an illustration and the cadaver to identify the cartilaginous landm arks that will be used as reference structures (FIG. 7.7) : [G 737; L 307; N 28; R 177] 1. Identify the h yo id b o n e (Gr. hyoideus, U-shaped) at the angle between the oor of the m outh and the superior end of the neck. Note that the hyoid bone is unique in that it does not articulate with another bone. 2. Inferior to the hyoid, identify the t h yro id cart ilag e (Gr. thyreoeides, shield) in the anterior m idline of the neck. On the thyroid cartilage, identify the laryn g e al p ro m in e n ce , or Adam ’s apple, an extension of cartilage dem arking the location of the vocal cords. 3. Identify the t h yro h yo id m e m b ran e stretching between the thyroid cartilage and the hyoid bone. 4. On the tem poral bone, identify the m ast o id p ro ce ss and the st ylo id p ro ce ss . 5. Exam ine the in n e r asp ect o f t h e m an d ib le and identify the d ig ast ric fo ssa , the m yloh yoid lin e , the sub m an d ib ular fo ssa , and the m ylo h yoid g ro ove . [G 641; L 327; N 17; R 52]

Platysma m. (cut) Anterior belly of digastric m. Mylohyoid m. Submandibular gland Stylohyoid m. Posterior belly of digastric m. Hypoglossal n. Carotid sheath Nerve to thyrohyoid m. Thyrohyoid m. Superior belly of omohyoid m.

Mental protuberance Mylohyoid raphe Hyoid bone Thyrohyoid membrane Laryngeal prominence of thyroid cartilage Cricothyroid membrane

Great auricular & transverse cervical nn.

Cricothyroid m.

Sternohyoid m.

Cricoid cartilage

Supraclavicular nn. Inferior belly of omohyoid m.

1st tracheal ring

External jugular v.

Isthmus of thyroid gland

Subclavian v.

Inferior thyroid v.

Sternocleidomastoid m. Sternothyroid m.

FIGURE 7.7

Anterior triangle of the neck.

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Disse ct io n In st ruct io n s

CLIN ICA L CORRELATION

Sup e r cial Fascia [G 739; L 306; N 31; R 176]

Trach e o t o m y Tracheotom y (tracheostom y) is the creation of an op ening into the trachea. As an em ergency op eration, it m ust be perform ed rapidly in cases with sudden obstruction of the airway (e.g., aspiration of a foreig n body, edem a of the larynx, or paralysis of the vocal folds). The opening is m ade in the m idline between the infrahyoid m uscles of the neck.

1. Follow the external jugular vein superiorly and observe that it is form ed by the joining of the posterior division of the re t ro m an d ib ular ve in and the p o st e rio r auricular ve in (FIG. 7.6) . 2. Identify the an t e rio r jug ular ve in in the super cial fascia near the anterior m idline (FIG. 7.6) . Observe that the anterior jugular vein begins near the hyoid b one and courses inferiorly near the m id line of the neck to the sup rasternal region where it penetrates the investing layer of deep cervical fascia. Inferiorly, the anterior jugular vein passes laterally, deep to the SCM, to join the external jugular vein in the root of the neck. 3. Look for a co m m un icat in g ve in connecting the com m on facial vein with the anterior jugular vein along the anterior border of the SCM. This vein, if present, can be very large.

Muscular Trian g le [G 739; L 307, 308; N 28; R 177] The contents of the m uscular t rian g le of the neck are the infrahyoid m uscles, the thyroid gland, and the parathyroid glands. 1. Using FIGURE 7.3 , observe that the m uscular t rian g le is bounded m e d ially by the m edian plane of the neck, sup e ro lat e rally by the sup erior belly of the om ohyoid m uscle, and in fero lat e rally by the anterior border of the SCM. 2. Near the m idline of the neck, use a probe to break through the investing layer of the deep cervical fascia and identify the st e rn o h yo id m uscle (FIG. 7.7) . 3. Use blunt dissection to loosen the m edial border of the sternohyoid m uscle from the structures that lie deep to it. Make an effort not to disrupt the lateral border of the m uscle because the nerves providing m otor innervation enter the m uscle along this edge. 4. Detach the sternohyoid from its inferior attachm ent to the sternum and re ect the m uscle sup eriorly. If the thorax has been dissected previously, the sternohyoid m uscle has already been detached from the sternum . 5. Lateral to the sternohyoid m uscle, identify the sup e rio r b e lly o f t h e o m o h yo id m uscle . 6. Use a probe to raise the m edial border of the superior belly of the om ohyoid m uscle and loosen it from deeper structures. Make an effort to not disrupt the lateral border of the m uscle because the nerves providing m otor innervation enter the m uscle along this edge. 7. Deep to the sternohyoid, identify the st e rn o t h yro id m uscle inferiorly and the t h yro h yo id m uscle superiorly (FIG. 7.7) .

8. The an sa ce rvicalis innervates three of the four infrahyoid m uscles (om ohyoid, sternohyoid, and sternothyroid) and will be identi ed later with the dissection of the carotid sheath. The n e rve t o t h e t h yro h yo id m uscle innervates the thyrohyoid m uscle and will sim ilarly be identi ed at a later stage in the dissection of the neck. 9. Review the attachm ents and actions of the infrahyoid m uscles (see TABLE 7.2). 10. Gently retract the right and left sternothyroid m uscles to widen the gap in the m idline. 11. Identify the laryn g e al p ro m in e n ce in the up per m idline of the neck (FIG. 7.7) . [G 735; L 308; N 31; R 177] 12. Trace your nger along the anterior edge of the thyroid cartilage and palpate the laryngeal prom inence. Continue inferiorly and identify the crico t h yro id lig am e n t . Observe that the cricothyroid ligam ent attaches along the inferior border of the thyroid cartilage and the superior border of the crico id cart ilag e . 13. Inferior to the cricoid cartilage, identify the rst t rach e al rin g and note its proxim ity to the ist h m us o f t h e t h yro id g lan d . Observe that the t h yro id g lan d is positioned bilaterally on either side of the trachea, deep to the sternothyroid m uscle.

Sub m an d ib ular Trian g le [G 739; L 312, 313; N 32; R 185] The contents of the sub m an d ib ular t rian g le are the subm andibular g land, facial artery, facial vein, stylohyoid m uscle, part of the hypoglossal nerve (CN XII), and lym ph nodes. 1. Using FIGURE 7.3 , observe that the sub m an d ib ular t rian g le is bounded sup e rio rly by the inferior border (body) of the m andible, an t e ro in fe rio rly by the anterior belly of the digastric m uscle, and p o st e ro in fe rio rly by the p osterior belly of the digastric m uscle. 2. The subm andibular triangle has a sup e r cial b o un d ary (ro o f) form ed by the investing layer of the d eep cervical fascia and a d e e p b o un d ary ( o o r) form ed by the m ylohyoid and hyoglossus m uscles.

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3. On the cadaver, identify the subm andibular gland and use a probe to de ne its borders (FIG. 7.8) . Note that a portion of the gland extends deep to the posterior border of m ylohyoid m uscle. 4. Elevate the platysm a and identify the facial art e ry and facial ve in crossing over the m argin of the body of the m andible. Observe that the facial artery is m ore tortuous than the facial vein and courses m ore anteriorly (FIG. 7.8) . If visibility of the vessels is lim ited by the platysm a, rem ove the m uscle on one side of the face. 5. Use blunt dissection to separate the facial artery and vein from the subm andibular gland. Observe that the facial vein p asses super cial to the subm andibular g land and follows a relatively straight p ath, whereas the facial artery courses deep to the gland. 6. Preserve the facial vessels and use scissors to rem ove the sup er cial part of the subm andibular g land on one side. Do not disturb the deep part of the gland. 7. Use blunt dissection to clean the super cial surface of the an t e rio r an d p o st erio r b e llie s o f t h e d ig ast ric m uscle (FIG. 7.8) . Observe that the two bellies attach to each other by an in t e rm e d iat e t e n d o n that is attached to the body and the greater horn of the hyoid bone by a brous sling. 8. Identify and clean the st ylo h yo id m uscle located anterior to the posterior belly of the digastric m uscle. Observe that the t e n d on o f t h e st ylo h yo id m uscle attaches to the body of the hyoid bone by stradd ling the interm ediate tendon of the digastric m uscle (FIG. 7.8) . 9. On the lateral aspect of the neck, identify the h yp o g lo ssal n e rve (CN XII) coursing lateral to the carotid arteries. Use a p robe to follow the hyp oglossal nerve through the subm andibular triangle toward

External carotid a. Accessory n. (XI) Hypoglossal n. (XII) Sternocleidomastoid m. (retracted) Internal jugular v. (cut) Internal carotid a. Common facial v. (cut) Lingual a. Greater horn of hyoid bone Internal laryngeal n. Superior laryngeal a. External carotid a. Thyrohyoid membrane Ansa cervicalis: Superior root Inferior root Vagus n. (X) Superior thyroid a. Common carotid a.

FIGURE 7.8

the tongue. Observe that the hypoglossal nerve enters the subm andibular triangle by passing deep to the posterior belly of the d igastric m uscle and then p asses deep to the m ylo h yo id m uscle within the subm andibular triangle to enter the oor of the m outh (FIG. 7.8) .

Sub m e n t al Triang le [G 734; L 307; N 31; R 176] The sub m e n t al t rian g le is an unpaired triangle that crosses the m idline. The contents of the subm ental triangle are the subm ental lym ph nodes. 1. Using FIGURE 7.3 , observe that the sub m e n t al t rian g le is bounded in fe rio rly by the hyoid bone and on the rig h t an d le ft by the anterior bellies of the right and left digastric m uscles. 2. The subm andibular triangle has a sup e r cial b o un d ary (ro o f) form ed by the investing layer of the d eep cervical fascia and a d e e p b o un d ary ( o o r) form ed by the m ylohyoid m uscle. 3. Clean the super cial fascia from the surface of the right and left m ylohyoid m uscles (FIG. 7.7) .

Caro t id Triang le [G 739; L 312, 313; N 32; R 184] The contents of the caro t id t rian g le are the carotid arteries (com m on, internal, and external), som e branches of the external carotid artery, part of the hypoglossal nerve (CN XII), and branches of the vagus nerve (CN X). 1. Using FIGURE 7.3 , observe that the caro t id t rian g le is bounded sup e rio rly by the p osterior belly of the digastric m uscle, in fe ro m e d ially b y the sup erior belly of the om ohyoid m uscle, and in fe ro lat e rally by the anterior border of the SCM.

Posterior belly of digastric m. Stylohyoid m. Facial v. (cut) Facial a. Anterior belly of digastric m. Mylohyoid m. Nerve to thyrohyoid m. Mylohyoid raphe Fibrous sling of digastric m. Hyoid bone Thyrohyoid m. External laryngeal n. Laryngeal prominence Superior belly of omohyoid m. Inferior pharyngeal constrictor m. Sternohyoid m.

Subm andibular and carotid triangles of the neck.

CHAPTER 7

2. Clean the anterior border of the SCM from its inferior attachm ents to the clavicle and sternum to its superior attachm ent on the m astoid process. If the thorax has been dissected previously, the inferior attachm ent of the SCM has been detached. 3. Ob serve th at at its sup erior en d , th e SCM is in con tact with th e p arotid g lan d . Sep arate th e SCM sup eriorly from th e p arotid g lan d usin g sh arp d issection . 4. If the thorax has not been dissected, detach the SCM from the sternum and clavicle cutting as close to the bone as possible. 5. Use blunt dissection to separate the SCM from the investing fascia that lies posterior to it and re ect it superiorly (FIG. 7.8) . While re ecting the SCM, attem pt to conserve the cutaneous b ranches of the cervical plexus that radiate from the p osterior border of the SCM and leave them attached to the cervical vertebral colum n. 6. Use your ngers to free the SCM from the investing fascia as far superiorly as the m astoid process. Doing so will facilitate the future dissection of the parotid region. 7. Find the acce sso ry n e rve (CN XI) where it crosses the deep surface of the SCM near the b ase of the skull and trace it superiorly as far as p ossible. Note that the accessory nerve p asses through the jugular

8.

9.

10.

11.

12.

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foram en to exit the skull but this relationship is too far superior to be seen at this tim e. Palpate the t ip o f t h e g re at e r h o rn o f t h e h yo id b o n e and note the close proxim ity of the h yp o g lo ssal n e rve (CN XII) (FIG. 7.8) . Identify the n e rve t o t h e t h yro h yo id m uscle , which appears to branch from the hypoglossal nerve. Note that nerve to thyrohyoid com es from spinal nerve C1, which travels with the hypoglossal nerve. [G 739; L 313; N 32; R 184] Clean a p ortion of the carotid sheath and identify the sup e rio r ro o t o f t h e an sa ce rvicalis , which travels with the hypoglossal nerve (FIG. 7.8) . The superior root of the ansa cervicalis is m ainly com posed of bers from the anterior ram us of the C1 spinal nerve. Identify the in fe rio r ro o t o f t h e an sa ce rvicalis (anterior ram i of C2, C3), which passes around the lateral side of the carotid sheath and joins the superior root to form a loop (L. ansa , handle) for which the structure is nam ed (FIG. 7.9) . Clean the ansa cervicalis and trace its delicate branches to the lateral borders of the infrahyoid m uscles (FIG. 7.9) . Use a probe to raise the posterior border of the thyrohyoid m uscle and identify the t h yro h yo id m e m b ran e that extends between the thyroid cartilage and the hyoid bone (FIG. 7.8) .

Platysma m. (cut) Facial n. branches Posterior belly of digastric m. External jugular v. (cut) Common facial v. Hypoglossal n. Nerve to thyrohyoid m. Superior root of ansa cervicalis Superior thyroid v. Inferior root of ansa cervicalis Thyrohyoid m. Internal jugular v. &common carotid a. Middle thyroid v. Omohyoid m: Superior belly Inferior belly Fascial sling Sternothyroid m. Sternohyoid m. (cut) Sternocleidomastoid m. (cut)

FIGURE 7.9

THE HEAD AND NECK

The ansa cervicalis.

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14. Identify the in t e rn al b ran ch o f t h e sup e rio r laryn g e al n e rve where it passes through the thyrohyoid m em brane (FIG. 7.8) . The internal branch of the superior laryngeal nerve supp lies sensory bers to the m ucosa of the larynx above the level of the vocal cords. 15. Follow the internal branch of the superior laryng eal nerve superiorly to the point where it joins the e xt e rn al b ran ch o f t h e sup e rio r laryn g e al n e rve to form the sup e rio r laryn g e al n e rve (FIG. 7.10) . Note that the superior laryngeal nerve may be too far superior to be seen at this stage of the dissection. Continue to look for it as you work superiorly in later dissections. 16. Trace the external branch of the superior laryngeal nerve inferiorly and observe that it innervates the cricot h yro id m uscle . Note that the external branch of the sup erior laryngeal nerve also innervates part of the inferior pharyngeal constrictor m uscle. 17. While p reserving the ansa cervicalis, use scissors to op en the caro t id sh e at h . The carotid sheath contains the co m m o n caro t id art e ry, in t e rn al caro t id art e ry, in t e rn al jug ular ve in , and vag us n e rve (CN X) . 1 8 . O b serve th at t h e in t e rn a l ju g u la r ve in is located lateral to th e co m m o n caro tid o r in tern al caro tid artery in t h e caro tid sh eat h ( FIG. 7 .1 1 ) . Use b lu n t d issectio n to sep arate th e in t ern al ju g u lar vein fro m t h e co m m o n an d in t ern al caro t id arteries. 19. Use an illustration and the cadaver to study the largest tributaries of the internal jugular vein, the co m m o n facial ve in , sup e rio r t h yro id ve in , and m id d le t h yro id ve in (FIG. 7.9) . To clear the dissection eld, you m ay rem ove the three tributaries of the internal jugular vein. 20. Near the level of the superior border of the thyroid cartilage, identify the origin of the e xt e rn al caro t id art e ry (FIG. 7.10) . Use blunt dissection to follow the external carotid artery sup eriorly until it passes on the m edial side of (deep to) the posterior belly of the d igastric m uscle (FIG. 7.8) . [G 742; L 314; N 34; R 185] 21. The external carotid artery has six branches in the carotid triangle, although only ve of them will be d issected at this tim e (FIG. 7.10) . Note that each b ranch has a com p anion vein that m ay be rem oved to clear the dissection eld. 22. Beginning inferiorly, identify and clean the sup e rio r t h yro id art e ry arising from the anterior surface of the external carotid artery near the level of the superior horn of the thyroid cartilag e. Follow the superior thyroid artery toward the superior pole of the lobe of the thyroid gland. 23. Identify the sup e rio r laryn g eal art e ry, a branch of the sup erior thyroid artery, which p ierces the thyrohyoid m em brane together with the internal branch of the sup erior laryngeal nerve.

24. Superior to the origin of the superior thyroid artery, off the anterior surface of the external carotid artery, identify the lin g ual art e ry near the level of the greater horn of the hyoid bone (FIG. 7.10) . Note that the lingual artery passes deeply into the m uscles of the tongue and will be isolated during a future dissection. 25. Id entify the fa cia l a rt e ry arising from the anterior surface of the external carotid artery im m ed iately sup erior to the ling ual artery (FIG. 7.10) . Follow the facial artery along its p ath and ob serve that it p asses m ed ial to the p osterior b elly of the d ig astric m uscle and d eep to the sup er cial p art of the sub m and ib ular g land . Recall that the facial artery crosses the inferior b ord er of the m and ib le to enter the face anterior to the corresp onding facial vein. Do not follow it into the face at this tim e. Note that in 20% of cases, the lingual and facial arteries arise from a com m on trunk. 26. On the posterior surface of the external carotid artery, identify the o ccip it al art e ry, which supplies blood to p art of the scalp (FIG. 7.10) . If the suboccip ital region was previously dissected, the distal portion of this vessel was previously identi ed. 27. Superior to the origin of the occip ital artery, identify the p o st e rio r auricular art ery. The posterior auricular artery arises from the posterior surface of the external carotid artery and passes posterior to the ear to supp ly p art of the scalp. Note that this branch m ay not be visible if the SCM was not re ected com p letely in the earlier part of the dissection.

Internal carotid a.

Superficial temporal a.

Vagus nerve (CN X)

Maxillary a.

Inferior vagal ganglion

External carotid a. Pharyngeal branch

Posterior auricular a.

Facial a.

Occipital a.

Lingual a.

Carotid branch

Middle pharyngeal constrictor m.

Superior thyroid a. Carotid sinus

Hyoid bone Thyrohyoid membrane

Superior laryngeal a.

Superior laryngeal n.

Carotid body

Internal laryngeal n.

Vagus nerve (CN X) Inferior pharyngeal constrictor m.

External laryngeal n. Cricothyroid m.

Common carotid a.

Inferior laryngeal n. (ghosted)

Inferior thyroid a.

Inferior laryngeal a.

Thyrocervical trunk

Esophagus

Vertebral a. Right subclavian a.

Tracheal rings Right recurrent laryngeal n. Brachiocephalic trunk

FIGURE 7.10 Branches of the external carotid artery and right vag us nerve (CN X) in the neck.

CHAPTER 7

28. Use blunt dissection to clean the b ifurcat ion of t h e com m on carot id art ery and identify the carot id sin us (FIG. 7.10) , a dilation of the internal carotid artery near its origin. The wall of the carotid sinus contains pressoreceptors (baroreceptors) that m onitor blood pressure. The carotid sinus is innervated by the glossopharyngeal nerve (CN IX) and the vagus nerve (CN X). 29. On the m edial aspect of the carotid bifurcation, m ake an effort to identify the caro t id b o d y (FIG. 7.10) , a sm all m ass of nerve tissue that contains chem oreceptors to m onitor changes in oxygen and carbon dioxide concentration of the blood. The carotid body is innervated by the glossopharyngeal nerve (CN IX) and the vagus nerve (CN X).

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30. The asce n d in g p h aryn g e al art e ry is the sixth branch of the external carotid artery and arises from its m edial surface close to the bifurcation of the com m on carotid artery. Use your ngers to retract the external carotid artery and look for the origin of the ascending pharyngeal artery. Note that the ascending pharyngeal artery is q uite sm all and is often dif cult to see from this orientation. 31. Identify and clean the vag us n e rve (CN X) within the carotid sheath where it lies between and p osterior to the com m on carotid artery and internal jugular vein. To see the vagus nerve, retract the internal jugular vein laterally and the com m on carotid artery m edially.

Disse ct io n Fo llo w-up 1. Replace the SCM and the infrahyoid m uscles in their correct anatom ical positions. Review the attachm ents and actions of the infrahyoid m uscles. 2. Review the cutaneous branches of the cervical plexus. 3. Use the dissected specim en to review the positions of the com m on carotid and internal carotid arteries, internal jugular vein, and vagus nerve within the carotid sheath. 4. Follow each branch of the external carotid artery through the regions dissected, noting their relationships to m uscles, nerves, and glands. 5. Trace the branches of the superior laryngeal nerve inferiorly and note their distribution. 6. Review the course of the hypoglossal nerve. 7. Review the ansa cervicalis and its relationship to the hypoglossal nerve and carotid sheath. 8. Note that the superior laryngeal nerve passes m edial to the internal and external carotid arteries and the hypoglossal nerve p asses lateral to the internal and external carotid arteries.

TABLE 7.2

Muscle s o f t h e An t e rio r Trian g le o f t h e Ne ck

INFRAHYOID MUSCLES Muscle

Superior Atta chments

Inferior Atta chments

Actions

Innerva tion

Sternohyoid

Body of hyoid bone

Posterior surface of manubrium of sternum

Depresses the hyoid

Omohyoid

Inferior border of hyoid bone

Superior border of scapula near suprascapular notch

Depresses and retracts the hyoid

Sternothyroid

Oblique line of the thyroid cartilage

Posterior surface of manubrium of sternum

Depresses thyroid cartilage and larynx

Thyrohyoid

Inferior border of body and greater horn of hyoid

Oblique line of thyroid cartilage

Depresses hyoid and elevates the thyroid cartilage and larynx

C1 via hypoglossal n. (CN XII)

Ansa cervicalis (C1–C3)

SUPRAHYOID MUSCLES Muscle

Superior Atta chments

Inferior Atta chments

Actions

Innerva tion

Digastric

Digastric fossa of mandible (anterior belly)

Mastoid process of the temporal bone (posterior belly)

Elevates hyoid and depresses mandible

Nerve to mylohyoid (CN V3 ) (anterior belly), Facial n. (CN VII) (posterior belly)

Stylohyoid

Styloid process

Body of the hyoid

Elevates hyoid

Facial n. (CN VII)

Mylohyoid

Mylohyoid line of mandible (lateral attachment)

Hyoid bone and the mylohyoid raphe (medial attachment)

Supports the oor of the oral cavity

N. to mylohyoid (CN V3 )

Abbreviations: C, cervical vertebrae; CN, cranial nerve; n., nerve.

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THYROID AND PARATHYROID GLANDS Disse ct io n Ove rvie w The thyroid gland and parathyroid glands lie between the infrahyoid m uscles and the larynx and trachea. [G 744–746; N 76, 78; R 186] The order of dissection will be as follows: The thyroid gland and associated vasculature will be identi ed. The recurrent laryngeal nerve will be identi ed and studied. The parathyroid glands will be identi ed.

Disse ct io n In st ruct io n s

CLIN ICA L CORRELATION

1. Re ect the sternocleidom astoid, sternohyoid, and sternothyroid m uscles superiorly. 2. Identify the t h yro id g lan d [L 308, 309]. The thyroid gland is located at vertebral levels C5–T1. Observe that laterally, the thyroid gland is in contact with the carotid sheath (FIG. 7.11) . 3. Identify the rig h t lo b e and le ft lo b e of the t h yro id g lan d . The two lobes are connected by the ist h m us , which crosses the anterior surface of tracheal rings 2 and 3 (FIG. 7.11) . 4. Frequently, the thyroid gland has a p yram id al lo b e that extends sup eriorly from the isthm us. The pyram id al lobe is a rem nant of em bryonic developm ent that shows the route of descent of the thyroid gland. 5. Identify the sup e rio r t h yro id art e ry where it enters the sup erior end of the thyroid gland lobe (FIG. 7.11) . Recall that the superior thyroid artery is a branch of the external carotid artery. The inferior thyroid artery will be dissected later. 6. Identify the sup erior an d m id d le th yroid vein s, which are tributaries of the internal jugular vein (FIG. 7.11) . Hyoid bone Thyroid cartilage Superior thyroid a. and v. Thyrohyoid &sternothyroid mm. (cut) Cricothyroid m. Cricoid cartilage Left lobe of thyroid gland Pyramidal lobe (inconstant) 1st tracheal ring Middle thyroid v.

Re curre n t Laryn g e al Ne rve If a recurrent laryngeal nerve is injured during thyroidectomy (removal of the thyroid gland) or compressed by a thyroid tumor, paralysis of the laryngeal muscles will occur on the affected side resulting in hoarseness of the voice. 7. Identify the in fe rio r t h yro id ve in s , which descend into the thorax on the anterior surface of the trachea to d rain into the right and left brachiocep halic veins. 8. Look for the t h yro id im a art e ry (L. im a , lowest). When present, the thyroid im a artery enters the thyroid gland inferiorly, near the m idline (FIG. 7.11) . The thyroid im a artery is a relatively rare (published reports p lace the incidence at 2% to 12% of the population) but clinically signi cant variant. 9. Use scissors to cut the isthm us of the thyroid gland . 10. Use blunt dissection to detach the isthm us from the tracheal rings and spread the lobes widely apart. 11. On both sides of the cadaver, use blunt dissection to display the re curre n t laryn g e al n e rve s that p ass im m ediately p osterior to the lobes of the thyroid gland in the groove between the trachea and esophagus. Note the close relationship of the recurrent laryngeal nerve to the thyroid gland. 12. Cut all blood vessels leading to or from the left lobe of the thyroid gland. Use a p robe to free the left lobe from surrounding connective tissue and rem ove it. 13. Exam ine the posterior aspect of the left lobe of the thyroid gland and attem pt to identify the p arat h yroid g lan d s . The parathyroid glands are about 5 m m in diam eter and m ay be darker in color and harder in texture than the thyroid gland. Usually, there are two parathyroid glands on each side of the thyroid gland but the num ber can vary from one to three.

Isthmus of thyroid gland Carotid sheath contents: Common carotid a. Vagus n. (X) Internal jugular v. Subclavian v. Thyroid ima a. Trachea Left inferior thyroid v.

FIGURE 7.11

Relationship s of the thyroid gland.

CLIN ICA L CORRELATION

Parat h yro id Glan d s The parathyroid glands play an im portant role in the regulation of calcium m etabolism . During thyroidectom y, these sm all endocrine glands are in danger of being d am aged or rem oved . To m aintain p roper serum calcium levels without m edication, at least one parathyroid gland m ust be retained during surgery.

CHAPTER 7

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Disse ct io n Fo llo w-up 1. Review the relationship of the thyroid gland to the infrahyoid m uscles, carotid sheaths, larynx, and trachea. 2. Use an illustration and the dissected cadaver to review the blood supply and venous drainage of the thyroid gland. Note that there are only two thyroid arteries on each side (superior and inferior) but there are three thyroid veins (superior, m iddle, and inferior). 3. Review the relationship of the parathyroid glands to the thyroid gland. Use an em bryology textbook to review the origin and m ig ration of the thyroid and p arathyroid glands during developm ent.

ROOT OF THE NECK Disse ct io n Ove rvie w The ro o t (b ase ) o f t h e n e ck is the junction between the thorax and the neck. The root of the neck is an im portant area because it lies superior to the sup e rio r t h o racic ap e rt ure and all structures that p ass between the head and thorax, or the upp er lim b and thorax, m ust pass through the root of the neck. [G 748; L 309; N 33; R 186] The order of dissection will be as follows: The branches of the subclavian artery will be d issected. The course of the vagus and p hrenic nerves will be studied. The m uscles that form the oor of the posterior cervical triangle will be studied. Som e of these structures will be followed sup eriorly or inferiorly beyond the root of the neck.

Disse ct io n In st ruct io n s The clavicle was cut at its m id length and the thoracic wall rem oved during dissection of the thorax. Rem ove the anterior thoracic wall and set it aside. 1. Re ect the sternocleidom astoid, sternohyoid, and sternothyroid m uscles superiorly. 2. Use blunt dissection to clean the in fe rio r b e lly o f t h e o m o h yo id m uscle (FIG. 7.9) . Observe that the inferior belly and superior belly of the om ohyoid are joined by an in t e rm e d iat e t e n d o n b ound to the clavicle by a fascial sling. 3. Review the attachm ents and actions of the om ohyoid m uscle (see TABLE 7.2). 4. Use scissors to cut the fascial sling that binds the interm ediate tendon of the om ohyoid m uscle to the clavicle. 5. Follow the e xt e rn al jug ular vein inferiorly from the upper part of the neck until it passes through the investing layer of deep cervical fascia near the clavicle. Note that the external jugular vein is the only tributary of the subclavian vein (FIG. 7.12) . 6. To expose the blood vessels in the root of the neck, rem ove the investing layer of deep cervical fascia that form s the roof of the lower p art of the posterior cervical triangle. Preserve the external jugular vein while rem oving the investing fascia. 7. Identify the sub clavian ve in and use blunt dissection to loosen it from the surrounding deep structures (FIG. 7.12) . 8. Follow the subclavian vein m edially to the point where it is joined by the in t ern al jug ular vein to form the b rach iocep h alic vein . Note that the vertebra l vein joins the posterior surface of the brachiocephalic vein in the root of the neck but it cannot be seen at this time.

9. Identify the sub clavian art e ry. Observe that the right subclavian artery is a branch of the brachiocephalic trunk and the left subclavian artery is a branch of the aortic arch. [G 750; L 309, 310; N 33; R 172, 186] 10. The subclavian artery has three parts that are de ned by its relationship to the anterior scalene m uscle (FIG. 7.13) . Identify the rst p art of the subclavian artery, from its origin to the m edial border of the anterior scalene m uscle. The rst p art o f t h e sub clavian art e ry has three branches, the vertebral artery, internal thoracic artery, and thyrocervical trunk. 11. Identify the ve rt e b ral art e ry, which courses superiorly between the anterior scalene m uscle and the longus colli m uscle (FIG. 7.13) . Trace the vertebral artery superiorly until it passes into the transverse foram en of vertebra C6. 12. Identify the in t e rn al t h o racic artery, which arises from the anteroinferior surface of the subclavian artery and passes inferiorly to supply the anterior thoracic wall (FIG. 7.13) . 13. Identify the t h yro ce rvical t run k, which arises from the anterosuperior surface of the subclavian artery (FIG. 7.13) . The thyrocervical trunk has three branches nam ed according to their respective paths or targets. 14. Branching off the thyrocervical trunk, identify the t ran sve rse ce rvical art e ry. The transverse cervical artery crosses the root of the neck 2 to 3 cm superior to the clavicle and deep to the om ohyoid m uscle (FIG. 7.12) and sup plies the trapezius. 15. Branching off the thyrocervical trunk, identify the sup rascap ular art e ry (FIG. 7.12) , which p asses laterally and posteriorly to the region of the suprascapular notch. In the shoulder, the suprascapular artery

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Sympathetic trunk

Longus capitis m.

Middle scalene m.

Middle scalene m. Carotid tubercle (C6)

Middle cervical ganglion

Anterior scalene m. Vertebral a.

Anterior scalene m.

Longus colli m.

Inferior cervical/stellate ganglion

Ascending cervical a.

Phrenic n.

Inferior thyroid a. Cervical pleura (cupula)

Right vagus nerve (X, cut)

Transverse cervical a.

Dorsal scapular a.

Dorsal scapular a. (variant)

Brachial plexus

Thyrocervical trunk Suprascapular a.

Right subclavian a.

Left subclavian a.

Right lymphatic duct

Left recurrent laryngeal nerve in tracheo-esophageal groove

Right internal jugular v. (cut)

External jugular v. (cut)

Right subclavian v.

Internal thoracic a.

Right recurrent laryngeal n.

Thoracic duct Left venous angle

Right brachiocephalic v.

Left common carotid a. (cut)

Sternohyoid m.

1st costal cartilage

Trachea and esophagus

Manubrium

FIGURE 7.12

16.

17. 18.

19.

20.

Root of the neck. The clavicles have been rem oved.

passes superior to the transverse scapular ligam ent and supplies the suprasp inatus and infraspinatus m uscles. The last branch off the thyrocervical trunk is the in fe rio r t h yro id art e ry (FIG. 7.12) , which passes m edially toward the thyroid gland. Trace the inferior thyroid artery toward the thyroid gland. Usually, the inferior thyroid artery passes posterior to the ce rvical sym p at h e t ic t run k. Branching off the inferior thyroid artery, ascending in the neck, identify the asce n d in g ce rvical art e ry. Return to the subclavian artery and identify the se co n d p art , which lies posterior to the anterior scalene m uscle. The se co n d p art o f t h e sub clavian art e ry has one branch, the co st o ce rvical t run k, which arises from its posterior surface (FIG. 7.13) . Use your ngers to elevate the subclavian artery from the surface of the rst rib and use blunt dissection to look for the costocervical trunk p assing posteriorly above the cupula of the pleura. The costocervical trunk divid es into the d e e p cervical art e ry and the sup re m e in t e rco st al art e ry. The suprem e intercostal artery gives rise to posterior intercostal arteries 1 and 2. Return to the subclavian artery and identify the t h ird p art between the lateral border of the anterior scalene m uscle and the lateral border of the rst rib.

21. The t h ird p art o f t h e sub clavian art e ry has one branch, the d o rsal scap ular art e ry. The dorsal scapular artery passes between the superior and m iddle trunks of the brachial plexus to supply the m uscles of the scapular region (FIG. 7.13) . Note that in about 30% of cases, the dorsal scapular artery arises from the transverse cervical artery instead of from the subclavian artery. 22. On the left side, nd the t h oracic d uct , which ascends from the thorax into the neck. The thoracic duct is posterior to the esophagus at the level of the superior thoracic aperture and then arches anteriorly and to the left to join the venous system near the left ven ous an g le at the junction of the left sub clavian vein and the left Common carotid artery (cut)

Second part of subclavian artery: Costocervical trunk

Anterior scalene muscle

Third part of subclavian artery: Dorsal scapular artery 3 Axillary artery

2

1

First part of subclavian artery: Vertebral artery Thyrocervical trunk Internal thoracic artery Brachiocephalic trunk

FIGURE 7.13

Branches of the subclavian artery.

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23.

24.

25.

26.

27.

28.

in t ern al jug ular vein (FIG. 7.12) . Note that the thoracic duct is usually a single structure, which has the diam eter of a sm all vein, but it m ay be represented by several sm aller ducts. [G 749; L 309; N 203; R 184] Use an illustration to observe that on the right side of the neck, several sm all lym phatic vessels join with lym ph vessels from the right upper lim b and right side of the thorax to form the rig h t lym p h at ic d uct . Note that the right lym phatic duct drains into the rig h t ve n o us an g le , the junction of the rig h t sub clavian ve in and rig h t in t e rn al jug ular ve in . On both sides of the neck, nd the vag us n e rve (CN X) in the carotid sheath and follow it into the thorax. Recall that the vagus nerve passes posterior to the root of the lung while it descends through the thorax. [G 748; L 309; N 32; R 186] As the right vagus nerve passes anterior to the subclavian artery, it gives off the rig h t re curre n t laryn g e al n e rve (FIG. 7.12) . Sim ilarly, as the left vagus nerve descends on the left side of the thorax anterior to the aortic arch, it gives off the le ft re curre n t laryn g e al n e rve . Follow the right and left recurrent laryngeal nerves superiorly along the lateral surface of the trachea and esophagus as far as the rst tracheal ring. Do not follow them into the larynx at this tim e. Verify that the p h re n ic n e rve crosses the anterior surface of the anterior scalene m uscle (FIG. 7.12) . Recall that the phrenic nerve arises from vertebral levels C3–C5 and innervates the diaphragm . Follow the p hrenic nerve into the thorax and con rm that it passes anterior to the root of the lung along its path to the diap hragm . Identify the cervical portion of the sym p at h e t ic t run k. Note that the in fe rio r ce rvical sym p at h e t ic g an g lio n is located low in the neck, near the superior thoracic aperture, and that the sup e rio r ce rvical sym p at h e t ic g an g lio n is located high in the neck near the level of the m astoid p rocess. Verify that the cervical sym pathetic trunk is continuous with the thoracic sym pathetic trunk.

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29. Exam ine the m uscles that form the oor of the posterior cervical triangle. Identify the sp le n ius cap it is , the le vat o r scap ulae , and the an t erio r , m id d le , and p o st e rio r scale n e m uscle s . [G 749; L 310; N 33; R 187] 30. Use blunt dissection to de ne the borders of the an t e rio r scale n e and m id d le scale n e m uscle s . Follow the anterior and m iddle scalene m uscles inferiorly to observe that they both attach to the rst rib. The rst rib and the adjacent borders of the anterior and m iddle scalene m uscles form the boundaries of the in t e rscale n e t rian g le . 31. Review the attachm ents, actions, and innervations of the scalene m uscles (see TABLE 7.3). 32. Observe that the sub clavian art e ry and the ro o t s o f t h e b rach ial p le xus p ass between the m iddle scalene m uscle and the anterior scalene m uscle (through the interscalene triangle) (FIG. 7.12) . 33. Crossing over the anterior surface of the anterior scalene m uscle, id entify the sub clavian ve in , t ran sve rse ce rvical art e ry, and sup rascap ular art e ry. 34. Use blunt dissection to clean the roots of the b rach ial p lexus at the level of the interscalene triangle. Identify the parts of the sup raclavicular p ortion of the b rach ial p lexus: ve roots, th ree trun ks, and six d ivision s. 35. If the upper lim b has been dissected previously, follow the suprascapular nerve as far laterally as the suprascapular notch where it is joined by the suprascapular artery. CLIN ICA L CORRELATION

In t e rscale n e Trian g le The in t e rscale n e t rian g le becom es clinically im portant when anatom ical variations (additional m uscular slips, an accessory cervical rib, or exostosis on the rst rib) narrow the interval. As a result, the subclavian artery and/ or roots of the brachial plexus m ay be com pressed, producing ischem ia or nerve dysfunction in the upper lim b.

Disse ct io n Fo llo w-up 1 . Rep lace th e an terior th oracic wall in it s correct an atom ical p o sitio n . Rep lace th e in frah yoid m uscles an d SCM in th eir co rrect an ato m ical p o sitio n s. Review t h e b o u n d aries o f th e p o sterio r cervical trian g le. Review th e attach m en ts o f th e in frah yo id m uscles. Review th e d istrib ution of t h e cutan eou s b ran ch es o f th e cervical p lexu s. 2. Rem ove the anterior thoracic wall. Review the origin and course of the brachiocephalic artery, left com m on carotid artery, and left subclavian artery in the sup erior m ediastinum . 3. Review the three parts and branches of the subclavian artery. 4. Review the distribution of the transverse cervical, suprascapular, and dorsal scapular arteries to the super cial m uscles of the back and scapulohum eral m uscles. 5. Use an illustration to review the course of the vertebral artery from its origin on the rst part of the subclavian artery to the cranial cavity.

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TABLE 7.3

GRANT’S DISSECTOR

Scale n e Muscle s

Muscle

Superior Atta chments

Anterior scalene

TP of C4–C6

Middle scalene

Posterior tubercles of TP of C2–C7

Posterior scalene

Posterior tubercles of TP of C4–C6

Inferior Atta chments

Actions

Innerva tion

First rib

Flexes neck, elevates rst rib during inspiration

Anterior rami C4–C6

Second rib

Anterior rami C2–C6

Flexes neck laterally, elevates second rib during inspiration

Anterior rami C7–C8

Abbreviations: C, cervical vertebrae; TP, transverse process.

HEAD The dissection of the head is forem ost a dissection of the course and distribution of the cranial nerves and the branches of the external carotid artery. All of the cranial nerves and m any blood vessels p ass through op enings in the skull. Therefore, the skull is an im portant tool with which to organize the study of the soft tissues of the head and neck. Parts of the skull will be studied as needed, and details will be added as the dissection of the head proceeds.

FACE Disse ct io n Ove rvie w Sensory innervation for the skin of the face is p rovided by three divisions (branches) of the trigem inal nerve (CN V) (FIG. 7.14) . The o p h t h alm ic d ivisio n (V1 ) innervates the skin of the forehead, upp er eyelids, and nose. The m axillary d ivisio n (V2 ) innervates the skin of the lower eyelid, cheek, and up per lip. The m an d ib ular d ivisio n (V3 ) innervates the skin of the lower face and part of the side of the head. Branches of ce rvical sp in al n e rve s 2 an d 3 innervate the skin of the posterior p art of the head (FIG. 7.14) . The g re at e r o ccip it al n e rve innervates the skin of the back of the head as far superiorly as the vertex. The le sse r o ccip it al n e rve innervates the skin behind the ear. The g re at auricular n e rve innervates the skin of the lower part of the ear and skin over the angle of the m andible and lower part of parotid gland. [G 607; L 324; N 2] The m otor innervation to all m uscles of facial expression is provided by the facial n e rve (CN VII) . [G 607; L 324, 325; N 24; R 80] The order of dissection will be as follows: The skin of the face will be rem oved to expose the super cial fascia. The p arotid duct and gland will b e identi ed. Branches of the facial nerve will be identi ed as they em erge from the anterior border of the parotid gland. Several facial m uscles will b e identi ed. Two im portant sphincter m uscles will receive p articular attention: the orbicularis oris (m outh) and the orb icularis oculi (eye). The term inal branches of the three divisions of the trigem inal nerve will be exposed where they em erge from op enings in the skull.

Surface An at o m y The surface anatom y of the face m ay be studied on a living subject or on a cadaver. On the cadaver, xation m ay m ake it dif cult to distinguish bone from well-preserved soft tissues. 1. Place the cadaver in the supine (face up) position. 2. Palpate the ve rt e x of the head, the m ost superior aspect (FIG. 7.15) .

V1

V1

V2

V3

V2 V3

C2,3

C2,3

FIGURE 7.14 and neck.

Cutaneous nerve distribution of the head

Vertex

Supraorbital margin

Zygomatic arch

Nasal bones Zygomatic bone Alveolar process of maxilla Angle of mandible Mental protuberance of mandible

FIGURE 7.15

Surface anatom y of the face.

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3. Superior to the orbit, palpate the sup rao rb it al m arg in and m ake an effort to identify the location of the sup rao rb it al n o t ch . 4. Along the superior aspect of the nose, palpate the transitions between the n asal b on e s and the n asal cart ilag e . 5. Work your ngers inferiorly along the lateral aspect of the nose towards the lips and palpate the alve o lar p ro ce sse s o f t h e m axilla . 6. At the chin, palpate from the m e n t al p ro t ub e ran ce o f t h e m an d ib le along the b o d y o f t h e m an d ib le to the an g le o f t h e m an d ib le . 7. Palpate the zyg o m at ic b o n e at the cheeks and p alpate posterolaterally along the zyg o m at ic arch toward the external ear.

Skull All parts of the skull are fragile, but the bones of the orbit and nasal cavity are exceptionally delicate. Because the m edial wall of the orbit is very easily broken, never hold a skull by placing your ngers into the orbits. Sim ilarly, the sm all bony projections (processes) extending from the inferior surface of the skull can easily be broken by resting the skull on its base without the support of the m andible.

An t e rio r Vie w o f t h e Skull Refer to a skeleton or disarticulated skull to identify the following skeletal features from an anterior view (FIG. 7.16) : [G 584; L 298; N 4; R 22] 1. Exam ine the bony cavity protecting the eye. Superior to the orbit, identify the fro n t al b o n e and observe that it extends superiorly to form the bony sup port of the forehead and posteriorly to form the roof of the orbit. 2. Identify the sup e rciliary arch , a thickened ridge along the superior m argin of the orbit. 3. Observe that right and left superciliary arches contain the sup rao rb it al n o t ch (fo ram e n ) and are separated by a sm all depression, the g lab e lla .

Frontal bone: Glabella Supraorbital notch Superciliary arch

Nasal bone

Nasion

Zygomatic bone Orbital margin

Anterior nasal aperture

Maxilla: Frontal process Infraorbital foramen Anterior nasal spine Alveolar process

Nasal septum

Mandible: Alveolar process Mental foramen Mental protuberance

FIGURE 7.16

The skull. Anterior view.

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4. Inferior to the glabella, identify the n asio n , the junction between the frontal and n asal b o n e s . Observe that the right and left n asal b o n e s form the sup erior extent of the bridge of the nose. 5. Posterior to the nasal bones, identify the thin fron t al p ro ce ss of the m axilla extending superiorly to the frontal bone. 6. On the anterior surface of the m axilla, identify the in frao rb it al fo ram e n and the alve o lar p ro cesse s , the thickened ridges corresponding to the attachm ent sites for the up per dentition (upp er teeth). 7. In the m idline where the m axillae m eet, identify the sm all bony p rojection of the an t e rio r n asal sp in e , oriented anterior and inferior to the n asal se p t um . 8. Observe that the an t e rio r n asal ap e rt ure is bounded by the nasal bones and m axillae. 9. Lateral to the m axillae, near the region of the cheek, identify the right and left zyg o m at ic b o n e s . 10. Observe that the o rb it al m arg in is form ed by three bones (frontal, m axillary, and zyg om atic). 11. Identify the m an d ib le , the jaw, and observe that it has alve o lar p ro ce sse s for the lower dentition (lower teeth). 12. In the m idline of the m andible, identify the m e n t al p ro t ub e ran ce , the thickened ridge m arking the fusion p oint of the right and left p ortions of the m andible during develop m ent. Note that the shape of a p erson’s chin is related to the shap e of the m ental p rotuberance and the bilaterally located ridgelike m e n t al t ub e rcle s . 13. On the anterior surface of the m andible, identify the bilateral openings of the m e n t al fo ram e n . Observe that the m ental foram en is alm ost in a direct line with the infraorbital foram en and the supraorbital foram en. We will see later that these three op enings are the exit points of the cutaneous branches of the trigem inal nerve, which, in addition to other functions, p rovides sensory innervation to the face.

Lat e ral Vie w o f t h e Skull Refer to a skeleton or disarticulated skull to identify the following skeletal features from a lateral view (FIG. 7.17) : [G 586; L 299; N 6; R 21] 1. Posterior to the fro n t al b o n e , identify the paired p arie t al b o n es . Observe that a parietal bone is relatively sm ooth with the exception of the sup e rio r t e m p o ral lin e and in fe rio r t e m p o ral lin e , which dem arcate the superior attachm ent of a large m uscle of m astication, the tem poralis.

Parietal bone: Superior temporal line Inferior temporal line Pterion

Sutures: Coronal Squamosal Lambdoid

Frontal bone

Sphenoid bone: Greater wing

Nasal bone Zygomatic bone: Frontal process Temporal process

Occipital bone: External occipital protuberance Temporal bone: Squamous part External acoustic meatus Mastoid process Zygomatic process

Maxilla

Mandible: Ramus Angle Body

FIGURE 7.17

Mandible

The skull. Lateral view.

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2. The b on es of the skull m eet along im m ovable b rous joints known as sut ure s . Ob serve that the p arietal b ones articulate anteriorly with the frontal b one along the co ro n a l su t u re and p osteriorly with the occip ital bone along the la m b d o id sut ure . 3. On the posterior aspect of the skull, identify the ext e rn al o ccip it al p ro t ub e ran ce along the m idline of the o ccip it al b o n e . The portion of the occipital bone that extends anteriorly along the base of the skull will be studied at a later tim e. 4. On th e lateral asp ect of th e skull, id en tify th e t e m p o ra l b o n e . Ob serve th at th e tem p oral b on e m eets th e p arietal b on e n early alon g th e en tire len g th of th e at p art of th e b on e, th e sq u a m o u s p a rt , alon g th e sq u a m o u s su t u re . Th e oth er p ortio n of th e tem p oral b on e, th e “rocklike” p e t ro u s p a rt , exten d s in to th e cran ial cavity an d will b e seen later. 5. On the lateral aspect of the tem poral bone, identify the opening of the e xt e rn al aco ust ic m e at us . Observe that this opening to the ear is located anterior to the large bony extension of the m ast o id p ro ce ss and p osterior to the zyg o m at ic p ro ce ss extending toward the zygom atic bone. 6. Observe that the zygom atic process of the tem poral bone m eets the t e m p o ral p ro ce ss of the zyg o m at ic b o n e to form the zyg o m at ic arch . Note that the processes forming the arch are nam ed for the bone they are directed at and not the bone from which they originate. 7. Observe that the zygom atic bone has a vertically oriented fro n t al p ro ce ss , sim ilarly nam ed for its extension toward, and articulation with, the frontal bone. 8. In the dep ression of the “tem ple,” identify the g re at e r win g o f t h e sp h e n o id b o n e . 9. Superior to the greater wing of the sphenoid, identify the p t e rio n , the junction of the frontal bone, parietal bone, greater wing of sphenoid bone, and squam ous part of the tem poral bone. The pterion is of clinical im portance because it is a com m on site of fracture putting the patient at risk of hem orrhage because it overlies a key artery inside the skull. 10. From a lateral persp ective, observe that the m an d ib le has a ram us (vertical p ortion) and a b o d y (horizontal portion), which are differentiated by the an g le . 11. Ob serve that the ram us of the m andible sp lits sup eriorly into two p rocesses sep arated by the m an d ib ula r n o t ch . The co ro n o id p ro ce ss is located anteriorly and the co n d ylar (co n d ylo id ) p ro ce ss posteriorly. The condylar process can b e further sub d ivid ed into a h e ad (co n d yle ) and neck. Note that the head of the m andible serves as the site of articulation for the tem p orom andib ular joint (TMJ), the only m oveable joint in the ad ult skull. [G 640; L 327; N 17 ; R 52 ] 12. Follow the b ase (in fe rio r b o rd e r) of the m andibular body anteriorly and con rm that the m e n t al fo ram e n is visible from the lateral perspective.

Sup e rio r Vie w o f t h e Skull Refer to a skeleton or disarticulated skull to identify the following skeletal features from the superior view (FIG. 7.18) : [G 588; L 300; N 9; R 29] 1. Identify the calvaria , the “skull cap,” form ed by parts of the frontal, parietal, and occipital bones connected through sutures. Note that m ost of the sutures of the calvaria are read ily identi able; however, the fro n t al (m e t o p ic) sut ure , which form s between the ossi cation centers of the p aired frontal bones, is usually not seen in the adult. 2. Ob serve th at th e co ro n a l su t u re , th e suture b etween th e fron tal b on e an d th e two p arietal b on es, is p erp en d icular to th e sa g it t a l su t u re , wh ich lies b etween th e two p arietal b o n es. Th e b re g m a is th e p o in t wh ere th e sag ittal an d coron al sutures m eet. 3. On th e p osterior asp ect of th e calvaria, id en tify th e la m b d o id su t u re b etween th e o ccip ital b o n e an d th e two p arietal b on es an d th e la m b d a , th e p oin t wh ere th e sag ittal an d lam b d oid sutures m eet.

Frontal bone Bregma Coronal suture

Sagittal suture

Parietal bone

Lambda Lambdoid suture

FIGURE 7.18

Occipital bone

Superior view of the calvaria of the skull.

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Disse ct io n In st ruct io n s Skin In cisio n s The skin of the face is very thin and rmly attached to the cartilage of the nose and ears, but it is m obile over other parts of the face. The mobility of the skin permits the muscles of facial expression to move the skin. The m uscles of facial expression are attached to the skin super cially and the bones of the skull deeply. The muscles of facial expression not only express emotion and assist in comm unication but also act as sphincters and dilators for the openings of the eyes, m outh, and nostrils. 1. Refer to FIGURE 7.19 . 2. In the m idline, m ake a shallow (2 m m ) skin incision that begins near the vertex, at a point superior to the forehead, above the level of the hairline (A) that p asses inferiorly to the nasion (B). 3. From the nasion, continue the m idline incision inferiorly along the bridge of the nose to a point just superior to the upper lip. 4. Encircle the m outh at the m argin of the lips. Make a m idline incision from the inferior border of the lower lip to the m ental protub erance (C). 5. Make an incision from the m ental protuberance (C) along the inferior border of the m andible to a p oint just sup erior to the angle of the m andible (D). If the neck was previously dissected, this incision has already been made. 6. On the lateral surface of the head, m ake a skin incision from the vertex (A) toward the upper p art of the ear. Continue the incision inferiorly by passing anterior to the ear toward the angle of the m andible and connect the vertical incision with the horizontal incision along the m arg in of the m andible (D).

A

B

D

C

FIGURE 7.19

Skin incisions.

7. Starting at the nasion (B), m ake an incision that encircles the orbital m argin. Do not yet rem ove the skin overlying the eyelids because this will be rem oved later. Extend the incision from the lateral angle of the eye to the incision near the ear. 8. Beginning at the m idline, rem ove the skin of the forehead. Note that the skin of the region adheres tightly to the tough subcutaneous connective tissue. Make an effort to leave the connective tissue intact and to not rem ove the thin frontalis m uscle with the skin. 9. Rem ove the skin of the lower face, beginning at the m idline and proceeding laterally. The super cial fascia of the face is thick and contains the m uscles of facial exp ression. 10. Detach the skin along the incision line from the forehead to the angle of the m andible (A to D), and p lace it in the tissue container.

Sup e r cial Fascia an d Facial Ne rve [G 602; L 324, 325; N 3; R 78] The super cial fascia of the face contains the p arotid gland, m uscles of facial expression, branches of the facial nerve (CN VII), branches of the trigem inal nerve (CN V), and branches of the facial artery and vein. The m uscles of facial exp ression are attached to the skin, and thus, these attachm ents were severed during skin rem oval. The goal of this stage of the dissection is to identify som e of the m uscles of facial expression and to follow branches of the facial nerve posteriorly into the parotid gland. Because the deeper dissection of the face will take place on the right side of the cadaver, m ake special effort to clearly identify the following super cial structures on the left. 1. Observe that the superior part of the p lat ysm a m uscle extends into the face along the inferior border of the m andible (FIG. 7.4) . Recall that the inferior attachm ent of the platysm a m uscle is the super cial fascia of the upp er thorax and that it form s a sheet of m uscle covering the anterior neck. Use blunt dissection to de ne the superior attachm ent of the platysm a m uscle on the inferior border of the m andible, skin of the cheek, and angle of the m outh. 2. On the lateral aspect of the face near the angle of the m andible, identify the m asse t e r m uscle . The m asseter is a large m uscle of m astication, not facial exp ression, and will be cleaned at a later stage in the dissection. 3. Identify the p aro t id d uct where it crosses the lateral surface of the m asseter m uscle about 2 cm inferior to the zyg om atic arch (FIG. 7.20) . Ob serve that the parotid duct is approxim ately the diam eter of a probe handle. 4. Use blunt dissection to follow the parotid duct anteriorly just p ast the anterior border of the m asseter m uscle where the duct turns m edially into the cheek.

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Frontalis m.

Orbicularis oculi m. Angular a. &v.

Occipitalis m.

Zygomaticus major m.

Auricular mm.

Anterior margin of parotid gland Facial n. (VII) branches: Posterior auricular Temporal Zygomatic Buccal Marginal mandibular Cervical

Superior labial a. &v. Parotid duct Orbicularis oris m. Buccal n. Buccinator m. Inferior labial a. &v. Depressor anguli oris m.

External jugular v.

Facial v. &a. Platysma m. (cut)

FIGURE 7.20

5.

6.

7. 8.

9.

Dissection of the face and facial nerve.

Note that the parotid duct pierces the buccinator m uscle of the cheek and drains into the oral vestibule lateral to the second m axillary m olar tooth. The rem aining anterior portion of the duct will be cleaned at a later stage in the dissection. Use blunt dissection to follow the parotid duct posteriorly and identify the anterior m argin of the p aro t id g lan d (FIG. 7.20) [G 603; L 325; N 24; R 78]. Note that in some individuals, an accessory parotid gland is present, which courses anteriorly along the parotid duct. Observe that the parotid gland is enclosed within the p aro t id sh e at h . The parotid sheath and the strom a of the parotid gland (connective tissue, blood vessels, nerves, and ducts) are continuous with the investing layer of the deep cervical fascia. The tough connective tissue surrounding the parotid gland will not yield to blunt dissection, thus scissors or the tip of the scalpel are recom m ended to rem ove this layer. Refer to FIGURE 7.20 and p review the branches of the facial nerve. On the cadaver, identify a b uccal b ran ch o f t h e facial n e rve coursing parallel to the p arotid duct either superiorly or inferiorly. Note that the buccal branch is typically not isolated but rather contains m ultiple branches coursing toward the cheek. Use blunt dissection to follow a buccal branch into the parotid gland, rem oving the p arotid tissue sup ercial to the nerve piece by piece. Within the parotid

10.

11.

12.

13.

14.

15.

gland, the nerve will join other facial nerve branches to form the p aro t id p le xus . From the parotid plexus, follow the other branches perip herally (toward the facial m uscles) beginning superiorly with the t e m p oral branch, which crosses the zygom atic arch. Between the tem poral branch and buccal branch, identify the zyg o m at ic b ran ch crossing the zygom atic bone. Inferior to the buccal branch, identify the m and ib ular b ran ch coursing parallel to the inferior m argin of the m andible and the cervical b ranch crossing the angle of the m andible to enter the neck. The last branch of the facial nerve, the p osterior auricular branch, passes posterior to the ear and will not be seen in this dissection. Follow the parotid plexus branches posteriorly and deeply (below the ear lobe) until they com bine to form a single nerve, the facial n e rve (CN VII) . Note that the facial nerve em erges from the base of the skull through the stylom astoid foram en in the tem poral bone. Do not attem p t to follow it at this tim e. De ne the anterior border of the m asseter m uscle while preserving the parotid duct and branches of the facial nerve. Anterior to the m asseter m uscle, identify the b uccal fat p ad . Rem ove the buccal fat pad and expose the b uccin at o r m uscle . Verify that the p aro t id d uct pierces the buccinator m uscle (FIG. 7.20) .

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16. Coursing on the lateral surface of the buccinator, identify the b uccal (lo n g b uccal) n e rve , a branch of the m andibular division of the trigem inal nerve (CN V3 ) em erging from deep to the m asseter m uscle. The buccal nerve is a sensory nerve that pierces the buccinator m uscle to provide sensory innervation to the m ucosa and skin of the cheek. Recall that m otor innervation to the buccinator m uscle was p rovided by the b uccal b ran ch o f t h e facial n e rve .

Facial Art e ry and Ve in [G 602; L 326; N 3; R 81] The facial artery and vein follow a winding course across the face, and m ay p ass either super cial or deep to the m uscles of facial expression. 1. Find the facial art e ry where it crosses the inferior border of the m andible at the anterior border of the m asseter m uscle (FIG. 7.20) . Observe that the facial artery is m ore tortuous and usually located anterior to the facial vein. Note that at this location, the facial artery and vein are covered only by the p latysm a m uscle and skin. 2. On the right side of the face, if not already done, cut the platysm a m uscle along the inferior b order of the m andible while preserving the facial vessels. Detach the platysm a from the angle of the m outh and p lace it in the tissue container. 3. Follow the facial artery inferiorly and recall that it p asses deep to the subm andibular gland in the neck then becom es super cial where it crosses the inferior b ord er of the m andible. 4. Follow the facial vein inferiorly and recall that it p asses super cial to the subm andibular gland in the neck. The facial vein m ay have been cut when a p ortion of the gland was rem oved earlier. 5. Use blunt dissection to trace the facial artery superiorly toward the angle of the m outh, and identify the in fe rio r lab ial and sup e rio r lab ial art e rie s arising from the facial artery (FIG. 7.20) . Observe that the facial artery has several loops or bends in this part of its course. 6. Continue to trace the facial artery superiorly as far as the lateral side of the nose, where its nam e changes to an g ular art e ry. 7. Use an illustration or the cadaver to observe that the facial ve in receives tributaries that correspond to the branches of the facial artery. The angular vein has a clinically im p ortant anastom otic connection with the ophthalm ic veins in the orbit, which will be described when the orbit is dissected.

Muscle s Aro un d t h e Orb it al Op e n in g [G 602; L 324, 325; N 25; R 60] 1. Carefully rem ove the skin of the up per and lower eyelids (FIG. 7.19) . Care m ust be taken because the skin

Epicranial aponeurosis Frontal belly of occipitofrontalis m.

Supraorbital nerve

Infraorbital nerve Levator anguli oris m.

Orbital part Palpebral part

Orbicularis oculi m.

Levator labii superioris alaeque nasi m. Nasalis m. Levator labii superioris m. Zygomaticus minor m. Zygomaticus major m.

Buccinator m.

Orbicularis oris m.

Mental nerve

Platysma m. Depressor anguli oris m. Depressor labii inferioris m. Mentalis m.

FIGURE 7.21

Muscles of facial expression.

of the eyelids is the thinnest skin in the body at only 1 to 2 m m in thickness. 2. Id en tify th e o rb icu la ris o cu li m u scle , wh ich en circles th e p a lp e b ra l ssu re (op en in g of th e eyelid ) (FIG. 7.21) . Th e o rb it a l p a rt of th e orb icularis oculi m uscle surroun d s th e orb ital m arg in an d is resp on sib le for th e tig h t closure of th e eyelid . Th e p a lp e b ra l p a rt , a th in n er p ortion , is con tain ed in th e eyelid s an d is resp on sib le for b lin kin g . 3. Review the attachm ents and actions of the orbicularis oculi m uscle (see TABLE 7.4).

Muscle s Aro un d t h e Oral Op e n in g [G 602, 606; L 324, 325; N 25; R 60] 1. Several m uscles alter the shape of the m outh and lips. Superior to the upper lip, use blunt dissection to de ne the borders of the levat o r lab ii sup e rio ris m uscle and the zyg o m at icus m ajo r m uscle (FIG. 7.21) . 2. Identify the orb icularis o ris m uscle , both superior and inferior portions, which surrounds the opening of the oral cavity. 3. Inferior to the lower lip, use blunt dissection to de ne the borders of the d e p re sso r an g uli o ris m uscle and the d e p re sso r lab ii in fe rio ris m uscle . 4. Open the oral cavity and palpate the thickness of the b uccin at o r m uscle lining the cheek. Recall that the buccinator m uscle is a m uscle of facial exp ression and contributes to the actions of whistling, sucking, and blowing. Additionally, the buccinator assists m astication by p roviding tension to hold food between the teeth.

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Facial Ne rve Bell’s palsy is a sudden loss of control of the m uscles of facial expression on one side of the face caused by injury to the facial nerve. The patient presents with drooping of the m outh and inability to close the eyelid on the affected side.

V2

V1

Zygomaticotemporal n.

Supraorbital n. Supratrochlear n.

Zygomaticofacial n.

Infratrochlear n.

Infraorbital n.

External nasal n. Lacrimal n.

5. Review the attachm ents, actions, and innervations of the m uscles of facial expression (see TABLE 7.4).

Se n so ry Ne rve s o f t h e Face [G 606; L 324; N 2; R 71] 1. Refer to FIGURE 7.22 and note that three branches of the trigem inal nerve sup ply sensory innervation to the face (FIG. 7.22) . 2. Observe that the sup rao rb it al n e rve , a branch of the ophthalm ic division of the trigem inal nerve (CN V1 ), p asses through the supraorbital notch (foram en) of the frontal bone to reach the skin above the eye. The supraorbital nerve will be seen in the cadaver when the scalp is studied. 3. The in frao rb it al n e rve , a branch of the m axillary division of the trigem inal nerve (CN V2 ), passes through the infraorbital foram en of the m axilla to supply sensory innervation to the inferior eyelid, side of the nose, and upp er lip . Observe that the infraorbital nerve is covered by the levator labii sup erioris m uscle. 4. On the right side of the face, use blunt dissection to de ne the borders of the levator labii superioris m uscle. 5. Transect the levator labii superioris m uscle close to the infraorbital m argin and re ect it inferiorly to exp ose the infraorbital nerve. 6. Observe that the in frao rb it al art e ry an d ve in also em erge from the infraorbital foram en. 7. The m e n t al n e rve , a branch of the m andibular division of the trigem inal nerve (CN V3 ), em erges from the m ental foram en (L. m entum , chin) of the m andible to supply sensory innervation to the lower lip and chin. Observe that the m ental nerve is covered by the depressor anguli oris m uscle. 8. On the right side of the face, use blunt dissection to de ne the borders of the depressor anguli oris m uscle.

V3 Auriculotemporal n.

V2,3

Buccal n. Mental n.

FIGURE 7.22

Cutaneous nerves of the face.

9. Transect the dep ressor anguli oris m uscle near the angle of the m outh and re ect it inferiorly to exp ose the m ental nerve. 10. Observe that the m e n t al art e ry an d ve in also em erge from the m ental foram en. 11. Several sm aller branches of the trigem inal nerve (lacrimal, infratrochlear, zygomaticofacial, zygomaticotemporal, etc.) also innervate the facial region. Do not attempt to dissect these small branches. The auriculotemporal nerve (a branch of CN V3 ) will be dissected later. CLIN ICA L CORRELATION

De n t al An e st h e sia Study the infraorbital foram en and infraorbital canal in the skull. For p urp oses of dental anesthesia, the infraorb ital nerve m ay be in ltrated with anesthetic where it em erges from the infraorbital foram en. The needle is inserted through the oral m ucosa deep to the upper lip and then directed superiorly.

Disse ct io n Fo llo w-up 1. Use the dissected specim en to trace the branches of the facial nerve from the parotid plexus to the m uscles of facial exp ression. 2. Review the attachm ents, action, and innervation of each m uscle that was identi ed in this dissection. 3. Use a skull and the dissected specim en to review the branches of the trigem inal nerve that were dissected and the op enings in the bones that they pass through. 4. Use an illustration and the dissected specim en to review the origin and course of the facial artery and vein.

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TABLE 7.4

GRANT’S DISSECTOR

Main Muscle s o f Facial Exp re ssio n

Muscle

Media l Atta chments

La tera l Atta chments

Actions

Innerva tion

Orbicularis oculi

Medial orbital margin, medial palpebral ligament, and lacrimal bone

Skin around the orbital margin

Tightly closes the eye (orbital part) Blinking (palpebral part)

Levator labii superioris

Upper lip (inferior attachment)

Maxilla just below the orbital margin (superior attachment)

Elevates upper lip

Zygomaticus major

Angle of the mouth

Zygomatic bone

Draws angle of mouth superiorly and posteriorly

Orbicularis oris

Maxilla, mandible, and skin in the median plane

Angle of the mouth

Sphincter of the mouth

Buccinator

Angle of the mouth

Pterygomandibular raphe and the lateral surfaces of the alveolar processes of the maxilla and mandible

Compresses cheek against molar teeth, keeping food on the occlusal surfaces during chewing

Depressor anguli oris

Angle of the mouth

Depressor labii inferioris

Lower lip (superior attachment)

Facial n. (CN VII)

Depresses the angle of the mouth Mandible

Depresses lower lip

Abbreviations: CN, cranial nerve; n., nerve.

PAROTID REGION Disse ct io n Ove rvie w The p arotid region is the area on the side of the face anterior to the ear and inferior to the zygom atic arch. The parotid bed is the area occupied by the parotid gland. The parotid gland develops as an evagination of the oral m ucosa. The parotid gland surrounds the posterior edge of the ram us of the m andible and therefore is in close contact with nerves, vessels, m uscles, bones, and ligam ents in the region. The super cial portion of the parotid gland was rem oved to expose the branches of the facial nerve. The goal of this dissection is to rem ove the rem ainder of the p arotid gland piece by piece, preserving the nerves and vessels that pass through it. The order of dissection will be as follows: The branches Greater wing of sphenoid bone of the facial nerve will be reviewed and followed posteriorly Zygomatic bone Temporal bone: toward the stylom astoid foram en. The m otor root of the faMaxilla cial nerve will be transected near the lobe of the ear and the Articular tubercle parotid plexus and its branches will be re ected anteriorly. Mandibular fossa The retrom andibular vein will then be followed superiorly External acoustic meatus through the parotid gland as the parotid tissue that lies suStyloid process per cial to it is rem oved. The external carotid artery will then Stylomastoid foramen be followed superiorly as additional parotid tissue is rem oved. Rem nants of the parotid gland that adhere to the posterior Mastoid process belly of the digastric m uscle and anterior border of the SCM will be removed in a nal cleanup step.

Ske le t o n o f t h e Paro t id Re g io n Refer to a skeleton or disarticulated skull to identify the following skeletal features (FIG. 7.23) :

Mandible: Head Neck Angle Ramus

Te m p o ral Bo n e [G 640; L 327; N 6; R 21] 1. On the inferior aspect of the tem poral bone, identify the depression of the m an d ib ular fo ssa . The m andibular fossa serves as the socket for the TMJ.

FIGURE 7.23

Skeleton of the parotid region. Lateral view.

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2. Posterior to the m andibular fossa, identify the opening of the e xt e rn al aco ust ic m e at us . 3. Medial to the m andibular fossa, identify the st ylo id p ro cess , a thin bony extension nam ed for its pen-like “stylus” appearance. 4. Posterior to the external acoustic m eatus, and posterolateral to the styloid process, identify the large round m ass of the m ast o id p ro ce ss . 5. Between the styloid and m astoid processes, identify the st ylo m ast o id fo ram e n , the exit point of the facial nerve (CN VII) at the base of the skull.

Man d ib le [G 630; L 327; N 17; R 52] 1. On the m andible, review the location of the ram us , an g le , n e ck and h e ad .

Bo un d arie s o f t h e Paro t id Be d [G 638; L 326; N 34; R 79] Refer to a skull with an articulated m andible and an illustration to identify the boundaries of the parotid bed (FIG. 7.24) : 1. Identify the p o st e rio r b o un d ary form ed by the m astoid p rocess and posterior belly of the digastric m uscle. 2. Identify the an t erior b oun d ary form ed by the m edial pterygoid m uscle, ram us of the m andible, and m asseter m uscle. 3. Identify the m e d ial b o un d ary form ed by the styloid process and associated m uscles (stylopharyngeus, styloglossus, and stylohyoid). 4. Identify the p o st e ro sup e rio r b o un d ary form ed by the oor of the external acoustic m eatus.

Auriculotemporal n. Superficial temporal a. &v. Retromandibular v. Posterior auricular v. Posterior division of retromandibular v. External carotid a. Anterior border of sternocleidomastoid m.

Parotid duct Parotid plexus: Temporofacial division Cervicofacial division

External jugular v. Anterior division of retromandibular v.

Masseter m.

Common facial v. Posterior belly of digastric m.

Facial v. Stylohyoid m.

FIGURE 7.24

Disse ct io n In st ruct io n s Perform the following dissection steps on only the right side of the head. Preserve the super cial structures on the left side of the head for review. 1. Id en tify th e g re a t a u ricu la r n e rve wh ere it crosses th e SCM an d n ote th at it en d s over th e an g le of th e m an d ib le. Detach th e g reat auricular n erve sup eriorly an d re ect it in feriorly off th e surface of th e SCM wh ile leavin g it attach ed to th e cervical p lexus. 2. Review the branches of the facial nerve: tem poral, zygom atic, buccal, m andibular, and cervical (FIG. 7.24) . [G 638; L 326; N 24; R 79] 3. Trace the facial nerve branches posteriorly toward the lobe of the ear and again id entify the m ain stem before it divides.

Parotid region.

4. Cut the facial nerve as far posteriorly as possible, leaving a stump emerging from the stylom astoid foramen. Reect the parotid plexus and all of its branches anteriorly. 5. Review the course of the p aro t id d uct . 6. Cut the p arotid duct where it exits the parotid g land and re ect the duct anteriorly leaving its passage through the buccinator m uscle undisturbed. 7. Identify the auriculo t e m p o ral n e rve (FIG. 7.24) , a branch of the m andibular division of the trigem inal nerve (CN V3 ). The auriculotem poral nerve passes b etween the head of the m andible and the external acoustic m eatus and crosses the zygom atic process of the tem poral bone to innervate the skin of the anterior side of the ear and tem poral region. Note that as the auriculotemporal nerve passes through the parotid gland, it delivers postsynaptic parasympathetic nerve bers from the otic ganglion.

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8. In the neck, nd the ext ern al jug ular vein (FIG. 7.24) . Use blunt dissection to follow the external jugular vein superiorly to the point where it is form ed by the joining of the posterior auricular vein and the retrom andibular vein. 9. Use blunt dissection to follow the retrom andibular vein superiorly into the parotid gland. 10. Trace the retrom andibular vein to the p oint where it is form ed by the joining of the m axillary ve in and the sup e r cial t e m p o ral ve in , rem oving parotid tissue as you progress sup eriorly. 11. Follow the sup e r cial t e m p o ral ve in superiorly until it crosses the super cial surface of the zygom atic arch, continuing to rem ove the parotid gland as you p roceed. The intent is to com pletely rem ove the p arotid tissue from the veins and adjacent structures (m andible and m asseter m uscle). Do not follow the m axillary vein at this tim e because it will be dissected later. 12. Return to the neck and nd the e xt e rn al caro t id art e ry (FIG. 7.24) [G 639; L 313, 314; N 34; R 81]. Use blunt dissection to follow the external carotid artery superiorly as far as the angle of the m andible, rem oving the lower p art of the p arotid gland . 13. Use an illustration to verify that the external carotid artery passes superiorly along the posterior edge of the ram us of the m andible (FIG. 7.24) , and near the neck of the m andible, it divides into its two term inal branches, the m axillary art e ry and the sup e r cial t e m p o ral art e ry. It will not be possible to follow the external carotid artery deep to the p osterior border of the m andible at this tim e because the retrom andibular vein lies sup er cial to it. 14. On th e lateral asp ect of th e h ead , id entify and clean th e su p e r cia l t e m p o ra l artery wh ere it

15.

16.

17.

18.

crosses the zyg om atic p rocess of the tem p oral b one just an terior to the extern al acoustic m eatus (FIG. 7.24) . Ob serve th at at this location , th e sup er cial tem p oral artery is an terior to th e auriculotem p oral n erve. Clean one or two of the branches of the super cial tem p oral artery and observe its distribution to the lateral p art of the scalp. Rem ove any rem aining p arotid tissue from the zyg om atic arch and lateral surface of the m asseter m uscle. Follow the p o st e rio r b e lly of the digastric m uscle and the st ylo h yo id m uscle superiorly toward the base of the skull and clean away any parotid tissue that rem ains on their anterior borders or lateral surfaces. Expose the digastric m uscle all the way to its attachm ent on the m astoid process. Return to the neck and identify the SCM . Preserve the posterior division of the retrom and ibular vein but rem ove all parotid tissue and the investing layer of deep cervical fascia that binds the SCM to deeper structures.

CLIN ICA L CORRELATION

Paro t id Glan d Because of the close relationship between the parotid gland and the external acoustic m eatus, swelling of the parotid gland (as occurs in m um ps) pushes the ear lobe superiorly and laterally and m ay cause com pression of the facial nerve. During parotidectom y (surgical excision of the parotid gland), the facial nerve is in danger of being injured. If the facial nerve is dam aged, the facial m uscles are p aralyzed.

Disse ct io n Fo llo w-up 1. Replace the facial nerve in its correct anatom ical position and approxim ate the cut ends. 2. Replace the parotid duct in its correct anatom ical position. 3. Use an illustration, a skull, and the dissected cadaver to review the course of the facial nerve from the internal acoustic m eatus to the facial m uscles. 4. Review the super cial venous drainage of the lateral side of the head and neck, beginning with the super cial tem p oral veins and ending with the subclavian vein in the root of the neck. 5. Review the origin, course, and branches of the external carotid artery. 6. Review the boundaries of the parotid bed.

SCALP Disse ct io n Ove rvie w The scalp consists of ve layers, three of which are rm ly bound together. The rst layer, or m ost super cial layer, of the scalp is the Skin . Deep to the skin, dense subcutaneous Co n n e ct ive t issue containing the vessels and nerves of the scalp

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form s the second layer. The third layer of the scalp is the Ap o n e uro sis (epicranial ap oneurosis) connecting the frontal belly to the occipital belly of the occipitofrontalis m uscle. These three layers are tightly bound to each other. Deep to the epicranial aponeurosis is the fourth layer form ed by Lo o se co n n e ct ive t issue that perm its the scalp to m ove over the skull. The fth and last layer is the Pe ricran ium or periosteum of the cranial bones. As an aid to m em ory, note that the rst letters of the nam es of the ve layers spell the word scalp . [G 612; L 344; R 87] The order of dissection will be as follows: The ve layers of the scalp will be re ected as one. The m uscles of the scalp will be exam ined on the cut surface of the scalp.

Disse ct io n In st ruct io n s

Epicranial aponeurosis

The following cuts should be m ade through the entire thickness of the scalp and the scalpel should contact the bone of the calvaria. 1. Refer to FIGURE 7.25 . 2. Make a m idline cut from the nasion (C) through the vertex (A) to the external occipital protuberance (G). If the face was previously dissected, a portion of this cut was already made. 3. Make a cut in the coronal plane bilaterally from the vertex (A) to a point anterior to the ear (D). If the face was previously dissected, a portion of this cut was m ade previously. 4. Beg in n in g at th e vertex, use forcep s to g rasp on e corn er of th e cut scalp an d in sert a ch isel b etween th e scalp an d th e calvaria. Use th e ch isel to loosen th e scalp from th e calvaria an d raise th e ap s of skin . 5. Once the ap of scalp is raised, grasp the ap with b oth hands and pull it inferiorly.

A

C D

G

Superior temporal line Frontal belly of occipitofrontalis (frontalis)

Temporalis

Orbicularis oculi Occipital belly of occipitofrontalis (occipitalis) Flap of scalp Flaps of scalp Auricularis muscles

FIGURE 7.26

How to re ect the scalp.

6. Re ect (do not rem ove) all four ap s of scalp d own to the level that a hatband would occupy (FIG. 7.26) but do not yet detach the aps. 7. Exam in e th e cut ed g e of th e scalp an d id en tify th e o ccip it o fro n t a lis m u scle (FIG. 7.26) . Ob serve th at the in ferior attach m en t of th e occip ital b elly is th e occip ital b on e an d its sup erior attach m en t is th e e p icra n ia l a p o n e u ro sis . Sim ilarly, ob serve th at th e sup erior attach m en t of th e fron tal b elly is th e ep icran ial ap on eurosis an d its in ferior attach m en t is th e skin of th e foreh ead an d eyeb rows. Both m uscle b ellies are in n ervated b y th e facial CLIN ICA L CO RRELATIO N

FIGURE 7.25

Scalp incisions.

Scalp The connective tissue layer of the scalp contains collagen bers that attach to the external surface of the blood vessels. When a blood vessel of the scalp is cut, the connective tissue holds the lumen open, resulting in profuse bleeding. If an infection occurs in the scalp , it can spread within the loose connective tissue layer. Therefore, the loose connective tissue layer is often called the “danger area.” From the “danger area,” the infection m ay pass into the cranial cavity through em issary veins.

256

8.

9.

1 0.

11.

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GRANT’S DISSECTOR

n erve (CN VII). [G 6 0 5 , 6 1 0 ; L 3 2 5 ; N 2 , 3 , 2 5 ; R 61, 65] Pull th e an terior scalp ap in feriorly to exp ose th e sup raorb ital m arg in . Id en tify th e su p ra o rb it a l n e r ve a n d ve sse ls wh ere th ey exit th e sup raorb ital n otch an d en ter th e d eep surface of th e scalp (FIG. 7.27) . Use an illustration to observe that nerves and vessels are contained within the aps of the scalp and enter the scalp from m ore inferior regions. On th e lateral surface of th e calvaria, n ote th at th e scalp h as sep arated from th e fascia th at covers th e t e m p o ra lis m u scle (t e m p o ra l m u scle ) (FIG. 7.26) . Carefully separate the layers of the scalp super cial to the occipitofrontalis m uscle and epicranial aponeurosis, m aking an effort to preserve the branches of the super cial tem poral artery and auriculotem poral nerve. Rem ove the sup er cial layers of the scalp (skin and dense connective tissue) from the dissection eld and place them in the tissue container.

Supratrochlear, V1 Supraorbital, V1

Supratrochlear Supraorbital

Zygomaticotemporal, V2

Auriculotemporal, V3

Superficial temporal

Posterior auricular

Lesser occipital, C2, C3

Greater occipital, C2

FIGURE 7.27

Occipital

Cutaneous nerves and blood vessels of the scalp.

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Replace the aps of rem aining scalp in their correct anatom ical positions. Use an illustration to review the course of nerves and vessels that supply the scalp. Use a skull and the dissected sp ecim en to review the course of the supraorbital nerve through the supraorbital notch. Use an illustration to study the course of the greater occipital nerve from the posterior cervical region to the posterior surface of the head. 5. Recall the attachm ents of the occipitofrontalis m uscle and review its two bellies in the sagittal scalp cut.

TEMPORAL REGION Disse ct io n Ove rvie w The tem p oral reg ion consists of two fossae: tem poral and infratem poral. The t em p oral fossa is located superior to the zygom atic arch and contains the tem poralis m uscle. The in frat em p oral fossa is inferior to the zygom atic arch and deep to the ram us of the m andible. The infratem poral fossa contains the m edial and lateral pterygoid m uscles, branches of the m andibular division of the trigem inal nerve (CN V3 ), and the m axillary vessels and their branches. The infratem poral and tem poral fossae are in open com m unication with each other through the area between the zygom atic arch and the lateral surface of the skull. The order of dissection will be as follows: The m asseter m uscle will be studied. The zygom atic arch will be detached, and the m asseter m uscle will be re ected inferiorly with the attached arch. The tem poralis m uscle will be studied. The coronoid process will be detached from the m andible, and the tem poralis m uscle will be re ected sup eriorly with the attached coronoid. The superior part of the ram us of the m andible will be rem oved, and the m axillary artery will be traced across the infratem poral fossa. The branches of the m andibular division of the trigem inal nerve will be dissected . The m edial and lateral pterygoid m uscles will be studied and the TMJ will be dissected.

Ske le t o n o f t h e Te m p o ral Re g io n Refer to a disarticulated m andible to identify the following skeletal features (FIG. 7.28) :

Man d ib le [G 640; L 327; N 17; R 52] 1. From a lateral view of the m andible, review the location of the b o d y, an g le , ram us , h e ad (co n d yle ) , n e ck, m an d ib ular n o t ch , and coro n o id p ro ce ss (FIG. 7.28A) .

CHAPTER 7 Mandibular condyle (head)

THE HEAD AND NECK

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257

Head

Mandibular notch Coronoid process

Coronoid process

Neck

Neck Lingula Mandibular foramen

Mylohyoid line

Ramus

Mylohyoid groove Attachment of medial pterygoid

Angle

Submandibular fossa(e)

A Lateral view

Body Mental foramen

Superior and inferior mental (genial) spines

B Medial view

Digastric fossa

FIGURE 7.28

Mandible. A. External surface. B. Internal surface.

2. On the internal surface of the ram us of the m andible, identify the sm all projection of the lin g ula , the inferior attachm ent site of the sphenom andibular ligam ent (FIG. 7.28B) . 3. Posterior to the lingual, identify the opening of the m an d ib ular fo ram e n , a passage for the inferior alveolar nerves and vessels to the lower dentition. 4. On the inner surface of the body of the m andible beginning at the m andibular foram en, identify the m ylo h yo id g ro o ve , a thin depression for the nerve to m ylohyoid and m ylohyoid vessels (FIG. 7.28B) .

Skull [G 641; L 327; N 6] On a skull with the m andible rem oved, review the following skeletal features (FIG. 7.29) : 1. From a lateral perspective, identify the sup e rio r an d in fe rio r t em p o ral lin es on the parietal bone. [G 640; L 327; N 6; R 21] 2. Observe that the t e m p o ral fo ssa is form ed by parts of four cranial bones: p arietal, frontal, sq uam ous part of tem p oral, and greater wing of sp henoid. Recall that the junction point of these bones form s the p t e rio n . 3. Review that the zyg o m at ic arch is form ed by t h e zyg o m at ic p ro ce ss o f t h e t e m p o ral b on e and the t em p o ral p ro ce ss o f t h e zyg o m at ic b o n e . 4. Review the location of the m an d ib ular fo ssa and the art icular t ub e rcle on the tem p oral bone. 5. Deep to the zygom atic arch, identify the p t e ryg o m axillary ssure between the lat e ral p lat e o f t h e p t e ryg o id p ro ce ss of the sphenoid bone and the m axilla . 6. Carefully insert a thin wooden stick, or pipe cleaner, through the superior end of the pterygom axillary ssure into the sp ace of the p t e ryg o p alat in e fo ssa . 7. On the m edial wall of the pterygop alatine fossa, identify the opening of the sp h e n o p alat in e fo ram e n . Carefully pass the p ipe cleaner through the sphenoSphenoid bone: palatine foram en and observe from an anterior view Greater wing Pterygomaxillary that this opening connects the nasal cavity to the fissure Lateral plate of pterygopalatine fossa. pterygoid process Inferior orbital 8. Anterior to the p terygom axillary ssure, observe that fissure the m axilla has an in frat e m p o ral surface inferior Temporal bone: Infratemporal to the in fe rio r o rb it al ssure , a gap between the External acoustic surface of maxilla meatus greater wing of the sphenoid bone and the m axilla. Mandibular fossa Pass the pipe cleaner through the inferior orbital Styloid process ssure and observe that this opening connects the infratem poral fossa to the orbit. Foramen spinosum Sphenopalatine foramen 9. From an inferior or superior p ersp ective, observe that Foramen ovale Pterygopalatine fossa the g re at e r win g o f t h e sp h e n o id b o n e contains the fo ram e n o vale and the fo ram e n sp in o sum . FIGURE 7.29 Skeleton of the infratem poral region.

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10. Reposition the m andible on the skull and identify the b o n y b o un d arie s o f t h e in frat e m p o ral fo ssa beginning with the lat e ral b o un d ary form ed by the ram us of the m andible. 11. Observe that the infratem poral fossa has an an t e rio r b o un d ary form ed by the infratem poral surface of the m axilla and a m e d ial b oun d ary form ed by the lateral plate of the pterygoid p rocess. 12. Observe that the ro o f of the infratem poral fossa is form ed by the curvature of the greater wing of the sp henoid bone curving out superior to the space.

Disse ct io n In st ruct io n s Masse t e r Muscle an d Re m o val o f t h e Zyg o m at ic Arch Perform the following dissection steps on only the right side of the head. Preserve the super cial structures on the left side of the head for review. 1. Re ect the facial nerve branches and the parotid duct anteriorly. 2. Clean the lateral surface of the m asse t er m uscle and de ne its borders inferiorly along the ram us of the m andible and superiorly along the inferior border of the zygom atic arch. [G 642; L 328; N 48; R 56] 3. Review the attachm ents and actions of the m asseter m uscle (see TABLE 7.5). 4. Review th e course of th e sup er cial tem p oral vessels an d auriculotem p oral n erve across th e zyg om atic arch . Detach th e an terior scalp ap from th e reg ion of th e zyg om atic arch , takin g care to p reserve th e vessels an d n erves wh ere th ey cross th e arch . 5. Make a vertical incision through the tem poral fascia and use a probe or your nger to elevate a portion of the tem poral fascia from the surface of the m uscle. Observe that the tem poralis m uscle is attached to the deep surface of the tem poral fascia. 6. Cut through the tem poral fascia along the superior tem p oral line and re ect it inferiorly. Because the tem p oralis is tightly ad hered to the fascia, it m ay be necessary to use a scalpel to cut the fascia from the surface of the m uscle. 7. Cut the tem poral fascia along the superior border of the zygom atic arch to rem ove it from the dissection eld. 8. Near the anterior end of the zygom atic arch, insert a probe deep to the zygom atic arch as close to the orbit as possible (FIG. 7.30) . The probe should follow a slightly obliq ue path if inserted properly. 9. Use a saw to cut th roug h th e zyg om atic b on e alon g th e ob liq ue lin e p arallelin g th e p rob e. Wear eye protection for all steps that require the use of a bone saw. 10. Insert the p robe d eep to the zygom atic arch near the anterior border of the head of the m andible (FIG. 7.30) .

11. Use a saw to cut through the zygom atic arch posteriorly in a line p arallel to the probe. 1 2 . Gently p ull th e m asseter m uscle and th e attached p ortion of th e zyg om atic arch laterally an d in feriorly and look for the m a sse t e ric ve sse ls a n d n e rve crossin g sup erior to th e m an d ib ular n otch, en tering th e d eep surface of the m asseter m uscle. 13. Re ect the m asseter and zygom atic arch in the inferior direction and cut through the m asseteric nerve and vessels. Use a scalpel to detach the m asseter m uscle from the superior part of the ram us of the m andible but leave the m asseter m uscle attached to m and ible near the angle.

Te m p o ral Re g io n [G 642; L 328; N 48] 1. Use a skull to review the skeletal boundaries of the tem p oral fossa. 2. On the right side of the cadaver, identify the t e m p oralis (t e m p o ral) m uscle . 3. Rem ove the overlying fascia and connective tissue to clean the inferior attachm ent of the tem poralis to the coronoid process of the m andible.

Cut 2

Zygomatic process of temporal bone

FIGURE 7.30

Cut 1

Temporal process of zygomatic bone

How to cut the zygom atic arch.

CHAPTER 7

4. On the left side of the cadaver, observe that the sup e r cial b o un d ary of the tem poral region is the t e m p o ral fascia . 5. Review the attachm ents and actions of the tem p oralis m uscle (TABLE 7.5).

In frat e m p o ral Fo ssa [G 644; L 329; N 51; R 82] 1. Use a skull to review the skeletal boundaries of the infratem poral fossa. Observe that the ram us of the m andible m ust be rem oved to view the contents of the infratem p oral fossa. 2. On the cadaver, gently insert a p robe through the m andibular notch posterior to the tem poralis tendon and push the probe anteroinferiorly toward the third m andibular m olar tooth. Keep the probe in close contact with the deep surface of the m andible and use it to create separation from the underlying structures deep to the m andible. 3. Use a saw to score a line (cut halfway) through the ram us of the m andible to create an inverted “T”-shap ed cut (FIG. 7.31) . The vertical cut should m eet the m andibular notch, and the horizontal portion should be just above the m idpoint of the ram us of the m andible. Pay attention to not cut through the full depth of the bone while m aking the score lines. 4. Use bone cutters, or a chisel, to carefully break the bone along the score lines. Wear eye protection for all steps that require the use of the bone saw, chisel, or bone cutters. 5. Re ect the coronoid p rocess, p ortions of the anterior sup erior corner of the ram us, and the attached tem p oralis m uscle in the superior direction.

Mandibular condyle (head) Coronoid process Cut 2 Cut 3

Cut 1

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259

6. Use blunt dissection to release the tem poralis m uscle from the skull and note that the deep tem poral nerves (branches of the m andibular division of the trigem inal nerve) and the d e e p t e m p o ral art e rie s enter the m uscle from its deep surface. Note that the d e e p t e m p o ral n e rve s , branches from CN V3 , p rovide m otor innervation to the tem poralis m uscle. 7. Insert a probe m edial to the neck of the m andib le and create separation between the underlying structures and the bone. 8. Use a saw to cut halfway through the neck of the m andible and then use bone cutters to break the b one along the score line. 9. Deep to the m andible, identify the in fe rio r alveo lar n e rve and ve sse ls (FIG. 7.32) . 10. Use bone cutters to carefully nibble away the superior posterior part of the mandible, beginning at the mandibular notch and proceeding inferiorly. Stop at the level of the lingual. While removing the bone, make small cuts and stop periodically to verify that you are staying on the lateral side of muscles, nerves, and vessels. 11. Rem ove the portions of bone superior to the horizontal score line and p lace it in the tissue container. 12. Clean the inferior alveolar nerve and artery and follow them inferiorly to the m and ibular foram en. 13. Identify the n e rve t o m ylo h yo id arising from the p osterior side of the inferior alveolar nerve just before it enters the m andibular foram en. Note that the nerve to m ylohyoid is a useful way to differentiate the inferior alveolar nerve from the nearby vessels. 14. The inferior alveolar nerve and vessels enter the m andibular foram en and pass anteriorly in the m an d ib ular can al. Note that the inferior alveolar nerve p rovides sensory innervation to the m an d ib ular teeth. 15. Near the chin, once again identify the m e n t al n e rve and recall that it is a branch of the inferior alveolar nerve, which p asses through the m ental foram en to innervate the chin and lower lip. 16. Medial to the cut ram us of the m andible, identify the lin g ual n e rve . Observe that the lingual nerve is located just anterior to the inferior alveolar nerve and that it does not enter the m andibular foram en. The lingual nerve passes m edial to the third m andibular m olar tooth and it provides sensory innervation to the m ucosa of the anterior two-thirds of the tongue and oor of the oral cavity.

Ramus

Maxillary Art e ry [G 645, 646; L 330; N 51; R 82]

FIGURE 7.31

How to cut the m andible.

1. Id en tify th e m a xilla r y a rt e ry wh ere it arises from th e b ifurcation of th e extern al carotid artery (FIG. 7.32 ) . Th e m axillary artery courses h orizon tally th roug h th e in fratem p oral fossa an d crosses eith er th e sup er cial surface (two-th ird s of cases)

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Posterior and anterior deep temporal nn. and aa. Masseteric n. &a. (cut)

Temporalis m. (cut) Maxillary division of trigeminal n. (V2) Sphenopalatine a.

Auriculotemporal n.

Inferior orbital a.

Superficial temporal a.

Descending palatine a.

Parotid n.

Posterior superior alveolar n. &a. Lateral pterygoid m.

Maxillary a.

Parotid duct

External carotid a.

Buccal n. &a.

Nerve to mylohyoid

Buccinator m.

Inferior alveolar n. &a.

Medial pterygoid m. Lingual n.

FIGURE 7.32

2.

3.

4.

5.

Arteries and nerves of the infratem poral fossa. Sup er cial dissection.

or th e d eep surface (on e-th ird of cases) of th e lateral p teryg oid m uscle. If the m axillary artery in your specim en passes deep to the lateral pterygoid m uscle, it m ay be necessary to rem ove portions of the m uscle while you identify the following branches of the m axillary artery. Use b lunt d issection to trace the m axillary artery through the infratem p oral fossa. Note that the m axillary artery has 15 b ranches, althoug h only 5 b ranches will b e isolated in this d issection (FIG. 7.32) . Near the point of origin of the m axillary artery from the external carotid artery, identify the m id d le m e n in g eal art e ry. The m id dle m eningeal artery arises m edial to the neck of the m andible and courses superiorly, p assing deep to the lateral pterygoid m uscle. Just below the base of the skull, the m iddle m eningeal artery is encircled by the auriculotem poral nerve. The artery then p asses through the foram en sp inosum to enter the m idd le cranial fossa and supp ly the dura m ater. Id entify and clean the d e e p t e m p o ra l a rt e rie s (a n t e rio r a n d p o st e rio r) . Ob serve that d eep tem p oral arteries arise from the sup erior asp ect of the m axillary artery and p ass sup eriorly and laterally across the roof of the infratem p oral fossa at b one level to en ter the d eep surface of the tem p oralis m uscle. Id entify and clean the rem aining p ortion of the m a sse t e ric a rt e ry (cut in a p revious d issection step ). The m asseteric artery courses laterally from the m axillary artery and p asses throug h the m andib ular notch to enter th e d eep surface of the m asseter m uscle.

6. Identify the in fe rio r alve o lar art e ry and follow it from where it entered the m andibular foram en with the inferior alveolar nerve inferiorly, back to its origin from the m axillary artery. 7. Th e last b ran ch of th e m axillary artery to b e d issected at th is tim e is th e b u cca l a rt e r y , wh ich p asses an teriorly on to th e b uccin ator m uscle to sup p ly th e ch eek. Note that the buccal artery m ay be quite sm all and is often difficult to dissect.

Pt e ryg o id Muscle s [G 648; L 329; N 49] 1. Id en tify th e la t e ra l p t e r yg o id m u scle coursing h orizon tally th roug h th e in fratem p oral fossa (FIG. 7.32) . 2. Use blunt dissection to clean the surface of the lateral pterygoid m uscle and identify the plane of separation between its two heads. The lateral pterygoid is innervated by branches of CN V3 along with the other m uscles of m astication. It is unique, however, in that it acts to open the jaw. 3. Review the attachm ents and actions of the lateral p terygoid m uscle (see TABLE 7.5). 4. In ferio r to th e lateral p teryg o id m u scle, id en tify th e m e d ia l p t e r yg o id m u scle (FIG. 7.32) . Reflect th e m asseter b ack an d forth to ob serve th at th e m ed ial p teryg oid h as a sim ilar fib er orien tation an d th u s wo uld act in a sim ilar fash io n to clo se th e jaw. 5. Ob serve th at th e lin g ual n erve an d in ferior alveolar n erve p ass b etween th e in ferior b ord er of th e lateral p teryg oid m uscle an d th e m ed ial p teryg oid m uscle.

CHAPTER 7

CLIN ICA L CORRELATION

De n t al An e st h e sia A m andibular nerve block is produced by injecting an anesthetic agent into the infratem poral fossa. Understand from your dissection that the m and ibular nerve block will anesthetize not only the inferior alveolar nerve but also the lingual nerve, resulting in anesthesia of the m andibular teeth, lower lip , chin, and the tongue.

6. Clean the surface of the m edial pterygoid m uscle using the lingual nerve as a guide to assist in identication of the plane of separation between the two pterygoid m uscles. 7. Review the attachm ents and actions of the m edial pterygoid m uscle (see TABLE 7.5). 8. De ne the inferior border of the lateral pterygoid m uscle by inserting a probe between it and the m edial pterygoid m uscle. 9. Use scissors to cut the lateral pterygoid m uscle close to its posterior attachm ents to the neck of the m andible and the articular disc. 10. Rem ove the m uscle in a piecem eal fashion to preserve super cially p ositioned nerves and vessels. If the m axillary artery coursed deep to the lateral pterygoid, then it m ay be possible to simply re ect the lateral pterygoid anteriorly and avoid removing it com pletely from the dissection eld. 11. Use blunt dissection to follow the in fe rio r alve o lar n e rve and the lin g ual n e rve sup eriorly toward the foram en ovale in the roof of the infratem poral fossa.

THE HEAD AND NECK

Te m p o ro m an d ib ular Jo in t [G 651; L 328; N 18; R 54] 1. Identify the capsule of the t e m p o ro m an d ib ular jo in t (TMJ) and use a pair of forcep s to observe that the joint capsule is loose to allow for increased m obility. Use an illustration to observe that the lateral surface of the joint capsule is reinforced by the lat eral lig am e n t (FIG. 7.33) . 2. Preserve the super cial tem poral vessels and auriculotem poral nerve by gently pulling them away from the TMJ. 3. Use a scalpel to trim away the lateral side of the joint capsule and the lateral lig am ent. 4. Within the joint, identify the articular disc and note its location between the m andibular fossa of the tem p oral bone and the head of the m andible. Note that the tendon of the lateral p terygoid m uscle is attached to

Temporalis m. (cut)

Masseteric n. (cut)

Pterygopalatine ganglion

Lateral ligament of temporomandibular joint

Infraorbital n. &a.

Auriculotemporal n. (cut) Middle meningeal a. entering foramen spinosum Chorda tympani Inferior alveolar n. Nerve to mylohyoid

Sphenopalatine a. entering pterygopalatine fossa Posterior superior alveolar n. &a. Descending palatine a. entering palatine canal Maxillary a. Buccal n. Medial pterygoid m.

Lingual n.

FIGURE 7.33

261

12. Identify the ch o rd a t ym p an i, a thin nerve that joins the posterior side of the lingual nerve high in the infratem poral fossa (FIG. 7.33) . 13. Follow the m axillary artery toward the p t e ryg o p alat in e fo ssa . 14. Ob serve th at p rior to en terin g th e p teryg op alatin e fossa, th e m axillary artery d ivid es in to four b ran ch es: p osterior sup erior alveolar artery, in fraorb ital artery, d escen d in g p alatin e artery, an d sp h en op alatin e artery. At th is tim e, id en tify on ly th e p o st e rio r su p e rio r a lve o la r a rt e ry , wh ich en ters th e in fratem p oral surface of th e m axilla (FIG. 7.33) . Th e oth er b ran ch es will b e d issected later.

Deep temporal nn.

Lateral pterygoid m. (cut)

•

Arteries and nerves of the infratem poral fossa. Deep dissection.

262

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7.

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both the neck of the m andible and the articular disc (FIG. 7.34) . Exam ine the articular disc and note that it is thin near its center and thicker near its edg es. Insert a probe both superior and inferior to the d isc and identify the sup e rio r an d in fe rio r syn o vial cavit ie s (FIG. 7.34) . Move th e sm all rem ain in g p ortion of th e h ead of th e m an d ib le an d ob serve th e two typ es of m ovem en ts th at occur in th e TMJ. Verify th at in th e sup erior syn ovial cavity, g lid in g m ovem en ts occur b etween th e articular d isc an d the m an d ib ular fossa (p rotrusion an d retrusion) an d th at in th e in ferior syn ovial cavity, h in g e m ovem en ts occur b etween th e head of th e m an d ib le an d th e articular d isc. Place your fth digit in the cartilaginous p ortion of your external acoustic m eatus. Palpate the head of the m andible as you elevate, dep ress, protrud e, and retrude your m andible.

Postglenoid tubercle Articular disc

Superior synovial cavity Articular tubercle

Lateral pterygoid m.

External acoustic meatus Styloid process

FIGURE 7.34 view.

Head of mandible

The right tem porom andibular joint. Sectional

Disse ct io n Fo llo w-up 1. Review the attachm ents and actions of the four m uscles of m astication (m asseter, tem poralis, m edial pterygoid, and lateral pterygoid). 2. Use an atlas illustration to study the origin of the m andibular division of the trigem inal nerve (CN V3 ) at the trigem inal ganglion and trace it to the foram en ovale. Follow the m and ibular division of the trigem inal nerve through the foram en ovale into the infratem poral fossa. Review the sensory and m otor branches of the m andibular division. 3. Follow the external carotid artery from its origin near the hyoid bone to the infratem poral fossa. 4. Review the course of the super cial tem poral artery and the m axillary artery. Follow the branches of the m axillary artery that were identi ed in dissection to their regions of supp ly. 5. Note the relationship of the m iddle m eningeal artery to the auriculotem poral nerve. 6. Use an illustration and the dissected cadaver to preview the term inal branches of the m axillary artery.

TABLE 7.5

Muscle s o f Mast icat io n

Muscle

Superior Atta chments

Inferior Atta chments

Actions

Innerva tion

Masseter

Inferior border and medial surface of zygomatic arch

Lateral surface of ramus and angle of mandible

Elevates and protrudes mandible

CN V3 via mandibular n.

Temporalis

Floor of temporal fossa and deep surface of temporal fascia

Tip and medial surface of coronoid process and anterior border of ramus of mandible

Elevates and retrudes mandible

CN V3 via deep temporal nn.

Medial pterygoid

Medial surface of lateral pterygoid plate (deep head) Tuberosity of maxilla (super cial head)

Medial surface of ramus of mandible

Elevates and protrudes mandible (bilateral) Side to side movement of mandible (unilateral)

CN V3 via medial pterygoid n.

Lateral pterygoid

Infratemporal surface and infratemporal crest of greater wing of sphenoid (superior head) Lateral surface of lateral pterygoid plate (inferior head)

Neck of mandible, articular disc, and capsule of TMJ

Depresses and protrudes mandible (bilateral) Side-to-side movement of mandible (unilateral)

CN V3 via lateral pterygoid n.

Abbreviations: CN, cranial nerve; n., nerve; nn., nerves; TMJ, temporomandibular joint.

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INTERIOR OF THE SKULL Disse ct io n Ove rvie w Many schools rem ove the brain before the cadaver is p laced on the dissection table. If the brain has been rem oved in your cadaver, skip ahead to the section entitled “Cranial Meninges.” If you m ust rem ove the brain yourself, proceed with the following instructions. The bones of the calvaria provide a protective covering for the cerebral hem ispheres. To view the internal features of the cranial cavity, the calvaria m ust be rem oved. The order of dissection will be as follows: The rem aining layers of scalp and the tem p oralis m uscle will be re ected inferiorly. The calvaria will be cut with a saw and rem oved. The dura m ater will be exam ined and then opened to reveal the arachnoid m ater and pia m ater.

Disse ct io n In st ruct io n s Re m o val o f t h e Calvaria 1. Refer to an isolated skull and rem ove the calvaria. 2. On the cut edge of the bone, observe that the bones of the calvaria have three layers. Note that both the outer lam in a and in n er lam in a are composed of compact bone, whereas the middle layer between the outer and inner lam inae, the d ip loë , is composed of spongy bone. 3. With the cadaver in the supine position, re ect the scalp inferiorly. 4. Use a scalpel to detach the tem poralis m uscle from the calvaria and re ect the m uscle inferiorly along with the re ected scalp (FIG. 7.35) . 5. Identify the p e ricran ium that covers the surface of the calvaria. 6. Use a scalpel or chisel to scrape the bones of the calvaria clean of p ericranium (periosteum ) and any rem aining m uscle bers. 7. Place a rubber band around the circum ference of the skull (FIG. 7.36, dashed line) . Anteriorly, the rubber

8.

9.

10.

11.

12. Coronal suture Frontal bone Sphenoid bone (greater wing)

Saw cut Parietal bone Superior temporal line Inferior temporal line

Saw cut

13.

Squamosal suture Lambdoid suture

Frontalis (reflected)

Occipitalis (reflected) Flap of scalp

Flaps of scalp Temporalis (reflected)

Temporal bone (squamous part)

FIGURE 7.35 How to re ect the tem poralis m uscle and m ark the calvaria for sawing.

14.

band should be about 2 cm superior to the supraorbital m argin. Posteriorly, the rubber band should cross the external occipital protuberance. Trace the circum ference of the calvaria with a pencil or m agic m arker following the rubber band . Once the com plete circum ference of the skull has been traced, rem ove the rubber band. Draw a vertical line from above the ear on one side of the head up and over the vertex of the skull to a similar location on the opposite side. The vertical line should effectively divide the skull into anterior and posterior halves. Use a saw to cut along the m arked lines passing only through the outer lam ina of the calvaria but not com pletely through the bone. If you saw through the inner lam ina, you m ay dam age the underlying dura m ater or the brain. Note that m oist red bone on the saw blade indicates that the saw is within the diploë. Be particularly careful when cutting the squam ous part of the tem poral bone, which is very thin. While sawing, turn the body alternately from supine to p rone and back to supine as you work your way around and over the superior aspect of the skull. After m aking a com plete circum ferential cut, break the inner lam ina of the calvaria by repeatedly inserting a chisel into the saw cut and striking the chisel gently with a m allet. Once the skull has been com pletely cut through, you should see a sm all am ount of m ovem ent between the portions of cut skull. Use a “T-tool” if available, or the edge of the chisel, to create a sm all am ount of m ovem ent and increase the space between the cut p ieces of bone and the circum ference of the skull, by inserting and twisting the instrum ent. While doing so, you will hear a distinct tearing sound as the dura m ater is separated from the overlying bone. Beginning with the anterior portion of sectioned bone, elevate the cut portion of bone by prying it from the dura m ater with a chisel. Continue to elevate the anterior half of the calvaria and rem ove the portion of bone by tilting it toward the forehead. Note that violent pulling m ay result in tearing the dura m ater and dam aging the brain.

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15. Using the cut edge of bone as a guide, insert the handle of a forceps under the posterior potion of bone and repeat the process to rem ove the rem aining half of the calvaria. Again, do not use m ore force than is necessary. 16. On the inner surface of the calvaria, identify the grooves formed by the middle meningeal artery. Compare the grooves with the visible vessels on the surface of the dura mater and recall that the middle meningeal artery arose from the maxillary artery in the infratemporal fossa.

Cran ial Me n in g e s [G 612; L 344; N 102, 103] The brain is covered with three m em branes called m eninges (Gr. meninx, m em brane). The d ura m ater is the outer layer of tough m em brane, the arach n oid m ater is the cobwebby interm ediate m em brane, and the p ia m ater is a delicate m em brane closely applied to the surface of the brain (FIG. 7.36) . 1. Identify the d ura m at er (L. dura mater, hard m other). The dura m ater consists of two layers, an external p eriost eal layer and internal m en in g eal layer (FIG. 7.36) . The two dural layers are indistinguishable except where they separate to enclose the d ural ven ous sin uses and form the falx cereb ri and falx cereb elli. 2. Identify the sup e rio r sag it t al sin us , a dural venous sinus coursing along the sup erior extent of the cranial cavity in the m idline (FIGS. 7.36 and 7.37) . [G 613; L 342, 343; N 102–105; R 89] 3. Use scissors to m ake a longitudinal incision in the superior sagittal sinus through the p eriosteal layer of dura m ater (FIG. 7.37) . Use forceps to gently spread open the sinus and verify that its inner surface is sm ooth because it is lined by endothelium . 4. Extend the incision all the way from the frontal b one anteriorly to the cut edge of the occipital bone posteriorly. Ob serve that the caliber of the superior sag ittal sinus increases from anterior to p osterior following the direction of venous blood ow. 5. Gently insert a probe into the lateral expansions along the wall of the sinus and identify the lateral venous

Sagittal suture Emissary vein Superior sagittal sinus

Arachnoid granulations Parietal bone Dura mater: Periosteal layer Meningeal layer Arachnoid mater Pia mater Vessels in subarachnoid space

Cerebral vein

Bridging vein Cerebral falx

FIGURE 7.36 Coronal section throug h the superior sagittal sinus showing the m eninges.

Dura mater: Periosteal layer Meningeal layer Arachnoid mater Subarachnoid space Pia mater Branches of middle meningeal a.

Superior sagittal sinus, opened Lateral venous lacuna, opened to show arachnoid granulations

FIGURE 7.37

The cranial m eninges. Superior view.

lacun ae . Within a lateral venous lacunae, identify the arach n oid g ran ulation s (FIG. 7.36) responsible for the return of cerebrospinal uid (CSF) to the venous system. 6. Exam ine the surface of the dura m ater that covers the cerebral hem ispheres and observe the branches of the m id d le m e n in g e al art e ry (FIG. 7.37) . The m iddle m eningeal artery supplies the dura m ater and adjacent calvaria. Note that the an t e rio r b ran ch of the m iddle m eningeal artery crosses the inner surface of the p t e rio n , where it m ay tunnel through the bone. 7. Exam ine the inner surface of the rem oved calvaria and identify the g ro o ve fo r t h e sup e rio r sag it t al sin us as well as the g ro o ve s fo r t h e b ran ch e s o f t h e m id d le m e n in g e al art e ry. [L 300; N 9] 8. Observe that additional shallow dep ressions, the g ran ular fo ve o lae , are present on the inner surface of the calvaria. The granular foveolae are form ed by the arachnoid g ranulations. CLIN ICA L CORRELATION

Ep id ural He m at o m a Fractures through the pterion m ay result in tearing the m iddle m eningeal artery causing an epidural hem orrhage (extradural hem atom a). When the m iddle m eningeal artery is torn in a head injury, blood accum ulates between the skull and the dura m ater resulting in life threatening com pression of the brain.

CHAPTER 7

Superior sagittal sinus (ghosted)

Cut dura along dashed line

14.

Lateral venous lacunae (ghosted)

15. Branches of middle meningeal a.

Stop cuts here

FIGURE 7.38

16.

Circum ferential cut to re ect the dura m ater.

9. Use scissors to cut through the dura m ater along the circum ference of the cut edge of the calvaria (FIG. 7.38) . Bilaterally, stop the cut posteriorly at a point about 3.5 cm lateral to the m idline. The objective is to perm it the dura m ater to be pulled free from the surface of the brain but to leave it attached posteriorly in the area of the superior sagittal sinus. 10. Using your ng ers, gently retract the anterior pole of the dura m ater and insert scissors between the cerebral hem ispheres to cut the falx ce reb ri (ce re b ral falx) where it attaches to the crista galli. The falx cerebri is an extension of the m ening eal layer of d ura m ater, which descends between the cerebral hem isp heres along the m idline to p hysically separate the right and left cerebral hem ispheres. 11. Grasp the anterior pole of the dura mater and gently pull it posteriorly, gradually working the falx cerebri free from between the cerebral hemispheres as you progress. 12. Observe b rid g in g vein s that pass from the surface of the brain into the superior sagittal sinus along its lateral sides. These bridging veins connect the superior cerebral veins to the superior sagittal sinus (FIG. 7.36) . 13. Cut the bridging veins as you pull the dura m ater posteriorly to perm it the falx cerebri to be com pletely retracted from between the cerebral hem ispheres.

17.

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Continue this procedure until the dura m ater is attached to the skull only near its posterior pole. The re ected portion of dura m ater will be rem oved along with the brain dissection. Deep to the location of the now re ected dura m ater, identify the arach n o id m at e r (Gr. arachnoeides, in reference to the spider web-like connective tissue strands in the subarachnoid space) covering the surface of the brain. Observe that the arachnoid m ater loosely covers the brain and spans across the ssures and sulci. In the living person, the arachnoid m ater is closely ap plied to the internal m eningeal layer of the dura m ater with no space between due to the pressure of ce re b ro sp in al uid (CSF) in the subarachnoid space (FIG. 7.36) . [G 613; L 344; N 103; R 87] Observe the ce re b ral ve in s that are visible through the arachnoid m ater. The cerebral veins em pty into the sup erior sagittal sinus via brid ging veins, which were cut during the re ection of the dura m ater. Use scissors to m ake a sm all cut (2.5 cm ) throug h the arachnoid m ater over the lateral surface of the brain. Use a probe to elevate the arachnoid m ater and observe the sub arach n o id sp ace . In the living p erson, the subarachnoid space is a real space that contains CSF. In the cadaver, the arachnoid m ater ap pears “de ated” because the CSF is no longer present. Through the opening in the arachnoid m ater, observe the p ia m at e r (L. pia m ater, tender m other) on the surface of the brain. The p ia m ater faithfully follows the contours of the brain, passing into all sulci and ssures. The pia m ater cannot be rem oved from the surface of the brain.

CLIN ICA L CORRELATION

Sub d ural He m at o m a At the point where the bridging veins enter the superior sagittal sinus, they m ay be torn in cases of head traum a. As a com plication of head injury, bridging veins m ay bleed into the potential space between the dura m ater and the arachnoid m ater. When this happens, the venous blood accum ulates between the dura m ater and arachnoid m ater (a “subdural space” is created), and this condition is called a subdural hem atom a.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Review the bones that form the calvaria. Review the external features of the cranial dura m ater and note that the external periosteal layer is attached to the skull. Review the features of the spinal dura m ater and com pare it to the cranial dura m ater. Return the re ected portion of dura m ater back to its anatom ical position. Review the extradural (epidural) space in the vertebral canal and recall that it contains fat and the internal vertebral venous plexus. Under norm al conditions, there is no extradural space in the cranial cavity. 6. Com pare and contrast the features of an epidural hem atom a and a subdural hem atom a.

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REMOVAL OF THE BRAIN Disse ct io n Ove rvie w The internal m eningeal layer of the dura m ater form s inwardly projecting folds (dural infoldings) that serve as incom plete partitions of the cranial cavity. Three of these folds (falx cerebri, tentorium cerebelli, and falx cerebelli) extend inward between parts of the brain. These infoldings m ust rst be cut before the brain can be rem oved. The anterior attachm ent of the falx cerebri was p reviously re ected in the p receding dissection. The order of dissection will be as follows: Bony features of the cranial cavity will be studied on a skull. The brain will be rem oved intact, along with the arachnoid m ater and pia m ater. The dura m ater will be left in the cranial cavity, where the dural infoldings will be studied.

Cran ial Fo ssae On a skull with the calvaria rem oved, review the following skeletal features (FIG. 7.39) : [G 593; L 302; N 11; R 30] 1. Within the cranial cavity, identify the three cran ial fo ssae . 2. Anteriorly, identify the an t e rio r cran ial fo ssa and observe that it is predom inantly form ed by the right and left o rb it al p lat es of the frontal bone. 3. Between the orbital plates, identify the crist a g alli, the sm all ridgelike process serving as the anterior attachm ent of the falx cerebri. Observe that to either side of the crista galli is the crib rifo rm p lat e , a sm all depression with m any ap ertures sup erior to the nasal cavity. 4. At the border between the anterior and m iddle cranial fossae, identify the ridge form ed by the le sse r win g o f t h e sp h e n o id . Ob serve that the ridge ends m edially as the rounded an t e rio r clin oid p ro ce ss . 5. Identify the m iddle cranial fossa and observe that it is form ed by the g re at e r win g o f t h e sp h e n o id and the p e t ro us p art o f t h e t e m p o ral b o n e . 6. In th e m id lin e of th e skull b etween th e rig h t an d left m id d le cran ial fossae, id en tify th e sad d le-sh ap ed d ep ression of th e h yp o p h yse a l fo ssa (se lla t u rcica ) . In th e livin g p erson , th e sella turcica sup p orts th e p ituitary g lan d . 7. On the posterior aspect of the sella turcica, identify the p o st e rio r clin o id p ro ce sse s . The posterior clinoid processes are p art of the sphenoid bone and are positioned sup erior to an extension of the o ccip it al b o n e anterior Crista galli to the large fo ram e n m ag n um within the p o st e rio r Cribriform plate cran ial fo ssa . Anterior clinoid process 8. Within the wall of the foram en m agnum , identify the Posterior clinoid process h yp o g lo ssal can al. 9. Observe that the ridge separating the m iddle and Superior border of p osterior cranial fossae is the sup e rio r b o rd e r o f t h e petrous part of p e t ro us p art o f t h e t e m p o ral b o n e . This border temporal bone serves as the anterior attachm ent of the tentorium Internal acoustic cereb elli. meatus 10. Follow the border laterally and observe that it is the sam e relative height as the anterior asp ect of the g ro o ve fo r t h e t ran sve rse sin us . Note that the transHypoglossal canal verse sinus is a dural venous sinus that courses in the lateral edge of the tentorium cerebelli. Jugular foramen 11. Trace the groove for the transverse sinus anteriorly and observe that it is continuous with the lateral Groove for asp ect of the g ro o ve fo r t h e sig m o id sin us , the desigmoid sinus p ression form ed by the sigm oid sinus. The groove for the sigm oid sinus follows the inferior border of the Foramen magnum p etrous portion of the tem p oral bone as it courses m edially and term inates at the jug ular fo ram e n . 12. Identify the in t e rn al aco ust ic m e at us on the vertical asp ect of the p e t ro us p art o f t h e t e m p o ral b o n e . Groove for transverse sinus The internal acoustic m eatus is the m edial opening leading to the inner and m iddle ear. FIGURE 7.39 Floor of the cranial cavity. Sup erior view.

CHAPTER 7

Disse ct io n In st ruct io n s If the brain has b een rem oved from your cadaver, skip ahead to the section entitled “Dural Infoldings and Dural Venous Sinuses.” 1. Use an atlas gure to help you identify the structures to be cut [G 616; L 346; N 105; R 77]. Note that the cut structures will be reviewed after the brain has been rem oved. 2. Use your ngers to gently elevate the frontal lobes. Use a probe to lift the olfactory bulb from the cribriform plate on each side of the crista galli. 3. As you elevate the anterior aspect of the cerebral hem ispheres, carefully use a scalp el to cut the following structures bilaterally: op tic nerve, internal carotid artery, and oculom otor nerve. Cut the stalk of the pituitary gland in the m idline. 4. On the right side, gently lift the tem poral lobe (lateral p art of brain) and identify the t e n t o rium ce re b e lli (ce re b e llar t e n t o rium ) (FIG. 7.40) . 5. Use a scalpel to cut the cerebellar tentorium as close to the sup erior border of the p etrous p art of the tem p oral bone as possible. The cut should begin anteriorly near the p osterior clinoid process and extend p osterolaterally to the end of the superior border of the petrous part of the tem poral bone, near the groove for the sigm oid sinus (FIG. 7.39) . 6. Repeat the cut of the tentorium cerebelli on the left side of the cadaver. 7. In ferior to th e cut ed g e of th e ten torium , en sure th at th e troch lear nerve, trig em in al n erve, and

8.

9.

10.

11.

12. 13.

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ab d ucent nerve were cut b ilaterally. With the cereb ellar tentorium cut, th e b rain m ay b e g en tly m oved to g ain access to structures that lie inferior to th e ten torium . Elevate the cereb rum and brainstem slightly and cut the following structures bilaterally: facial and vestibulocochlear nerves near the internal acoustic m eatus; glossopharyngeal, vag us, and accessory nerves near the jug ular foram en; and the hypog lossal nerves near the hypog lossal canal within the walls of foram en m agnum . Use a scalpel to sever the two vertebral arteries where they enter the skull through the foram en m agnum and the cervical spinal cord as low in the foram en m agnum (or cervical vertebral canal) as you can reach. Support the cerebral hem ispheres from behind with the palm of one hand. Insert the other hand (palm facing superiorly) between the frontal lobes and the skull with your m iddle nger extending down the ventral surface of the brainstem . Insert the tip of your m iddle nger into the cut that was m ade across the cervical spinal cord to support the brainstem and cerebellum . Using upward pressure on the cut end of the cervical sp inal cord, roll the brain, brainstem , and cerebellum posteriorly and out of the cranial cavity in one piece. If d one p roperly, the m eningeal infolding s of the dura m ater will be left attached to the skull. Return the d ura m ater to its correct anatom ical p osition. The brain should be stored in a bath of preservative uid.

Disse ct io n Fo llo w-up 1. Review the bones that form the oor of the cranial cavity in each of the three cranial fossae. 2. Review the surface features of the brain on a xed specim en. 3. Review the location of the tentorium cerebelli and the aspects of the brain that are separated by this structure.

DURAL INFOLDINGS AND DURAL VENOUS SINUSES Disse ct io n Ove rvie w As m entioned previously, the two layers of the dura m ater sep arate from each other in several locations to form dural venous sinuses. The dural venous sinuses collect venous drainage from the brain and cond uct it out of the cranial cavity. The order of dissection will be as follows: The dura m ater will be repositioned to recreate its three-dim ensional m orphology during life. The infoldings of the dura m ater and the associated dural venous sinuses will be identi ed.

Disse ct io n In st ruct io n s Dural Info lding s [G 614; L 342, 343; N 104; R 89] 1. Id entify the falx ce re b ri (ce re b ral falx) b etween the cerebral hem ispheres (FIG. 7.40) . The cereb ral falx is attached to the crista galli at its anterior end ,

to the calvaria on both sides of the groove for the superior sagittal sinus, and to the tentorium cerebelli p osteriorly. 2. Id entify the t e n t o riu m ce re b e lli (ce re b e lla r t e n t o riu m ; L. tentorium , tent) (FIG. 7.40) . The tentorium cereb elli is attached to the clinoid p rocesses of th e

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sp henoid b one, the sup erior b ord er of the p etrous p ortion of the tem p oral b one, and the occip ital b one on b oth sid es of the g roove for the transverse sinus. 3. Identify the t e n t o rial n o t ch (t e n t o rial in cisure ) , the opening in the cerebellar tentorium between the right and left sides that allows passage of the brainstem . The cerebellar tentorium is between the cerebral hem ispheres and the cerebellum . 4. Identify the falx ce re b e lli (ce re b e llar falx) , a low ridge of dura m ater located inferior to the tentorium cerebelli in the m idline (FIG. 7.40) . Note that the falx cerebelli is attached to the inner surface of the occipital bone, and that it is located between the cerebellar hem isp heres.

4.

5.

6.

7.

Dural Ve n o us Sin use s [G 615; L 342, 343; N 105; R 89] 1. Review the position of the sup e rio r sag it t al sin us (FIG. 7.40) . Observe that the superior sagittal sinus begins near the crista galli anteriorly and ends by draining into the co n ue n ce o f sin use s . 2. Id entify the in fe rio r sag it t al sin us in the inferior m arg in of the falx cereb ri (FIG. 7.40) . The inferior sag ittal sinus b egins anteriorly and end s near the tentorium cerebelli by draining into the anterior end of the st raig h t sin us . Note that the inferior sag ittal sinus is m uch sm aller in diam eter than the sup erior sagittal sinus. 3. Identify the location of the straight sinus in the line of junction of the falx cerebri and the tentorium

Sigmoid sinus

8.

Inferior sagittal sinus

cerebelli. At its anterior end, the straight sinus receives the inferior sagittal sinus and the g re at ce re b ral ve in and drains into the con uence of sinuses. Note that the great cerebral vein was torn when the brain was rem oved. Identify the t ran sve rse sin use s (right and left). Each transverse sinus carries venous blood from the con uence of sinuses to the sigm oid sinus. On one side, use a scalpel to op en the lum en of the transverse sinus and note that it is lined with sm ooth endothelium . Identify the right and left sig m o id sin use s (FIG. 7.40) . Each sigm oid sinus begins at the lateral end of the transverse sinus and ends at the jugular foram en. On o n e sid e, use a scalp el to op en th e lum en of th e sig m oid sin us an d trace it m ed ially to th e jug ular foram en . Note th at th e in t e rn a l ju g u la r ve in form s at th e extern al surface of th e jug ular fo ram en . On the oor of the cranial cavity, ob serve that the d ura m ater covers all of the b ones and contains op ening s throug h which the cranial nerves p ass. Note that ad d itional sm all d ural venous sinuses are located b etween the layers of the d ura m ater in the oor of the cranial cavity. Because these sm all d ural venous sinuses are d if cult to d em onstrate, use an atlas illustration to stud y them . Using the illustration, id entify the sp h e n o p a rie t a l sin us , ca ve rn o u s sin u s , su p e rio r p e t ro sa l sin us , in fe rio r p e t ro sa l sin us , and b a sila r p le xus (FIG. 7.40) . [G 6 1 5 ; L 3 4 2 ; N 105; R 89]

Bridging vein

Superior sagittal sinus

Transverse sinus

Cerebral falx

Great cerebral v.

Intercavernous sinus

Straight sinus

Infundibulum

Confluence of sinuses

Supraorbital v. Angular v.

Cerebellar tentorium

Superior ophthalmic v.

Edge of tentorial notch

Facial v. Petrosal sinuses: Inferior Superior

FIGURE 7.40

Cavernous sinus

Inferior ophthalmic v.

Dural infold ings and dural venous sinuses.

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Disse ct io n Fo llo w-up 1. Review the infoldings of the dura m ater and obtain a three-dim ensional understanding of their arrangem ent. 2. Nam ing all venous structures encountered along the way, trace the route of a drop of blood from a superior cerebral vein to the internal jugular vein, from the sphenoparietal sinus to the sigm oid sinus, and from the great cerebral vein to the internal jugular vein.

GROSS ANATOMY OF THE BRAIN Disse ct io n Ove rvie w The study of brain anatom y is highly specialized and is usually reserved for a neuroscience course. The description that is provided here is intended to relate the m ajor features of the external surface of the brain to the parts of the skull that will be studied in subsequent dissections. An additional goal of this study is to establish a m ental picture of the continuity of the arteries and nerves of the brain with those sam e structures that are left behind in the cranial fossae after brain rem oval.

Disse ct io n In st ruct io n s On a brain that has been stored in a bath of preservative uid, review the following neural features (FIG. 7.41) :

Brain [G 698; L 348; N 106; R 94]

2.

1. Observe that the hum an brain is subdivided according to large points of separation created by two m ajor

Occipital lobe

Temporal lobe

Parietal lobe

Post-central Central Pre-central gyrus sulcus gyrus Lateral sulcus Frontal lobe

Transverse fissure

3.

4. 5. 6.

Brainstem

7.

Cerebellum

8.

ssure s . The lo n g it ud in al ssure separates the cerebrum into rig h t and le ft ce re b ral h e m isp h e re s , and the t ran sve rse ssure sep arates the cerebrum from the ce re b e llum , with the b rain st em acting as the bridge between the two. Examine the surface of the brain and observe that it is composed of gyri (raised regions) and sulci (grooves). On the lateral surface of the b rain , identify the central sulcus between the p recentral g yrus (primary motor cortex) of the frontal lob e and the p ostcentral g yrus (primary sensory cortex) of the p arietal lob e . Identify the t em p o ral lo b e of the brain laterally and ob serve that it is sep arated from the frontal and parietal lobes by the lat eral sulcus . On the p osterior aspect of the brain, identify the o ccip it al lo b e superior to the transverse ssure. Refer to a skull and identify the t h re e cran ial fo ssae : an t e rio r , m id d le , and p o st e rio r (FIG. 7.39) . Use the cadaver and the brain to verify that the fron t al lo b e is located in the an t e rio r cran ial fossa , that the t e m p o ral lo b e is located in the m id d le cran ial fo ssa , and that the ce re b e llum is located in the p o st e rio r cran ial fo ssa . [N 11] Observe that the o ccip it al lo b e is located superior to the tentorium cerebelli and therefore sup erior to the groove of the transverse sinus. Observe that the b rain st em becom es continuous with the cervical spinal cord at the fo ram en m ag n um .

Blo o d Sup p ly t o t h e Brain [G 622; L 347, 351; N 140; R 95] Posterior cranial fossa

FIGURE 7.41 nial fossae.

Middle cranial fossa

Anterior cranial fossa

The brain and its relationship to the three cra-

On a brain that has been stored in a bath of preservative uid, review the following neural features (FIG. 7.42) : 1. Exam ine the inferior surface of the brain and observe that it is covered by arachnoid m ater. 2. Use a probe to peel back the arachnoid m ater and expose the arteries on the inferior surface of the brain.

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Vessels

Nerves Olfactory bulb and tract (I)

Anterior cerebral artery

Optic nerve (II) Anterior communicating artery Ophthalmic artery Optic chiasm

Internal carotid artery

Oculomotor nerve (III) Middle cerebral artery Trochlear nerve (IV) Posterior communicating artery

Trigeminal nerve (V)

Posterior cerebral artery Superior cerebellar artery

Abducent nerve (VI) Facial nerve (VII)

Pontine branches Basilar artery

Vestibulocochlear nerve (VIII)

Anterior inferior cerebellar artery

Glossopharyngeal nerve (IX)

Vertebral artery Vagus nerve (X)

Anterior spinal artery

Accessory nerve (XI)

Posterior inferior cerebellar artery

Hypoglossal nerve (XII)

Vertebral artery Posterior spinal artery

FIGURE 7.42

Blood vessels and cranial nerves at the base of the brain.

3. Identify the four arteries that supply blood to the brain, the two vertebral arteries posteriorly and the two internal carotid arteries anteriorly. 4. Observe that each ve rt e b ral art e ry gives rise to one p o st e rio r in fe rio r ce re b e llar art e ry (PICA) prior to com bining to form the b asilar art e ry. The b asilar art e ry gives off the an t e rior in fe rio r ce re b e llar art e ry (AICA) , the sup e rio r ce re b e llar art e ry, and several p o n t in e b ran ch e s . 5. Follow the basilar artery superiorly and observe that it term inates by branching into two p o st e rio r ce re b ral art e rie s . Observe that each posterior cerebral artery gives a p o st e rio r co m m un icat in g art e ry that anastom oses with the in t ern al caro t id art e ry. 6. Within the cranial cavity, identify the cut edge of the internal carotid artery. Observe that the rst branch of the internal carotid artery, the op h t h alm ic art ery, arises m edial to the anterior clinoid process and passes through the optic foram en with the op t ic n erve .

7. On the inferior aspect of the brain, observe that each internal carotid artery terminates by dividing into a m id d le cereb ral artery and an anterior cerebral artery. 8. Gently sep arate the frontal lobes and observe that the anterior cerebral arteries are joined across the m idline by the an t erio r co m m un icat in g art e ry. 9. The ce re b ral art e rial circle (circle o f Willis) is form ed by the posterior cerebral, posterior com m unicating, internal carotid, anterior cerebral, and anterior com m unicating arteries. The cerebral arterial circle essentially form s an anastom osis in the brain ensuring adequate blood sup ply to all regions.

Cran ial Ne rve s It is im portant to note that the cranial nerves are called such b ecause of their interaction with the skull, or cranium , and not because they originate off the brain. In the following sequence, we will review the 12 cran ial n e rve s (CN)

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by nam e and num ber from an inferior view of the brain. The foram en associated with each cranial nerve will be reviewed in the next dissection. 1. Refer to FIGURE 7.42 . 2. On the rostral (anterior) inferior surface of the brain, identify the olfactory bulb and tract . The olfactory nerve (CN I) consists of a bundle of small nerve bers originating from the olfactory bulb. The nerve bers are probably not visible because they were likely torn during the separation of the brain from the anterior cranial fossa. 3. Identify the op t ic n erve (CN II) passing bilaterally through the op t ic ch iasm . The optic chiasm is the point where visual inform ation from the m edial retina (lateral visual eld) of each eye crosses to the contralateral side of the brain prior to reaching the op t ic t ract s. 4. Identify the oculom otor n erve (CN III) em erging from the m idbrain between the cereb ellar p ed un cles. 5. Identify the thin t ro ch le ar n e rve (CN IV) and follow it posteriorly around the lateral aspect of the

6. 7. 8.

9.

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brainstem to where it originates from the posterior surface of the m idbrain. Identify the relatively large t rig e m in al n e rve (CN V) arising from the anterolateral aspect of the pons. Identify the thin ab d ucen t (ab d ucen s) n erve (CN VI) along the anterior (ventral) inferior surface of the pons. Lateral to the origin of the abducent nerve, identify the facial nerve (CN VII) and vestibulocochlear n erve (CN VIII) near the junction of the pons with the medulla. Along the lateral aspect of the m edulla posteriorly, identify the g lossop haryn g eal nerve (CN IX) , vag us nerve (CN X) , and sp in al accessory n erve (CN XI) all arising in sequential order. Note that the spinal accessory nerve originates from the spinal cord but was considered a cranial nerve because it exits the base of the skull through the jugular foram en with CN IX and CN X. Medial (ventral) to the CN IX, CN X, and CN XI, identify the h yp o g lo ssal n e rve (CN XII) between the olive and pyram id of the m edulla oblongata.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5.

Review the lobes of the brain and the cranial fossae in which they are found. Review the infoldings of the dura m ater and their relationships to the cerebral hem ispheres and cerebellum . Review the form ation of the cerebral arterial circle (circle of Willis). Recall the origins of the internal carotid and vertebral arteries and the route that each takes to enter the cranial cavity. Review the location and nam e of each of the 12 cranial nerves in sequential order.

CRANIAL FOSSAE Disse ct io n Ove rvie w The order of dissection will be as follows: The bones of the oor of the cranial cavity will be studied, and the boundaries of the cranial fossae will be identi ed. The vessels and the nerves of each cranial fossa will b e stud ied. Because the oor of the cranial cavity is covered by d ura m ater, the dissection is m uch easier if a dry skull is held next to the cadaver during dissection to perm it direct observation of the foram ina.

Ske le t o n o f t h e Cran ial Base On a skull with the calvaria rem oved, review the following skeletal features (FIG. 7.43) : [G 592, 593; L 302; N 11; R 30] 1. Review the location of the three cranial fossae. 2. Within the anterior cranial fossa, identify the crist a g alli and crib rifo rm p lat e of the et h m o id b o n e located between the o rb it al p art of the fro n t al b o n e s . 3. Observe that the an t e rio r cran ial fo ssa is sep arated from the m id d le cran ial fo ssa by the right and left sp h e n o id al cre st s and the sp h e n o id al lim b us . 4. The m iddle cranial fossa is separated from the p o st e rio r cran ial fo ssa by the superior border of the petrous part of the right and left tem p oral bones and the d orsum sellae. Note that the tentorium cerebelli is attached to the superior border of the petrous part of the tem poral bone and it form s the roof of the posterior cranial fossa.

Sp h e n o id Bo n e 1. Observe that the posterior aspect of the anterior cranial fossa is form ed by the le sse r win g of the sp h e n o id b o n e . 2. Identify the sup e rio r o rb it al ssure between the lesser wing and the g re at e r win g o f t h e sp h e n o id . Pass a pip e cleaner through the opening and verify that the superior orbital ssure connects the orbit with the cranial cavity. 3. From an anterior perspective through the orbit, identify the sm ooth round opening of the o p t ic can al superior and m edial to the superior orbital ssure. Pass a pipe cleaner through the optic canal and observe that it passes m edial to the an t e rio r clin o id p ro ce ss within the cranial cavity.

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Frontal bone: Orbital part Sphenoid bone: Lesser wing Sphenoidal crest

Greater wing of sphenoid bone: Foramen rotundum Foramen ovale

Superior orbital fissure Sphenoidal limbus Anterior clinoid process

Foramen spinosum

Optic canal

Foramen lacerum

Hypophyseal fossa Posterior clinoid process

Occipital bone: Clivus Jugular foramen

Dorsum sellae

Hypoglossal canal

Temporal bone:

Groove for sigmoid sinus Foramen magnum

Squamous part Superior border of petrous part

Groove for transverse sinus

Groove for sigmoid sinus

Internal occipital protuberance

Internal acoustic meatus

FIGURE 7.43

Features of the three cranial fossae.

4. In the m idline of the sphenoid bone, identify the h yp o p h yse al fo ssa (p art o f t h e se lla t urcica) and recall that this is the location of the p ituitary gland. 5. Observe that the hyp op hyseal fossa is p ositioned between the two an t e rio r clin o id p ro ce sse s anteriorly and the two p o st e rio r clin o id p ro ce sse s p osteriorly. 6. Lateral to the sella turcica, within the oor of the m iddle cranial fossa, identify the oval-shap ed fo ram e n o vale . 7. Observe that the foram en ovale is positioned anterom edially to the sm all round opening of the fo ram e n sp in o sum . The foram en spinosum is the entrance point of the m iddle m eningeal artery, and grooves form ed by this vessel ought to be visible within the m iddle cranial fossa em anating from this foram en. 8. Within the m iddle cranial fossa anteriorly and m edially, identify the fo ram e n ro t un d um inferior to the sup erior orbital ssure. 9. Identify the fo ram e n lace rum , which is form ed by portions of the greater wing of the sphenoid bone and the tem poral bone. 10. Look through the nasal cavity from an anterior perspective and observe that the b o d y o f t h e sp h e n o id is visible. Note that the sphenoid is connected to the nasal septum by the sp h e n o id al cre st , a ridge on the anterior surface of the sp henoid.

Te m p o ral Bo n e 1. Observe that the tem poral bone has a at vertically oriented sq uam o us p art and a horizontal m edially oriented p e t ro us p art . Note that the petrous p art form s the bony protection for the m iddle and inner ear. 2. Observe that the petrous part form s the posterior aspect of the m iddle cranial fossa and the anterior aspect of the p osterior cranial fossa. 3. Inferior to the petrous ridge, identify the internal acoustic m eatus. 4. Observe that the petrous portion of the tem poral bone is bordered posteriorly by the g ro o ve fo r t h e sig m o id sin us .

Occip it al Bo n e 1. Observe that the g ro o ve fo r t h e sig m o id sin us is form ed by both the tem p oral bone anteriorly and the occipital bone posteriorly and that it term inates m edially at the jug ular fo ram e n .

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2. In the center of the posterior cranial fossa, identify the largest foram en of the skull, the fo ram e n m ag n um . Observe that the foram en m agnum is bound com pletely b y the occipital b one. 3. Within the walls of foram en m agnum , identify the h yp o g lo ssal can als on both the right and left sides. 4. Anterior to the foram en m agnum , identify the clivus , the sm ooth portion of the occipital bone posterior to the sella turcica. Note that the clivus is positioned anterior to the p ons of the brainstem . 5. Follow the groove for the sigm oid sinus laterally and observe that it is continuous with the g ro o ve fo r t h e t ran sve rse sin us . Observe that the right and left grooves for the transverse sinuses m eet posteriorly at the in t e rn al o ccip it al p ro t ub e ran ce .

Disse ct io n In st ruct io n s An t e rio r Cran ial Fo ssa [G 616; L 346; N 105; R 77] 1. On the right side of the cadaver only, use a probe to loosen the dura m ater along the cut edge of the frontal bone. Grasp the dura m ater and pull it posteriorly as far as the lesser wing of the sphenoid bone. Use scissors to detach the dura m ater along the sphenoidal crest and along the m idline and place it in the tissue container. 2. Observe that the sphenoparietal venous sinus is located along the sphenoidal crest and that its lum en m ay now be visible where you detached the dura m ater.

Superior sagittal sinus

3. Identify the three bones that participate in the formation of the anterior cranial fossa : sphenoid bone, ethmoid bone, and orbital part of the frontal bone (FIG. 7.43) . 4. Identify the crist a g alli in the m idline of the anterior cranial fossa, and recall that before the brain was rem oved the falx cerebri was attached here and the frontal lobe of the brain rested on the orbital part of the frontal bone. Note that the orbital part of the frontal bone form s the roof of the orbit. 5. Identify the openings of the cribriform plate and recall that the olfactory bulb rests on the cribriform plate and the bers of the olfactory n erve (CN I) pass through these openings to enter the nasal cavity (FIG. 7.44) .

Ophthalmic artery Internal carotid artery

Olfactory bulb

Oculomotor nerve (III)

Optic nerve (II)

Trochlear nerve (IV)

Anterior intercavernous sinus

Ophthalmic nerve (V1)

Stalk of pituitary gland

Maxillary nerve (V2)

Posterior intercavernous sinus

Mandibular nerve (V3)

Cavernous sinus

Trigeminal ganglion

Oculomotor n. (III)

Middle meningeal artery

Trochlear n. (IV)

Trigeminal nerve (V)

Trigeminal n. (V)

Abducent nerve (VI)

Superior petrosal sinus

Facial nerve (VII)

Inferior petrosal sinus

Superior petrosal sinus

Abducent n. (VI)

Vestibulocochlear nerve (VIII) Labyrinthine artery

Glossopharyngeal nerve (IX) Vagus nerve (X)

Sigmoid sinus Hypoglossal nerve (XII)

Accessory nerve (XI)

Transverse sinus

Transverse sinus Cerebellar tentorium

Vertebral artery

Great cerebral vein Cerebral falx (cut) Straight sinus

FIGURE 7.44

Inferior sagittal sinus Superior sagittal sinus

Nerves and vessels in the cranial fossae.

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Mid d le Cran ial Fo ssa [G 616, 620; L 346, 355; N 105; R 75] 1. Identify the m id d le cran ial fo ssa and recall that it contains the tem poral lobe of the brain. 2. Observe the dura m ater that covers the oor of the m iddle cranial fossa. The dura m ater hides all of the op enings in the skull as well as the nerves and vessels that p ass through them (FIG. 7.44) . 3. Identify the m id d le m e n in g e al art ery visib le through the dura m ater (FIG. 7.44) on the oor of the m iddle cranial fossa. The m iddle m eningeal artery app ears as a dark line extending laterally from the deepest point of the m iddle cranial fossa. 4. Grasp the dura m ater along the sphenoidal crest and p eel it posteriorly as far as the sup erior border of the petrous part of the tem poral bone. Note that the m iddle m eningeal artery adheres to the external surface of the dura m ater. Use a p robe to tease the p roxim al p art of m iddle m eningeal artery away from the dura m ater and leave it in the skull. 5. Use a probe to clean the m iddle m eningeal artery within the m iddle cranial fossa and observe that it enters the m iddle cranial fossa by p assing through the fo ram en sp in o sum . 6. Use scissors to detach the dura m ater along the superior border of the petrous part of the tem poral bone and p lace it in the tissue container. Do not cut the cranial nerves that cross the anterior end of the sup erior border of the petrous part of the tem poral bone (oculom otor, trigem inal, trochlear, and abducent). 7. Observe that the lum en of the sup e rio r p e t ro sal sin us can be seen along the line of the cut dura m ater parallel to the petrous ridge (FIG. 7.44) . 8. Observe that the oor of the m iddle cranial fossa is form ed by two bones: sphenoid and tem p oral (FIG. 7.43) . 9. Identify the o p t ic n e rve (CN II) (FIG. 7.44) . The optic nerve passes through the o p t ic can al to enter the orbit. The optic nerve is surrounded by a sleeve of dura m ater as it exits the m iddle cranial fossa. 10. Use a probe to identify the superior orbital ssure that is located inferior to the lesser wing of the sphenoid bone (FIG. 7.43) . Note that three cranial nerves (CN III, CN IV, CN VI) and part of a fourth (CN V1) exit the middle cranial fossa by passing through the superior orbital ssure. 11. Identify the o culo m o t o r n e rve (CN III) where it p asses over the superior border of the p etrous part of the tem poral bone to pass anteriorly within the lateral wall of the cavernous sinus. 12. Identify the t ro ch le ar n e rve (CN IV) where it courses anteriorly within the lateral wall of the cavernous sinus im m ediately inferior to the oculom otor nerve (FIG. 7.45) . Note that the trochlear nerve is a very sm all nerve often found in a sleeve of dura m ater at

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

the anterior end of the tentorial notch. CN IV m ay have been cut during b rain rem oval but should be intact farther anteriorly. Id entify the a b d u ce n t n e rve (CN VI) where it enters the d ura m ater covering the clivus of the occip ital b one (FIG. 7.44) . The ab ducent nerve p asses anteriorly within the cavernous sinus in close relationship to the lateral surface of the internal carotid artery. The last nerve to pass through the superior orbital ssure is the o p h t h alm ic d ivision of t h e t rig em in al n erve (CN V1 ) . The ophthalm ic division of the trigem inal nerve arises from the trigem inal ganglion and passes anteriorly along the lateral wall of the cavernous sinus inferior to the trochlear nerve (FIG. 7.44) . Use a probe to clean the nerves that pass through the superior orbital ssure. Note that three of these nerves are located along the lateral wall of the cavernous sinus (CN III, IV, V1 ) and one is within the cavernous sinus (CN VI) (FIG. 7.45) . In order to follow the nerves, it may be necessary to further remove the tightly adhered dura m ater overlying the cavernous sinus. Identify the t rig e m in al n e rve (CN V) where it crosses the sup erior border of the p etrous part of the tem p oral bone (FIG. 7.44) . Follow the trigem inal nerve anteriorly and carefully rem ove the overlying dura m ater to identify the t rig e m in al g an g lio n (FIG. 7.44) . Use a probe to de ne the three divisions (nerves) that arise from the anterior bord er of the trigem inal g anglion (ophthalm ic [CN V1 ], m axillary [CN V2 ], and m andibular [CN V3 ]). Note that these three divisions are nam ed according to their reg ion of distribution and are num bered from superior to inferior as they arise from the trigem inal ganglion. Identify the m axillary d ivision of the trig em inal n erve (CN V2 ) and follow it anteriorly to the foram en rotundum where it exits the middle cranial fossa (FIG. 7.45) . The maxillary division courses along the lateral wall of the cavernous sinus just inferior to the ophthalmic division of the trigeminal nerve (CN V1 ) (FIG. 7.45) . Identify the m an d ib ular d ivisio n o f t h e t rig e m in al n e rve (CN V3 ) and follow it inferiorly to the foram e n o vale , which is where it exits the m iddle cranial fossa and enters the infratem poral fossa (FIG. 7.44) . Return to the area of the cavernous sinus and use a p robe to retract the cranial nerves and identify t h e in t e rn al carot id art e ry (FIG. 7.44) . The internal carotid artery enters the cranial cavity by passing through the caro t id can al. Observe that the internal carotid artery m akes an S-shaped bend in the cavernous sinus and em erges near the op tic nerve. Note that cranial nerves III, IV, V1 , V2 , and VI cross the lateral side of the internal carotid artery. Am ong this group of nerves, the

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Po st e rio r Cran ial Fo ssa [G 616, 618; L 346; N 105; R 69] Plane of section

Sellar diaphragm

Trabeculae in the cavernous sinus

Dura mater Oculomotor nerve (III)

Pituitary gland

Trochlear nerve (IV)

Dura mater

Internal carotid artery

Sphenoid bone

Ophthalmic nerve (V1)

Abducent nerve (VI)

Maxillary nerve (V2)

Sphenoidal sinus

FIGURE 7.45

23.

24.

25.

26.

Coronal section throug h the cavernous sinus.

abducent nerve (CN VI) is m ost closely related to the internal carotid artery (FIG. 7.45) . Identify the region of the h yp op h yse al fo ssa . The hypophyseal fossa is covered by the se llar d iap h rag m (d iap h rag m a se llae) , which is a d ural infolding (FIG. 7.45) . Identify the stalk of the pituitary gland, which passes through an opening in the sellar diaphragm . Note that the pituitary gland is located in the hypophyseal fossa. Anterior and p osterior to the stalk of the pituitary gland are two sm all dural venous sinuses called the an t e rio r an d p o st e rio r in t e rcave rn o us sin use s (FIG. 7.44) . The intercavernous sinuses connect the right and left cavernous sinuses across the m idline. Do not attem pt to dissect the intercavernous sinuses. Use an atlas illustration to identify all of the veins and venous sinuses that drain into or out of the cavernous sinus. [G 615; L 342; N 105; R 89]

The features of the posterior cranial fossa will be studied with the dura m ater intact. 1. Identify the posterior cranial fossa and recall that it contains the cerebellum and the brainstem . Note that at the foram en m agnum , the brainstem becom es continuous with the cervical spinal cord, now visible with the brain rem oved. 2. Identify the facial n e rve (CN VII) and the ve st ib ulo co ch le ar n e rve (CN VIII) where they enter the internal acoustic m eatus (FIG. 7.44) . Do not follow them into the bone at this tim e. 3. Identify the rootlets of the g lo sso p h aryn g e al n erve (CN IX) , the vag us n e rve (CN X) , and the acce sso ry n e rve (CN XI) where they enter the jugular foram en (FIG. 7.44) . Because CN IX and X are form ed by rootlets, it is d if cult to distinguish one nerve from the other as they enter the jugular foram en. However, the ce rvical ro o t o f t h e acce sso ry n e rve can be positively identi ed because it enters the posterior cranial fossa through the foram en m agnum and crosses the inner surface of the occip ital bone (FIG. 7.44) . 4. Review the course of the transverse sinus and sigm oid sinus. Observe that the sig m oid sinus ends at the jugular foram en posterior to the exit p oint of CN IX, X, and XI. 5. Identify the h yp o g lo ssal n e rve (CN XII) where it enters the h yp o g lo ssal can al (FIG. 7.44) . 6. On the left (undissected) side of the cranial cavity, identify the cranial nerves in order from anterior to posterior (FIG. 7.44) . CLIN ICA L CORRELATION

Cave rn o us Sin us In fractures of the base of the skull, the internal carotid artery m ay rup ture within the cavernous sinus. The release of arterial blood into the cavernous sinus creates an abnorm al re ux of blood from the cavernous sinus into the ophthalm ic veins. As a result, the orb it is engorged and the eyeball is p rotruded and is pulsating in synchrony with the radial pulse (pulsating exop hthalm os).

Disse ct io n Fo llo w-up 1. Review the bones that form the oor of the cranial cavity. 2. In the cadaver, review the course of each cranial nerve and nam e the opening through which each passes to exit the cranial cavity. In the skull, review the openings (foram ina and ssures) through which the cranial nerves pass. 3. If the brain is still available, hold it beside the cranial cavity so that you can see its ventral surface and review the cranial nerves and severed vessels on both the brain and the cadaver. 4. Read a description of the dural venous sinuses as you review them in the cadaver.

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ORBIT Disse ct io n Ove rvie w The orbit contains the eyeball and extraocular m uscles. The eyeball is about 2.5 cm in diam eter and occup ies the anterior half of the orbit. The p osterior half of the orbit contains fat, extraocular m uscles, branches of cranial nerves, and blood vessels. Som e vessels and nerves p ass through the orbit to reach the scalp and face. Th e ord er o f d issection will b e as follows: Th e b on es of th e orb it will b e stud ied . On th e rig h t sid e on ly, th e flo or of th e an terior cran ial fossa (roof of th e orb it) will b e rem oved an d th e rig h t orb it will b e d issected from a sup erior ap p ro ach . CN III, IV, V1 , an d VI will b e follo wed th roug h th e sup erior orb ital fissure in to th e orb it. Th e extraocular m uscles will b e id en tified . On th e left sid e on ly, th e an atom y of th e eyelid will b e stud ied . Th e orb it will b e d issected fro m an an terio r ap p roach an d th e eyeb all will b e rem oved . Th e attach m en ts o f th e extraocu lar m uscles will b e stu d ied .

Ske le t o n o f t h e Orb it Refer to a skull and identify the bones that participate in form ing the walls of the orbit (FIG. 7.46) : [G 626; L 352; N 4; R 46] 1. The bones of the orbit form a four-sided pyram id with the base of the pyram id form ed by the o rb it al m arg in and the apex of the p yram id at the o p t ic can al. From an anterior perspective, identify the orbital m argin, noting the p resence of the sup rao rb it al n o t ch along the superior m argin. 2. Identify the sup e rio r o rb it al ssure between the le sse r win g and g re at e r win g o f t h e sp h e n o id b o n e . Observe that the sup erior orbital ssure is inferolateral to the round opening of the o p t ic can al. 3. Identify the in fe rio r o rb it al ssure , a gap between the m axilla and the greater wing of the sphenoid bone. 4. The bones of the orbit are lined with periosteum called p e rio rb it a . At the optic canal and the sup erior orbital ssure, the periorbita is continuous with the dura m ater of the m id dle cranial fossa. 5. Observe that when viewed from above, the m edial walls of the two orbits are parallel to each other and about 2.5 cm apart and that the lateral walls of the two orbits form a right angle to each other. 6. Identify the ro o f o f t h e o rb it form ed by the o rb it al p lat e o f t h e fro n t al b o n e and the le sse r win g o f t h e sp h e n o id b o n e . Note that the roof of the orbit is related to the anterior cranial fossa.

Frontal bone: Supraorbital notch Orbital surface Lacrimal fossa

Ethmoidal foramina : Posterior Anterior Ethmoid bone Lacrimal bone: Posterior lacrimal crest Lacrimal groove

Sphenoid bone: Optic canal Lesser wing Superior orbital fissure Greater wing

Maxilla: Anterior lacrimal crest Infraorbital groove Infraorbital foramen Zygomatic bone Inferior orbital fissure Lateral

FIGURE 7.46

Walls of the right orb it. Anterior view.

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7. Identify the o o r o f t h e o rb it form ed by the m axilla , zyg o m at ic b o n e , and a sm all p ortion of the p alat in e b o n e . Note that the oor of the orbit is related to the m axillary sinus. 8. On the oor of the orbit, identify the in frao rb it al g ro o ve coursing toward the in frao rb it al fo ram e n . Anterior cranial 9. Identify the m ed ial wall o f t h e o rb it form ed by the fossa o rb it al p lat e o f t h e e t h m o id b o n e , the lacrim al Crista galli b o n e , the fro n t al p ro ce ss o f t h e m axilla , and sm all portion of the b o d y o f t h e sp h e n o id . Note that the Orbit: m edial wall of the orbit is related to the ethm oid air Roof cells. Medial wall Ethmoidal Floor 10. On the m edial wall of the orbit, identify the an t e rio r cells and p o st e rio r e t h m o id al fo ram in a . 11. On the anterior aspect of the m edial wall of the orbit, identify the lacrim al fo ssa , a depression bordered Middle meatus by the p o st e rio r lacrim al cre st posteriorly and Orifice of Maxillary the an t e rio r lacrim al cre st anteriorly. The lacrim al maxillary Inferior sinus sinus fossa leads to the lacrim al can al, which houses the meatus nasolacrim al duct. Nasal 12. Identify the lat e ral wall o f t h e o rb it form ed by the septum frontal process of the zygom atic bone and the orbital plate of the greater wing of the sphenoid. Note that the lateral wall of the orbit is the thickest wall of the orbit. In contrast, the part of the ethm oid bone that FIGURE 7.47 Coronal section of the skull to show the form s the m edial wall is paper-thin and, for this rearelationships of the orbit. son, it is called the lam in a p ap yrace a . 13. Exam ine a coronal section through the orbit and review the bones that form the walls of the orbit as well as the associated sp aces beyond each wall (FIG. 7.47) .

Surface An at o m y o f t h e Eye b all Use a m irror, or recruit the assistance of your lab partner, to inspect the living eye and identify the following features (FIG. 7.48) : [G 626, 627; L 353; N 83; R 136] 1. Identify the p alp e b ral ssure (rim a) , the opening between the eyelids, and observe that it is lined by the e ye lash e s (cilia) . 2. Identify the m e d ial an d lat e ral p alp e b ral co m m issure s , the points where the up per and lower eyelids join to form the m e d ial an d lat e ral an g les (can t h i) , or corners of the eye. 3. In the m edial angle of the eye, identify the lacrim al carun cle , a pink eshy bum p. Observe that uid accum ulates at the lacrim al lake , the area surrounding the lacrim al caruncle. 4. On the m edial aspect of each eyelid, identify the sm all bum p of the lacrim al p ap illa and observe that each Lacrimal caruncle Eyelashes features a sm all opening at its apex, the lacrim al p un ct a . Palpebral 5. Identify the scle ra , the whitish, posterior ve-sixths of fissure (rima) the brous tunic of the eyeball. The sclera is continuous with the co rn e a , the transp arent, anterior onesixth of the brous tunic of the eyeball. Lateral palpebral 6. Identify the iris , the colored diaphragm seen through commissure Sclera the cornea. Observe that the iris surrounds the p up il, the aperture in the center of the eye perm itting light Iris Medial palpebral to enter the eye. commissure Pupil 7. Evert the lower lid slightly and observe that the m arg in o f t h e e yelid is at and thick, and that the e ye lash e s (cilia) are arranged in two or three irregular FIGURE 7.48 Surface anatom y of the eye. rows.

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Co n jun ct iva Use an illustration to study the following features and relate them to the living eye (FIG. 7.49) : [G 631; L 353; N 83; R 134] 1. The anterior aspect of the orbit, including the eyelids and eyeball, are lined by conjunctiva, a specialized, protective m ucous m em brane. The conjunctiva on the surface of the eyeball is called b ulb ar co n jun ct iva , and it is continuous with the p alp eb ral co n jun ct iva , the m em brane that lines the inner surface of the eyelids (FIG. 7.49) . 2. Th e su p e rio r a n d in fe rio r co n ju n ct iva l fo rn ice s (L. fornix , arch ) are th e reg ions wh ere th e b ulb ar con jun ctiva is con tin uous with th e p alp eb ral con jun ctiva. 3. The potential space between the bulbar conjunctiva and the palpebral conjunctiva is known as the co n jun ct ival sac (FIG. 7.49) .

Orbital part of orbicularis oculi m. Levator palpebrae superioris m. Superior rectus m.

Orbital septum

Orbital fat Superior tarsal plate Cilia

Conjunctival sac

Inferior tarsal plate

Optic nerve (II)

FIGURE 7.49

Disse ct io n In st ruct io n s Eye lid an d Lacrim al Ap p arat us [G 627, 631; L 352, 353; N 83, 84; R 135] Perform the following dissection of the eyelid and lacrim al gland only in the left eye. 1. Review the attachm ents of the o rb icularis o culi m uscle (see TABLE 7.4). 2. Use a probe to raise the lateral part of the o rb it al p o rt io n o f t h e o rb icularis o culi m uscle and re ect the m uscle m edially. 3. Raise the thin p alp e b ral p o rt io n o f t h e o rb icularis o culi m uscle off the underlying t arsal p lat e s and re ect it m edially. 4. Use an illustration to identify the o rb it al se p t um , a sheet of connective tissue that is attached to the p eriosteum at the m argin of the orbit and to the tarsal p lates (FIGS. 7.49 and 7.50). Note that the orbital septum separates the super cial fascia of the face from the contents of the orbit. 5. Identify the t arsal p lat e s , which give shape to the eyelids (FIG. 7.50) . Retract the upper eyelid superiorly to see the shap e of the up per tarsal plate along its posterior surface. Note that t arsal g lan d s are em bedded in the p osterior surface of each tarsal p late. Tarsal glands secrete an oily substance onto the m argin of the eyelid via sm all ori ces that are located p osterior to the eyelashes. The oil prevents the overow of lacrim al uid (tears). 6. Use an illustration to identify the lacrim al g lan d and observe that it occupies the lacrim al fossa in the frontal bone (FIG. 7.51) . 7. To nd the lacrim al gland in the cadaver, use a scalpel to cut through the orbital septum ad jacent to the or-

Inferior rectus m.

Orbital septum

Bony floor of orbit

Parasagittal section through the orbit.

bital m argin in the superolateral quadrant of the left orbit. 8. Pass a p robe through the incision and free the lacrim al gland from the lacrim al fossa. Note that the lacrim al gland drains into the sup erior conjunctival fornix by 6 to 10 short ducts (FIG. 7.51) . 9. Use a skull to identify the lacrim al g roove at the m edial side of the orbital m argin. Observe that the an terior lacrim al crest of the m axilla form s the anterior border of the lacrim al groove. Note that the m ed ial p alp eb ral

Supraorbital n.

Superior tarsal plate Lacrimal gland

Orbital septum

Lateral palpebral ligament

Lacrimal sac

Medial palpebral ligament

Nasolacrimal duct opening into nasal cavity Infraorbital a. Infraorbital n.

FIGURE 7.50

Inferior tarsal plate

Palpebral fissure

Orbital septum and tarsal p lates.

CHAPTER 7

Superior lacrimal papilla and punctum

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CLIN ICA L CORRELATION

Lacrimal ducts Lacrimal gland

Lacrimal caruncle

Lacrimal sac

Tarsal Glan d s If the duct of a tarsal (m eibom ian) gland becom es obstructed, a chalazion (cyst) will develop. A chalazion will be located deep to the tarsal plate, between it and the conjunctiva. In contrast, a hordeolum (stye) is the in am m ation of a sebaceous gland associated with the follicle of an eyelash and will be located super cial to the tarsal p late.

Nasolacrimal duct

Inferior nasal concha

Inferior lacrimal papilla and punctum

Lacrimal canaliculi

FIGURE 7.51

Parts of the lacrim al apparatus.

lig am ent is attached to the anterior lacrim al crest and that the lacrim al sac lies posterior to the m edial palpebral ligament in the lacrim al groove (FIG. 7.50) . 10. Two lacrim al can aliculi drain lacrim al uid from the m edial angle of the eye into the lacrim al sac. The n aso lacrim al d uct extends inferiorly from the lacrim al sac and enters the inferior m eatus of the nasal cavity (FIG. 7.51) . 11. Lacrim al uid ows from the lacrim al gland across the eyeball to the m edial angle of the eye. During crying, excess lacrim al uid cannot be em ptied through the lacrim al canaliculi and tears over ow the lower eyelids. Increased drainage of tears into the nasal cavity stim ulates snif ing, which is characteristic of crying.

5. Push a probe posteriorly between the roof of the orbit and the periorbita. The probe should pass inferior to the lesser wing of the sphenoid bone, through the superior orbital ssure, and into the middle cranial fossa. Elevate the probe to break the lesser wing of the sphenoid bone. 6. Use bone cutters to rem ove the fragm ents of the lesser wing of the sphenoid b one. Chip away the roof of the optic canal and rem ove the anterior clinoid process (FIG. 7.52) . 7. Exam ine the periorbita and note that the frontal nerve m ay be visible through it. 8. Use scissors to incise the p eriorb ita from the apex of the orbit to the m idpoint of the sup erior orbital m argin avoiding the frontal nerve. 9. Use forceps to lift the periorbita off deeper structures and m ake a transverse incision through the p eriorbita close to the superior orbital m argin. Use a probe to tease open the aps of p eriorbita and use scissors to rem ove them from the orbit. Supratrochlear n.

Supraorbital n. and vessels

Infratrochlear n. Levator palpebrae superioris m.

Superior oblique m.

Rig h t Orb it fro m t h e Sup e rio r Ap p ro ach [G 628; L 356–358; N 88; R 138] Dissect only the right orbit from the superior approach. Wear eye protection for all steps that require the use of bone cutters. 1. In the oor of the anterior cranial fossa, tap the orbital part of the frontal bone with the side of the bone cutters until the bone cracks. Use forceps to pick out the bone fragm ents. 2. Enlarge the opening in the ro o f o f t h e o rb it with the bone cutters and rem ove the roof of the orbit as far anteriorly as the superior orbital m argin (FIG. 7.52) . 3. Anteriorly, the fron tal sinus of the frontal bone m ay extend into the roof of the orbit. Medially, the eth m oid al cells of the ethm oid bone may extend into the roof of the orbit. If either situation occurs in your cadaver, use a probe to push the m ucous m em brane that lines the sinuses away from the roof of the orbit and rem ove the associated layer of thin bone to open the orbit. 4. Identify the p e rio rb it a , the m em brane just deep to the roof of the orbit that lines the bones of the orbit.

Lacrimal gland

Anterior ethmoidal n.

Ethmoidal cells

Lacrimal n. and a.

Trochlear n. (IV) Common tendinous ring

FIGURE 7.52

Superior rectus m. Frontal n.

Right orbit. Sup erior view.

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Co n t e n t s o f t h e Orb it The use of a ne probe and ne forceps is recom m ended from this point onward in the dissection of the right orbit. Use the forcep s to pick out the fat that lls the intervals between m uscles, nerves, and vessels. 1. Use an illustration and the cadaver to observe that three nerves enter the apex of the orbit by passing superior to the extraocular m uscles. 2. Identify the fro n t al n e rve (a branch of CN V1 ) that courses from the apex of the orbit toward the superior orbital m argin (FIG. 7.52) . Trace the frontal nerve anteriorly and observe that it divides into the sup rat ro ch le ar n e rve and the sup rao rb it al n e rve . 3. On the lateral aspect of the orbit, identify the lacrim al n erve (a branch of CN V1 ), which passes through the superior orbital ssure lateral to the frontal nerve. Observe that the lacrim al nerve is m uch sm aller than the frontal nerve (FIG. 7.52) . Follow the lacrim al nerve anterolaterally toward the lacrim al gland. 4. On the medial aspect of the orbit, identify the trochlear n erve , which passes through the superior orbital ssure medial to the frontal nerve (FIG. 7.52) . Follow the trochlear nerve to the superior border of the sup erior ob liq ue m uscle , which it innervates. Note that the trochlear nerve usually enters the superior border of the superior oblique muscle in its posterior one-third. 5. While p reserving the nerves, use forcep s to p ick out lobules of fat and expose the superior surface of the le vat o r p alp eb rae sup e rio ris m uscle (FIGS. 7.50 and 7.52). The levator palpebrae superioris m uscle attaches to the up per eyelid, which it elevates. 6. Transect the levator palpebrae superioris m uscle as far anteriorly as p ossible and re ect it posteriorly. 7. Identify the sup e rio r re ct us m uscle that lies im m ediately inferior to the levator palpebrae superioris m uscle (FIGS. 7.50 and 7.52). Clean the superior rectus m uscle and observe that it is attached to the eyeball b y a thin, broad tendon. 8. Transect the superior rectus m uscle close to the eyeb all and re ect it p osteriorly (FIG. 7.53) . Observe that a branch of the superior division of the o culo m o t o r n e rve (CN III) reaches the inferior surface of the superior rectus m uscle. Note that a branch of the superior division passes around the m edial side of the superior rectus m uscle to innervate the levator palp ebrae superioris m uscle. [G 628; L 357; N 88; R 139] 9. On the m edial side of the orbit, identify and clean the sup e rio r o b liq ue m uscle and trace it anteriorly (FIG. 7.53) . Observe that the tendon of the superior oblique m uscle passes through the trochlea (L. trochlea , pulley), bends at an acute angle, and attaches to the posterolateral portion of the eyeb all. 10. On the lateral side of the orbit, identify and clean the lat e ral re ct us m uscle (FIG. 7.53) . Note that the lateral rectus m uscle arises by two heads from the co m m o n t e n d in o us rin g .

11. Use an illustration to observe that the com m on tendinous ring surrounds the optic canal and part of the sup erior orbital ssure and that it is the posterior attachm ent of the four rectus m uscles. The optic nerve (CN II), nasociliary nerve, oculom otor nerve (CN III), and abducent nerve (CN VI) pass through the com m on tendinous ring. 12. Use scissors to cut the com m on tendinous ring b etween the attachm ents of the superior rectus and lateral rectus m uscles. All structures passing through the com m on tendinous ring are now exposed. 13. Identify the ab d ucen t n erve (CN VI) on the m edial surface of the lateral rectus m uscle near the apex of the orbit (FIG. 7.53) . Note that the abducent nerve passes between the two heads of the lateral rectus m uscle and enters the m edial surface of the lateral rectus m uscle. 14. Identify the n aso ciliary n e rve , which is a branch of V1 (FIG. 7.53) . Trace the nasociliary nerve obliquely through the orbit and note that it is m uch sm aller than the frontal nerve. Observe that the nasociliary nerve crosses superior to the optic nerve and gives several lo n g ciliary n e rve s to the posterior aspect of the eyeball. 15. Follow the nasociliary nerve toward the m edial wall of the orbit and identify the an terior eth m oid al n erve , which passes through the anterior ethm oidal foram en. The anterior ethm oidal nerve is a branch of the nasociliary nerve and supplies part of the m ucous m em brane in the nasal cavity. Note that the term inal branch of the anterior ethm oidal nerve is the extern al nasal n erve that innervates the skin at the tip of the nose. 16. Identify the sup e rio r o p h t h alm ic ve in in the orbit. Use an atlas illustration to observe that at the m edial Trochlea Levator palpebrae superioris m. Superior rectus m. Lacrimal gland Anterior ethmoidal n. Long ciliary nerves Optic n. (II) Lacrimal n. Short ciliary nerves

Superior oblique m. and trochlear n. (IV)

Lateral rectus m. and abducent n. (VI)

Nasociliary n. Medial rectus m. Levator palpebrae superioris m.

FIGURE 7.53

Ciliary ganglion Superior rectus m.

Superior division of oculomotor n. (III)

Deeper dissection of right orbit. Superior view.

CHAPTER 7

17. 18.

19.

20.

21.

angle of the eye, the superior ophthalm ic vein anastom oses with the ang ular vein, which is a tributary of the facial vein. [G 634, 635; L 356; N 87] To increase visibility of the other structures within the orbit, the sup erior ophthalm ic vein m ay be rem oved. In the middle cranial fossa, identify the oculom otor nerve running along the lateral wall of the cavernous sinus. Follow the oculomotor nerve through the superior orbital ssure into the orbit where it branches into two divisions. The superior d ivision innervates the levator palpebrae superioris and the superior rectus muscles, whereas the inferior division innervates the medial rectus, inferior rectus, and inferior oblique muscles. Note that the media l rectus, inferior rectus, and inferior oblique muscles are not easily seen from the superior approach and thus will be identi ed from the anterior approach. Identify the ciliary g an g lio n , a parasym pathetic ganglion located between the op tic nerve and the lateral rectus m uscle. The ciliary ganglion looks like a sm all knot in the nerve, roughly 2 m m in diam eter, approxim ately 1 cm anterior to the apex of the orbit (FIG. 7.53) . Note that short ciliary nerves connect the ciliary ganglion to the posterior surface of the eyeball. Use an illustration and additional text to study the autonom ic function of the ciliary ganglion. Identify the o p t ic n e rve (CN II) (FIG. 7.53) . The op tic “nerve” is actually a brain tract surrounded by the three m eningeal layers: dura m ater, arachnoid m ater, and pia m ater. Identify the o p h t h alm ic art e ry where it branches from the internal carotid artery (FIG. 7.54) . In its course through the orbit, observe that the ophthalm ic artery usually crosses superior to the op tic nerve and reaches the m edial wall of the orbit. Supraorbital a.

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Op h t h alm ic Ve in s Anastom oses between the angular vein and the superior and inferior op hthalm ic veins are of clinical im p ortance. Infections of the upp er lip , cheeks, and forehead m ay spread through the facial and angular veins into the ophthalm ic veins and then into the cavernous sinus. Throm bosis of the cavernous sinus m ay result, leading to involvem ent of the abducent nerve and dysfunction of the lateral rectus m uscle.

22. Use a probe to try and gently tease out the posterior ciliary arteries that supply the eyeball arising from the op hthalm ic artery.

Le ft Orb it fro m t h e An t e rio r Ap p ro ach [G 627; L 354; N 84, 86; R 136] 1. Use a probe to explore the co n jun ct ival sac . Verify that the bulbar conjunctiva is attached to the sclera and that it is continuous with the palpebral conjunctiva on the inner surface of the eyelids (FIG. 7.49) . 2. Use scissors to rem ove both eyelids and the orbital septum . 3. Exam ine the orbit from the anterior view and observe that the lacrim al g lan d is located sup erolaterally and that the t ro ch le a is located superom edially. 4. Gently elevate the eye and observe that the in fe rio r o b liq ue m uscle is attached inferom edially. 5. Review the attachm ents, actions, and innervations of the extraocular m uscles on the eyeball (see TABLE 7.6). 6. Use a probe to pick up the tendon of each rectus m uscle and transect it with scissors (FIG. 7.55) .

Levator palpebrae superioris m. (cut)

Superior oblique m. Superior rectus m. (cut)

Supratrochlear a.

Superior rectus m.

Trochlea

Superior oblique m.

Lateral rectus m.

Anterior ethmoidal a.

Cutting the medial rectus m.

Medial rectus m. Posterior ethmoidal a. Central a. of the retina Ophthalmic a.

Lateral rectus m.

Inferior oblique m.

Lacrimal a. Posterior ciliary aa. Optic nerve (II)

FIGURE 7.54 right orbit.

Inferior rectus m.

Internal carotid a.

Branches of the ophthalm ic artery in the FIGURE 7.55

How to transect the m uscles of the left eye.

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Levator palpebrae superioris m. Superior oblique m. Common tendinous ring

Superior rectus m.

Trochlea

Trochlear n. (IV)

Optic n. (II) Central a. of retina

Lateral rectus m.

Medial rectus m. Oculomotor n. (III) Superior division Inferior division

Abducent n. (VI)

Inferior rectus m. Ciliary ganglion and parasympathetic root of CN III

Inferior oblique m.

FIGURE 7.56 The left orbit in anterior view. The com m on tendinous ring and its relationship to the four rectus m uscles and CN II, III, IV, and VI.

7. Use forceps to grasp the rem aining anterior portion of the lateral rectus tendon and p ull it anteriorly to adduct the eyeball (turn it m edially). 8. Insert scissors into the orbit on the lateral side of the eyeball and cut the op tic nerve. 9. Pull the eyeball farther anteriorly and transect the superior and inferior obliq ue tendons near the surface of the eyeball p osteriorly. 10. Rem ove the eyeball from the orbit. 11. Study the enucleated orbit (FIG. 7.56) . Use forceps to p ick out lobules of fat from the posterior portion of the orbit. 12. Find the nerve to the inferior oblique m uscle and follow it posteriorly to the in ferior d ivision of t h e oculom ot or n erve (CN III) . [G 622; L 354; N 85; R 137]

13. Trace the four rectus m uscles to their attachm ents on the co m m on t e n d in o us rin g . 14. Identify the structures that pass through the com m on tendinous ring: the o p t ic n e rve (CN II) an d ce n t ral art e ry o f t h e re t in a , sup e rio r an d in fe rio r d ivisio n s o f t h e o culo m o t o r n erve (CN III) , ab d uce n t n e rve (CN VI) , and n aso ciliary n e rve (FIG. 7.56) . 15. Exam ine the cut surface of the optic nerve and try to identify the central artery of the retina, which m ay be seen as a dark spot on the cut surface. 16. If the rem oved eyeball is in dissectible condition, use a new scalpel blade to cut it in half in the coronal plane. 17. Rem ove the vit re o us b o d y from the p osteriorly located vitreous cham ber. 18. Observe that the le n s separates the anterior and posterior cham bers of the eye (FIG. 7.57) . Note that the lens m ay be replaced by a prosthetic im p lant in som e cadavers. 19. Observe that the eye is com posed of three layers or tunics. Identify the b ro us (o ut e r) laye r com posed of the sclera (p osterior ve-sixths) and co rn e a (anterior one-sixth). [G 636; L 359; N 89; R 140] 20. Identify the ch o ro id , ciliary b o d y, and iris com prising the vascular (m id d le ) laye r (FIG. 7.57) . 21. Use a probe to gently m ove the partially detached re t in a , which form s the n e rvo us (in n e r) laye r . Observe that the retina is attached posteriorly near the o p t ic d isc (b lin d sp o t ) where the op tic nerve and retinal vessels enter or leave. 22. In well-preserved specim ens, it m ay be possible to identify the m acula , the highest center for visual acuity in hum ans, along the posterior aspect of the retina. 23. When you have nished your study of the explanted eye, p lace it in the tissue container.

Line of coronal cut Fibrous tunic (sclera) Vascular tunic (choroid) Nervous tunic (retina) Anterior (aqueous) chamber Cornea Macula

Pupil

Optic nerve Lens Iris Suspensory ligaments Ciliary body

FIGURE 7.57

Posterior (vitreous) chamber

Internal anatom y of the eye. Sagittal section.

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Disse ct io n Fo llo w-up 1. Use a skull to review the bones that form the m argin of the orbit, the walls of the orbit, and the openings at the ap ex of the orbit. Exam ine the m iddle cranial fossa and review the optic canal and superior orbital ssure. 2. Use the dissected specim en to review the nerves that course along the lateral wall of the cavernous sinus and pass through the sup erior orbital ssure to reach the apex of the orbit. Review the orbital course and function of each of these cranial nerves. 3. Review the course of the internal carotid artery through the cavernous sinus and note its relationship to the optic nerve near the optic canal. Note the origin of the op hthalm ic artery and its course through the optic canal and orbit. 4. Review the course of the optic nerve through the optic canal, com ing from the eyeball. 5. Use the cadaver to nd each of the six extraocular m uscles and levator palpebrae superioris and review the attachm ents of each. 6. Use an illustration to review the m ovem ents of the eyeball and relate each m ovem ent to the extraocular m uscles that are responsible. 7. Review the ciliary ganglion and note the origin of its presynaptic parasympathetic axons and the course of its postsynaptic axons to the eyeball. State the function of the two smooth muscles that are innervated by the ciliary ganglion. TABLE 7.6

Ext rao cular Muscle s

Muscle

Anterior Atta chments

Posterior Atta chments

Actions

Levator palpebrae superioris

Tarsal plate of the upper eyelid

Sphenoid bone

Elevation and retraction of the upper eyelid

Superior rectus

Sclera (anterior, superior surface)

Common tendinous ring

Elevation and adduction of the eye

Superior oblique

Sclera (posterior, lateral, superior surface)

Sphenoid bone

Depression, intorsion, and abduction of the eye

Trochlear n. (CN IV)

Lateral rectus

Sclera (anterior lateral surface)

Abduction of the eye

Abducent n. (CN VI)

Medial rectus

Sclera (anterior, medial surface)

Inferior rectus

Sclera (posterior, lateral, inferior surface)

Inferior oblique

Sclera (anterior, inferior surface)

Common tendinous ring

Innerva tion

Adduction of the eye Depression and adduction of the eye

Maxilla

Superior division of oculomotor n. (CN III)

Inferior division of oculomotor n. (CN III)

Elevation, extorsion, and abduction of the eye

Note that the above actions are referenced from a neutral position of the eye. Abbreviations: CN, cranial nerve; n., nerve.

DISARTICULATION OF THE HEAD Disse ct io n Ove rvie w The head m ust be detached from the vertebral colum n to allow a posterior approach to the cervical viscera. The order of dissection will be as follows: The retropharyngeal space will be opened from the base of the skull to the superior thoracic aperture. A wedge-shaped cut will be m ade in the occipital bone that will perm it the skull to be rem oved from the vertebral colum n.

Ske le t o n o f t h e Sub o ccip it al Re g io n Refer to an articulated skeleton and identify the following: [G 9, 13; L 7, 8; N 19, 22, 23; R 194] 1. Observe that the atlas (C1) does not have a body and the axis (C2) has the d ens, which is the body of C1 that became fused to C2 during developm ent (FIG. 7.58) . 2. Identify the p o st e rio r arch and the p o st e rio r t ub e rcle at its m idp oint and the an t e rio r arch and the an t e rio r t ub e rcle at its m idpoint. Ob serve that the atlas does not have a spinous process (FIG. 7.58) . 3. Use an illustration to identify the t ran sve rse lig am en t o f t h e at las and observe that it holds the dens to the anterior arch of the atlas (FIG. 7.58)

Anterior tubercle of atlas (C1)

Anterior arch

Superior articular facet Atlas (C1)

Dens

Transverse process

Transverse foramen Axis (C2)

Transverse ligament of atlas Vertebral foramen

FIGURE 7.58

Facet for dens Space for dens

Superior articular facet Posterior arch

Skeleton and ligam ents of the atlantoaxial joint.

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4. On the superior aspect of C1 bilaterally, identify the sup e rio r art icular face t s and note their horizontal orientation (FIG. 7.58) . On an articulated skeleton, observe that the articulation between the superior articular surfaces with the o ccip it al co n d yle s at the b ase of the skull creates the at lan t o -o ccip it al jo in t , which allows nodding m ovem ent, or the “yes” type of m otion, between the head and neck. 5. On the superior aspect of C2 bilaterally, identify the sup e rio r art icular face t s for articulation with the at las . On an articulated skeleton, observe that the articulation between C1 and C2 creates the at lan t o axial jo in t , which allows rotational m ovem ent, or the “no” type of m otion, between the head and neck. 6. Identify the roughened area of the p h aryn g e al t ub e rcle on the inferior surface of the occip ital bone anterior to the fo ram e n m ag n um (FIG. 7.59) . 7. From the inferior view, identify the foram en m agnum (FIG. 7.59) . Review the structures that pass through the foram en m agnum : brainstem , vertebral arteries (left and right), and cervical roots of the accessory nerves (left and right). [G 593; L 302; N 11; R 30] 8. Identify the h yp o g lo ssal can al (FIG. 7.59) and recall that the hypoglossal nerve (CN XII) p asses through it. 9. Identify the jug ular fo ram e n (FIG. 7.59) and review the structures that p ass through it: glossopharyngeal nerve (CN IX), vagus nerve (CN X), accessory nerve (CN XI), and venous blood from the sigm oid sinus.

Disse ct io n In st ruct io n s Re t ro p h aryn g e al Sp ace 1. Return to the cervical region and bilaterally gather the ends of the cutaneous branches of the cervical plexus (transverse cervical, great auricular, lesser occip ital) and re ect them p osteriorly so that they rem ain attached to the vertebral colum n. 2. Clean the anterior and posterior borders of both SCMs to their superior attachm ents at the m astoid processes. 3. Re ect each SCM superiorly, taking care to preserve the accessory nerve. 4. Use your ngers to create a gap posterior to the right and left carotid sheaths. Push your ngers m edially until they touch in the m idline and open up the space p osterior to the pretracheal fascia surrounding the viscera of the neck. 5. Push your ngers superiorly and inferiorly in the re t ro p h aryn g e al (re t ro visce ral) sp ace and enlarge the sep aration between the viscera and p retracheal fascia anteriorly and the vertebral colum n and p revertebral fascia posteriorly (FIG. 7.60) . 6. Place a probe in the retropharyngeal space posterior to the carotid sheaths so it passes com pletely across

Occipital bone: Hypoglossal canal Occipital condyle Basilar part Pharyngeal tubercle Foramen magnum External occipital protuberance

FIGURE 7.59

Occip ital bone. Inferior view.

the neck within the retrop haryng eal space. Keep the probe in the space and once again m ove your ngers superiorly all the way up to the base of the skull. Move your ngers inferiorly and observe that the retrop haryng eal space extends into the m ediastinum of the thorax.

Trachea

Pretracheal fascia

Thyroid gland Esophagus Common carotid a. Internal jugular v. Vagus n. Carotid sheath Retropharyngeal space

FIGURE 7.60 Transverse section through the neck showing the retropharyngeal space.

CHAPTER 7

Disart iculat io n o f t h e He ad The head will be separated from the vertebral colum n at the atlanto-occip ital joint after m aking a wedge-shap ed cut in the occipital bone. 1. With the cadaver in the supine position, rotate the head until you can identify the accessory nerve and the structures that exit the jugular foram ina at the base of the skull. Verify the location of these structures bilaterally because you will keep them attached to the head during re ection. 2. Use a saw to m ake two ob liq ue cuts th roug h th e occip ital b on e, p osterior to th e jug ular foram in a, in ord er to p reserve th e structures p assin g th roug h it, an d p osterior to th e h yp og lossal can als at th e fo ram en m ag n um (FIG. 7.61) . Th e two cuts sh o uld b e p a ra lle l t o t h e p e t ro u s rid g e o f t h e t e m p o ra l b o n e . Extern ally, th e saw cuts sh ould p ass p o sterior to th e m astoid p ro cess of th e tem p oral b o n e so th e attach m en ts o f th e SCMs rem ain in tact. 3. Slide a thin chisel along the base of the skull adjacent to the atlanto-occip ital joint. 4. Use a scalpel to cut through the joint capsule and use the chisel to separate the articular surfaces. Repeat this process bilaterally. If the joint is dif cult to access from the supine position, the cadaver m ay be rotated to the prone position. 5. In order to free the head for re ection, the longus capitis and rectus cap itis anterior m uscles and the anterior atlanto-occipital m em brane need to be cut. Push the head anteriorly and insert a scalpel into the m ost superior part of the retropharyngeal space to cut the adhered soft tissues. Gently continue to force the head forward until it is freed from the C1. Note that it rem ains attached to the pharynx. 6. With the head fully detached, but not yet re ected, identify the sym p at h e t ic t run k and the sup e rio r

THE HEAD AND NECK

Pre ve rt e b ral an d Lat e ral Ve rt e b ral Re g io n s [G 750; L 310; N 131; R 186] 1. On the anterior surface of the cervical vertebral colum n, exam ine the p re ve rt e b ral fascia . Observe that the prevertebral fascia covers the p reverteb ral m uscles (lo n g us co lli and lo n g us cap it is m uscle s ) and the lateral vertebral m uscles (an t e rio r , m id d le , and p o st e rio r scale n e m uscle s ) (FIG. 7.62) . 2. On the left side of the cervical vertebral colum n, identify the sup e rio r , m id d le , and in fe rio r ce rvical sym p at h e t ic g an g lia of the sym p at h e t ic t run k. Note that frequently, the inferior cervical ganglion is fused with the rst thoracic ganglion to form the ce rvico t h o racic (st e llat e ) g an g lio n . 3. Identify the g ray ram i co m m un ican t e s that connect the sym pathetic ganglia with the anterior ram i of cervical spinal nerves.

Jugular process

Basilar part of occipital bone

Rectus capitis anterior m.

Rectus capitis lateralis m.

Levator scapulae m. Cervical plexus

Longus capitis m. Hypoglossal canal Cut 3

Jugular foramen

285

ce rvical sym p at h e t ic g an g lio n on the anterior surface of the cervical vertebral colum n. [G 751; L 310; N 30] 7. On the right side, leave the internal carotid nerve intact and isolate the sym pathetic trunk. 8. Re ect the right sym p athetic trunk and superior cervical ganglion with the head, cervical viscera, and associated neurovascular structures anteriorly until the chin rests on the thorax. 9. Inspect the re ected base of the skull from the p osterior perspective and look for the structures associated with the jugular foram en and the hypoglossal canal.

Transverse process: of atlas of axis

Superior border of petrous part of temporal bone

•

Longus colli m. Scalene muscles: Anterior Middle Posterior Brachial plexus

Cut 2

Cut 1

1st rib 2nd rib

FIGURE 7.61

Cuts for head disarticulation.

FIGURE 7.62

Phrenic n.

Prevertebral m uscles.

Subclavian a.

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4. Review the contributions to the brachial plexus m ade by the anterior ram i of spinal nerves C5–C8. 5. At the base of the neck, follow the right and left vertebral arteries into the transverse foram ina of vertebra C6. Use an illustration to ap preciate that as the verteb ral artery ascends within the neck, it is well protected within the transverse foram ina.

6. Superiorly, at the cut edge of the C1 vertebra, identify where the verteb ral artery em erges from the transverse foram en of the atlas (C1). Recall that the right and left vertebral arteries ascend into the skull through foram en m agnum p rior to form ing the basilar artery.

Disse ct io n Fo llo w-up 1. Use a skull to review the anatom y of the occip ital bone. 2. In the cadaver, review the structures that pass through the foram en m agnum , hypoglossal canal, and jugular foram en. 3. Review the course of the sym pathetic trunk from the upper thorax to the base of the skull. 4. Review the origin and relationships of the roots of the brachial plexus. 5. Return the disarticulated head and attached structures of the neck back to anatom ical position.

PHARYNX Disse ct io n Ove rvie w The pharynx extends from the base of the skull to the inferior border of the cricoid cartilage (vertebral level C6). The pharynx can be subdivided from superior to inferior as the nasopharynx, oropharynx, and laryngopharynx. Use an illustration to observe that the airway crosses the digestive tract in the pharynx. The p h aryn g e al wall consists of three layers. The outerm ost layer is com posed of b ucco p h aryn g e al fascia , the adventitia of the pharynx. Note that it is continuous with the connective tissue covering the buccinator m uscle. The m iddle layer is a m uscular laye r com posed of an outer circular part and an inner longitudinal part. The innerm ost layer is com posed of a m uco us m e m b ran e with a thick subm ucosa that contributes to the pharyngobasilar fascia. The order of d issection will be as follows: The external surface of the pharynx will be dissected from the posterior direction. The p haryngeal plexus of nerves will be identi ed and the borders of the pharyngeal constrictor m uscles will be de ned. The stylop haryngeus m uscle and glossopharyngeal nerve will be id enti ed. The contents of the carotid sheath will be exam ined, and CN IX, X, XI, and XII will be followed from the base of the skull to their regions of distribution. The sym pathetic trunk will be studied.

Disse ct io n In st ruct io n s Muscle s o f t h e Ph aryn g e al Wall [G 758, 760; L 315, 316; N 67; R 169] 1. With the cadaver in the supine position, lift the head and place the chin on the thorax. The pharynx should now be exposed along its posterior surface. 2. Palpate the tips of the g re at e r h o rn s o f t h e h yo id b o n e and the p o st e rio r asp e ct o f t h e t h yro id cart ilag e . 3. On the posterior aspect of the m uscular pharynx, identify the b ucco p h aryn g e al fascia . As each m uscle is identi ed in the following dissection steps, rem ove the b ucco p h aryn g e al fascia from the p osterior surface of the m uscle. 4. In the m idline of the posterior pharynx, identify the p h aryn g e al rap h e , the posterior attachm ent of the

three p haryngeal constrictor m uscles to each other (FIG. 7.63A) . 5. Beginning inferiorly on the posterior aspect of the pharynx at the height of the thyroid cartilage, identify the in fe rio r p h aryn g e al co n st rict o r m uscle (FIG. 7.63B) . 6. The inferior pharyngeal constrictor can be subdivided into the t h yro p h aryn g e us and crico p h aryn g e us m uscle s based on the anterior attachm ents of the bers (FIG. 7.63B) . Note that the bers of the crico p h aryn g e us m uscle are continuous with the circular m uscle bers of the esophagus. 7. Identify the m id d le p h aryn g e al co n st rict o r m uscle at the height of the g reater horn of the hyoid bone (FIG. 7.63B) . Observe that the inferior part of the m iddle pharyngeal constrictor m uscle lies deep to the inferior p haryng eal constrictor m uscle.

CHAPTER 7

A

THE HEAD AND NECK

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287

B

Pharyngeal tubercle Stylopharyngeus m.

Pharyngobasilar fascia

Posterior belly of digastric m.

Pterygomandibular raphe

Superior pharyngeal constrictor m. Middle pharyngeal constrictor m.

Stylohyoid m. Greater horn of hyoid bone

Stylohyoid ligament

Pharyngeal raphe

Inferior pharyngeal constrictor m.: Thyropharyngeal part

Thyroid gland

Cricopharyngeal part

Hyoid bone Thyrohyoid ligament Thyroid cartilage Cricothyroid ligament

Parathyroid glands

Cricoid cartilage Esophagus

FIGURE 7.63

Muscles of the pharynx. A. Posterior view. B. Lateral view.

8. Superior to the m iddle pharyngeal constrictor m uscle, identify the sup e rio r p h aryn g e al co n st rict o r m uscle (FIG. 7.63A) . Observe that the inferior part of the superior pharyngeal constrictor m uscle lies deep to the m iddle p haryng eal constrictor m uscle. Clear the b uccopharyngeal fascia from the p osterior surfaces of all the pharyngeal constrictors. 9. Review the attachm ents and actions the pharyngeal constrictor m uscles (see TABLE 7.7). 10. Use b lunt d issection to d e ne the sup erior b ord er of the sup erior p haryng eal constrictor m uscle and id entify the p h a ryn g o b a sila r fa scia , the d ense conn ective tissue m em b rane that attaches the sup erior ed g e of the sup erior constrictor to th e b ase of the skull. 11. Identify the st ylo p h aryn g e us m uscle located on the lateral asp ects of the pharynx app roxim ately one nger’s width above the greater horn of the hyoid b one. Follow the stylopharyngeus m uscle superiorly and p alpate its attachm ent to the m edial surface of the styloid p rocess. Follow it inferiorly to the point where it pierces the pharynx. 12. Ob serve that the stylop haryng eus m uscle enters the p haryng eal wall b y p assing b etween the sup erior and m id d le p haryng eal constrictor m uscles (FIG. 7.63A) . 13. Review the attachm ents and actions the stylopharyng eus m uscle (see TABLE 7.7).

Ne rve s o f t h e Ph aryn x [G 758; L 316; N 71; R 167] 1. Use a probe to clean the posterior and lateral surfaces of the stylopharyngeus m uscle and identify the g lo sso p h aryn g e al n e rve (CN IX) that crosses the posterior and lateral surfaces of the stylopharyngeus m uscle to enter the pharynx (FIG. 7.64A) . 2. Identify the p h aryn g e al p le xus o f n e rve s (FIG. 7.64A) . The pharyngeal plexus is located on the posterolateral aspect of the p harynx. Note that the p haryngeal plexus receives branches from the glossopharyngeal nerve (sensory to the pharyngeal m ucosa), vagus nerve (m otor to the pharyngeal constrictor m uscles), and the superior cervical sym pathetic ganglion (vasom otor). 3 . Id en t ify t h e co n t e n t s o f t h e ca ro t id sh e a t h fro m th e p o st erio r view ( FIG. 7 .6 4 A) . Fo llo w th e in t ern al caro t id artery su p erio rly as far as p o ssib le an d o b serve th at it lies m ed ial to th e in tern al ju g u lar vein . 4. Identify the g lo sso p h aryn g e al n e rve (CN IX) , vag us n e rve (CN X) , and acce sso ry n e rve (CN XI) where they exit the jugular foram en m edial to the internal jugular vein (FIG. 7.64A) . 5. Follow the g lo sso p h aryn g e al n e rve (CN IX) inferiorly and observe that it passes between the internal and external carotid arteries as it approaches the stylopharyngeus m uscle.

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Pharyngeal tubercle

Superior cervical sympathetic ganglion

Cranial nerves IX, X, XI at jugular foramen

XII

Internal jugular v. Internal carotid n. Glossopharyngeal n. (IX)

Parotid gland

Ascending pharyngeal a.

Hypoglossal n. (XII)

Stylopharyngeus m.

Accessory n. (XI) entering sternocleidomastoid m.

Submandibular gland

Sympathetic trunk (retracted) Glossopharyngeal n. (IX)

Common carotid a.

Pharyngeal plexus

Superior laryngeal n.:

Vagus n. (X)

Internal br. External br.

Vagus n. (X)

Thyroid gland

Cricothyroid m. Internal jugular v.

Esophagus

A

B Recurrent laryngeal nerves

FIGURE 7.64

Right recurrent laryngeal nerve

Nerves and vessels related to the pharyngeal wall. A. Posterior view. B. Lateral view.

6. Follow the vag us n e rve inferiorly to the thorax and observe that it lies p osterior to the internal carotid artery and internal jugular vein in the carotid sheath. 7. Identify the sup e rio r laryn g e al n e rve arising from the vagus nerve about 2.5 cm inferior to the base of the skull. Trace the branches of the superior laryngeal nerve to the larynx (FIG. 7.64B) . 8. Identify the p h aryn g e al b ran ch o f t h e vag us n e rve arising near the base of the skull. Follow the pharyngeal branch to the pharyngeal plexus. 9. Identify the accesso ry n e rve (CN XI) , which usually passes between the internal jugular vein and the internal carotid artery to reach the deep surface of the SCM (FIG. 7.64A) . 10. Identify the h yp o g lo ssal n e rve (CN XII) in the subm andibular triangle and follow it posteriorly and superiorly as far as the base of the skull (FIG. 7.64B) . Observe that the hypoglossal nerve passes lateral to the internal and external carotid arteries but m edial to the internal jugular vein. 11. On the right side of the cadaver, verify that the sup e rio r ce rvical sym p at h e t ic g an g lio n and the sym p at h e t ic t run k are posterior and m ed ial to the carotid sheath (FIG. 7.64A) .

Op e n in g t h e Ph aryn x 1. Use a scalpel to m ake a sm all incision through the posterior wall of the pharynx in the m idline at the approxim ate level of the oral cavity.

2. Use scissors to extend the incision sup eriorly and inferiorly through the pharyngeal raphe up to the pharyngeal tubercle at the base of the skull and down to the esop hagus. [L 317] 3. Sp read the cut edges of the p harynx and observe that the lum en of the pharynx com m unicates anteriorly with three cavities: nasal cavity, oral cavity, and larynx (FIG. 7.65) . 4. Identify the parts of the p harynx: n aso p h aryn x , o ro p h aryn x , and laryn g o p h aryn x (FIG. 7.65) . 5. From superior to inferior, identify the p o st e rio r n asal ap e rt ure s on either side of the n asal sep t um , the uvula an d so ft p alat e , the b ase o f t h e t o n g ue , the e p ig lo t t is and e p ig lo t t ic valle culae , and the laryn g e al in le t (FIG. 7.65) .

Bise ct io n o f t h e He ad A sagittal cut m ust be m ade through the skull very close to the m edian p lane. The objective during the head bisection is to keep the nasal septum intact while cutting as close to the m idline as possible. Exam ine each nasal cavity and decide on which side of the nasal septum the saw cut should be m ad e in order to avoid cutting the septum . 1. Begin the bisection of the head on the posterior aspect of the pharynx. Use a scalpel to divide the uvula and the soft palate along the m edian plane. 2. Turn the head and use a scalpel to cut through the upp er lip and the cartilages of the external nose on one side of the nasal septum , just off the m idline.

CHAPTER 7

THE HEAD AND NECK

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289

Nasal septum (cut) Choana

Nasopharynx

Oropharynx

Pharyngeal recess Pharyngeal tonsil Torus tubarius Opening of pharyngotympanic tube

Palate

Fauces

Palatoglossal fold Palatine tonsil Palatopharyngeal fold Epiglottic vallecula

Tongue

Epiglottis Laryngopharynx

Vocal folds of larynx Esophagus Trachea

FIGURE 7.65

Regions of the pharynx. Sagittal cut.

3. Align a saw just lateral to the crista galli in line with your intended cut lateral to the septum so that as you cut through the skull from superior to inferior, you preserve the crista galli. 4. Cut inferiorly through the frontal and nasal bones until you reach the ethm oid bone in the oor of the anterior cranial fossa. 5. Once past the nasal septum , aim to cut through the m idline of structures as m uch as possible. 6. Continue the m idline cut through the sphenoid bone and into the basilar part of the occipital bone. Cut through the hard palate stop ping when the saw is free of the bone and rests in the oral cavity. Do not cut the tongue or m andible at this tim e. 7. The two superior halves of the head should separate from each other and expose the superior aspect of the tongue.

3.

4.

5.

6.

7.

In t e rn al Asp e ct o f t h e Ph aryn x [L 318, 319; N 64; R 157] 1. In the bisected head, observe that the n aso p h aryn x lies posterior to the nose and superior to the soft palate (FIG. 7.65) . 2. Identify the p o st e rio r n asal ap e rt ure (ch o an a) , the transition region from the nasal cavity to the nasop harynx. Ob serve that the left and right choanae

8.

9.

are separated by the posterior aspect of the nasal septum . [G 766; L 318; N 68] On the lateral wall of the nasopharynx, identify the o p e n in g o f t h e p h aryn g o t ym p an ic t ub e (aud it o ry t ub e , e ust ach ian t ub e ) . Superior to the opening of the pharyngotym p anic tub e, identify the t o rus t ub arius , the cartilage of the pharyngotym panic tube covered by m ucosa (FIG. 7.65) . Extending posteroinferiorly from the torus tubarius, identify the salp in g o p h aryn g eal fo ld . Note that the salpingop haryngeal fold is the m ucosal fold overlying the salp ingopharyngeus m uscle. Superior and p osterior to the torus tubarius, identify the p h aryn g e al re ce ss . The p h aryn g e al t o n sil (ad e n o id ) is located in the m ucous m em brane above the pharyngeal recess. Observe that the o ro p h aryn x lies posterior to the oral cavity and is bounded superiorly by the soft palate. The oropharynx extends inferiorly to the level of the epiglottis (FIG. 7.65) . In the oropharynx, identify the p alat o g lo ssal fo ld s . The palatoglossal folds form a dividing line between the oral cavity and the oropharynx. The transitional region between the oral cavity and oropharynx is called the fauce s . Identify the p alat o p h aryn g e al fo ld s p osterior to

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the palatoglossal folds. The palatopharyngeal folds d escend along the lateral wall of the oropharynx. 10. Identify the location of the p alat in e t o n sil b etween each palatoglossal fold and p alatop haryngeal fold. 11. Identify the laryn g o p h aryn x p osterior to the larynx. The laryngopharynx extends from the hyoid bone to the lower border of the cricoid cartilage (FIG. 7.65) . [G 762; L 317, 318; N 66; R 165] 12. In the m idline of the laryngopharynx, identify the cut edge of the e p ig lo t t is superior to the laryn g e al in le t (ad it us) . Observe that the m argins of the laryngeal inlet are form ed laterally by the arye p ig lo t t ic fold s , which arch posteroinferiorly from the epiglottis.

13. Gently press the tip of the p robe inferolateral to the aryep iglottic fold along the p ath of the p irifo rm rece ss . Note that the p iriform recess is bordered m edially by the laryn x , laterally by the t h yro id cart ilag e , and posteriorly by the in fe rio r p h aryn g e al co n st rict o r m uscle . CLIN ICA L CORRELATION

Ad e n o id s Enlarged pharyngeal tonsils are called adenoids. Adenoids obstruct the ow of air from the nose throug h the nasopharynx, m aking m outh-b reathing necessary.

Disse ct io n Fo llo w-up 1. Review the attachm ents, innervation, and action of the pharyngeal constrictor m uscles. 2. Use a textbook description and the cadaver to review the pharyngeal plexus. 3. Trace each of the following cranial nerves from the posterior cranial fossa to its area of distribution: glossopharyngeal (CN IX), vagus (CN X), accessory (CN XI), and hypoglossal (CN XII). 4. Review the relationships of the contents of the carotid sheath. 5. Review the boundaries and contents of each part of the pharynx. 6. Return the bisected head to anatom ical position.

TABLE 7.7

Muscle s o f t h e Ph aryn x

Muscle

Anterior Atta chments

Posterior Atta chments

Superior pharyngeal constrictor

Pterygoid hamulus and pterygomandibular fascia

Pharyngeal tubercle and pharyngeal raphe

Middle pharyngeal constrictor

Greater horn of the hyoid bone and inferior portion of the stylohyoid ligament

Inferior pharyngeal constrictor

Oblique line of the thyroid cartilage and lateral surface of the cricoid cartilage

Stylopharyngeus

Styloid process (superior attachment)

Pharyngeal raphe

Posterior and superior borders of thyroid cartilage with palatopharyngeus (inferior attachment)

Actions

Innerva tion

Constrict wall of pharynx during swallowing

Vagus n. (CN X) via pharyngeal plexus

Elevate pharynx and larynx during swallowing and speaking

Glossopharyngeal nerve (CN IX)

Abbreviations: CN, cranial nerve; n., nerve.

NOSE AND NASAL CAVITY Disse ct io n Ove rvie w There are two nasal cavities: right and left. The nostril (naris) is the anterior entrance to the nasal cavity. Posteriorly, each nasal cavity opens into the nasopharynx through a choana. The nasal cavity is lined by m ucosa that is attached directly to bones and cartilages. The bones and cartilages give the walls of the nasal cavity their characteristic contours. The superior one-third of the nasal m ucosa is olfactory in nature, and the lower two-thirds is resp iratory in nature. The nasal m ucosa is highly vascular and capable of engorg em ent. The order of dissection will be as follows: The skeleton of the nasal cavity and nasal cartilages will be studied. The nasal septum will be exam ined. The features of the lateral nasal wall will be studied. The openings of the paranasal sinuses will be identi ed. The m axillary sinus will be exam ined.

CHAPTER 7

Ske le t o n o f t h e Nasal Cavit y

THE HEAD AND NECK

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291

Nasal bone

Refer to a skeleton or disarticulated skull to identify the following skeletal features from an anterior view (FIG. 7.66) : [G 585; L 298; N 4; R 22] 1. Identify the an t e rio r n asal ap e rt ure and observe that it is roughly heart shap ed, with the ap ex of the “heart” directed sup eriorly toward the n asal b o n e s on the bridge of the nose and the broader aspect of the “heart” centered around the an t e rio r n asal sp in e inferiorly. 2. Follow the m argin of the nasal aperture superiorly and identify the fro n t al p ro ce ss o f t h e m axilla between the n asal b o n e and lacrim al b o n e . 3. Identify the bony part of the n asal se p t um ap proxim ately in the m idline of the skull. Observe that the nasal sep tum creates a division between the rig ht and left nasal cavities. 4. On the lateral wall of the nasal cavities, identify the p aired in ferio r n asal co n ch a curving away from the lateral walls into their respective nasal cavities. 5. Superior to the inferior nasal concha, identify the m id d le n asal co n ch a . Note that the m iddle nasal concha is part of the ethm oid bone, whereas the inferior nasal concha is an independent bone.

Lacrimal bone

Maxilla: Frontal process Anterior nasal aperture Anterior nasal spine

Middle nasal concha Inferior nasal concha Nasal septum

Use an illustration to identify the bony features of the lateral nasal wall (FIG. 7.67) : [G 667; L 337; N 37; R 48]

FIGURE 7.66

Skeleton of the nasal region.

1. Identify the e t h m o id b o n e and ob serve that it form s part of the oor of the anterior cranial fossa and the roof of the nasal cavities. The ro o f o f t h e n asal cavit y is a narrow region bounded by the nasal septum and by parts of three other bones: nasal bone, ethm oid bone (cribriform plate), and sphenoid bone. 2. Identify the crib rifo rm p lat e and recall that the sm all apertures contain the branches of the olfactory nerve (CN I). 3. Observe that the p e rp e n d icular p lat e o f t h e e t h m o id b o n e form s p art of the bony nasal septum in the m idline or m e d ial wall o f t h e n asal cavit y. 4. Observe that the sup e rio r n asal co n ch a and m id d le n asal co n ch a form part of the lateral wall of each nasal cavity. The rem ainder of the lat e ral wall o f t h e n asal cavit y consists of the m axilla , lacrim al b o n e , in fe rio r n asal co n ch a , and p e rp en d icular p lat e o f t h e p alat in e b o n e (FIG. 7.67) . Frontal bone Nasal bone Sphenopalatine foramen

Sphenoid bone: Opening of sphenoidal sinus

Ethmoid bone: Cribriform plate

Sphenoidal sinus

Superior nasal concha

Body

Middle nasal concha

Medial plate

Lacrimal bone

Lateral plate

Inferior nasal concha

of pterygoid process

Pterygoid hamulus

Maxilla: Palatine process Incisive canal

Palatine bone: Perpendicular plate Horizontal plate

FIGURE 7.67

Skeleton of the lateral wall of the right nasal cavity.

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5. The perpendicular plate of the palatine bone lies anterior to the m e d ial p lat e o f t h e p t e ryg o id p ro ce ss of the sp h e n o id b o n e . 6. Pass a pipe cleaner or the tip of a probe gently through the sp h e n o p alat in e fo ram e n and observe that this op ening connects the nasal cavity with the pterygopalatine fossa. 7. In the sagittal cut, identify the sp h e n o id al sin us in the b o d y o f t h e sp h e n o id and observe that it is connected to the nasal cavity via the o p e n in g o f t h e sp h e n o id al sin us . 8. Identify the in cisive can al within the p alat in e p ro cess o f t h e m axilla . Observe that the palatine process of the m axilla form s the anterior aspect of the o o r o f t h e n asal cavit y and hard palate, whereas the h o rizo n t al p lat e o f t h e p alat in e b o n e form s the posterior aspect of the oor of the nasal cavity and hard palate.

Disse ct io n In st ruct io n s

Anterior ethmoidal n. (V1)

Ex t e rn al No se [G 666; N 35; R 49] 1. On the cadaver, palpate the nasal bones and the lat e ral n asal cart ilag e s (FIG. 7.68) . Observe that the lateral nasal cartilages give shape to the bridge of the nose. 2. Identify the se p t al cart ilag e that sep arates the right and left nasal cavities and form s the anterior part of the nasal septum . Note that the lateral nasal cartilages are an extension of the sep tal cartilag e. 3. Lateral to the septal cartilage, palpate the alar cart ilag e s , the cartilages that give shape to the m edial side of the nostrils (FIG. 7.68) . 4. In the cadaver, observe that the bones and cartilages of the nasal cavity are obscured by the m ucosa that covers them . Note that the vessels and nerves of the nasal cavity are contained within this m ucosa.

Nasal Se p t um [G 667; L 336, 340; N 38; R 148] 1. Exam ine the half of the head that contains the n asal se p t um . 2. In the m ucosa of the nasal septum , use blunt dissection to identify the n aso p alat in e n e rve and the sp h e n o p alat in e art e ry (FIG. 7.69) . 3. Observe that the nasopalatine nerve and the sphenopalatine artery pass diagonally down the nasal septum

Region of olfactory epithelium

Sphenopalatine foramen Nasopalatine n. (V2) Sphenopalatine a. Incisive canal

FIGURE 7.69 Nerve and arterial sup ply to the m ucosa of the nasal septum . Left side of septum is shown.

from the sphenopalatine foram en to the incisive canal. Note that in addition to the nasal septum , the nasopalatine nerve and sphenopalatine artery supply a portion of the oral m ucosa that covers the hard palate. 4. The m ucosa near the cribriform plate is the olfact ory area (FIG. 7.69) . The olfactory area also extends down the lateral wall of the nasal cavity for a short distance. 5. Strip the m ucosa off the visible side of the nasal septum and identify the p erp end icular p late of th e ethm oid b on e , the vom er , and the sep t al cartilag e (FIG. 7.70) .

Nasal bone Nasal cartilages: Lateral Septal

Frontal bone Nasal bone

Alar

Perpendicular plate of ethmoid Septal cartilage

Vomer

Nostril

FIGURE 7.68

Cartilages of the external nose.

FIGURE 7.70

Left side of the nasal septum .

CHAPTER 7

Lat e ral Wall o f t h e Nasal Cavit y [G 670, 671; L 338, 340; N 36; R 146, 147] 1. Exam ine the half of the head that does not contain the nasal sep tum . 2. In sp ect th e la t e ra l w a ll o f t h e n a sa l ca vit y an d id en tify th e sp h e n o e t h m o id a l re ce ss p osterior to th e su p e rio r n a sa l co n ch a (FIG. 7.71) . In ferior to th e sup erior n asal con ch a, p lace th e tip of th e p rob e in to th e sp ace of th e su p e rio r m e a t u s. 3. Identify the m id d le co n ch a curving superior to the m id d le m e at us and the in fe rio r co n ch a curving superior to the in fe rio r m e at us . 4. Identify the ve st ib ule , the area superior to the nostril and anterior to the inferior m eatus and the at rium . The atrium is the area superior to the vestibule and anterior to the m iddle m eatus. 5. Use scissors to rem ove the in fe rio r co n ch a . 6. Inferior to the cut edge of the inferior concha, identify the op ening of the n aso lacrim al d uct (FIG. 7.72) . 7. Elevate the m id d le co n ch a until you hear the bone b reak and the concha can be re ected superiorly. Leave the m iddle attached by the m ucosa. 8. In the m iddle m eatus, identify a curved slit, the se m ilun ar h iat us (h iat us se m ilun aris) (FIG. 7.72) . 9. Posterior to the curvature of the sem ilunar hiatus, identify the e t h m o id al b ulla (b ulla et h m o id alis) , which bulges into the nasal cavity. 10. Within the sem ilunar hiatus, identify three openings. From anterior to posterior, they are the o p e n in g o f t h e fro n t al sin us , the o p e n in g o f t h e an t e rio r e t h m o id al ce lls , and the o p e n in g o f t h e m axillary sin us (FIG. 7.72) . A piece of wire m ay be passed through the openings to verify the orientation and continuity of each space with the nasal cavity.

Frontal sinus

THE HEAD AND NECK

Frontal sinus

Sphenoidal sinus

Middle concha Inferior concha

Atrium

Vestibule

Superior meatus Middle meatus Inferior meatus

Opening of the pharyngotympanic tube

FIGURE 7.71 Conchae and m eatuses of the lateral wall of the rig ht nasal cavity.

11. On the sum m it of the ethm oidal bulla, identify the o p e n in g o f t h e m id d le e t h m o id al ce lls . 12. Identify the op e n in g o f t h e p o st erio r e t h m oid al ce lls in the superior m eatus. 13. Identify the op e n in g o f t h e sp h e n o id al sin us in the sp henoethm oidal recess. 14. Exam ine the sp h e n o id al sin us (FIG. 7.72) . Observe that the sphenoidal sinus is a p aired structure lined by m ucosa that is continuous with the m ucosa of the nasal cavity. Note that the sphenoidal sinus lies directly inferior to the hypophyseal fossa and pituitary gland . [G 674; L 336; N 43; R 146] 15. Note that the e t h m o id al ce lls are located between the nasal cavity and the orbit (FIG. 7.73) . The ethm oidal cells m ay be observed from the

Openings of posterior ethmoidal cells Superior concha (cut)

Rod entering opening of frontal sinus Opening of anterior ethmoidal cells

Hypophyseal fossa

Opening of maxillary sinus

Opening of middle ethmoidal cells

Sphenoidal sinus Opening of pharyngotympanic tube

Inferior concha (cut)

Nasal vestibule

FIGURE 7.72

293

Sphenoethmoidal recess

Superior concha

Semilunar hiatus:

Opening of nasolacrimal duct

•

Ethmoidal bulla

Op enings in the lateral wall of the right nasal cavity.

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Crista galli

Orbital part of frontal bone

Frontal sinus

Crista galli

Anterior ethmoidal cells Middle ethmoidal cells Ethmoidal cells

Sphenoidal sinus

FIGURE 7.73

Posterior ethmoidal cells

Orbit

Middle meatus

Opening of maxillary sinus

Maxillary sinus

Inferior meatus

Paranasal sinuses. Superior view. Inferior nasal concha

superior persp ective by reviewing the dissection of the orbit com pleted previously. 16. In an im age of a coronal cut of the head, observe that the m axillary sin us is a three-sided pyram id with an average adult capacity of about 15 m L (FIG. 7.74) . 17. Observe that the oor of the orbit form s the roof of the m axillary sinus. The infraorbital nerve innervates the m ucosa of the sinus. The op ening of the m axillary sinus is near its roof, thus the m axillary sinus drains superiorly (FIG. 7.74) . 18. Observe that the oor of the m axillary sinus is the alveolar process of the m axilla and that the roots of the m axillary teeth m ay project into the m axillary sinus. CLIN ICA L CORRELATION

Sp h e n o id al Sin us Surgical approaches to the pituitary gland take advantage of the fact that the sphenoidal sinus and nasal cavity provide a direct approach.

Nasal septum Tooth Middle nasal concha

FIGURE 7.74

Coronal section through the m axillary sinus.

CLIN ICA L CORRELATION

Max illary Sin us When the head is in the up right position, the m axillary sinus cannot drain. If infections of the m axillary sinus persist, an opening m ay be surgically created through the inferior m eatus near the oor of the m axillary sinus to p rom ote drainage. If the roots of m axillary teeth project into the m axillary sinus, they are covered only by m ucosa. During extraction of a m axillary m olar or p rem olar tooth, the m ucosa superior to the projecting root m ay be torn. As a result, a stula m ay form between the oral cavity and the m axillary sinus.

Disse ct io n Fo llo w-up 1. Use an illustration and the dissected cadaver to review the features of the lateral wall of the nasal cavity. 2. Review the relationship of the paranasal sinuses to the orbit, anterior cranial fossa, and nasal cavity. 3. Review the drainage point of each paranasal sinus.

HARD PALATE AND SOFT PALATE Disse ct io n Ove rvie w The palate form s the oor of the nasal cavity and the roof of the oral cavity. The palate consists of two portions: The h ard p alat e form s the anterior two-thirds, and the so ft p alat e constitutes the posterior one-third. The palate is covered by nasal m ucosa on its superior surface and oral m ucosa on its inferior surface. Num erous m ucous glands (p alat in e g lan d s) are present on the oral surface of the palate.

CHAPTER 7

THE HEAD AND NECK

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295

The order of dissection will be as follows: The m ucosal folds of the inner pharyngeal wall will be reviewed. The m ucosa will be stripped from the inner surface of the pharynx, and the m uscles that constitute the inner longitudinal m uscle layer will be exam ined. Muscles that m ove the soft palate will then be studied. The nerves and blood vessels of the palate will be identi ed. The palatine canal and pterygopalatine fossa will be dissected from the m edial aspect. The pterygopalatine ganglion will be identi ed. The nerves and vessels of the nasal cavity and palate will be sum m arized.

Ske le t o n o f t h e Palat e Refer to a disarticulated skull to identify the following skeletal features from an inferior view (FIG. 7.75) .

Maxilla: Incisive foramen

Hard Palat e [G 658; L 301; N 10; R 45] 1. Exam ine the upper teeth on the inferior aspect of the m axilla . Observe that each tooth has an individual socket dem arcated b y an alve o lar p ro ce ss . 2. Posterior to the incisors, identify the in cisive fo ram e n between the p alat in e p ro ce sse s o f t h e m axillae . Observe that the palatine processes of the m axillae form the anterior aspect of the hard palate, whereas the h o rizo n t al p lat e s of t h e p alat in e b o n e s form the posterior aspect of the hard p alate. 3. Between the m axilla and palatine bone, identify the larger, m ore anteriorly located g re at er p alat in e fo ram e n and the slightly sm aller, m ore p osteriorly located le sse r p alat in e fo ram e n . 4. In the m idline of the palatine bones on the posterior m argin of the hard palate, identify the p o st e rio r n asal sp in e inferior to the nasal septum . 5. Identify the “hooklike” process of the p t e ryg o id h am ulus on the inferior aspect of the m edial plate of the pterygoid process of the sp h e n o id b o n e . 6. Observe that the m edial plate of the pterygoid process is separated from the lat e ral p lat e o f t h e p t e ryg o id p ro ce ss by the depression of the p t e ryg o id fo ssa .

Alveolar process Palatine process Palatine bone: Horizontal plate Greater palatine foramen Lesser palatine foramen Posterior nasal spine

Sphenoid bone: Lateral plate Hamulus of medial plate Medial plate Scaphoid fossa Pterygoid canal

FIGURE 7.75

Skeleton of the palate. Inferior view.

In frat e m p o ral Fo ssa [G 641; L 327; N 6] 1. Identify the in fe rio r o rb it al ssure between the m axilla and greater wing of the sphenoid (FIG. 7.76) . 2. Identify the p t e ryg o m axillary ssure between the lateral p late of the pterygoid p rocess and the m axilla. 3. Pass a p ipe cleaner through the pterygom axillary ssure and into the sm all cavity of the p t e ryg o p alat in e fo ssa (FIG. 7.76) . 4. On the m edial wall of the pterygopalatine fossa, identify the sm all opening of the sp h e n o p alat in e fo ram en . Pass the pipe cleaner through the sphenop alatine foram en and con rm that this opening connects the nasal cavity with the pterygop alatine fossa. 5. From an inferior view, identify the sm all opening of the p t e ryg o id can al in the anterior m argin of the fo ram e n lace rum . Pass a thin wire through the p terygoid canal and observe that it connects to the p terygop alatine fossa.

Inferior orbital fissure

Sphenopalatine foramen Pterygopalatine fossa

Lateral plate of pterygoid process Pterygomaxillary fissure

Maxilla

FIGURE 7.76 Entry to the p terygop alatine fossa and nasal cavity from the infratem poral fossa.

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Disse ct io n In st ruct io n s

Inferior nasal concha

So ft Palat e [G 766, 767; L 318, 319; N 68; R 146] 1. Exam ine the edge of the so ft p alat e where it is cut in the sagittal plane and observe that m uscles attach to its posterior two-thirds (FIG. 7.77) . The m uscles of the soft p alate p rovide the associate m obility of the structure. 2. Use an illustration to observe that the thickness of the soft palate is p artly due to the presence of p alatine glands and that the strength of the soft palate is due to the palatine ap oneurosis. 3. On the inner pharyngeal wall, identify the o p e n in g o f t h e p h aryn g o t ym p an ic t ub e inferior to the m ucous lined cartilage of the t o rus t ub arius (FIG. 7.77) . The p h aryn g o t ym p an ic t ub e (aud it o ry t ub e ) connects the nasopharynx to the tym p anic cavity. Note that the part of the pharyngotym p anic tube that is closest to the pharynx is cartilaginous (approxim ately two-thirds of its length) and the part that is closest to the m iddle ear p asses through the tem poral bone. 4. Within the opening of the p haryngotym panic tube, identify the t o rus levatorius, the “bum p ” of m ucosa overlying the le vat o r ve li p alat in i on the oor of the p h aryn g o t ym p an ic (aud it o ry o r e ust ach ian ) t ub e . 5. Identify the salp in g o p alat in e fo ld arising from the anterior asp ect of the torus tubarius and coursing to the soft p alate. 6. Identify the salp in g o p h aryn g e al fo ld arising from the p osterior aspect of the torus tubarius and coursing inferiorly into the pharynx. 7. Identify the p alat o g lo ssal fo ld (an t e rio r fauce s) , arching from the palate to the tongue, and the p alat op h aryn g e al fo ld (p o st e rio r fauce s) , arching from the p alate to the pharynx.

Pharyngeal tonsil Torus tubarius Pharyngeal recess Pharyngotympanic tube Torus levatorius Palatine aponeurosis Salpingopharyngeal fold Palatine glands Soft palate Palatopharyngeal fold Palatine tonsil Palatoglossal fold Epiglottis

FIGURE 7.77

Mucosal folds in the pharynx.

8. Use blunt dissection to rem ove the m ucosa from the palatoglossal fold and identify the p alat o g lo ssus m uscle , which lies within the fold (FIG. 7.78) . 9. Rem ove the m ucosa from the palatopharyngeal fold and identify the p alat o p h aryn g e us m uscle (FIG. 7.78) . 10. Rem ove the m ucosa from the salpingopharyngeal fold and identify the salp in g o p h aryn g e us m uscle (FIG. 7.78) . Note that the palatopharyngeus and salpingop haryngeus m uscles b lend together and contribute to the inner longitudinal m uscle layer of the pharynx. 11. Review the attachm ents, actions, and innervations of the palatoglossus, palatopharyngeus, and salp ingopharyngeus m uscles (see TABLE 7.8). 12. Rem ove the rem aining m ucosa from the inner surface of the nasop harynx and orop harynx. Id entify

Pharyngotympanic tube

Pharyngeal tonsil

Medial pterygoid plate

Pharyngeal tubercle

Inferior nasal concha

Levator veli palatini m.

Tensor veli palatini m. and tendon

Salpingopharyngeus m.

Lesser palatine a. Pterygoid hamulus

Superior pharyngeal constrictor m.

Musculus uvulae in soft palate

Palatopharyngeus m.

Palatoglossus m.

Tonsillar branch of facial a.

Tongue Glossopharyngeal n. (IX)

Middle pharyngeal constrictor m.

Stylohyoid ligament

Stylopharyngeus m.

Hyoid bone

Epiglottis

FIGURE 7.78

Muscles of the p haryngeal wall. Deep dissection.

CHAPTER 7

13. 14.

15.

16. 17.

18.

the st ylo p h a ryn g e us m uscle , which enters the p harynx b etween the sup erior and m id d le p haryng eal constrictor m uscles (FIG. 7.78) . Ob serve that the stylop haryng eus m uscle lies anterior and p arallel to the p alatop haryng eus and salp ing op haryng eus m uscles and that all three b lend near their inferior end s. Review the attachm ents and actions the stylopharyngeus m uscle (see TABLE 7.7). Use an illustration to ob serve that the p h a ryn g o b a sila r fa scia closes the g ap b etween the sup erior b ord er of the sup erior p haryng eal constrictor m uscle and the b ase of the skull. Passing throug h this g ap in th e p haryng ob asilar fascia are the p haryng otym p anic tub e and the levator veli p alatini m uscle (FIG. 7.78) . Rem ove the m ucosa from the torus levatorius and identify the le vat o r ve li p alat in i m uscle (FIG. 7.78) . Observe that the bers of the levator veli palatini course along the oor of the auditory tube. Rem ove the m ucosa from the m edial aspect of the m e d ial p lat e o f t h e p t e ryg o id p ro ce ss (FIG. 7.78) . Carefully use bone cutters to chip away portions of the m edial p late and identify the t e n so r ve li p alat in i m uscle . The belly of the tensor veli palatini m uscle is located between the m edial and lateral plates of the pterygoid process. Palpate the h am ulus o f t h e m e d ial p t e ryg o id p lat e and nd the tendon of the tensor veli palatini m uscle, which turns m edially around the ham ulus and attaches to the p alat in e ap o n e uro sis .

THE HEAD AND NECK

Greater palatine nerve and artery Lesser palatine nerve and artery Palatine aponeurosis

Openings of ducts of palatine glands

Buccinator m. Tensor veli palatini tendon

Palatine glands (mucosa removed)

Hamulus of medial pterygoid plate

Palatoglossal arch

Superior pharyngeal constrictor m.

Palatine tonsil in tonsillar bed

Levator veli palatini m.

Palatopharyngeal arch

Palatoglossus m. Uvula

Palatopharyngeus m. Musculus uvulae

FIGURE 7.79

297

19. Along the cut edge of the uvula, identify the m usculus uvulae . The m usculus uvulae arises from the posterior nasal spine and elevates and retracts the uvula. As the m usculus uvulae and levator veli p alatini m uscles contract, the soft palate thickens centrally and closes the pharynx between the nasopharynx and oropharynx. 20. Review the attachm ents and actions the levator and tensor veli p alatini m uscles and the m usculus uvulae (see TABLE 7.8). 21. Refer to Table 7.8 and note that ve m uscles of the soft palate and p harynx are innervated by the vagus nerve (CN X) via the pharyngeal plexus: salpingopharyngeus, levator veli palatini, palatoglossus, palatopharyngeus, and m usculus uvulae. Note that the tensor veli p alatini m uscle is innervated by the m andibular division of the trigem inal nerve (CN V3 ), not the vagus nerve. 22. Use a p rob e to raise the m ucosa on the inferior surface of the hard p alate where it was cut d uring head b isection. Grasp the m ucosa with forcep s or a hem ostat and use blunt dissection to p eel it from m ed ial to lateral. Detach the m ucosa along the m edial sid e of the alveolar p rocess of the m axilla. [G 659; N 57 ; R 149] 23. Identify the g re at e r p alat in e n e rve an d art e ry where they em erge from the g re at e r p alat in e foram e n (FIG. 7.79) . 24. Use blunt dissection to follow the greater palatine nerve and artery anteriorly. Note that the n aso p alat in e n e rve and the distal end of the sp h e n o p alat in e Nasopalatine n. and sphenopalatine a. in incisive foramen

Transverse folds of mucous membrane of palate

•

Muscles, nerves, and vessels of the palate. Inferior view.

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art e ry supp ly the m ucosa over the anterior p art of the hard palate (FIG. 7.79) . 25. Posterior to the greater palatine nerve, identify the lesse r p alat in e n e rve an d art e ry. Use blunt dissection to follow them to the soft palate, which they supp ly.

Anterior ethmoidal n.

Pterygopalatine ganglion

Olfactory bulb

Ridge over pterygoid canal

To n sillar Be d [G 768; L 318; N 68; R 149] 1. Identify the p alatin e t on sil (FIG. 7.79) . Note that in older individuals, the palatine tonsil m ay be inconspicuous or m ay have been surgically rem oved. When present, the palatine tonsil is located in the ton sillar b ed . 2. Identify the an t e rio r b o un d ary of the tonsillar bed form ed by the p alat o g lo ssal fo ld and the p o st e rio r b o un d ary of the tonsillar bed form ed by the p alat o p h aryn g e al fo ld . 3. Use an illustration to observe that the lat e ral b o un d ary of the tonsillar bed is form ed by the sup e rio r p h aryn g e al co n st rict o r m uscle . 4. If the cadaver has a palatine tonsil, use blunt dissection to rem ove it (FIG. 7.77) . Section the tonsil and observe the cryp t s that extend into its surface. 5. Rem ove the m ucosa from the tonsillar bed and identify the g lo sso p h aryn g e al n e rve (CN IX) (FIG. 7.78) . Note that the glossopharyngeal nerve passes between the superior and the m iddle pharyng eal constrictor m uscles to enter the tonsillar bed. The glossopharyngeal nerve innervates the m ucosa of the posterior one-third of the tongue and the posterior wall of the pharynx.

Nasapalatine n.

Descending palatine a.

Greater palatine n. and a.

FIGURE 7.80 Nerve and arterial sup ply to the m ucosa of the lateral wall of the nasal cavity. Pterygop alatine ganglion.

6.

7.

Sphe no palat ine Fo ram e n and Pt e ryg o palat ine Fo ssa [G 659; L 340; N 41; R 149] 1. Do not dissect the arterial network of the lateral nasal wall but use an atlas illustration to study the branches of the sp h e n o p alat in e art e ry. Identify the p o st e rio r lat e ral n asal art e rie s supplying the lateral nasal wall and the p o st e rio r se p t al b ran ch supplying the superior part of the nasal sep tum . [G 669; L 340; N 40; R 148] 2. Rem ove the m ucosa from the posterior part of the lateral nasal wall. 3. Use a probe to locate the sp h en o p alat in e fo ram e n , which is located at the posterior end of the m iddle nasal concha (FIG. 7.80) . 4. Insert a probe into the sphenopalatine foram en and d irect it inferiorly toward the greater palatine foram en. Pull the probe m edially to break the m edial wall of the greater palatine canal. 5. Identify the g re at e r p alat in e n e rve , the le sse r p alat in e n e rve , and the d e sce n d in g p alat in e art e ry in the greater palatine canal (FIG. 7.80) . Recall that

Lesser palatine n. and a.

8.

9.

10.

the descending p alatine artery is one of the term inal branches of the m axillary artery. At the inferior end of the greater palatine canal, use a ne probe or needle to separate the nerves and vessels. Observe that the descending palatine artery divides to give rise to the g re at er p alat in e art ery and the le sse r p alat in e art e ry (FIG. 7.80) . Place a ne probe between the greater palatine nerve and the lesser palatine nerve and slide it superiorly until it m eets resistance at the inferior border of the p t e ryg o p alat in e g an g lio n (FIG. 7.80) . The pterygopalatine ganglion is the site of synapse of p resynap tic p arasym pathetic axons from the facial nerve (CN VII) that course rst in the greater petrosal nerve and then in the nerve of the p terygoid canal (Vidian nerve). Postsynap tic axons that arise in the pterygopalatine ganglion distribute with branches of the m axillary division of the trigem inal nerve (CN V2 ). The pterygopalatine ganglion stim ulates secretion from the m ucosa of the nasal cavity, paranasal sinuses, nasopharynx, roof of the m outh, and soft palate. The pterygopalatine ganglion also stim ulates the lacrim al gland. Rem ove the m ucosa from the oor of the sp henoid sinus and look for a ridge in the oor that m arks the location of the pterygoid canal (FIG. 7.80) . Use a probe to break open the ridge and identify the nerve of the p terygoid canal, which enters the pterygopalatine fossa posteriorly. Con rm that the nerve of the pterygoid canal ends anteriorly in the pterygopalatine ganglion. The nerve of the pterygoid canal contains presynaptic parasym p athetic axons from the greater petrosal nerve

CHAPTER 7

and p ostsynap tic sym pathetic axons from the deep petrosal nerve. 11. Turn the cadaver’s head and approach it from the lateral aspect. Deep in the in fratem p oral fossa , identify the m axillary artery, where it courses deeply toward the pterygom axillary ssure. [G 645; L 330; N 72; R 82] 12. Near the pterygom axillary ssure, observe that the m axillary artery gives rise to the sp h e n o p alat in e art e ry, which passes through the pterygopalatine fossa and then through the sphenopalatine foram en to enter the nasal cavity. 13. Branching from the m axillary artery, identify the d e sce n d in g p alat in e art e ry, which descends to enter

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the greater p alatine canal where it was dissected from the m edial side. 14. Identify the in frao rb it al artery, which passes through the inferior orbital ssure to enter the infraorbital canal and em erge on the face through the infraorbital foram en. 15. Id en tify the m a xilla ry d ivisio n o f t h e t rig e m in a l n e rve (CN V2 ) wh ere it courses from th e foram en rotun d um to th e in ferior orb ital ssure. Ob serve th at th e m axillary d ivision p asses th roug h th e p teryg op alatine fossa and g ives p teryg op alatine b ranch es that will form the g reater and lesser p alatin e n erves.

Disse ct io n Fo llo w-up 1. Use th e d issected cad aver an d an illustration to recon struct th e b ran ch in g p attern of th e m axillary d ivision of the trig em inal nerve. Use a skull and the d issected cad aver to follow the m axillary d ivision from the trig em inal g an g lion th roug h th e foram en rotun d um , p teryg op alatin e fossa, an d in ferior orb ital ssure to th e in fraorb ital g roove. 2. Review the distribution of the following branches of the m axillary division of the trigem inal nerve: greater palatine, lesser palatine, nasopalatine, and infraorbital nerves. 3. Return to the carotid triangle of the neck and follow the external carotid artery superiorly into the infratem p oral fossa. Review the origin of the m axillary artery and its course through the infratem poral fossa. Review all branches of the m axillary artery that you dissected p reviously. Use an illustration to review the term inal branches of the m axillary artery (posterior superior alveolar, infraorbital, descending palatine, and sphenopalatine) and use the dissected cadaver to review these branches where you have dissected them . 4. Review the m uscles that m ove the soft palate. State their attachm ents and actions. 5. Review the pharyngeal wall, placing the pharyngeal constrictor m uscles and the m uscles of the soft palate into the correct m uscle layers (inner longitudinal or outer circular). 6. Review the pharyngeal plexus on the posterior surface of the pharynx and recall its role in innervation of the pharyngeal m ucosa and the m uscles of the pharynx and soft palate. 7. Use the dissected cadaver and an illustration to review the course of the glossopharyngeal nerve from the jugular foram en to the posterior one-third of the tongue. 8. Recall the pattern of innervation of the m uscles of the soft palate.

TABLE 7.8

Muscle s o f t h e Palat e an d Ph aryn x

Muscle

Superior Atta chments

Inferior Atta chments

Actions

Palatoglossus

Palatine aponeurosis

Lateral aspect of the tongue

Elevates tongue and depresses soft palate

Palatopharyngeus

Hard palate and palatine aponeurosis

Salpingopharyngeus

Cartilage of pharyngotympanic tube

Thyroid cartilage and pharyngeal wall

Elevates larynx during swallowing and speaking

Musculus uvulae

Posterior nasal spine (anterior attachment)

Levator veli palatini Tensor veli palatini

Cartilage of pharyngotympanic tube and petrous part of temporal bone Scaphoid fossa and spine of sphenoid bone

Abbreviations: CN, cranial nerve; n., nerve.

Innerva tion

Vagus n. (CN X) via pharyngeal plexus

Elevates and retracts uvula Palatine aponeurosis Tenses the soft palate

Mandibular division of trigeminal n. (CN V3 )

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ORAL REGION Disse ct io n Ove rvie w The o ral re g io n includ es the oral cavity and its contents (teeth, g um s, and tongue), the palate, and the part of the oropharynx that contains the palatine tonsils. The palate and palatine tonsils have been dissected previously. The o ral cavit y can be subdivided into the o ral ve st ib ule , the area bounded by the lips and cheeks externally and the teeth and gum s internally, and the o ral cavit y p ro p e r , the area between the alveolar arches and teeth. The largest content of the oral cavity proper is the tongue. The order of dissection will be as follows: The super cial features of the oral region will be exam ined on a living person. On the cadaver, the tongue will be inspected and the tongue and m andible will be bisected in the m idline. The intrinsic m uscles of the tongue will be exam ined. The sublingual region will be studied, and the dissection of the deep part of the subm andibular gland will be com p leted. Finally, the extrinsic m uscles of the tongue will be studied.

Surface An at o m y o f t h e Oral Ve st ib ule [L 333; N 56] Palpate the following structures through the m ucosa that lines the oral vestibule on the cadaver or use a m irror and a clean nger to exam ine your m outh (FIG. 7.81) : 1. On the m axilla , identify the alve o lar p ro ce sse s and the an t e rio r surface (above the alveolar process). 2. On the m an d ib le , identify the alve o lar p ro ce sse s . 3. Palpate posteriorly along the lower dentition and identify the anterior border of the ram us of the m andible. 4. Recall that the ram us of the m andible extends superiorly and ends as the co ro n o id p ro ce ss anteriorly and the co n d ylo id p ro ce ss posteriorly. 5. On the lateral aspect of the cadaveric head, identify the coronoid process and the t en d on of t h e t em p oralis m uscle . 6. On the lateral aspect of the face, palpate the m asseter m uscle. Note that the m asseter is best palpated in a living individual when the teeth are clenched. 7. Identify the co m m un icat io n b e t we e n t h e o ral ve st ib ule an d t h e o ral cavit y p ro p e r posterior to the third m olar tooth. 8. Turn down the lower lip and lift the up per lip and id entify the fre n ulum in the m idline of each lip. 9. Exam ine the inner surface of the cheek and identify the o p e n in g o f t h e p aro t id d uct located lateral to the second m axillary m olar.

Surface An at o m y o f t h e Oral Cavit y Pro p e r Palpate the following structures in the oral cavity on the cadaver or use a m irror and a clean nger to exam ine your m outh (FIG. 7.81) : 1. Observe that the an t e rio r an d lat e ral b o rd e rs of the oral cavity are the teeth and gum s of the upper and lower dentition. 2. The sup e rio r b o rd e r (ro o f) of the oral cavity is the hard p alate, whereas the in fe rio r b o rd e r ( o o r) is the m ucosa covering the tongue and sub lingual area. 3. The p o st e rio r b o rd e r of the oral cavity is de ned by the p alatoglossal folds (right and left). 4. Elevate the tong ue and examine the subling ual area . In the midline, identify the frenulum of th e tong ue (sub ling ual frenulum ) , the mucosal fold connecting the inferior aspect of the tongue to the oor of the mouth. 5. To either side of the frenulum of the tongue, identify a sub lin g ual fo ld (p lica sub lin g ualis) and the associated bum p of the sub lin g ual carun cle . On the surface of the sublingual caruncle, identify the o p e n in g o f sub m an d ib ular d uct . 6. In a living individual, observe that d e e p lin g ual ve in s are visible beneath the m ucosa on either side of the frenulum of the tongue.

Superior lip Gingivae (gums)

Superior labial frenulum

Hard palate Palatoglossal arch

Soft palate

Palatopharyngeal fold

Uvula Palatine tonsil

Oropharynx Tongue

Duct of submandibular gland

Lingual frenulum Gingivae (gums)

Vestibule Inferior labial frenulum

Inferior lip

FIGURE 7.81

Oral cavity. Anterior view.

CHAPTER 7

Disse ct io n In st ruct io n s To n g ue [G 652; L 334; N 60; R 151] 1. Exam ine the t o n g ue and identify its ap e x , b o d y (the anterior two-thirds), and ro o t (the p osterior one-third). Observe that the body and root of the tongue are delineated by the t e rm in al sulcus (sulcus t e rm in alis) (FIG. 7.82) . 2. Observe that the lin g ual t o n sils lie p osterior to the term inal sulcus on the root of the tongue. 3. On the d o rsum of the tongue, follow the m e d ian sulcus p osteriorly to the term inal sulcus and identify the fo ram e n ce cum in the m idline. 4. Observe the surface of the dorsum of the tongue and identify the lin g ual p ap illae . Note that there are four types of ling ual pap illae: vallate, liform , fung iform , and foliate (FIG. 7.82) . 5. Observe that the b o d y o f t h e t o n g ue lies horizontally in the oral cavity and the ro o t o f t h e t o n g ue lies m ore vertically. Note that the root of the tongue constitutes the lower part of the anterior boundary of the oropharynx. 6. At the root of the tongue, identify the m e d ian g lo sso e p ig lo t t ic fo ld , a m idline fold of m ucosa b etween the dorsum of the tongue and the e p ig lo t t is (FIG. 7.82) .

Median glossoepiglottic fold

Epiglottis

Epiglottic vallecula Lateral glossoepiglottic fold

Foramen cecum Terminal sulcus Lingual tonsil

Root

Lingual papillae: Vallate

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301

7. Lateral to the m edian glossoep iglottic fold, identify the lat e ral g lo sso e p ig lo t t ic fo ld between the dorsum of the tongue and the lateral border of the epiglottis. 8. Identify the e p ig lo t t ic valle culae , the depressions between the m edian and right and left lateral glossoepiglottic folds.

Bise ct io n o f t h e To n g ue an d Man d ib le 1. Turn the cadaver to expose the subm ental triangle. 2. Use a scalpel to cut the m ylo h yo id m uscle s along their m edian raphe. 3. Use a probe to separate the m ylohyoid m uscles from deeper structures. 4. Deep to the m ylohyoid m uscle, identify the g e n io h yo id m uscle (FIG. 7.83) . 5. Use blunt dissection to separate the geniohyoid m uscles in the m idline. 6. Use a saw to cut through the m andible in the m edian plane. Do not allow the saw to pass between the genioglossus m uscles on the deep side of the m andible. Do not bisect the epiglottis, the hyoid bone, or the larynx at this tim e. 7. Use a scalpel to bisect the tongue in the m edian plane, beginning at the ap ex and proceeding toward the ep iglottis. Cut as far inferiorly as the hyoid bone. 8. On the sectioned surface of the tongue, identify the g e n io g lo ssus m uscle . 9. Review the attachm ents, actions, and innervations of the geniohyoid and genioglossus m uscles (see TABLE 7.9).

Sub lin g ual Re g io n [G 755; L 332; N 56; R 155] Perform the following dissection sequence on only one side of the head. 1. Carefully use a scalpel to incise the m ucous m em brane along the m edial surface of the m andible. Start the incision at the frenulum of the tongue and

Filiform Foliate

CLIN ICA L CORRELATION

Fungiform

Hyp o g lo ssal Ne rve The genioglossus m uscle protrudes the tongue. If one genioglossus m uscle does not function (hypoglossal nerve dysfunction on that side), the tongue cannot be protruded in the m idline. The functional side of the tongue p rotrudes norm ally and the side with the dysfunctional nerve is protrud ed less or not at all. Therefore, in testing for hypoglossal nerve lesions, the p rotruded tongue deviates toward the side of the nerve lesion.

Body Median sulcus

Apex

FIGURE 7.82

Dorsum of the tongue.

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Lingual nerve curving under submandibular duct

Deep part of right submandibular gland Soft palate (cut)

Cut edge of sublingual mucosa

Styloglossus m. (cut)

Sublingual gland

Stylohyoid ligament

Sublingual fold

Middle pharyngeal constrictor m.

Opening of submandibular duct on sublingual caruncle

Hypoglossal n. (XII) lateral to hyoglossus m. Lingual a. medial to hyoglossus m.

Mandible (cut) Genioglossus m. (cut)

Hyoglossus m. (cut) Geniohyoid m. (cut)

FIGURE 7.83

2.

3.

4.

5.

6.

7. 8.

Hyoid bone

Mylohyoid m. (cut)

Dissection of sublingual region. Right side, tongue rem oved .

stop near the second m andibular m olar. Use a prob e and forceps to peel the m ucosa m edially. Identify the sub lin g ual g lan d im m ediately deep to the m ucosa (FIG. 7.83) . Observe that the sublingual gland rests on the m ylohyoid m uscle. The sublingual gland has about 12 short ducts that drain along the sum m it of the sublingual fold. Use a probe to dissect along the m edial side of the sublingual gland and nd the sub m an d ib ular d uct (FIG. 7.83) . Follow the subm andibular duct anteriorly to its op ening on the sublingual caruncle. Use a p rob e to trace the sub m and ib ular d uct p osteriorly to the d e e p p a rt o f t h e sub m a n d ib ula r g la n d . Note that the d eep p art of the sub m and ib ular g land is located on the d eep sid e of the m ylohyoid m uscle. Turn th e cad aver to exp ose th e in fratem p oral fossa. Fin d th e lin g u a l n e rve an d trace it in to th e sub lin g ual reg ion . Ob serve th at th e lin g ual n erve rst p asses lateral, th en in ferior, th en m ed ial to the sub m an d ib ular d uct (FIG. 7.83) . Th e lin g ual n erve h as several b ran ch es th at sup p ly th e m ucosa of th e an terior two-th ird s of th e ton g ue with g en eral sen sation an d taste b ers. [G 7 5 5 ; L 3 3 2 ; N 4 6 ; R 155] Near the third m and ib ular m olar, id entify the su b m an d ib ula r g an g lio n suspended from the ling ual nerve. Read a textb ook d escrip tion of the p arasym p athetic function of the subm and ib ular ganglion. Turn the cadaver so the subm andibular triangle is exp osed. Use blunt dissection to de ne the attachm ent of the m ylohyoid m uscle to the hyoid bone.

9. Use scissors to detach the m ylohyoid m uscle from the hyoid bone and re ect the m uscle superiorly. 10. Find the h yp o g lo ssal n e rve (CN XII) and use a p robe to trace it into the sublingual region where it passes between the deep part of the subm andibular gland and the hyoglossus m uscle (FIG. 7.83) . 11. Identify the h yo g lo ssus m uscle (FIG. 7.84) . Observe that both the hyp oglossal nerve and the lingual nerve p ass between the hyoglossus m uscle and the m ylohyoid m uscle to enter the sublingual region. Note that the course of the hypoglossal nerve is inferior to the course of the lingual nerve. 12. Near the superior end of the hyoglossus m uscle, identify the st ylo g lo ssus m uscle (FIG. 7.84) . [G 653; N 59]

Deep lingual a.

Styloglossus m Lingual a.

Styloid process

Dorsal lingual a.

Lingual n.

Sublingual gland

Tongue

External carotid a.

Sublingual a. Hypoglossal n. (XII)

Hyoglossus m.

Submandibular ganglion

FIGURE 7.84

Genioglossus m. Geniohyoid m.

Submandibular duct

Blood supply to the tongue. Lateral view.

CHAPTER 7

13. Review the attachments, actions, and innervations of the hyoglossus and styloglossus muscles (see TABLE 7.9). 14. Use an atlas illustration to study the in t rin sic m uscle s o f t h e t o n g ue and note that they consist of ve rt ical, t ran sve rse , sup e rio r lo n g it ud in al, and in fe rio r lo n g it ud in al g ro up s o f b e rs [G 656; L 333; N 47; R 151]. Note that the intrinsic m uscles of the tongue and the three extrinsic m uscles of the tongue (styloglossus, genioglossus, and hyoglossus) are all innervated by the h yp o g lo ssal n e rve (CN XII) .

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15. Return to the carotid triangle and locate the lin g ual art e ry where it arises from the external carotid artery (FIG. 7.84) . 16. Follow the ling ual artery sup eriorly until it p asses m ed ial to the hyog lossus m uscle. Note that wh en the su b lin g ua l a rt e ry b ranches from the ling ual artery, the ling ual artery’s nam e chang es to d e e p lin g ua l a rt e ry . The d eep ling ual artery is usually located within 5 m m of the inferior surface of the tong ue.

Disse ct io n Fo llo w-up 1. 2. 3. 4. 5. 6. 7. 8. 9.

Review the surface features of the tongue. Review the innervation of the lingual m ucosa. Follow the subm andibular duct from the subm andibular triangle to the sublingual caruncle. Trace the lingual nerve from the infratem poral fossa to the tongue. Note the relationship of the lingual nerve to the subm andibular duct, hyoglossus m uscle, and m ylohyoid m uscle. Review the chorda tym pani and the role that it plays in sensory innervation of the tongue and parasym pathetic innervation of the subm and ibular and sublingual glands. Locate the subm andibular ganglion and state its function. Trace the hyp oglossal nerve from the base of the skull to the tongue, noting its relationship s to arteries and m uscles. Organize the m uscles of the tongue into extrinsic and intrinsic groups. State the attachm ents, innervation, and action of each extrinsic m uscle. Use an illustration and the dissected cadaver to review the origin and course of the facial and lingual arteries.

TABLE 7.9

Muscle s o f t h e To n g ue an d Oral Cavit y

Muscle

Superior Atta chments

Inferior Atta chments

Actions

Innerva tion

Geniohyoid

Inferior mental spine of mandible (anterior attachment)

Body of hyoid bone (posterior attachment)

Pulls the hyoid bone anteriorly

C1 via the Hypoglossal n. (CN XII)

Genioglossus

Superior mental spine of the mandible (anterior attachment)

Hyoid bone and tongue (posterior attachment)

Depresses and protrudes tongue

Hyoglossus

Side and inferior aspect of tongue

Body and greater horn of the hyoid bone

Depresses and retracts tongue

Styloglossus

Styloid process and stylohyoid ligament

Side and inferior aspect of tongue

Retracts tongue and draws it superiorly

Hypoglossal n. (CN XII)

Abbreviations: C, cervical vertebrae; CN, cranial nerve; n., nerve.

LARYNX Disse ct io n Ove rvie w The larynx is the entrance to the airway, and it contains the g lo t t is , a valve that serves the dual function of controlling the airway and producing sound during phonation. The intrinsic m uscles of the larynx control the glottis. The extrinsic m uscles of the larynx (infrahyoid m uscles, suprahyoid m uscles, and stylopharyngeus m uscle) control the p osition of the larynx in the neck. In its neutral position, the larynx is located at vertebral levels C3–C6. The larynx is contained in the visceral com partm ent of the neck with the thyroid gland lateral to it and the pharynx posterior to it.

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The order of dissection will b e as follows: Illustrations and m odels will be used to study the cartilages of the larynx. The m ucosa of the larynx will be rem oved from the posterior part of the larynx to expose two intrinsic m uscles. The left lam ina of the thyroid cartilage will be rem oved to expose the rem aining intrinsic m uscles. The larynx will be opened, and the m ucosal features will be studied. Finally, the nerves to the larynx will be reviewed.

Ske le t o n o f t h e Laryn x [G 770; L 320; N 79; R 160] The ske le t o n o f t h e laryn x is resp onsib le for m aintaining a p atent airway. It consists of a series of articulated cartilag es united by thin m em branes. Use an illustration and a m odel of the larynx to study the cartilag es and m em branes (FIG. 7.85) . 1. Id entify the e p ig lo t t ic ca rt ila g e , an unp aired cartilag e that lies p osterior to the tong ue and hyoid b one. Ob serve that the st a lk of the ep ig lottic cartilag e is attached to the inner surface of the ang le form ed b y the thyroid lam inae. 2. Inferior to the hyoid bone, identify the t h yro id cart ilag e . Observe that the thyroid cartilage is form ed by two lam in ae joined in the anterior m idline to form the laryn g e al p ro m in en ce (Ad am ’s ap p le ) . 3. Identify the t h yro h yo id m e m b ran e between the sup erior border of the thyroid cartilage and the inferior bord er of the hyoid bone. Note that when the suprahyoid and infrahyoid m uscles m ove the hyoid bone, the larynx also m oves because of the thyrohyoid m em brane. 4. Observe that the sup e rio r h o rn of the thyroid cartilage p rojects superiorly, whereas the in ferio r h o rn of the thyroid cartilage projects inferiorly and articulates with the cricoid cart ilag e through the crico t h yro id jo in t s . 5. Observe that the crico id cart ilag e is shaped like a ring (Gr. krikos, ring). Its lam in a is a broad at area that is positioned posteriorly, and its arch is located anteriorly. 6. On the posterior asp ect of the sup erior border of the lam ina of the cricoid cartilage, identify the aryt e n o id cart ilag e s . 7. Observe that each arytenoid cartilage is p yram id-shap ed and that it articulates with the cricoid cartilage through a synovial joint. Each arytenoid cartilage has a m uscular p ro ce ss for attachm ent of intrinsic laryngeal m uscles and a vo cal p ro ce ss for attachm ent of the vocal ligam ent. 8. Use an illustration or supplem ental text to con rm that the arytenoid cartilages are cap able of several m ovem ents. Each arytenoid cartilage can tilt anteriorly and posteriorly, slide toward the other (adduction), slide away from the other (abduction), and rotate. 9. Use an illustration to identify the vo cal lig am e n t s (FIG. 7.85) . The p osterior end of each vocal ligam ent is attached to the vocal process of an arytenoid cartilage. The anterior end of each vocal ligam ent is attached to the inner surface of the thyroid cartilage at the angle form ed by the lam inae.

Epiglottic cartilage Hyoid bone Thyrohyoid membrane Thyroid cartilage: Superior horn Lamina Laryngeal prominence Arytenoid cartilage: Muscular process Vocal process Vocal ligament

Stalk of epiglottic cartilage

Cricoid cartilage: Lamina Arch

Cricothyroid ligament

Medial View

FIGURE 7.85

Posterior View

Cartilages of the larynx.

CHAPTER 7

Disse ct io n In st ruct io n s In t rin sic Muscle s o f t h e Laryn x [G 774, 775; L 321–323; N 80; R 162] 1. Review the location of the infrahyoid m uscles (sternohyoid, om ohyoid, sternothyroid, and thyrohyoid m uscles). 2. Review the location of the suprahyoid m uscles (g eniohyoid , m ylohyoid , stylohyoid, and d igastric m uscles). 3. Identify the external and internal branches of the superior laryngeal nerve. Recall that the internal branch of the sup erior laryngeal nerve pierced the thyrohyoid m em brane with the superior laryngeal artery. 4. On one side of the neck, follow the external branch of the sup erior laryngeal nerve inferiorly and identify the crico t h yro id m uscle on the external surface of the larynx. 5. To expose the posterior surface of the larynx, m ove the cadaver’s head forward and allow the chin to rest on the thoracic wall. 6. Open the posterior wall of the pharynx to expose the posterior surface of the larynx. Palpate the lam in a o f t h e crico id cart ilag e . Lateral to the lam ina, identify the p irifo rm re ce ss . 7. Use blunt dissection to rem ove the m ucosa from the piriform recess. Im m ediately deep to the m ucosa, identify the in t e rn al b ran ch o f t h e sup e rio r laryn g e al n e rve and the superior laryngeal artery.

THE HEAD AND NECK

Aryepiglottic muscle Thyroepiglottic muscle Arytenoid muscle: Transverse Oblique Posterior cricoarytenoid m. Inferior laryngeal n. Cricothyroid joint

Lateral cricoarytenoid m.

Trachea

Recurrent laryngea n. Posterior View

Lateral View

FIGURE 7.86

305

8. Continue to rem ove the m ucosa inferiorly and identify the in fe rio r laryn g e al n e rve (FIG. 7.86) . Observe that the recurrent laryngeal nerve enters the larynx by passing posterior to the crico t h yro id jo in t . At this location, the nam e of the recurrent laryngeal nerve changes to in fe rio r laryn g e al n e rve . 9. Use blunt dissection to strip the m ucosa from the lam ina of the cricoid cartilage and expose the p o st e rio r crico aryt e n o id m uscle (FIG. 7.86) . Note that the p osterior cricoarytenoid m uscle is the only m uscle that opens the rim a glottidis. 10. Superior to the posterior cricoarytenoid m uscle, identify the aryt e n o id m uscle (FIG. 7.86) . The arytenoid m uscle attaches to both arytenoid cartilages. Observe that the arytenoid m uscle has t ran sve rse b e rs and o b liq ue b e rs . The arytenoid m uscle slides the arytenoid cartilages together (adduction of the vocal folds). 11. On the left side only, use scissors to d isarticulate the cricothyroid joint. Note that the cricothyroid joint is a synovial joint that is reinforced by short ligam ents. 12. Use scissors to carefully cut the thyrohyoid m em brane. 13. Make a vertical incision through the left lam ina of the thyroid cartilage 5 m m to the left of the m idline. Re ect the thyroid lam ina inferiorly and detach it from the cricothyroid m uscle. 14. Med ial to the thyroid lam ina that was rem oved , id entify the la t e ra l crico a ryt e n o id m uscle (FIG. 7.86) .

Epiglottic cartilage

Thyroarytenoid m.

•

Intrinsic m uscles of the larynx.

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15. Identify the t h yro aryt e n o id m uscle , which is located superior to the lateral cricoarytenoid m uscle (FIG. 7.86) . Note that the vocalis m uscle is form ed b y the m edial bers of the thyroarytenoid m uscle. The vocalis m uscle is attached to the vocal ligam ent and m odi es the tension in localized parts of the vocal fold, m odulating pitch. The vo calis m uscle cannot be seen in dissection. 16. Use an illustration to identify the other delicate m uscles of the larynx sup erior to the thyroarytenoid m uscle (thyroepiglottic m uscle and aryep iglottic m uscle). Do not attem pt to dissect them . 17. Review the attachm ents, actions, and innervations of the m uscles of the larynx (see TABLE 7.10). 18. Observe the vocal folds from a superior view. Note that the interval between the vocal folds is called the rim a g lot tid is (L. rima, a cleft or crack). The rim a glottidis and the vocal folds collectively are called the g lott is.

In t e rio r o f t h e Laryn x [G 773; L 318; N 64; R 163] 1. In the posterior m idline, use scissors to bisect the larynx. Cut the arytenoid m uscle, lam ina of the cricoid cartilage, and trachea as well as the arch of the cricoid cartilage in the m idline anteriorly. 2. Open the larynx and observe the laryn g e al cavit y (FIG. 7.87) . 3. Inspect the m ucosa that lines the interior of the larynx and identify the ve st ib ular fo ld (false vo cal fo ld ) sup eriorly and the vo cal fo ld (t rue vo cal fo ld ) inferiorly. The vo cal lig am e n t is located within the vocal fold. 4. Note that the laryngeal cavity can be subdivided into the ve st ib ule , the space superior to the vestibular folds; the ve n t ricle , the depression between the vestibular fold and the vocal fold; and the in frag lo t t ic

CLIN ICA L CORRELATION

Glo t t is Laryngospasm is a spasm odic closure of the glottis and is life threatening. Spasm s of the intrinsic laryngeal m uscles that close the glottis m ay be produced by irritating chem icals, by severe allergic reactions, and som etim es as a side effect of m edications. The vocal folds can be readily visualized and insp ected with the aid of a m irror (indirect laryngoscopy) or with a laryngoscope (direct laryngoscopy). Persistent hoarseness is an indication for laryngoscopy. Persistent hoarseness m ay be caused by changes of the vocal folds or it m ay indicate that the recurrent laryngeal nerve is com prom ised in the thorax or neck.

5. 6.

7.

8.

9.

cavit y, the region inferior to the vocal folds continuous with the trachea. Exam ine the e p ig lo t t is and note that it m oves posteriorly during swallowing to close the laryngeal inlet. Exam ine the ven t ricle . Note that the ventricle m ay extend into a recess called the saccule . Use a blunt probe to explore the ventricle and saccule. Use an illustration and the cadaver to review the following n e rve sup p ly t o t h e laryn x . Observe that the in t e rn al b ran ch o f t h e sup e rio r laryn g e al n e rve provides sensory innervation to the m ucosa of the vocal fold and the m ucosa sup erior to the vocal folds. Observe that the e xt e rn al b ran ch o f t h e sup e rio r laryn g e al n e rve innervates the cricothyroid m uscle and the inferior pharyngeal constrictor m uscle. Observe that the in fe rio r laryn g eal b ran ch o f t h e re curre n t laryn g e al n e rve innervates all of the intrinsic m uscles of the larynx except the cricothyroid m uscle and p rovides sensory innervation to the m ucosa inferior to the vocal folds.

Tongue Epiglottis Pharyngeal constrictor muscles Laryngeal vestibule: Aryepiglottic fold Vestibular fold Ventricle

Hyoid bone Hyoepiglottic ligament Median thyrohyoid ligament Thyroid cartilage

Vocal fold

Median cricothyroid ligament

Esophagus

Cricoid cartilage Trachea

FIGURE 7.87

Mucosal features of the larynx. Medial view.

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Disse ct io n Fo llo w-up 1. Replace the head and larynx in their correct anatom ical positions. 2. Use a cross-sectional drawing of the neck and the dissected specim en to review the relationship of the larynx to the vertebral colum n, carotid sheaths, and other cervical viscera. 3. Trace the right and left vagus nerves into the thorax and follow the right and left recurrent laryngeal nerves from the thorax to the larynx. Note the differences. 4. Review the branches of the external carotid artery. 5. Follow the superior thyroid artery to the thyroid gland and review the course of the superior laryngeal artery as it passes through the thyrohyoid m em brane to enter the larynx. Recall that the superior laryngeal artery courses with the internal branch of the sup erior laryngeal nerve. 6. Review the course of the superior laryngeal nerve from the vagus nerve to its bifurcation. Follow the external laryngeal branch to the cricothyroid m uscle. 7. Use the dissected specim en to review the attachm ents and action of each intrinsic laryngeal m uscle that was identied during dissection. 8. Review the m ovem ents of the vocal folds during phonation, quiet breathing, and rapid breathing. 9. Review the function of the intrinsic m uscles of the larynx. Th e p o st erio r crico aryt en o id m uscle is t h e o n ly m uscle t h at o p e n s t h e rim a g lo t t id is. The cricothyroid m uscle tilts the thyroid cartilage anteriorly and tenses the vocal fold (higher pitch of voice). The thyroarytenoid m uscle tilts the thyroid cartilage posteriorly and relaxes the vocal fold (lower p itch of voice).

TABLE 7.10

Muscle s o f t h e Laryn x

Muscle

Superior Atta chments

Inferior Atta chments

Actions

Innerva tion

Cricothyroid

Inferior margin and inferior horn of thyroid cartilage

Anterolateral surface of cricoid cartilage

Tilts the thyroid cartilage anteriorly to lengthen (tense) the vocal folds

External branch of the superior laryngeal n. (CN X)

Posterior surface of the lamina of cricoid cartilage

Rotates arytenoid cartilage laterally to abduct vocal folds

Arch of cricoid cartilage

Rotates arytenoid cartilage medially to adduct vocal folds

Posterior surface of thyroid cartilage

Tilts arytenoid cartilage anteriorly to relax vocal folds

Posterior cricoarytenoid muscle Lateral cricoarytenoid muscle

Muscular process of arytenoid cartilage

Thyroarytenoid

Inferior laryngeal branch of the recurrent laryngeal n. (CN X)

Abbreviations: CN, cranial nerve; n., nerve.

EAR Disse ct io n Ove rvie w The ear is com p osed of three parts: external ear, m iddle ear, and internal ear. The external ear consists of the auricle and the e xt e rn al aco ust ic m e at us . The m iddle ear is within the t ym p an ic cavit y o f t h e t e m p o ral b o n e and contains the o ssicle s (bones of the m iddle ear). The in t e rn al e ar (vestibulocochlear organ) is the neurologic part of the ear and is contained within the petrous portion of the tem poral bone. The order of dissection will be as follows: The parts of the external ear will be exam ined. The facial nerve will be followed from the posterior cranial fossa into the internal acoustic m eatus, and the roof of the tym panic cavity will be rem oved. The auditory ossicles will be identi ed and one ossicle will be rem oved. The tem poral bone will be cut to reveal the m edial and lateral walls of the tym panic cavity. The tym panic m em brane will be studied. Features of the m edial wall of the tym panic cavity will be exam ined.

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Surface An at o m y o f t h e Ext e rn al Ear

Antihelix

Articular cartilage

Helix 1. Exam ine the auricle (p in n a) , the visible portion of the external ear of the cad aver (FIG. 7.88A) . [G 679; L 361; N 95; R 126] Concha 2. Identify the h e lix , the rim of the auricle. Observe that the helix is paralleled by a m ore anteriorly located External rounded prom inence of auricular cartilage, the an t iacoustic h e lix . meatus 3. Follow the helix superiorly and anteriorly until it curves around the antihelix and leads to the co n ch a , Tragus the deepest p art of the auricle. Helix 4. Anterior to the opening of the e xt e rn al aco ust ic m e Antitragus at us , identify the t rag us . Observe that the tragus is A B d irected posteriorly toward the an t it rag us . Lobule of auricle 5. On the inferior aspect of the auricle, identify the lo b FIGURE 7.88 A. External ear. B. Auricular cartilage. ule o f t h e auricle (earlo b e) . Observe that the auricular cart ilag e gives the auricle its shape (FIG. 7.88B) . Note that there is no cartilage in the lobule. 6. Palpate the auricular cartilage and verify that it is continuous with the cartilage of the external acoustic m eatus. Note that the external acoustic m eatus begins at the d eep est part of the concha and end s at the tym panic m em brane (a distance of about 2.5 cm in adults). The wall of the outer one-third of the external acoustic m eatus is cartilaginous and the inner two-thirds is bony. 7. Use an illustration to observe that the external acoustic m eatus is S-shaped, rst curving posterosuperiorly and then anteroinferiorly. The external acoustic m eatus is straightened for exam ination by pulling the auricle up ward, outward, and backward. 8. Study an illustration of the external surface of the tym panic m em brane and relate its surface features to the structures that lie in the m iddle ear. [G 682; L 361; N 95; R 129]

Ske le t o n o f t h e Ear On a skull with the calvaria rem oved, review the following skeletal features.

In t racran ial Surface o f t h e Te m p o ral Bo n e [G 685; L 362; N 11; R 30] 1. On the oor of the m iddle cranial fossa, identify the t e g m e n t ym p an i, the p ortion of tem poral bone that form s the roof of the tym panic cavity (FIG. 7.88) . 2. Identify the g ro o ve fo r t h e g re at e r p et ro sal n e rve coursing m edially near the roof of the carotid canal. 3. On the surface of the tem poral bone within the p osterior cranial fossa, identify the in t e rn al aco ust ic m e at us (FIG. 7.89) . Temporal bone:

Ext e rn al Surface o f t h e Te m p o ral Bo n e [G 591; L 362; N 10; R 32] 1. From a lateral view, identify the e xt e rn al aco ust ic m e at us anterior to the m ast o id p ro ce ss . 2. Rotate the skull and from an inferior view, identify the st ylo m ast o id fo ram e n between the m astoid process and the styloid p rocess. 3. Medial to the stylom astoid foram en, identify the jugular fossa, the depression im m ediately anterior to the jugular foram en. Observe the close relationship of the jugular fossa and the o p e n in g o f t h e caro t id can al. 4. Anterior to the round opening of the carotid canal, identify the irregular borders leading to the b o n y p o rt io n o f t h e p h aryn g o t ym p an ic t ub e .

Groove for the greater petrosal n. Tegmen tympani Internal acoustic meatus

Foramen magnum

FIGURE 7.89

Tem p oral bone. Superior view.

CHAPTER 7 Tegman tympani

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309

Medial wall: Round window

Posterior wall:

Stapes in oval window

Aditus

Promontory

Pyramidal eminence

Tendon of tensor tympani m.

Lateral wall (opened):

Tympanic plexus

Incus Malleus

Anterior wall:

Chorda tympani

Tensor tympani m.

Tympanic membrane

Pharyngotympanic tube

Floor

FIGURE 7.90 Schem atic drawing of the walls of the tym panic cavity. Right ear with the lateral wall opened, in anterolateral view.

Mid d le Ear (Tym p an ic Cavit y) [G 682, 686, 687; L 363; N 94; R 125] Refer to a schem atic illustration of the m iddle ear and orient yourself to the features of the walls of the tym panic cavity (FIG. 7.90) : 1. Use an illustration to verify that the t ym p an ic cavit y is an air- lled space within the tem poral bone. Observe that the tym panic cavity is separated from the external acoustic m eatus by the t ym p an ic m e m b ran e and from the m iddle cranial fossa by the t e g m e n t ym p an i. 2. Identify the lat e ral wall of the tym panic cavity and observe that it is form ed by the t ym p an ic m e m b ran e . 3. Along the superior aspect of the p o st e rio r wall of the tym panic cavity, identify the ad it us (L. aditus, inlet or access), an opening into the m ast o id air ce lls within the m astoid process. 4. Identify the m e d ial wall of the tym panic cavity. Observe that the m edial wall contains the rounded p ro m o n t o ry and the o val win d o w (fe n e st ra ve st ib uli) , which contains the base (footplate) of the st ap e s . 5. Observe that the an t e rio r wall of the tym panic cavity contains the opening of the p h aryn g o t ym p an ic t ub e . 6. Identify the sup e rio r wall (ro o f) of the tym p anic cavity and observe that it is form ed by the tegm en tym p ani of the tem p oral bone. 7. Observe that the in fe rio r wall ( o o r) of the tym panic cavity is closely related to the jug ular fo ssa and the jug ular b ulb .

Disse ct io n In st ruct io n s Mid d le Ear ( Tym p an ic Cavit y) [G 684; L 360; N 99; R 132] The tym panic cavity will be ap proached by rem oving the tegm en tym pani portion of the oor of the m iddle cranial fossa on only one side of the head. Wear eye protection when cutting bone. 1. If the dura m ater is still present in the m iddle cranial fossa of the specim en, peel it off the superior surface of the tem p oral bone. Start at the superior border of the petrous p art of the tem poral bone and peel the dura m ater in an anterior direction. 2. Look for the g re at e r p e t ro sal n e rve in the groove for the greater petrosal nerve (FIG. 7.91) . Note that the greater p etrosal nerve lies between the dura m ater and the bone.

3. In the posterior cranial fossa, identify the facial n e rve (CN VII) and the ve st ib ulo co ch lear n e rve (CN VIII) as they enter the internal acoustic m eatus (FIG. 7.91) . 4. Use a ham m er and the tip of a probe or sm all chisel and gently break through the roof of the internal acoustic m eatus. Follow the facial and ve st ib ulo co ch le ar n e rve s laterally as they pass through the internal acoustic m eatus, rem aining sup erior to the nerves when cutting the internal acoustic m eatus (FIG. 7.91) . [G 685; L 362; N 96] 5. Rem ove the sm all portions of the broken tegm en tym pani, and follow the facial nerve laterally until it m akes a sharp bend in the posterior direction. At this bend in the facial nerve, identify the g e n iculat e g an g lio n and the origin of the g reat e r p e t ro sal n e rve (FIG. 7.91) . Note that the geniculate ganglion con-

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Geniculate ganglion Greater petrosal nerve

Ossicles:

Lesser petrosal nerve

Malleus Incus

Cochlea Entering internal acoustic meatus: Facial nerve (CN VII) Nervus intermedius (CN VII) Vestibulocochlear nerve (CN VIII)

Facial nerve

Anterior semicircular canal

FIGURE 7.91 view.

Tegmen tympani (cut)

Middle ear after rem oval of the tegm en tym pani, right side. Superior

tains cell bod ies of sensory neurons. The greater petrosal nerve carries p resynap tic p arasym pathetic bers to the pterygopalatine ganglion for innervation of the m ucous m em branes of the nasal and upp er oral cavities, and to the lacrim al gland. The presynaptic parasym pathetic nerve bers do not synapse in the geniculate ganglion. 6. Make an effort to follow the greater p etrosal nerve where it courses anterom edially within the tem poral bone to em erge on the oor of the m iddle cranial fossa at the h iat us fo r t h e g re at e r p e t ro sal n e rve . 7. Follow the greater p etrosal nerve and observe that it passes inferiorly and m edially in the g ro o ve fo r t h e g re at e r p et ro sal n e rve ( on the surface of the tem poral bone) to enter the carotid canal. On the surface of the internal carotid artery, the greater petrosal nerve joins the deep p etrosal nerve to form the n e rve o f t h e p t e ryg o id can al. The nerve of the p terygoid canal carries the presynaptic bers of the greater petrosal nerve to the pterygopalatine ganglion. 8. Use an illustration to verify that the facial nerve enters the facial canal at the geniculate ganglion. The facial nerve travels a short distance in a p osterolateral direction and then turns inferiorly to exit the skull at the stylom astoid foram en. Do not attem p t to follow the facial nerve through the tem poral bone.

9. Use an illustration to observe that the co ch le a lies anterior to the internal acoustic m eatus in the angle form ed by the facial nerve, the geniculate ganglion, and the greater petrosal nerve (FIG. 7.91) . 10. In the dissected cadaver, rem ove a p ortion of the tegm en tym pani anterior to the facial nerve to identify the m odiolus of the cochlea. The visibility of the m odiolus in the cadaveric largely depends on the plane of the cut. 11. In the dissected cadaver rem ove a portion of the tegm en tym pani posterior to the facial nerve and identify the sem icircular canals. The sem icircular canals m ay be seen as a series of tiny holes in the bone posterior to the internal acoustic m eatus. 12. To op en the tym p anic cavity, use forcep s to rem ove ad d itional p ortions of the t e g m e n t ym p a n i laterally. 13. Within the tym panic cavity, identify the aud it o ry o ssicle s (FIG. 7.91) . Observe that the m alle us is attached to the tym panic m em brane, the in cus occup ies an interm ediate position, and the st ap e s is the m ost m edial of the auditory ossicles. The m alleus and incus should easily be seen from the sup erior view. Note that the stapes is located m ore inferiorly and it m ay be harder to see. 14. Use ne forceps to rem ove the incus. Leave the m alleus attached to the tym p anic m em brane (FIG. 7.92) .

CHAPTER 7

15. Looking down from above, identify the t ym p an ic m e m b ran e on the lateral wall of the tym panic cavity. Attem pt to identify the tend on of the tensor tym p ani m uscle, a thin strand of tissue that spans from the m edial wall of the tym panic cavity to the handle of the m alleus.

THE HEAD AND NECK

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Line of scalpel cut

Malleus Incus removed

Walls o f t h e Tym p an ic Cavit y [G 686; L 363; N 96; R 129] The following dissection approach is intended for use on a decalci ed tem poral bone. If a decalci ed tem poral bone is not available, refer to an illustration for review of the following structures. 1. With the blade angled parallel to the internal surface of the tym panic m em brane, insert a scalpel blade into the opening created by rem oving the incus (FIG. 7.92) . Make a cut that extends anteriorly down the pharyngotym panic tube that divides the m iddle ear into m edial and lateral walls (FIG. 7.92) . Note that the cut through the pharyngotym panic tube should course p arallel to the sup erior border of the p etrous p art of the tem poral bone. 2. On the lateral wall of the tym panic cavity, observe the tym panic m em brane and identify the ch o rd a t ym p an i (FIG. 7.93B) . Observe that the chorda tym pani passes between the m alleus and the incus. [G 687; L 363; N 96; R 129] 3. On the m edial wall of the tym panic cavity, identify the elevation of the p ro m o n t o ry (FIG. 7.93A) . 4. Superior to the prom ontory, identify the st ap es still attached to the o val win d o w (fe n e st ra ve st ib uli) .

Tegmen tympani (cut)

FIGURE 7.92 Angle of cut to separate the m edial and lateral walls of the tym p anic cavity.

Look for the st ap e d ius t e n d o n , about 1 m m long, passing from the pyram idal em inence to the stapes. Note that the stapedius m uscle is innervated by the facial nerve (CN VII). 5. Inferior to the stapes, identify the ro un d win d o w (fe n e st ra co ch le ae ) posteroinferior to the prom ontory. 6. Identify the t e n so r t ym p an i m uscle , which attaches to the pharyngotym panic tube and sphenoid bone m edially and to the m anubrium (handle) of the m alleus laterally.

Tendon of stapedius m. emerging from pyramidal eminence

Tegmen tympani

Incus

Malleus Geniculate ganglion

Chorda tympani Tensor tympani: Tendon Muscle

A A Promontory Round window Facial canal

POSTERIOR

FIGURE 7.93

ANTERIOR

B B

Pharyngotympanic tube Internal carotid a. and internal jugular v.

Tympanic membrane ANTERIOR

Facial nerve in facial canal

POSTERIOR

Walls of the right tym panic cavity, opened like a book. A. Medial wall. B. Lateral wall.

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7. Observe that the tendon of the tensor tym pani m uscle crosses the tym panic cavity. The tensor tym pani m uscle is innervated by the m andibular division of the trigem inal nerve (CN V3 ). 8. Observe that the tym p anic cavity and its associated recesses and air cells are covered with m ucous m em brane. Note that the g lo sso p h aryn g e al n e rve (CN IX) innervates the m ucous m em brane of the tym panic cavity and that it form s the t ym p an ic p le xus under the m ucosa covering the prom ontory.

In t e rn al Ear [G 690; L 365; N 98; R 131] The vestibulocochlear organ is best seen in sectioned histologic m aterial. If you wish to dissect the internal ear, use a decalci ed tem poral b one. Refer to appropriate atlas illustrations and use a single-edge razor blade to cut thin slices of the tem poral bone. This p rocedure will expose the canals, cham bers, and nerve pathways of the internal ear. A dissecting m icroscope should be used to visualize these structures.

Disse ct io n Fo llo w-up 1. 2. 3. 4.

Use an illustration to review the external appearance of the tym panic m em brane. Relate the tym panic m em brane to the handle of the m alleus and the chorda tym pani. Review the course of the facial nerve from the internal acoustic m eatus to the facial m uscles. Review the course of the greater petrosal nerve from the geniculate ganglion to the pterygopalatine ganglion. Sum m arize the distribution of the postsynaptic axons that arise in the pterygopalatine ganglion. 5. Review the course of the special sensory bers contained in the chorda tym pani beginning at the tongue and ending at the internal acoustic m eatus. Where are the cell bodies for these sensory axons located? 6. Review the course of the presynaptic parasym pathetic axons that synapse in the subm andibular ganglion. Review the distribution of the p ostsynaptic axons that arise from the subm andibular g anglion. 7. Review all branches of the glossopharyngeal nerve, including those that give rise to the lesser petrosal nerve.

Index Page n u m bers in italics in d icate gu res; th ose followed by “b” in d icate boxes; an d th ose followed by “t” in d icates tables.

A Abdom en Qu ad ran t system , 99, 100, 110, 111 Region al system , 100, 100, 111 Su rface an atom y, 100 Abdom in al viscera, 113–114, 114 Posterior, 131–136 Abdom in al wall An terolateral Fascia of, 99, 99–102 Mu scles of, 110 t Skeleton of, 103 Posterior, 132, 136–137, 137 Mu scles of, 139 t Acetabu lar labru m , 223 Ad du ctor can al, 191 Ad du ctor h iatu s, 191, 196 Ad en oid s, 290 b Alar cartilage, 292 An al Can al Fem ale, 176–177 Male, 159, 159 Hiatu s, 163, 181 Trian gle, 141, 142 Valves, 150 An al can al, 126 An atom ical sn u ffbox, 64, 64 An sa cervicalis, 235 Su p erior root of, 237, 237 An tebrach iu m . see Forearm Aortic h iatu s, 140 Aortic sin u s, 88 Ap p en dix, 114, 126, 126, 130 Arach n oid gran u lation s, 264 Arach n oid m ater, 20, 264, 265 Arm , 23, 39–44 An terior ( exor) com p artm en t, 40–41, 41 Fascia of, 39 Mu scles of, 44 t Neu rovascu latu re of, 41–42 Posterior (exten sor) com p artm en t, 27 t, 60–63 Skeleton of, 24, 39–40 Arm p it. see Axilla Arteries An gu lar, 250 Aorta, 77, 84, 95 Abdom in al, 132, 136 Arch of, 86, 94 Ascen d in g, 87 Descen d in g (th oracic), 84, 95–97 Ap p en dicu lar, 123, 126 Arcu ate, 215

Ascen d in g p h aryn geal, 239 Axillary, 36, 36 Basilar, 270 Brach ial, 36, 41–42, 42 b, 47 Brach iocep h alic tru n k, 94 Bron ch ial, 82, 97 Bu ccal, 260 Carotid Extern al, 238, 238, 274 In tern al, 231, 238 Celiac tru n k, 118–119, 119 Cerebellar An terior in ferior (AICA), 270 Posterior in ferior (PICA), 270 Su p erior, 270 Cerebral An terior, 270 Mid d le, 270 Posterior, 270 Cerebral arterial circle (circle of Willis), 270 Cervical Ascen d in g, 242 Deep , 242 Tran sverse, 11, 243 Circu m ex h u m eral An terior, 36–37 Posterior, 36–37 Circu m ex iliac Deep , 161, 178, 190 Su p er cial, 190 Colic Left, 126 Mid d le, 124 Righ t, 124 Com m on carotid , 238, 239 Left, 94 Righ t, 94 Com m on h ep atic, 118–119 Com m on iliac, 132, 136, 160, 178, 178 Com m u n icatin g, 270 Coron ary, 87–89, 89 b Left, 88 Righ t, 88 Deep fem oral (p rofu n d a fem oris), 190, 195 Dorsal scap u lar, 242 Dorsalis p ed is (d orsal artery of th e foot), 215, 219 Ep igastric In ferior, 108, 111–112 Su p er cial, 101, 190 Su p erior, 106, 108 Facial, 236, 238, 250 Fem oral, 189–190, 192

Fibu lar, 210 Gastric Left, 119 Righ t, 118 Gastrod u od en al, 119, 127 Gastro-om en tal (gastroep ip loic), 119 Left, 119 Righ t, 119 Gen icu lar, 203, 204 Glu teal, 198–200 In ferior, 161 Su p erior, 160, 162, 179–180 Gon ad al. see Ovarian an d Testicu lar Greater p an creatic (p an creatica m agn a), 128 b Hep atic artery p rop er, 118 Ileocolic, 123, 124 Iliolu m bar, 160, 178 In ferior alveolar, 260 In ferior m esen teric, 125 , 125–126 In ferior p h ren ic, 136 In fraorbital, 251 In tern al th oracic, 241 In testin al, 124 Labial In ferior, 250 Su p erior, 250 Laryn geal In ferior, 238, 305 Su p erior, 238, 305 Lateral circu m ex fem oral, 193 Lateral sacral, 160, 178 Lateral tarsal, 215 Lateral th oracic, 36 Lin gu al, 238 Lu m bar, 136 Margin al, of colon , 126 Masseteric, 260 Maxillary, 254, 259–260, 299 Mid d le m en in geal, 264, 274 Obtu rator, 161, 179 Aberran t, 161, 179 Occip ital, 9, 9, 238 Op h th alm ic, 281, 281 Ovarian , 133 Palatin e, 297, 298 Palm ar d igital, 54 Pan creaticod u od en al, 119, 123, 127–128 Pen is, 152 Deep , 153 Su p er cial, 153 Perforatin g, 195 Perin eal Su p er cial bran ch of, 150, 168

313

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Arteries (Continued) Plan tar Deep , 215, 219 Lateral, 217–218 Medial, 217–218 Pop liteal, 192, 203, 207 Posterior au ricu lar, 238 Posterior scrotal, 150 Pu d en d al, 145, 200 Bran ch es of, 153 In tern al, 161, 169, 179 Su p er cial extern al, 190 Pu lm on ary, 82 Pu lm on ary tru n k, 84, 86, 87 Rad ial, 41, 47, 64 Recu rren t bran ch of, 43, 47 Rectal, 177 In ferior, 150 Mid dle, 161 Su p erior, 126, 159 Ren al, 134 Sigm oid , 126 Sp h en op alatin e, 298, 299 Sp len ic, 119 Su bclavian , 36, 94, 241, 242, 242, 243 Su blin gu al, 303 Su bscap u lar, 36 Su p er cial p alm ar arch , 54 Su p erio r m esen t eric, 122–125, 124, 127 Su p erior th oracic, 36 Su p raorbital, 256 Su p raren al, 134, 135 Su p rascap u lar, 26, 241, 243 Su p rem e in tercostal, 242 Tem p oral Deep , 260 Su p er cial, 254, 256 Testicu lar, 133, 147 Th oracoacrom ial, 33, 34 Th oracod orsal, 11 Th yroid In ferior, 242 Su p erior, 240 Th yroid im a, 240 Tibial, 207–208, 210 An terior, 213 Posterior, 210 Uln ar, 41, 47, 49, 54 Deep p alm ar bran ch of, 57 Uln ar collateral In ferior, 42 Su p erior, 42 Um bilical, 160, 179 Uterin e, 176, 179, 179 b Vagin al, 176, 179 Vertebral, 16, 241, 270 Vesical In ferior, 161 Su p erior, 161, 179 Aryep iglottic fold s, 290 Aryten oid cartilage, 304 Atlas (C1), 7, 16, 16 . see also Cervical vertebrae Au d itory ossicles, 310 Au ricle (p in n a), 308 Au ricu lar cartilage, 308. see also Ear

Axilla, 35, 35–39, 36 Fascia of, 33 Mu scles of, 39 t Nerves of, 24, 37, 38 b Axillary fold An terior, 28, 73 Posterior, 6, 28 Axillary sh eath , 35 Axis (C2), 7, 16, 16, 230 Den s, 16, 230

B Back Mu scles of Deep layer, 5, 14, 15 t In term ed iate layer, 5, 13, 13, 15 t Su p er cial layer, 5, 12 t Su rface an atom y of, 5, 6 Trian gles of, 11 b Basilar p lexu s, 268 Bell’s p alsy, 251 b Bicip ital ap on eu rosis, 41, 43 Biliary system Bile (com m on bile) d u ct, 118 Blad d er. see Urin ary blad d er Com m on h ep atic d u ct, 118 Cystic d u ct, 118, 121 Brach ial p lexu s, 35, 37, 38, 243 Brach iu m . see Arm Brain , 266–267, 269 Blood su p p ly of, 269–270 Cerebral h em isp h eres, 269 Fissu res of Lon gitu d in al, 269 Tran sverse, 269 Gyru s, 269 Postcen tral, 269 Precen tral, 269 Lobes of, 269 Su lcu s, 269 Cen tral, 269 Lateral, 269 Tran sverse ssu re, 269 Breast, 31, 32 b Bregm a, 247 Bu ccal fat p ad , 249 Bu rsa Om en tal, 116 Rad ial, 55 Troch an teric, 199 Uln ar, 55

C Calvaria, 247, 247 Cap u t m ed u sae, 102 b Carin a, 95 Carotid Bod y, 239 Sh eath , 231, 238, 287 Sin u s, 239 Carp al bon es, 29, 52 Cap itate, 52 Ham ate, 52 Hook of, 52, 70 Lu n ate bon e, 52, 70

Pisiform bon e, 45, 52 Scap h oid bon e, 52, 70 Tu bercle of, 52 Trap eziu m , 52 Tu bercle of, 52 Trap ezoid , 52 Triq u etru m , 52, 70 Carp al tu n n el, 53, 53, 55, 55 Syn d rom e, 55 b Cau d a eq u in a, 20 Caval foram en , 140 Cerebellar p ed u n cles, 271 Cerebral arterial circle (circle of Willis), 270 Cerebrosp in al u id (CSF), 265 Cervical sym p ath etic tru n k, 243 Ch orda tym p an i, 261 Ciliary bod y, 282 Clavicle, 5, 6, 73 Lateral (acrom ial) en d , 5, 6, 66 Med ial (stern al) en d , 6, 66 Clin oid p rocess Posterior, 266, 272 Clitoris, 166–168 Cru s of, 169 Fren u lu m of, 166 Glan s of, 166 Clivu s, 273 Coccygeal p lexu s, 161, 179 Coccyx, 6, 7, 8 Tip of, 143 Coch lea, 310 Colon , 114, 125–127, 127, 129–130 Ascen d in g, 114, 126 Descen d in g, 114 Left colic (sp len ic) exor, 114, 126 Righ t colic (h ep atic) exu re, 114, 126 Sigm oid , 114 Tran sverse, 114, 126 Com m on exor ten don , 46 Com m on ten d in ou s rin g, 280 Con ch ae, 293, 293 Con ju n ctiva, 278 Con ju n ctival sac, 281 Con oid ligam en t, 66 Con u s m ed u llaris (m ed u llary con e), 20 Coron ary (atrioven tricu lar) su lcu s, 87 Costocervical tru n k, 242 Costocoracoid m em bran e, 34 Costod iap h ragm atic recess, 79 Costom ed iastin al recesses, 79 Cran ial fossae, 266, 266, 269, 269, 271–276, 272, 273 An terior, 273 Mid d le, 274 Posterior, 275 Cran ial n erves, 270–271 Abd u cen t (abd u cen s) (CN VI), 271, 274, 280 Facial (CN VII), 244, 271, 275, 309 Glossop h aryn geal (CN IX), 271, 275, 287, 298, 312 Hyp oglossal (CN XII), 271, 275, 288, 302 Ocu lom otor (CN III), 271, 274, 280, 282 Olfactory (CN I), 271, 273 Op tic (CN II), 271, 274, 282 Sp in al accessory (CN XI), 271, 275, 287

INDEX Trigem in al (CN V), 271, 274, 299 Troch lear (CN IV), 271, 274 Vagu s (CN X), 77, 86, 94, 96, 275, 287 Vestibu lococh lear (CN VIII), 271, 275, 309 Cribriform p late, 291 Cricoid cartilage, 234, 235, 305 Crista term in alis, 90 Cu bital fossa, 28, 42–43 Bou n d aries of, 42

D Deltop ectoral groove, 30, 33 Deltop ectoral trian gle, 30, 33 Den tal an esth esia, 251 b, 261 b Diap h ragm , 77, 139, 139–140, 140 b Cen tral ten d on of, 84, 139 Costal p art, 139 Cru s of, 139 Lu m bar p art, 139 Stern al p art, 139 Digital syn ovial sh eath s, 55 Dip loë, 263 Du ctu s deferen s (vas d eferen s), 147, 157, 165 Du oden u m , 113–114, 127 Am pulla or duoden al cap (bulb), 127, 129 Ascen d in g p art, 127 Blood su p p ly of, 128 Descen din g p art, 127, 130 Horizon tal p art, 127 Major (greater) p ap illa, 129 Min or (lesser) p ap illa, 129 Du ra m ater, 20, 264, 265 Men in geal layer, 264 Periosteal layer, 264 Du ral in fold in gs, 267, 268 Du ral sac, 20 Du ral ven ou s sin u ses, 264, 268, 268 Cavern ou s, 268, 275, 275 b Con u en ce of, 268 Petrosal sin u s In ferior, 268 Su p erior, 268 Sagittal In ferior, 268 Su p erior, 264, 264, 268 Sigm oid, 268 Groove of, 266 Straigh t sin u s, 268 Tran sverse, 85, 266, 268, 272

E Ear, 308 An tih elix, 308 An titragu s, 308 Au ricle (p in n a), 308 Lobu le of (earlobe), 308 Extern al, 307–308, 308 Helix, 308 In tern al, 312 Mid d le, 309. see also Tym p an ic cavity Ossicles of, 309–311 Tragu s, 308 Ejacu latory d u cts, 157

En d oth oracic fascia, 84 Ep icran ial ap on eu rosis, 255 Ep id id ym is, 147, 148 Bod y of, 147 Head of, 147 Tail of, 147 Ep id u ral (extrad u ral) sp ace, 20 Ep id u ral h em atom a, 264 b Ep igastric an astom oses, 108 b Ep iglottic cartilage, 304 Ep iglottic vallecu lae, 288 Ep iglottis, 288, 301, 306 Esop h ageal h iatu s, 129, 139 Esop h agu s, 77, 84, 96, 230 Eth m oid bon e, 271, 291 Cribriform p late, 266, 271, 291 Crista galli, 266, 271, 273 Perp en d icu lar p late, 291 Eth m oid al bu lla (bu lla eth m oid alis), 293 Exten sor exp an sion , 60, 62 Exten sor m u scles of forearm Deep layer, 62, 63 Su p er cial layer, 60, 61 Exten sor retin acu lu m , 60, 62 Su p erior an d in ferior, 213 Eye (eyeball), 277, 277–278, 278, 282 Ch oroid , 282 Corn ea, 277, 282 Extraocu lar m u scles, 283 t Iris, 282 Macu la, 282 Retin a, 282 Sclera, 277, 282 Eyelash es (cilia), 277 Eyelid , 278

F Face, 248, 249 Su p er cial fascia of, 248 Su rface an atom y of, 244, 244–245 Falx cerebelli (cerebellar falx), 268 Falx cerebri (cerebral falx), 264, 267 Fascia Bu ccop h aryn geal, 286 Bu ck’s, 151 Cam p er’s, 99, 165 Clavip ectoral, 30, 33 Crem asteric, 147 Cru ral, 188, 205 Dartos, 146, 149, 149, 151, 165 En d op elvic, 158, 175 En d oth oracic, 78, 84 Pedal, 188 Pretrach eal, 230 Prevertebral, 230 Su p er cial An terior abdom in al wall, 99, 99–102, 101 An terior th oracic wall, 31 Back, 9–10 Up p er lim b, 28 Th oracolu m bar, 14 Tran sversalis, 108 Fem oral can al, 190 Fem oral rin g, 190 Hern ia, 191 b

•

315

Fem oral trian gle, 189–190, 189 b, 190 Ap ex of, 191 Fem u r Ad du ctor tu bercle, 184 Glu teal tu berosity, 198 Greater troch an ter, 184, 198 Head, 222–223, 223 b Ligam en t of, 222–223 In tercon d ylar fossa, 223 In tertroch an teric lin e, 184 Lateral con d yle, 184, 223 Lateral ep icon d yle, 184 Lateral lip of lin ea asp era, 201 Lesser troch an ter, 184, 198 Med ial ep icon d yle, 184 Med ial lip of lin ea asp era, 201 Neck, 223 b Fib ro u s jo in t cap su le, 2 22 , 22 2 –2 2 3 , 223 Fibu la Head , 184, 202, 206 Lateral con d yle, 202 Lateral m alleolu s, 206, 225 Med ial con d yle, 202 Med ial m alleolu s, 225 Neck, 206 Sh aft (bod y), 206 Filu m term in ale Extern u m , 20 In tern u m , 20 Fim briae, 174 Foot Arch es of, 219 Dorsal ven ou s arch of, 185 Dorsu m of, 215 Mu scles, 216 t Plan tar ap on eu rosis, 216 Skeleton of, 206, 207 Sole of, 216–221, 217 First layer, 217, 218 Fou rth layer, 219 Mu scles, 221 t Secon d layer, 218, 219 Th ird layer, 218–219, 220 Foram en cecu m , 301 Forearm , 23 An terior ( exor) com p artm en t of, 44–51, 51 t An terior (forearm ) fascia, 30, 39 Flexor retin acu lu m , 52 Mu scles, 51 t, 65 Deep layer, 50–51 In term ed iate layer, 47 Su p er cial layer, 45–47 Neu rovascu latu re of, 41–42 Posterior (exten sor) com p artm en t of, 59–65, 65 t Skeleton of, 44–45 Fron tal bon e, 245, 246 Fron tal sin u s, 293

G Gallblad d er, 113–114, 117, 122 Sp iral valve, 121 Gast ro in t est in al t ract , 1 1 3 –114 , 129–131

316

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INDEX

Gen italia Fem ale extern al, 166, 166–167 Fem ale in tern al, 173–175 Male extern al, 146–148 Male in tern al, 155–157, 157 Glabella, 245 Glen oid labru m , 68 Glossoep iglottic fold , 301 Glottis, 306 b Glu teal region , 197–201 Glu teal ap on eu rosis, 198 Mu scles of, 198, 199, 201 t Skeleton of, 197, 197 Greater om en tu m , 113–114, 114, 115 Greater p eriton eal sac, 116 Gu bern acu lu m , 147

H Han d (m an u s), 23, 53 Dorsu m of, 59–65, 64 Extrin sic m u scles of, 52 In trin sic m u scles of, 52, 59 t Palm of, 52–60. see also Palm Skeleton of, 52 Heart, 84–86, 85 Ap ex of, 86 Base of, 86 Ch am bers of, 85, 89–92, 90, 91 Con d u ctin g system of, 90 Extern al featu res of, 86–89 In tern al featu res of, 89–93 Valves of, 87, 88, 90, 91, 92 Hem orrh oid s, 159 b, 177 b Hesselbach ’s (in gu in al) trian gle, 106 b Hip bon e. see also Pelvis Acetabu lu m , 142 Hu m eru s, 24, 39 An atom ical n eck, 67 Bicip ital (in tertu bercu lar) groove, 24 Cap itu lu m , 39 Coron oid fossa, 39 Deltoid tu berosity, 39 Greater tu bercle, 24 Head , 24, 67 In tertubercular sulcus (bicipital groove), 24 Lateral ep icon d yle, 28, 39 Lesser tu bercle, 24 Medial an d lateral supracon dylar ridge, 45 Medial ep icon dyle, 24 Olecran on fossa, 39 Rad ial groove, 24, 26 Sh aft, 24 Su rgical n eck, 24 Troch lea, 39 Hyoid bon e, 234 Greater h orn of, 237, 286 Hyp ogastric p lexu s (p elvic p lexu s), 136, 180 b In ferior, 161, 162, 179 Su p erior, 162, 180 Hyp oth en ar Em in en ce, 29, 52

I Ileocecal ori ce, 130 Ileocecal valve, 130

Ileu m , 114, 123, 124, 130, 130 . see also Sm all in testin e Iliop u bic em in en ce, 142 Iliotibial tract, 188, 193 Iliu m , 6, 7, 142, 197, 222 An terior in ferior iliac sp in e (AIIS), 184 An terior su p erior iliac sp in e (ASIS), 100, 103, 142, 183 Glu teal lin es, 197 Greater sciatic n otch , 197 Iliac crest, 5, 7, 100, 197 Iliac tu bercle, 100, 103 Posterior su p erior iliac sp in e (PSIS) 5, 7 In cu s, 309–311 In ferior m eatu s, 293 In fram esocolic com p artm en t, 116 In fratem poral fossa, 256–259, 260, 261, 295 In gu in al can al, 102, 105, 109 In gu in al h ern ia, 106 b, 107 In gu in al rin g, 102 Deep , 108–109, 111, 157 Su p er cial, 103, 104 In tercostal sp ace, 73, 75 In terscalen e trian gle, 243, 243 b In tervertebral d isc, 7 In tervertebral foram en , 7, 21 In traglu teal in jection s, 200 b In trap eriton eal (p eriton eal) organ s, 113 Isch ioan al (isch iorectal) fossa, 144–145, 145 Isch iopu bic ram u s, 142, 143, 150, 168, 184 Isch iu m , 142, 197, 222 Isch ial sp in e, 142, 197 Isch ial tu berosity, 142, 143, 150, 168, 197, 201

J Jeju n u m , 113–114, 123, 124, 130, 130 Join ts Acrom ioclavicu lar (AC), 66, 67 An kle, 225 b, 225–226, 226 Atlan toaxial, 283 Atlan to-occip ital, 284 Carp om etacarp al, 70 Elbow, 40, 68, 69 Glen oh u m eral. see Sh ou ld er Hip , 222–223 In terp h alan geal, 70, 71 Kn ee, 223–224, 224 Metacarp op h alan geal, 70 Mid carp al, 70 Rad iocarp al. see Wrist Rad iou ln ar Distal, 45, 69–70, 70 In term ed iate, 69 Proxim al, 40, 68 Sacroiliac, 143 Sh ou ld er, 23, 67, 67 Stern oclavicu lar (SC), 66, 66 Su btalar, 227 Tem p orom an dibu lar, 261–262, 262 Wrist, 69–70, 70 Articu lar d isc of, 66, 70 Ju gu lar Bu lb, 309 Foram en , 266, 272 Fossa, 309 Notch , 28, 73, 75

K Kid n ey ston es, 134 b, 158 b, 176 b Kid n eys, 133, 133–135 Calices of, 135 In tern al featu res of, 134, 135 Ren al cortex, 134 Ren al fascia, 134 Ren al m ed u lla, 134 Ren al p ap illa, 135 Ren al p elvis, 134 Ren al sin u s, 135

L Labia m ajora, 165 Labia m in ora, 166 Labial com m issu re, 166 Lacrim al Ap p aratu s, 278, 279 Bon e, 291 Can alicu li, 279 Caru n cle, 277 Crest, 278 Glan d , 278, 281 Groove, 278 Lake, 277 Pap illa, 277 Sac, 279 Lam bd a, 247 Lam in a p ap yracea, 277 Lam in ectom y, 19 Large in testin e, 114, 125–127, 125, 129–130. see also Colon Cecu m , 114, 130, 130 Hau stra, 126, 130 Om en tal ap p en d ices (ep ip loic ap p en d ages), 126 Sem ilu n ar folds (plicae sem ilu n ares), 130 Ten iae coli, 126 Laryn geal cavity, 306 Laryn geal in let (ad itu s), 288, 290 Laryn geal p rom in en ce (Ad am ’s ap p le), 234, 235, 304 Mu cosal featu res of, 306 Mu scles of, 305, 305, 307 t Laryn geal in let, 288 Laryn gop h aryn x, 290 Laryn x, 230, 303–307 Cartilages of, 304, 304 Leg. see also Lower lim b Com p artm en ts of, 204–214, 205, 209, 212 Mu scles of, 211 t, 212, 216 t Skeleton of, 206, 206 Lesser om en tu m , 115, 118 Lesser p eriton eal sac, 116 Ligam en ts An n u lar, 69 An terior sacroiliac, 143 Arcu ate, 139–140 Arcu ate p op liteal, 224 Broad , of th e u teru s, 171, 172, 174 Calcan eo bu lar, 226 Coccygeal, 20 Collateral, 225 Con oid , 66 Coracoacrom ial, 67 Coron ary, 115

INDEX Costoclavicu lar, 66 Cricoth yroid , 235 Cru ciate, 225 Den ticu late, 21 Falciform , 111, 115, 121 Fibu lar (lateral) collateral, 224 Gastrop h ren ic, 116 Gastrosp len ic (gastrolien al), 116 Glen oh u m eral, 67 Hep atodu oden al, 115, 118, 118 Hep atogastric, 115, 118 Iliofem oral, 222–223 Iliolu m bar, 143 In gu in al, 99, 103, 104, 189 In tersp in ou s, 19 Isch iofem oral, 222 Ligam en ta ava, 19 Med ial (d eltoid ), 225 Medial p alp ebral, 278–279 Obliq u e p op liteal, 224 Ovarian , 172 Patellar, 225 Patellar (ten don ), 192 Re ex, 193 b Ph ren icocolic, 116 Plan tar, 227, 227 Plan tar calcan eon avicu lar (sp rin g), 227, 227 Posterior cru ciate, 224 Posterior sacroiliac, 143 Pu bocervical (p u bovesical), 172 Pu bofem oral, 222 Pu bop rostatic, 158 Pu bovesical, 175 Pu lm on ary, 79 Radial collateral, 69 Radiocarp al, 70 Rou n d Of th e liver, 115 Of u teru s, 102, 171 Sacrosp in ou s, 142 Sacrotu berou s, 142, 143, 197 Scrotal, 147 Sp len oren al (lien oren al), 116 Su p rasp in ou s, 19 Su sp en sory Of breast, 31 Of d u od en u m , 125 Of ovary, 172, 174 Talo bu lar An terior, 226 Posterior, 226 Tibial (m ed ial) collateral, 224 Tibiocalcan eal, 225 Tibion avicu lar, 225 Tibiotalar, 225 Posterior, 225 Tran sverse acetabu lar, 223 Tran sverse carp al, 55 Tran sverse cervical (card in al ligam en t), 172 Tran sverse h u m eral, 40 Tran sverse scap u lar, 26 Trap ezoid , 66 Trian gu lar, 116 Uln ar collateral, 68 Um bilical, 179 Medial, 161

Uterosacral (sacrogen ital), 172 Vocal, 304, 306 Ligam en tu m Arteriosu m , 86 Teres h ep atis, 115 Ven osu m , 121 Lin ea alba, 102, 106–107 Liver, 113–114, 117, 120 Diap h ragm atic su rface of, 117, 120 Lobes of, 117, 121 Visceral su rface of, 117, 120 Lower lim b. see also Foot; Leg; Th igh Fascia of, 185–187 Join ts of, 222–227 Su p er cial vein s an d cu tan eou s n erves of, 183–188 Su rface an atom y of, 183, 183 Lu m bar p lexu s, 137, 137 Lu m bar p u n ctu re, 20 b Lu m bar trian gle, 11 b Lu m bosacral tru n k, 138, 162, 179–180 Lu n gs, 80, 81 Bron ch op u lm on ary segm en t, 82 Card iac n otch , 81 Costal su rface, 80 Diap h ragm atic su rface, 80 Fissu res of, 80 Lin gu la, 82 Lobar (secon d ary) bron ch i, 82 Lobes of, 80 Main (p rim ary) bron ch u s, 82, 94 Med iastin al su rface of, 80, 81, 82 Root of, 79, 82, 84 Segm en tal (tertiary) bron ch i, 82 Lym p h n od es, 35 Celiac, 121 Drain age of Breast, 31 Labia m ajora, 165 b Scrotu m , 148 b Hep atic, 121 Iliac Com m on , 165, 182 Extern al, 165, 182 In tern al, 165, 182 In gu in al Deep , 188 Su p er cial, 188, 188 Lu m bar, 165, 182 Mesen teric, 123, 126 Righ t lym p h atic d u ct, 243 Sacral, 165, 182 Trach eobron ch ial, 95 Vessels, 35, 118

M Malleu s, 309–311 Man d ible, 252, 256–257, 257, 259, 301 An gle of, 245 Bod y of, 247 Con d ylar (con d yloid) p rocess, 247 Coron oid p rocess, 247 Digastric fossa, 234 Man d ibu lar can al, 259 Man d ibu lar foram en , 257 Man d ibu lar n otch , 247 Man d ibu lar teeth , 259

•

317

Men tal foram en , 246 Men tal p rotu beran ce of, 245–246 Men tal tu bercles, 246 Ram u s of, 247 Man u briu m , 66, 73, 75 Man u s. see Han d Mastoid p rocess, 5, 6 Maxilla, 295 Alveolar p rocess of, 245, 246 Fron tal p rocess of, 246, 291 In fraorbital foram en , 246 Maxillary teeth , 295 Maxillary sin u s, 293, 294, 294 b Med ial in term u scu lar sep tu m , 41 Arm , 40–41 Med iastin u m , 77, 83, 83–86 Bord ers of, 83 In ferior, 93–95, 95 Posterior, 95–98, 97 Su p erior, 93–95, 95 Men in ges. see also Arach n oid m ater; Du ra m ater; Pia m ater Cran ial, 264, 264 Sp in al, 18, 20, 21 Men iscu s Lateral, 224 Med ial, 224 Mesen tery (p rop er), 116, 124, 125 Mesoap p en d ix, 116, 126 Mesosalp in x, 171 Mesovariu m , 171 Metacarp als, 70 Mon s p u bis, 166 Mu scles, 236 Abd u ctor d igiti m in im i, 57, 217 Abd u ctor h allu cis, 217 Abd u ctor p ollicis lon gu s, 62 Ad du ctor brevis, 194 Ad du ctor h allu cis, 219 Ad du ctor lon gu s, 189, 194 Ad du ctor m agn u s, 194, 196 Ham strin g p art of, 202 Ad du ctor p ollicis, 52, 57 An al sp h in cter, 159, 159, 177, 177 An con eu s, 60 Aryten oid , 305 Bicep s brach ii, 40, 42, 68 Lon g h ead , 40 Sh ort h ead , 40 Bicep s fem oris, 202 Brach ialis, 40, 41, 43 Brach iorad ialis, 42–43, 60 Bu ccin ator, 249, 250 Bu lbosp on giosu s, 150, 168 Coccygeu s, 163, 182 Con u s arteriosu s (in fu n d ibu lu m ), 91 Coracobrach ialis, 40, 41 Crem aster, 105 Crem asteric, 147 Cricoaryten oid , 305 Cricop h aryn geu s, 286 Cricoth yroid , 238, 305 Dartos, 146 Deep tran sverse p erin eal, 170 Deltoid , 23, 28 Dep ressor an gu li oris, 250 Dep ressor labii in ferioris, 250 Detru sor, 158

318

•

INDEX

Mu scles (Continued) Digastric An terior belly of, 236 Posterior belly of, 254 Dorsal in terossei, 58, 58 Dorsu m of foot, 216 t Erector sp in ae, 5, 13, 14 Iliocostalis, 14 Lon gissim u s, 14 Sp in alis, 14 Exten sor carp i radialis brevis, 60 Exten sor carp i radialis lon gu s, 60 Exten sor carp i u ln aris, 60 Exten sor d igiti m in im i, 60 Exten sor d igitoru m , 60 Exten sor d igitoru m brevis, 215 Exten sor d igitoru m lon gu s, 213 Exten sor h allu cis brevis, 215 Exten sor h allu cis lon gu s, 213 Exten sor in d icis, 62 Exten sor p ollicis brevis, 62, 64 Exten sor p ollicis lon gu s, 62, 64 Extern al an al sp h in cter (sp h in cter u reth rae), 145 Extern al obliq u e, 102, 103, 104, 105 Extraocu lar, 283 t Facial, 250, 250, 252 t Fibu laris brevis, 211 Fibu laris lon gu s, 211 Fibu laris tertiu s, 213, 215 Flexor carp i radialis, 46–47 Flexor carp i u ln aris, 46–47 Flexor d igiti m in im i, 219 Flexor d igiti m in im i brevis, 57 Flexor d igitoru m brevis, 217 Flexor d igitoru m lon gu s, 210, 218 Flexo r d igit o ru m p ro fu n d u s, 50 –51, 55 Flexor d igitoru m su p er cialis, 47, 55 Flexor d igitoru m lon gu s, 205 Flexor h allu cis brevis, 218 Flexor h allu cis lon gu s, 205, 210, 218–219, 220 Flexor p ollicis lon gu s, 51–55 Gastrocn em iu s, 205, 207 Gem ellu s, 200 Gen ioglossu s, 301 Gen ioh yoid , 301 Glu teu s m axim u s, 144, 198 Glu teu s m ed iu s, 199–200 Glu teu s m in im u s, 199–200 Gracilis, 194, 204 Hyoglossu s, 302 Iliacu s, 137 Iliococcygeu s, 163, 182 Iliocostalis, 14 Iliop soas, 137, 188, 190, 222 In ferior obliq u e, 281 In frasp in atu s, 25–26 In tercostal Extern al, 73, 75, 77 t In n erm ost, 73, 75, 77 t, 97 In tern al, 73, 75, 77 t In tern al obliq u e, 102, 104–105, 105 In tern al u reth ral sp h in cter, 175 In terosseou s, 52, 219 Dorsal in terossei, 219 Palm ar in terossei, 219

Isch iocavern osu s, 150, 168 Lateral rectu s, 280 Latissim u s d orsi, 5, 10, 11, 38 Levator an i, 163, 182 Levator labii su p erioris, 250 Levator p alp ebrae su p erioris, 280 Levator scap u lae, 10, 12, 243 Levator veli p alatin i, 297 Lon gu s cap itis, 285 Lon gu s colli, 285 Lu m bricals, 52, 56, 218 Masseter, 248, 258 Mastication , 262 t Mu lti d u s, 13, 15 Mu scu lu s u vu lae, 297 Myloh yoid , 301 Obliq u u s cap itis in ferioris, 16 Obliq u u s cap itis su p erioris, 16 Obtu rator extern u s, 194, 222 Obtu rator in tern u s, 163, 181–182 Occip itofron talis, 255 Om oh yoid In ferior belly of, 241 Su p erior belly of, 235 Op p on en s d igiti m in im i, 57 Op p on en s p ollicis, 57 Orbicu laris ocu li, 250 Orbital p ortion of, 278 Palatoglossu s, 296 Palatop h aryn geu s, 296 Palm ar in terossei, 57, 58 Palm aris brevis, 54 Palm aris lon gu s, 46–47, 54 Pap illary, 91 Pectin ate, 90 Pectin eu s, 190, 194 Pectoralis m ajor, 33, 33 Pectoralis m in or, 33, 33 Perin eal Deep tran sverse, 153 Su p er cial tran sverse, 150, 168 Ph aryn geal con strictor, 286, 298 In ferior Cricop h aryn geu s, 286 Th yrop h aryn geu s, 286 Mid dle, 286 Piriform is, 160, 179, 199 Plan taris, 205, 207 Platysm a, 31, 232, 232, 248 Pop liteu s, 204, 205, 210 Pron ator q u ad ratu s, 50, 51 Pron ator teres, 42, 46–47 Psoas m ajor, 137 Psoas m in or, 137 Pterygoid Lateral, 260 Med ial, 260 Pu bococcygeu s, 163, 182 Pu borectalis, 163, 182 Pyram id alis, 106 Qu ad ratu s fem oris, 188, 192, 200 Qu ad ratu s lu m boru m , 137 Qu ad ratu s p lan tae, 218 Rectu s abd om in is, 102, 106–107, 108, 109 Rectu s cap itis p osterior m ajor, 16 Rectu s cap itis p osterior m in or, 16 Rectu s fem oris, 192

Rh om boid m ajor, 10, 11 Rh om boid m in or, 10, 11 Rotator cu ff, 25–26, 38 Rotatores, 13 Salp in gop h aryn geu s, 296 Sartoriu s, 188, 191–192, 204 Scalen e, 243, 244 t, 285 Sem im em bran osu s, 202 Sem isp in alis, 13 Cap itis, 14 Cervicis, 14–15 Sem iten d in osu s, 202, 204 Serratu s an terior, 38, 75 Serratu s p osterior in ferior, 13 Serratu s p osterior su p erior, 13 Soleu s, 205, 207 Sp len iu s cap itis, 13, 14, 243 Sp len iu s cervicis, 13, 14 Stern ocleid om astoid (SCM), 66, 77, 233 t, 240–241 Stern oh yoid , 235 Styloglossu s, 302 Styloh yoid , 236 Stylop h aryn geu s, 287 Su bclaviu s, 34 Su bscap u laris, 25 Su p erior, 287 Su p erior obliq u e, 280 Su p erior rectu s, 280 Su p in ator, 43 Su p rasp in atu s, 25–26 Tem p oralis, 256, 258, 263 Ten sor of fascia lata, 188, 189, 193 Ten sor tym p an i, 311 Teres m ajor, 25, 38 Teres m in or, 24–25 Th yroaryten oid , 306 Th yroh yoid , 235–236 Tibialis an terior, 213 Tibialis p osterior, 205 Trabecu lae carn eae, 91 Tran sversosp in ales, 13 Tran sversu s abd om in is, 102, 105–106, 106, 137 Tran sversu s th oracis, 78 Trap eziu s, 5, 9–10 Tricep s brach ii Lateral h ead, 25, 26 Lon g h ead , 26, 26 Med ial h ead , 25, 26 Vastu s in term ed iu s, 192 Vastu s lateralis, 192 Vastu s m ed ialis, 192 Vocalis, 306 Zygom aticu s m ajor, 250

N Nasal Bon es, 245, 291 Cartilage, 245, 292 Cavity, 291, 291 Lateral wall of, 293, 293, 298 Con ch a, 291 Sep tal cartilage, 292 Sep tu m , 246, 288, 292, 292 Sp in e, 291 An terior, 246

INDEX Nasal ap ertu re An terior, 246 Posterior (ch oan ae), 288–289 Nasion , 246 Nasolacrim al d u ct, 279, 293 Neck Bon es an d cartilages of, 234 Nerve p oin t of, 232 Root (base) of, 241–244, 242 Skeleton of, 229–230 Trian gles of An terior, 234, 234–239 Carotid, 236, 236 Mu scu lar, 235 Posterior, 231, 231–232, 232 Su bm an d ibu lar, 235–236 Su bm en tal, 236, 236 Nerve in ju ries, 38 b Nerves, 238, 238 Abd u cen t (abd u cen s) (CN VI), 271, 274, 280 Accessory, 233, 237. see Sp in al accessory Alveolar In ferior, 261 Su p erior, 261 An terior eth m oid al, 280 Au ricu lotem p oral, 253 Au ton om ic, 118 Bu ccal (lon g bu ccal), 250 Cervical p lexu s, 232 Clu n eal, 185–187 Com m on bu lar, 202 Cran ial. see Cran ial n erves Cu tan eou s An terior, 32 Face, 251 Fem oral bran ch es, 190 Foot, 216 Head an d n eck, 244 Lateral Forearm , 41 Lateral fem oral (of th igh ), 138, 187 Lower lim b, 186 Medial, of arm , 37 Medial, of forearm , 37, 41 Posterior, of th igh , 185–187, 200, 203 Scalp , 256, 256 Tru n k, 32, 101–102 Up p er lim b, 30 Dorsal digital, 187, 211 Dorsal scap u lar, 12 Esop h ageal p lexu s of, 96 Extern al n asal, 280 Facial, 248, 249 Facial (CN VII) Bran ch es of, 249 Bu ccal bran ch of, 249 Sen sory bran ch es of, 251 Fem oral, 138, 189 Bran ch es of, 193, 193 Fibu lar Com m on , 214, 215 b Deep , 187, 214 Su p er cial, 187 Fron tal, 280 Gen itofem oral, 137–138 Glossop h aryn geal (CN IX), 271, 275, 287, 298, 312

Glu teal, 198–200 Great au ricu lar (C2), 232, 244, 253 Greater occip ital, 9, 9, 14, 244 Greater p etrosal, 308, 309 Hyp ogastric, 162 Hyp oglossal (CN XII), 236, 237, 271, 275, 288, 301 b, 302 Ilioh yp ogastric, 101, 105, 138 Ilioin gu in al, 105, 138 In ferior rectal (an al), 145 In fraorbital, 251, 251 b In tercostal, 101 Laryn geal In ferior, 305, 306 Left recu rren t, 86, 94, 94 b, 243 Recu rren t, 240, 240 b, 306 Righ t recu rren t, 94, 243 Su p erior, 238, 288, 305, 306 Lesser occip ital (C2), 232 Lin gu al, 259, 261, 302 Lon g ciliary, 280 Lon g th oracic, 38 Med ian , 37, 39, 41, 43, 47–55 Recu rren t bran ch of, 54, 56 b Men tal, 251 Mu scu locu tan eou s, 37, 41 Nasociliary, 271, 274, 280, 282 Nasop alatin e, 292 Obtu rator, 138, 161, 179, 187, 195 Bran ch es of, 195, 195–196 Ocu lom otor (CNIII), 271, 274, 280, 282 Olfactory (CN I), 271, 273 Op tic (CN II), 271, 274, 282 Palatin e, 297, 298 Palm ar d igital, 55 Pectoral Lateral, 37 Med ial, 33–34 Pelvic sp lan ch n ic (n ervi erigen tes), 162, 180 Pen is, 152 Deep d orsal, 151 Perforatin g, 187 Perin eal Su p er cial bran ch of, 150, 168 Ph ren ic, 80, 94, 94, 140, 243 Plan tar Lateral, 217–218 Med ial, 217–218 Posterior scrotal, 150 Pu d en d al, 145, 162, 180 Bran ch es of, 153 Rad ial, 27, 37 Su p er cial bran ch , 30–47 Ram i com m u n ican tes, 97, 138 Gray, 162, 180 Sap h en ou s, 187, 192 Sciatic, 162, 179, 202 b Fibu lar d ivision , 200 Tibial d ivision , 200 Sp in al, 17 An terior (ven tral) ram u s, 11, 21, 162, 180 An terior (ven tral) roots, 21 Posterior (d orsal) ram u s, 10, 21 Posterior (d orsal) roots, 21 Sp in al accessory (CN XI), 10, 233, 237, 271, 275, 287

•

319

Sp lan ch n ic Greater, 97, 140 Least, 97 Lesser, 97, 140 Lu m bar, 138 Pelvic, 138 Sacral, 138, 162 Su bcostal, 101, 138 Su boccip ital, 16 Su bcap su lar Lower, 37–38 Up p er, 37–38 Su p erior bu lar, 211 Su p erior m esen teric p lexu s of, 123 Su p raclavicu lar (C3, C4), 233, 233 b Su p raorbital, 251, 256, 280 Su p rascap u lar, 26 Su p ratroch lear, 280 Su ral, 185 Th oracod orsal, 11, 37, 38 b Tibial, 202–203, 207–208, 210 Tran sverse cervical (C2), 233 Trigem in al (CN V), 271, 274, 299 Man d ibu lar d ivision (V3), 244 An esth esia of, 261 b Maxillary d ivision (V2), 244 Op h th alm ic d ivision (V1), 244 Troch lear (CN IV), 271, 274 Uln ar Deep bran ch , 57 Dorsal bran ch , 30 Su p er cial bran ch , 54 Vagal tru n k An terior, 96 Posterior, 96 Vagu s (CN X), 77, 86, 94, 96, 275, 287 Ph aryn geal bran ch of, 288 Vestibu lococh lear (CN VIII), 271, 275, 309 Nip p le, 31 Nose. see also Nasal Extern al, 292, 292

O Obtu rator can al, 163 Obtu rator foram en , 142, 184 Occip ital bon e, 6, 266, 272 Extern al occip ital p rotu beran ce, 5, 6, 6, 7, 9, 16, 247 Foram en m agn u m , 16, 266, 273 Hyp oglossal can al, 266, 273 In ferior n u ch al lin e, 6, 16 In tern al occip ital p rotu beran ce, 273 Occip ital con d yles, 284 Su p erior n u ch al lin e, 6, 16 Olfactory bu lb an d tract, 271 Om en tal bu rsa, 116 Om en tal (ep ip loic) foram en , 116 Op tic can al, 276 Op tic ch iasm , 271 Op tic d isc, 282 Op tic tracts, 271 Oral cavity Mu scles of, 303 t Prop er, 300, 300 Vestibu le, 300

320

•

INDEX

Orbit, 245, 276, 276–283, 277 Orbital m argin , 245 Orbital sep tu m , 278, 278 Su p erciliary arch , 245 Su p raorbital n otch , 245 Orbital ssu re In ferior, 276, 295 Posterior, 272, 276 Oval win d ow (fen estra vestibu li), 309 Ovaries, 174 Fossa of, 174 Su sp en sory ligam en t of, 172, 174

P Palate Hard , 294–299, 295, 297 Soft, 288, 294–299, 296, 297 Mu scles of, 299 t Palatin e ap on eu rosis, 297 Palatin e bon e, 291 Palatin e foram en , 295, 297 Palatin e glan d s, 294 Palatin e ton sil, 290, 298 Palatoglossal fold (an terior fau ces), 289, 296, 298 Palatop h aryn geal fold (p osterior fau ces), 296, 298 Palm Deep , 57 Fascia of, 30 Su p er cial, 54 Palm ar ap on eu rosis, 53, 54 Palp ebral com m issu res Medial an d lateral, 277 Palp ebral ssu re (rim a), 250, 277 Pan creas, 127, 127–128 Accessory du ct, 128 Blood su p p ly of, 128 Head , 127 Main p an creatic du ct, 128 Neck, 127 Un cin ate p rocess, 127 Paracolic gu tter, 116 Param etriu m , 174 Paran asal sin u ses, 294, 294 Pararectal fossa, 155, 171 Parath yroid glan d s, 230, 240–241, 240 b Paravesical fossa, 171 Parietal bon es, 246 Parotid Bed , 253 Du ct, 248, 253 Glan d , 249, 254 b Plexu s, 249 Region , 252, 252–254, 253 Patella, 183 Patellar retin acu la, 225 Su rface of, 184, 223 Pectin ate lin e, 150, 177 Pectoral gird le, 23. see also Sh ou ld er Pectoral region , 31–34 Blood su p p ly to, 34 Fascia of, 31, 33 Mu scles of, 32–34, 34 t Pelvic In let, 141 Ou tlet, 143

Pelvic cavity Fem ale, 171–175 Male, 141, 154–157 Pelvic diap h ragm , 141 Fem ale, 180–182, 181 In ferior su rface of, 145 Male, 163, 164 Pelvis, 103, 141, 143, 184 Blood vessels of, 160–161, 161, 178, 178–179 False (greater), 142 Fem ale, 172–173, 173 Male, 155, 156, 158 Nerves, 161–162, 162 b Skeleton of, 142 Pen is, 151, 151–152 Bod y (sh aft) of, 151 Bu lb of, 151 Corp u s cavern osu m , 151, 152 Corp u s sp on giosu m , 151, 152 Cru s of, 150–151 Deep fascia of (Bu ck’s fascia), 151 Dorsal su rface of, 151 Fren u lu m of, 151 Glan s, 151, 152 Coron a of, 151 Prep u ce (foreskin ) of, 151, 166 Root of, 151 Su p er cial fascia of (Dartos fascia), 146, 149, 149, 151 Pericard ial cavity, 84 Obliq u e sin u s, 96 Tran sverse sin u s, 85, 266 Pericard iu m , 80, 84, 84, 84–86, 86 b, 95 Serou s, 84, 85 Pericran iu m , 255, 263 Perim etriu m , 174 Perin eal Bod y, 150, 169 Mem bran e, 150–151, 153, 155, 167, 168 Perin eal p ou ch Fem ale d eep , 169, 169–170 Fem ale su p er cial, 150, 167–168, 168 Male d eep , 153, 153, 154 t Male su p er cial, 149–150, 149 b, 150, 154 t Perin eu m , 141 Fem ale extern al, 167 Su p er cial fascia (Colles’ fascia), 167, 167–168 Male extern al, 146–148, 149 Su p er cial fascia (Colles’ fascia), 150 Periorbita, 276, 279 Periton eal cavity, 113–117, 115, 115, 116 Periton eu m , 113–117 Fem ale, 171, 171, 171 b Male, 154, 154–155, 155 b Parietal, 108, 113, 115, 115 Visceral, 113, 115, 115 Perp en d icu lar p late, 291 Pes an serin u s, 204 Ph aryn geal Plexu s, 287 Rap h e, 286 Recess, 289 Ton sil (ad en oid ), 289 Wall, 286, 288 Mu scles of, 296

Ph aryn gobasilar fascia, 287 Ph aryn gotym p an ic tu be, 289, 296, 308, 309 Ph aryn x, 230, 286–290, 287, 289 In tern al asp ect of, 289 Laryn gop h aryn x, 288 Mu cosal fold s of, 295, 296 Mu scles of, 286–287, 287, 290 t, 299 t Nasop h aryn x, 288 Nerves of, 287–288 Orop h aryn x, 288 Pia m ater, 20, 265 Piriform recess, 305 Pleu ra Parietal, 84 Cervical, 78 Costal, 78, 84 Diap h ragm atic, 78 Med iastin al, 78, 84 Visceral, 79 Pleu ral cavities, 77–79, 79, 79 b Pop liteal fossa, 202–204, 204 Mu scles of, 205 t Porta h ep atis, 117 Portal h yp erten sion , 128 b Portal triad , 118 Preaortic gan glia, 136 Prevertebral fascia, 285 Prostate, 157–162 Prostatic u tricle, 157 Prostatic ven ou s p lexu s, 151, 160 Pterion , 247, 257 Pterygoid fossa, 295 Pterygoid h am u lu s, 295 Pterygoid p rocess (p late), 257 Lateral, 295 Med ial, 297 Pterygom axillary ssu re, 257 Pterygop alatin e fossa, 257, 261, 298 Pterygop alatin e gan glion , 298 Pu bic Bon es, 103 Crest, 100, 103 Sym p h ysis, 99, 103, 142 Tu bercle, 100, 103, 142, 183–184 Pu bis, 142, 222 Arch of, 142 Pecten , 184 Su p erior ram u s of, 142, 184 Pu d en d al can al, 145 Pu d en d al n erve block, 170 b Pyloric sp h in cter, 117, 129

Q Qu ad ran gu lar sp ace, 24–25 Qu ad rate tu bercle, 198

R Rad iu s, 39–40 Articu lar su rface of, 70 Head, 39, 45 In terosseou s bord er, 45 Neck, 39, 45 Rad ial tu berosity, 40, 45 Styloid p rocess, 29, 45 Uln ar n otch , 45

INDEX Rectovesical p ou ch , 154 Rectovesical sep tu m , 157 Rectu m , 114, 126 An orectal exu re of, 159, 163, 176, 182 Fem ale, 176–177, 177 Am p u lla of, 176 Tran sverse rectal fold s, 176 Male, 159, 159 Am p u lla of, 159 Tran sverse rectal fold s, 159 Ven ou s p lexu s of, 160, 178 Ren al. see Kid n eys Retrom am m ary sp ace, 31 Retrop eriton eal (extrap eriton eal) organ s, 113 Retrop h aryn geal sp ace, 230, 284, 284 Retrop u bic sp ace (p revesical sp ace), 158, 175 Rib, 6, 74 Articu lar facets, 74 Costal an gle, 74 Costal cartilage, 74, 103 Costal groove, 74 False, 74 Floatin g, 75 Tru e, 74 Tu bercle, 74 Rim a glottid is, 306

S Sacral foram en An terior, 142 Posterior, 142 Sacral p lexu s, 161, 162, 179, 180 Sacru m , 6, 7, 8, 8 An terior bord er of th e ala (win g) of, 142 Cu rvatu re of, 7 Med ian sacral crest, 8 Prom on tory, 142 Sacral can al, 18 Sacral foram in a, 8 Sacral h iatu s, 8 Salp in gop h aryn geal fold, 289, 296 Sap h en ou s Hiatu s, 187 Op en in g, 189 Scalp , 254–255, 255 b Ap on eu rosis of, 255 Con n ective tissu e of, 254, 255 Skin , 254 Scap u la, 5, 7 Acrom ion p rocess, 23, 73 Borders of, 5, 6, 7 Coracoid p rocess, 66 Glen oid cavity, 68 In fraglen oid tu bercles, 24 Su p raglen oid tu bercles, 24, 40 In ferior an gle, 5, 6, 7 In frasp in ou s fossa, 23–25, 27 t Sp in e of, 5, 6, 7, 23 Su p rascap u lar n otch , 23 Su p rasp in ou s fossa, 23 Scap u lar an astom oses, 26 Scarp a’s fascia, 99 Sciatic foram en Greater, 142 Lesser, 142, 145

Sciatic n otch Greater, 142, 197 Lesser, 142 Scrotu m , 146, 146 Sep tu m , 147 Sem ilu n ar h iatu s (h iatu s sem ilu n aris), 293 Sem ilu n ar lin e, 103–104 Sem in al vesicle, 157 Sigm oid m esocolon , 116, 126 Sku ll, 245, 245–246 Calvaria, 245, 246, 247, 263, 263 In terior asp ect of, 263–265 Sm all in testin e, 113–114, 114, 122–125, 123, 124, 129–130 Circu lar fold s (p licae circu lares), 129 Du od en ojeju n al ju n ction , 124, 125 Sp erm atic Cord , 102, 146, 146–147, 147 Gu bern acu lu m , 147 Fascia Crem asteric, 105 Extern al, 103, 147 In tern al, 147 Sp h en oeth m oid al recess, 293 Sp h en oid bon e, 271–272, 295 Bod y of, 272 Foram en laceru m , 272 Foram en ovale, 257, 272 Foram en rotu n d u m , 272 Foram en sp in osu m , 257, 272, 274 Greater win g of, 247, 257, 271, 276 Hyp op h yseal fossa (sella tu rcica), 266, 272 Lesser win g of, 266, 276 Sp h en oid al crest, 271, 272 Sp h en oid al lim bu s, 271 Sp h en oid al sin u s, 293, 294 b Sp h en op alatin e foram en , 257, 292 , 298 Sp h en op arietal sin u s, 268 Sp in al cord , 18 Cervical en largem en t, 18 Lu m bar en largem en t, 18, 20 Sp in al gan glion , 21 Sp leen , 120, 120 b Diap h ragm atic su rface of, 120 Visceral su rface of, 120 Sq u am ou s su tu re, 247 Stap ed iu s ten d on , 311 Stap es, 309–311 Stern u m Stern al an gle (xip h istern al ju n ction ), 28, 73, 75, 99, 103 Stom ach , 113–114, 117, 129, 129 An gu lar in cisu re (n otch ), 117 Bod y of, 117 Card ia, 117 Fu n d u s, 117, 121 Gastric fold s (ru gae), 129 Greater cu rvatu re, 117 Lesser cu rvatu re, 117 Pyloru s, 117 Su barach n oid sp ace, 20, 265 Su bd u ral h em atom a, 265 b Su blin gu al Caru n cle, 300 Fold (p lica su blin gu alis), 300 Glan d , 302 Region , 301–302, 302

•

321

Su bm an d ibu lar Du ct, 300, 302 Glan d , 302 Su boccip ital region , 16–17 Mu scles of, 16–17, 17 t Skeleton of, 16, 283, 283 Trian gle, 16–17, 17 Su bp eriton eal organ s, 158 Su p er cial fascia An terior abdom in al wall Mu scles of, 102–110 Su p raren al (ad ren al) glan d s, 135, 135 b Blood su p p ly of, 135 Su tu res Coron al, 246, 247 Fron tal (m etop ic), 247 Lam bd oid , 246, 247 Sagittal, 247 Sq u am ou s, 247 Sym p ath etic gan glion Celiac, 140 Cervical, 243 Cervicoth oracic (stellate), 285 Gan glion im p ar, 180 Sym p ath etic tru n k, 97, 138, 180, 243, 285 Cervical, 242, 243 Sacral, 162

T Tarsal Glan d s, 279 b Plates, 278, 278 Tarsal bon es Calcan eu s, 206 Calcan eal tu berosity, 206 Cu boid , 206 Cu n eiform , 206 Navicu lar, 206 Talu s, 206 Su sten tacu lu m tali, 206, 220 Tegm en tym p an i, 308, 309 Tem p oral bon e, 6, 246, 252 Extern al acou stic m eatu s, 253, 307 Extern al su rface of, 308–309 In t ern al aco u st ic m eat u s, 266, 307, 308 In tracran ial su rface of, 308, 308 Man d ibu lar fossa, 252 Mastoid air cells, 309 Mastoid p rocess, 5, 6, 234, 308 Petrou s p art, 247, 266, 272 Sq u am ou s p art, 247, 272 Styloid p rocess, 29, 45, 234 Stylom astoid foram en , 308 Tym p an ic cavity of, 307 Zygom atic p rocess of, 257 Tem p oral fossa, 256, 257 Tem p oral lin es In ferior, 246, 257 Su p erior, 246, 257 Tem p oral region , 256–257, 257, 258 Ten torial n otch (ten torial in cisu re), 268 Ten toriu m cerebelli (cerebellar ten toriu m ), 267 Term in al su lcu s, 301 Testicu lar varicocele, 133 b

322

•

INDEX

Testis, 146, 147–148, 148 Lobu les of, 148 Sem in iferou s tu bu les of, 148 Lym p h atic drain age of, 148 b Sep ta of, 148 Th en ar Em in en ce, 29, 52 Mu scles of, 52, 54 Th igh An terior (exten sor) com p artm en t of, 188, 188, 192, 194 t Medial (add u ctor) com p artm en t of, 188, 194–195, 195, 196 t Posterior ( exor) com p artm en t of, 188, 201–205, 203, 205 t Skeleton of, 184, 184, 201, 201 Th oracic d u ct, 77, 96, 242. see also Lym p h n od es Th oracic wall An terior, 78 b Su rface an atom y of, 74 Th ym u s, 93 Th yrocervical tru n k, 241 Th yroh yoid m em bran e, 234 Th yroid cartilage, 234, 304 Th yroid glan d , 230, 240–241 Isth m u s of, 235, 240 Pyram id al lobe, 240 Relation sh ip s of, 240 Tibia An terior bord er of, 184 In tercon d ylar em in en ce, 206, 223 Lateral con d yle, 184, 206, 223 Medial con dyle, 184, 206, 223 Medial m alleolu s, 206 Soleal lin e, 202, 206 Tu berosity, 184 Ton gu e, 301, 301, 302 Foram en cecu m , 301 Fren u lu m , 300 Lin gu al p ap illae, 301 Lin gu al ton sils, 301 Mu scles of, 303 t Ton sillar bed , 298 Toru s tu bariu s, 289, 296 Trach ea, 77, 94, 230 Bifu rcation of, 95 b Rin gs of, 95, 235 Trach eotom y (trach eostom y), 235 b Tran sverse in term u scu lar sep tu m Leg, 205, 208 Tran sverse m esocolon , 116 Trian gle of au scu ltation , 11 b Trian gu lar in terval, 27 Trian gu lar sp ace, 25 Triradiate cartilage, 142 Troch lea, 225, 281 Tu n ica albu gin ea, 148 Tu n ica vagin alis, 147 Cavity of, 147 Parietal layer, 147 Visceral layer, 147 Tym p an ic cavity (m id d le ear), 307, 309, 309, 310 Walls of, 311, 311 Tym p an ic m em bran e, 309 Tym p an ic p lexu s, 312

U Uln a, 39–40 Coron oid p rocess, 40, 45 Olecran on p rocess, 40, 45 Rad ial n otch , 40 Styloid p rocess, 29 Troch lear n otch , 40, 45 Um bilical fold, 112 Lateral, 111 Med ial, 111 Med ian , 111 Um bilicu s, 99 Un cin ate p rocess, 127 Up p er lim b. see also Arm ; Forearm ; Han d Deep fascia of, 30 Join ts of, 65–71 Scap u lar region an d p osterior arm , 23–27 Su p er cial vein s an d cu tan eou s n erves of, 28–31 Su rface an atom y of, 28 Ureter, 134 Ureteric ori ces, 158, 176 Ureth ra Fem ale, 176 Male, 152, 152–153, 156 Bu lbou reth ral glan d s, 152, 153 Mem bran ou s, 152–153, 155 Navicu lar fossa, 152 Prep rostatic, 152–153, 156 Prostatic, 152–153, 156 Sp on gy (p en ile), 152–153, 156 Ureth ral crest, 156 Ureth ral ori ce Fem ale Extern al, 166, 173 In tern al, 176 Male Extern al, 151, 152 In tern al, 158 Ureth ral sp h in cter Extern al, 169 In tern al, 158, 175 Urin ary blad d er Ap ex of, 175 Base of, 175 Bod y of, 175 Fem ale, 175, 176 Fu n d u s of, 175 In ferolateral su rface of, 175 In teru reteric crest, 158, 176 Neck of, 175 Posterior su rface of, 158, 175 Su p erior su rface of, 158, 175 Trigon e of, 158, 176 Wall of, 158, 175 Urin ary trigon e, 158 Urogen ital diap h ragm , 153, 170 Urogen ital h iatu s, 163, 181 Urogen ital trian gle Fem ale, 141, 142 Male, 148–154 Uterin e p lexu s, 178 Uterin e tu bes, 171, 174 Am p u lla, 174 In fu n d ibu lu m , 174

Uterosacral fold , 172 Uteru s, 174 Broad ligam en t of, 171, 172, 174 Fu n d u s of, 174 Isth m u s, 174 Myom etriu m , 174 Rou n d ligam en t of, 102, 171 Uvu la, 288

V Vagin a, 173 Forn ix of, 174 Ori ce of, 166 Ven ou s p lexu s of, 178 Vasa recta, 123 Vasectom y, 147 b Vein s Accessory sap h en ou s, 187 Axillary, 35 Azygos, 94, 96 Basilic, 30 Brach iocep h alic, 94, 241 Brid gin g, 265 Card iac, 87, 87–88 Cep h alic, 30, 33 Com m u n icatin g, 235 Coron ary sin u s, 87 Dorsal ven ou s arch , 30 Facial, 236, 238, 250 Fem oral, 189, 190, 192 Gastric, 120 Glu teal, 198–200 Gon ad al. see Ovarian , Testicu lar Great card iac, 87 Great sap h en ou s, 187, 187 b Hem iazygos, 96 Hep atic, 121 Iliac Extern al, 174 In tern al, 160, 178 In ferior m esen teric, 126 In ferior ven a cava, 77, 84, 121, 133, 136 In fraorbital, 251 In tercostal An terior, 96 Posterior, 96–97 Ju gu lar Extern al, 232, 241, 254 In tern al, 231, 238, 241, 243, 268 Lin gu al Deep , 300 Maxillary, 254 Med ian cu bital, 30 Op h th alm ic, 280–281, 281 b Ovarian , 133, 134 Pam p in iform p lexu s of, 147 Pen is Deep dorsal, 151, 160 Su p er cial d orsal, 151 Perforatin g, 30 Pericard iacop h ren ic, 80, 84 Pop liteal, 203 Portal, 118, 119–120, 123, 128, 128–129 Posterior au ricu lar, 235

INDEX Pu d en d al, 145, 200 In tern al, 161, 169 Su p er cial extern al, 151, 187 Pu lm on ary, 82, 92 Ren al, 134 Retrom an d ibu lar, 235 Sm all (lesser) sap h en ou s, 185 Sp len ic, 126, 128 Su bclavian , 241, 243 Left, 242 Su p er cial circu m ex iliac, 187 Su p er cial ep igastric, 101, 187 Su p er cial p erin eal p ou ch , 150 Su p er cial tem p oral, 254 Su p erior lobar bron ch i, 82 Su p erior m esen teric, 123, 126, 128 Su p erior rectal, 150, 177 Su p erior ven a cava, 84, 94 Su p raorbital, 256 Testicu lar, 133, 134 Th yroid In ferior, 240 Mid d le, 238, 240 Su p erior, 238, 240 Tibial, 207–208, 210 Vertebral, 241 Vertebral ven ou s p lexu ses, 20 Vesical ven ou s p lexu s, 160, 178

Ven ae com itan tes, 42 Ven ou s lacu n ae Lateral, 264 Verm iform ap p en d ix. see Ap p en d ix Vertebra p rom in en s, 7, 8 Vertebrae Cervical, 7–8, 8, 229–230, 230 An terior arch an d tu bercle, 229–230 Bod y of, 230 Lam in a, 230 Posterior tu bercle, 230 Sp in ou s p rocess of, 230 Tran sverse foram en (foram en tran sversariu m ), 8, 16, 230 Vertebra p rom in en s (C7), 5, 7, 8, 230 In ferior articu lar p rocess, 7 In ferior vertebral n otch , 7 Lu m bar, 7–8, 8, 18 Sp in ou s p rocess, 5, 6, 7, 17 Su p erior articu lar p rocess, 7 Su p erior vertebral n otch , 7 Th oracic, 5, 7, 7, 18, 74, 74 Dem ifacets, 7 Tran sverse costal facets, 7, 74 Tran sverse p rocess, 7, 16 Vertebral Arch , 7 Bod y, 7

•

Can al, 18, 18, 19, 21 Foram en , 7 Vertebral colu m n , 6 Lu m bar cu rvatu re, 7 Th oracic cu rvatu re, 7 Vesicou terin e p ou ch , 171 Vestibu lar fold (false vocal fold ), 306 Vestibu le Bu lb of, 169 Vitreou s bod y, 282 Vocal fold (tru e vocal fold ), 306 Vocal p rocess, 304 Volar p late, 70 Vu lva, 166

X Xip h ist ern al ju n ct io n , 28, 7 3, 99, 103 Xip h oid p rocess, 73, 99, 103

Z Zygom atic arch , 246, 257, 258, 258 Zygom atic bon e, 245 Fron tal p rocess of, 247 Tem p oral p rocess of, 257

323