Mannan’s Regional Dissection and Surface Anatomy [14 ed.] 9741283608, 9789386322111

Table of contents :
Mannan’s Regional Dissection and Surface Anatomy 14th Edition
Half Title
Title Page
Copyright
Dedication
Preface
Acknowledgments
Contents
Chapter 1 Introduction to Regional Dissection
Chapter 2 Head, Neck and Face
Chapter 3 Superior Extremity
Chapter 4 Inferior Extremity
Chapter 5 Abdomen
Chapter 6 Thorax
Chapter 7 Neurovascular and Lymphatic System
Chapter 8 Introduction to the Surface Anatomy
Chapter 9 Surface Anatomy of the Thorax
Chapter 10 Surface Anatomy of the NecK
Chapter 11 Surface Anatomy of the Face
Chapter 12 Surface Anatomy of the Head
Chapter 13 Surface Anatomy of the Abdomen
Chapter 14 Surface Anatomy of the Superior Extremity
Chapter 15 Surface Anatomy of the Inferior Extremity
Chapter 16 Surface Anatomy of Small Bones
Appendices
Relations
Levels
Dimensions
Length
Weights
Capacities
Units of Measurement
Glossary
Index

Citation preview

Mannan’s

Regional Dissection and Surface Anatomy

Mannan’s

Regional Dissection and Surface Anatomy Fourteenth Edition

Md Ali Noor MBBS Estate Medical Officer Deanston Division, Finlay Tea Sreemangal, Dhaka Bangladesh

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Website: www.jaypeebrothers.com Website: www.jaypeedigital.com © 2017, Jaypee Brothers Medical Publishers The views and opinions expressed in this book are solely those of the original contributor(s)/author(s) and do not necessarily represent those of editor(s) of the book. All rights reserved. No part of this publication may be reproduced, stored or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission in writing of the publishers. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The publisher is not associated with any product or vendor mentioned in this book. Medical knowledge and practice change constantly. This book is designed to provide accurate, authoritative information about the subject matter in question. However, readers are advised to check the most current information available on procedures included and check information from the manufacturer of each product to be administered, to verify the recommended dose, formula, method and duration of administration, adverse effects and contraindications. It is the responsibility of the practitioner to take all appropriate safety precautions. Neither the publisher nor the author(s)/editor(s) assume any liability for any injury and/ or damage to persons or property arising from or related to use of material in this book. This book is sold on the understanding that the publisher is not engaged in providing professional medical services. If such advice or services are required, the services of a competent medical professional should be sought. Every effort has been made where necessary to contact holders of copyright to obtain permission to reproduce copyright material. If any have been inadvertently overlooked, the publisher will be pleased to make the necessary arrangements at the first opportunity. Inquiries for bulk sales may be solicited at: [email protected] Mannan’s Regional Dissection and Surface Anatomy First Edition: 1959 Fourteenth Edition: 2017 ISBN: 978-93-86322-11-1

Dedicated to My departed father

Dr MA Mannan and my mother May Allah grant Eternal peace to their sacred souls

Preface The study of human surface anatomy has brought out a significant changes in medical curricula owing to varied pathological conditions and situations, and it needs to be studied by medical students in an integrated, applied, relevant, and contextual framework. Mannan’s Regional Dissection and Surface Anatomy provides an in-depth understanding of the human body. It describes various internal structures of human body that course beneath the skin, i.e. nerves, arteries, veins, etc. The central goal of this book is to allow greater efficiency in the use of students’ time in the laboratory, as well as in examination preparation and review. The method of dissection described in this book represents a regional approach. Although the anatomy is presented extensively, it focuses mainly on the head, neck and face, abdomen, thorax, extremities, bones, nerves and vessels of the human body. The book is divided into two sections: Regional Dissection and Surface Anatomy of human body that further divided into 16 chapters. A sequence of dissection steps defines which structures are to be identified and distinctly directs students how and where to cut and reflect given structures. Color version of important images are provided separately in 23 Color Plates for better understanding of the regional structures. Appendices and Glossary further enhance readers’ learning of the subject. A few errors might have crept in during process of publication of the book. Your suggestions and comments are welcomed for improvement in the next edition. Md Ali Noor

Acknowledgments Thanks to Almighty, I have been able to bring out this Fourteenth Edition, fulfilling the wishes of my departed father Dr MA Mannan. I am thankful to the following reference books that helped in the preparation and revision of this text: Gray’s Anatomy, Review of Gross Anatomy, Cunningham’s Practical Anatomy, Snle’s Applied Anatomy, Grant’s Atlas of Anatomy, and Dissection Manual, Living and Cross Sectional Anatomy (Author: Sibani Mazumdar). I am also thankful to all the production staff of M/s Jaypee Brothers Medical Publishers (P) Ltd., New Delhi, India for their constant support and cooperation in the publication of this edition.

Contents SECTION 1: REGIONAL DISSECTION

1. Introduction to Regional Dissection

3

2. Head, Neck and Face

8

Advice to the Dissectors 3 Steps of Dissection  4

• Scalp and Temporal Region  8 Scalp 8 Temporal Region (Temple)  8 Layers of the Scalp  9 Muscles of the Scalp  11 Layers of the Temporal region  11 Nerve Supply of the Scalp and Temporal Region  12 Artery supply of the Scalp and Temporal region  14 Veins of the Scalp and Temporal region  16 Muscles of the Eyeball  18 • Face 21 Skin Incisions 21 Vessels and Nerves of the Face  22 Facial Muscles  31 Parotid Gland  38 • Anterior Triangle  42 Boundary 42 Skin Incisions  43 Platysma 44 Muscular Triangle  50 Thyroid Gland  51 Larynx or Voice box  54 Cartilages of the Larynx  54 Carotid Triangle  56 Digastric Triangle  70 Submental Triangle  74 • Posterior Triangle  81 Boundaries 81 Skin Incisions 82 Occipital Triangle 83 Supraclavicular Triangle  84 Suboccipital Triangle  87 Articulation of the Head, Neck and Vertebral Column 97 Cranial Nerves  98 Cervical Plexus  99

xii Mannan’s Regional Dissection and Surface Anatomy

3. Superior Extremity

102

• Clavipectoral Fascia  102 Skin Incisions  102 • Quadrangular and Triangular Spaces  108 Skin Incisions  108 Quadrangular Space 108 Triangular Space  110 • Axilla 112 Skin Incision  112 Applied Anatomy  120 • Front of the Arm  125 Skin Incisions  125 • Back of the Arm  132 Skin Incisions  132 • Cubital Fossa  137 Skin Incisions  137 • Front of the Forearm  141 Skin Incisions  141 • Back of the Forearm   153 Skin Incisions  153 • Palm of the Hand  161 Skin Incisions  161 Applied Anatomy  177 Muscles of the Hand  179 • Dorsum of the Hand  181 Skin Incision  181 • Superficial Dissection of the Back and Scapular Region  191 Skin Incision  191 • Deep Dissection of the Back  195 Joints of the Upper Limb  195

4. Inferior Extremity • Femoral Triangle  201 Skin Incisions  201 Lymphatic Drainage of the Lower Limb  215 Superficial Lymph Nodes  216 Deep Lymph Nodes  216 Lymph Vessels or Lymphatics  217 • Adductor Canal  219 Skin Incisions  219 • Gluteal Region  224 Skin Incisions  224 Clinical Importance of Gluteal Muscles  226 Structures Lie Deep to the Gluteus Maximus  226 • Back of the Thigh  239 Skin Incisions  239 • Popliteal Fossa  244 Skin Incisions  244

201

Contents xiii • Front of the Leg  254 Skin Incisions  254 Anterior Crural Muscles  255 Lateral Crural Muscles  259 • Back of the Leg  261 Skin Incisions  261 • Flexor Retinaculum of the Foot  269 Skin Incisions  269 • Dorsum of the Foot  271 Skin Incisions  271 • Sole of the Foot  279 Skin Incisions  279 Muscles of the 1st Layer  281 Muscles and Tendons of the 2nd Layer  286 Muscles of the 3rd Layer  288 Muscles and Tendons of the 4th Layer  291 Lumbricals 296

5. Abdomen • Rectus Sheath  305 Skin Incisions  305 Rectus Sheath Formation  307 Umbilicus 313 • Inguinal Region  314 Skin Incisions  314 Superficial Inguinal Ring  316 Deep Inguinal Ring  317 Inguinal Canal  318 Spermatic Cord  320 Hernia 326 • Anterolateral Wall of the Abdomen  328 Skin Incisions (for the Whole Region)  328 • Kidney from the Back  333 Kidney 333 • Perineum 343 Perineum—Position and Shape  343 • Anal Triangle (Anal Region)  345 Skin Incisions  345 Ischiorectal Fossa  346 Urinary Bladder  351 • Urogenital Triangle in Male  352 Skin Incisions  352 Superficial Perineal Muscles  355 Perineal Membrane  357 Deep Perineal Muscles  358 • Urogenital Triangle in Female  361 Skin of this Region  361 Clitoris 366 Vagina 367

305

xiv Mannan’s Regional Dissection and Surface Anatomy Perineal Membrane (in Female)  368 Uterus 369 • Male Genital Organs  371 Scrotum 372 Testes 373 Epididymis 375 Penis 376 Male Urethra  378 Female Urethra  379 Duodenum, Jejunum and Ileum  379 Pancreas 381 Spleen 382 Large Intestine  383 Liver 385 Stomach 387

6. Thorax

392

• Anatomy 392 Shape of the Thorax  392 Boundaries of the Thorax  392 Apertures of the Thorax  392 • Thoracic Wall  395 Anterior Wall  395 Lateral Wall  396 Posterior Wall  397 Dissection of the Intercostal Space  397 Intercostal Nerves  400 Intercostal Arteries  402 Posterior Intercostal Veins  403 Anterior Intercostal Arteries  404 Anterior Intercostal Veins  404 Transversus Thoracic  406 Levatores Costorum  407 Serratus Posterior Superior  407 Serratus Posterior Inferior  407 • Female Breast  410 Normal Anatomy  410 Male Breast  414

7. Neurovascular and Lymphatic System • Arterial System  415 Ascending Aorta  415 Heart 415 Coronary Artery  417 Arch of the Aorta  418 Diaphragm 431 • Venous System  433 Cardiac Veins  433 Veins of the Upper Limbs (Venous Drainage of the Upper Limb)  434 Veins of the Head, Face and Neck (Venous Drainage of the Head, Face and Neck)  436

415

Contents xv The Veins of the Thorax  443 Veins of the Lower Limbs (Venous Drainage of the Inferior Extremity)  447 Veins of the Abdomen and Pelvis (Venous Drainage of the Abdomen)  450 • Lymphatic Drainage  454 Lymphatic Drainage of the Head and Neck  454 • Nervous System  463 Cranial Nerve  464 Sympathetic System of the Body  486 Vascular Branches  489 Brain 490

SECTION 2: SURFACE ANATOMY

8. Introduction to the Surface Anatomy 9. Surface Anatomy of the Thorax

505 507

10. Surface Anatomy of the NecK

515

11. Surface Anatomy of the Face

518

12. Surface Anatomy of the Head

521

13. Surface Anatomy of the Abdomen

523

Heart 507 Median Plan  509 Sternal Angle  509 Xiphisternal Junction  509

Thyroid Gland  515 Carotid Artery  515 Jugular Vein  516 Facial Artery (in the Neck)  516 Nerves in the Neck  516

Artery and View  518 Parotid Gland  518 Parotid Duct  519 Palatine Tonsil  519 Supraorbital Notch (by a Point)  520 Condylar Process of the Mandible  520 Anatomical Points  521 Central Sulcus  522 Lateral Sulcus  522 Motor Area  522 Sensory Area  522

Anatomical Points  523 Stomach 525 Duodenum 525 Pancreas 526 Spleen 526 Liver 526 Fundus of the Gallbladder (by a Point)  526 Bile Duct  527 Portal Vein  527

xvi Mannan’s Regional Dissection and Surface Anatomy Cecum 527 Ileocolic Orific and Valve  527 McBurney’s Point  527 Vermiform Appendix  527 Colon 528 Kidney 528 Ureter 529

14. Surface Anatomy of the Superior Extremity

532

15. Surface Anatomy of the Inferior Extremity

537

16. Surface Anatomy of Small Bones

544

Arteries 532 Anatomical Snuff Box  533 Arches 533 Nerves 533

Key Features  537 Muscles Required for Surface Marking 543

• Identification and Anatomical Position of the Small Bones  544 Carpal Bones  544 Tarsal Bones  545 Metacarpal and Metatarsal Bones  546 Phalanges 547 Patella 548

Appendices

549

Appendix 1: Relations  551 Appendix 2: Levels  561 Appendix 3: Dimensions  564 Appendix 4: Length  571 Appendix 5: Weights  573 Appendix 6: Capacities  574 Appendix 7: Units of Measurement  575

Glossary

577

Index

615

Section

1

Regional Dissection ŠŠ Introudction to Regional Dessection ŠŠ Head, Neck and Face ŠŠ Superior Extremity ŠŠ Inferior Extremity ŠŠ Abdomen ŠŠ Thorax ŠŠ Neurovascular and Lymphatic System

1

Introduction to Regional Dissection

I ADVICE TO THE DISSECTORS At the very outset, it may be pointed out that the "dissection" is a fine art and for which a dissector requires honest labor, skill, pa ·ence and perseverance to make it a success. To many it might be disgusting to deal with the obnoxious dead bodies, but it is the strength of mind and the earnest inquisitiveness to know the beauties of creation that are hidden inside our body, will really count towards one's progress. So, it is desired that the dissectors should be conscious of their responsibilities to learn the subject of Anatomy by means of dissection as advised below: • Acquire some theoretical knowledge for the attachments of muscles and ligaments in relation to the particular bones before you start the dissection. • Procure a set of "dissecting instruments" in a case at least with the followings: - Two knives-One fo rough use and the other for delicate works. - Two pairs of dissecting forceps-One with broad and the other with fine points. - One seeker (prove) with curved end-for exploring the vessels and nerves from the areolar tissue and fat. - A pair of scissors. - A pair of hooks with chains. • Cut your nails short and wear a long apron. • Do not use gloves unless otherwise badly necessary. • Be steady at dissection; remember that an unsteady dissector cannot be a good surgeon in future. • Put stress to find out all the main and important structures and identify them correctly. • Do not waste time to search for the unimportant and very minute structures specially at the time of examination. • Consult the diagrams if and when necessary from the textbooks.

4 Mannan’s Regional Dissection and Surface Anatomy • Note the structural peculiarities (if any) found in course of dissection. • While in confusion, better submit to your teacher or examiner than committing a gross error. • Try to make the whole area of dissection very impressive by its neat and clean appearance. • Prepare answers for, all the possible cross questions of the findings in each individual part. • Make thorough review of the whole thing at the end of dissection. • Pay due respect to the dead body or any of its part.

STEPS OF DISSECTION Skin First clean and fix the region of the body you want to dissect. Then give clear incisions to the skin according to the direction given under the individual part and reflect the skin in flaps without any injury to it. No subcutaneous fat should be taken away with the skin.

Fascia a. Superficial fascia—The cutaneous vessels and nerves which are found ramifying in this layer on their way to and from the skin should be carefully searched out and separated first from the fascia; then it is reflected as far as possible intact like the skin leaving the important cutaneous structures lying over the deep fascia. In the lower part of the abdomen, perineum and upper part of the thigh where this fascia consists of two layers—fatty (superficial) and fibrous (deep), it should be reflected separately. Note: The superficial fascia underlies the skin over the entire surface of the body. It consists of fibro-areolar tissue containing variable amount of fat in its meshes. As the fat is a bad conductor of heat, it retains warmth of the body. “Fat” is absent from the superficial fascia in the following places: 1. Eyelids 2. Scrotum 3. Penis 4. Labia minora 5. Nipple and areola of the breast. The fat of the superficial fascia is replaced by the thin sheet of muscle: 1. In the scrotum by the dartos muscle. 2. In the neck and upper part of the chest by the platysma. In the scalp, back of the neck, palm of the hand and sole of the foot, the superficial fascia is very thick and firmly adherent with the skin by fibrous strands, but in other parts of the body, it is loose enough to allow the skin to move freely.

Introduction to Regional Dissection 5 b. Deep fascia—It has to be reflected in flaps by incisions as are given for the skin taking care that the important cutaneous structures are preserved in their respective positions. Note: The deep fascia is a dense fibrous membrane situated under the superficial fascia. It is devoid of fat. It covers the muscles and also affords attachment to some of them and forms a strong investment around the limbs being attached to the subcutaneous bony points and to the ligaments of joints. From its deep surface intermuscular septa are given off which at certain places ensheath the muscles, vessels, nerves and glands. Cutaneous vessels and nerves derived from the deeply placed vessels and nerves, pierce the deep fascia and lie at first between the superficial and deep fascia but gradually pass through the superficial fascia to end in the skin.

Muscles Clean the muscles and look for their attachments and relative position with other structures and while doing so, carefully preserve their arteries and nerves of supply. Do not cut any muscle if not badly required for the exposure of deeper structures. Lastly, study the character, origin, insertion, nerve supply and action of the skeletal muscles which are exposed in the dissected region. Note: The muscles are the ‘red fleshes’ of the body, responsible for bringing about different kinds of movements and constitute nearly half of the body weight. They are classified as follows:

a. Voluntary or skeletal muscle—Found in the limbs head, neck and trunk. b. Involuntary or plain muscle—Found in the walls of viscera, ducts of glands and blood vessels. c. Cardiac muscle—Found in the walls of the heart. They are involuntary in action. It is commonly known that a “muscle” is supplied by a motor nerve but in reality it is supplied by a mixed nerve, which contains about three-fifths motor and two-fifths sensory fibers together with some sympathetic nerve filaments.

Shape or Form of the Muscles (1) Longitudinal or strap-like, (2) longitudinal with tendinous intersections, (3) triangular, (4) quadrangular, (5) fusiform, (6) digastric, (7) bicipital, (8) tricipital, (9) unipennate, (10) bipennate, (11) multipennate, (12) radial, (13) spiral and (14) cruciate. Muscle fibers—Two types: a. Red fiber b. White fiber. Differences between red and white fibers are shown in Table 1.1.

6 Mannan’s Regional Dissection and Surface Anatomy Table 1.1: Differences between red and white fibers Trait

Red fibers

White fibers

Color

Reddish

Whitish

Myoglobin

Present in large amount

Present in small amount

Sarcoplasm

Relatively abundant

Relatively less

Mitochondria

Numerous in sarcoplasm

Less

Myofibrils

Few in sarcoplasm

Proportionately more

Cross striation

Less

More

Mode of action

Slow but capable of more sustained contraction, without fatigue

Rapid and capable of more powerful contraction but fatigue develops early

Aponeurosis: A flat fibrous sheet of connective tissue that serves to attach muscle to bone or other tissues. Sometimes serves as a fascia.

Deep vessels and nerves Thoroughly clean the main arteries and their important branches. Keep only the big Venous trunks and remove all other clumsy smaller veins (which rather create much disturbances if preserved). Trace all the nerves to their destination and leave them uninjured. Identification a. Arteries—It can be easily detected as thick-walled reddish tubes in comparison to the bluish veins. b. Veins—These are rather thin-walled and collapsible. c. Nerves—These will be found as white rounded cord-like structures but without lumen.

Study the course, relation and branches of the main arteries, veins and nerves.

Lymph nodes These are solid rounded bodies of different sizes connected with very fine lymph vessels. A few nodes may be preserved at a convenient place, wherever found in course of dissection.

Synovial sheaths and bursa These are found at the frictional points of the body, as between the bones and tendons or between the bones and muscles. They prevent destruction and facilitate free movement of the parts. Generally, they remain discrete, but sometimes found communicated with the neighbouring joint cavity.

Bursa It is a closed fibrous sac lined with synovial membrane containing a lubricating fluid, egg-white in nature, called “synovia”.

Introduction to Regional Dissection 7 Types of bursa 1. Subtendinous—Between the tendon and bone or ligament or between the two rendons, e.g. biceps bursa. 2. Submuscular—Between the muscle and bone, tendon or ligament. 3. Subfascial—Beneath a fascia or aponeurotic sheet. 4. Interligamentous—Between two ligaments. 5. Subcutaneous—Between the skin and a bony prominence, e.g. prepatellar bursa. 6. Articular—Acts as a joint cavity, e.g. the bursa between the dens of the axis and transverse ligament of the atlas.

Synovial sheaths (mucous sheaths) They are similar in structure and function to the bursa but are found to ensheath the long tendons as in the hands and feet. Study the modes of distribution of the sheaths which may be incised to display the tendons and vincula.

Ligaments These are strong bands of white fibrous tissue formed by localized thickening of the fibrous capsule connecting the bones at joints. They are named according to their mode of attachments to the ends of bones concerned for a particular joint. All the ligaments are very tough but flexible and exert unyielding tension to the abnormal movements of joint. While dissecting, learn their attachments and relations thoroughly.

Tendons The tendons are the collection of collagen fibers by which the voluntary muscles are attached to a bone and they run parallel to the muscle fibers.

Head, Neck and

2

Face SCALP AND TEMPORAL REGION

SCALP The soft structure that covers the skull extending from tHe eyebrows in.front to the superior nuchal lines behind and from one superior temporal line to the other superior temporal line at the sides is k:nown as the scalp, or it may be defined as the covering of the cranial vault. It consists of5 layers which are indicated by letters contained in this word asfollows1. S-Skin. 2. C-Connective tissue (superficial fascia). 3. A-Aponeurosis (epicranial aponeurosis) and the epicranius. 4. L-Loose areolar tissue. 5. P-Pericranium.

I TEMPORAL RE It is the region on either side of the head which lies between the superior

temporal line above and the zygomatic arch below. The temporal region consists of the following 6 layersI. Skin. 2. Superficial fascia. 3. A thin layer of fascia continued downwards from the lateral margin of the epicranial aponeurosis to the zygomatic arch along with the extrinsic muscles ofthe auricle. 4. Temporal fascia. 5. Temporalis muscle. 6. Pericranium. Note: Befo re you sta rt the dissection, see t hat t he head is we ll shaved and the body is placed on the table in supine position .

Head, Neck and Face  9

Skin Incisions (for the scalp and temporal region) 1. A longitudinal incision along the sagittal suture from the root of the nose to the external occipital protuberance. 2. A curved incision along the superciliary arch from the root of the nose to the frontozygomatic suture. 3. Another curved incision along the superior temporal line from the frontozygomatic suture to a point about an inch above the tip of the mastoid process. Dissection note: Reflect all the layers separately as enumerated above from the scalp backwards and for the temporal region downwards over the auricle but before reflecting the superficial fascia, trace the cutaneous vessels and nerves in it as mentioned later and turn them conveniently forwards, laterally or backwards detaching their terminal ends from the fascia. Show the middle and deep temporal arteries which pass upwards lying superficial and deep to the temporalis muscle, respectively. Frontal belly may be detached from the epicranial aponeurosis and reflected anteriorly over the face but carefully preserve the temporal branches of facial nerve which supply this muscle.

LAYERS OF THE SCALP 1. Skin: Fairly thick and contains numerous hair follicles and sebacious glands. It is firmly adherent to the epicranial aponeurosis by the underlying connective tissue layer and as such the 1st, 2nd and 3rd layers of the scalp behave as a single layer which can be moved freely over the loose areolar tissue. It is covered with hairs except over the forehead. 2. Superficial fascia (subcutaneous connective tissue): It is a dense fibrofatty layer containing abundant vessels and nerves and as such scalp injury bleeds freely but heals quickly. It acts as a firm bond of union between the skin and the epicranial aponeurosis. It is less fibrous over the fleshy bellies of the occipitofrontalis muscle. 3. Epicranial aponeurosis (galea aponeurotica): It is the intermediate tendinous sheet that connects the bellies of the occipitofrontalis covering the vault of the cranium. It represents the deep fascia of the scalp. Behind, it is continuous with the occipital bellies and is attached to the external occipital protuberance and the highest nuchal lines: in front, continuous with the frontal bellies. On either side, it is adherent to the superior temporal line and then continued downwards as a thin prolongation over the temporal fascia to be attached to the zygomatic arch and gives origin to the auricularis anterior and superior (Fig. 2.1). 4. Loose areolar tissue (subaponeurotic areolar tissue): It is a very delicate and loose layer intervened between the epicranius and pericranium containing a few blood vessels. It forms a “potential space” which is limited by the epicranius and its aponeurosis as follows— a. Posteriorly—By the attachment of the occipital bellies to the superior nuchal line.

10  Mannan’s Regional Dissection and Surface Anatomy

Fig. 2.1: Epicranial aponeurosis: (1) Skin, (2) Connective tissue, (3) Aponeurosis, (4) Loose areolar tissue, (5) Pericranium, (6) Dipole of parietal bone, (7) Dura, (8) Arachnoid, (9) Pia, (10) Superior sagittal sinus, (11) Arachnoid granulations, (12) Cerebral cortex, (13) Falx cerebri and (14) Inferior sagittal sinus



b. Laterally—By the attachment of the aponeurosis to the zygomatic arch. c. Anteriorly—As the frontalis has no bony attachment the space is continuous with the root of the nose and the eyelids. For this reason a blackish condition of the eyelids (black eye) may occur, when due to a blow on the skull the extravasated blood in this space slowly tracks down into the eyelids. Of course, it usually occurs as a result of local violence causing subcutaneous hemorrhage in the eyelids. This space is often called the dangerous zone of the scalp as the condition of the patient may become very fatal when any septic focus spreads into the intracranial sinuses through the emissary veins. 5. Pericranium: Is the periosteum of the cranial vault. It is loosely attached to the outer surface of the bones except at the sutures where it is firmly held with the endosteal layer of dura mater by means of sutural ligaments.

Functional Significance of Different Layers of the Scalp 1. Superficial fascia: This layer is so dense that subcutaneous hemorrhages are never extensive and inflammations in this layer cause less swelling but much pain. 2. Epicranial aponeurosis: Because of special attachment of this layer, wounds of the scalp do not gap unless the galea is divided transversely. 3. Loose areolar tissue: As frontalis muscle has no bony attachment, this layer extends up to the eyelids anteriorly, so blood collection in this space

Head, Neck and Face  11 causes generalized swelling of the scalp which may extend anteriorly into the root of the nose and eyelids causing a black eye. In newborn, this blood collection is known as caput succedaneum when it is serum and traumatic cephalohydrocele when it is cerebrospinal fluid. 4. Pericranium: As it is firmly attached to the sutures, so the fluid collection take the shape of the related bones, which is called cephalhematoma.

MUSCLES OF THE SCALP The muscles of the scalp are collectively named as the epicranius which consists of two main parts: (a) occipitofrontalis, (b) temporoparietalis— 1. Occipitofrontalis—Consists of two muscular parts, frontalis or frontal part and occipitalis or occipital part connected in the middle by the epicranial aponeurosis. a. Frontalis—It lies in the forehead and consists of two bellies or parts which are united in the median plane. It has no bony attachments. – Origin—From the anterior part of the epicranial aponeurosis. – Insertion—Into the skin and subcutaneous tissue in the region of the eyebrows and root of the nose where it blends with the fibers of the orbicularis oculi laterally and the corrugator and procerus medially. – Nerve supply—By temporal branches of the facial nerve. – Action—It raises the eyebrows and causes transverse wrinkles of the skin on the forehead. b. Occipitalis—It consists of two bellies which are separated from cach other by a backwards extension of the epicranial aponeurosis. – Origin— 1. From the lateral two thirds of the superior nuchal line. 2. From the mastoid part of the temporal bone. – Insertion—Into the epicranial aponeurosis. – Nerve supply—By the posterior auricular branch of the Facial nerve. – Action—It pulls the scalp backwards. 2. Temporoparietalis—Is a rarely developed muscle and when present, it lies between the frontalis above and the auricularis anterior and auricularis superior muscles below. –– Nerve supply—It is supplied by the nerve as that of frontalis.

LAYERS OF THE TEMPORAL REGION 1. Skin: Farely thin and not adherent with the underlying tissues. So, it can be separately moved over the loose superficial fascia. 2. Superficial fascia: Much less fibrous but contains usual fat and cutaneous vessels and nerves. 3. A thin fascial extension: From the epicranial aponeurosis to the zygomatic arch along with the extrinsic muscles of the auricle which are— a. Auricularis anterior—Arises from the epicranial aponeurosis and is inserted to the anterior part of the root of the auricle.

12  Mannan’s Regional Dissection and Surface Anatomy b. Auricularis superior—Arises from the epicranial aponeurosis and is inserted to the top of the root of the auricle. c. Auricularis posterior—Arises from the mastoid part of the temporal bone and is inserted to the back of the root of the auricle. • Nerve supply: Auricularis anterior and superior are supplied by the temporal branches of the facial nerve, but the auricularis posterior is supplied by its posterior auricular branches. 4. Temporal fascia—Is a strong fascia that covers the temporalis muscle and represents the deep fascia of the temporal region. It is attached above to the whole extent of the superior temporal line; but below, it splits into two layers which are attached to the upper border of the zygomatic arch. The following structures are the contents between the two layers of this fascia— a. Zygomatic branch of the superficial temporal artery along with the vein. b. Zygomatico—Is the temporal branch of the maxillary nerve. c. Small quantity of fat and areolar tissue. 5. Temporalis: • Origin— 1. From the whole of the temporal fossa (except the part formed by the zygomatic bone). 2. From the deep surface of the temporal fascia. • Insertion— 1. Into the apex, anterior and posterior borders and medial surface of the coronoid process of the mandible. 2. Into the anterior border of the ramus of the mandible. • Nerve supply—By the deep temporal branches of the anterior trunk of the mandibular nerve. • Action— 1. It elevates the mandible so as to close the mouth. 2. Posterior fibers retract the mandible after it has been protruded. 6. Pericranium—Is the periosteal lining over the bones of this region.

NERVE SUPPLY OF THE SCALP AND TEMPORAL REGION On each side of the head there are 10 superficial nerves, of which 5 are placed in front of the ear and 5 behind it. Out of 5 of each group, 1 is motor and 4 are sensory.

In Front of the Ear Sensory Nerves (from medial to lateral) 1. Supratrochlear nerve—This is the smaller terminal branch of the frontal nerve. It emerges from the orbit about 1/2 lateral to the median plane; gives branches to the conjunctiva and to the skin of the upper eyelid, then it pierces the frontalis and supplies the skin of the forehead near the median plane.

Head, Neck and Face  13 2. Supraorbital nerve—This is the larger terminal branch of the frontal nerve. It emerges from the orbit through the supra orbital notch or foramen about 1 lateral to the median plane; gives branches to the conjunctiva and to the skin of the supper eyelid, then it turns upwards and divides into medial and lateral branches which pierce the frontal belly and the aponeurosis respectively and supply the skin of the forehead and scalp as for as the lambdoid suture. 3. Zygomaticotemporal nerve—This is a branch of the zygomatic branch of the maxillary nerve. It emerges through the temporal surface of the zygomatic bone pierces the temporal fascia behind; the frontal process of the zygomatic bone and supplies the skin of the anterior part of the temple. 4. Auriculotemporal nerve—This is branch of the mandibular nerve. It arises by two roots which encircle the middle meningeal artery. It ascends over the posterior root of the zygomatic process just in front of the auricle lying posterior to the superficial temporal vessels and finally supplies the skin of the temporal region. It gives the following branches— a. Anterior auricular b. Superficial temporal c. Articular to the mandibular joint d. Secretomotor to the parotid gland e. Nerves to the external auditory meatus.

Motor Nerve 1. Temporal branches of facial nerve—Emerge from the upper part of the parotid gland. They pass upwards and forwards crossing the zygomatic arch to the side of the head and forehead and supply the following muscles— a. Auricularis anterior and superior b. Intrinsic muscles of the auricle c. Frontalis d. Orbicularis oculi e. Corrugator.

Behind the Ear Nerves behind the ear are discussed below and show in Figure 2.2.

Sensory Nerve (from lateral to medial) 1. Great auricular nerve—It arises from the anterior primary rami of the 2nd and 3rd cervical nerves. It winds round the posterior border of the sternocleidomastoid, then pierces the fascia colli and ascends upon that muscle beneath the platysma and divides into two branches— a. Anterior branch—It supplies the skin of the face over the parotid gland. b. Posterior branch—It supplies the skin over the mastoid process and the lower part on the back of the auricle. 2. Lesser occipital nerve—It arises from the anterior primary ramus of the 2nd cervical nerve. It ascends along the posterior border of the

14  Mannan’s Regional Dissection and Surface Anatomy

Fig. 2.2: Sensory nerves behind the ear

sternocleidomastoid hooking round the accessory nerve from below, then pierces the fascia colli and supplies the skin of the head and neck behind the auricle, as well as the skin of the upper part on the back of the auricle. 3. Greater occipital nerve—This is the larger medial branch of the posterior primary ramus of the 2nd cervical nerve. It ascends from below the obliques capitis inferior and enters the scalp by piercing the semispinalis capitis, trapezius and the fascia colli about 1″ lateral to the external occipital protuberance and supplies the skin of the back of the head as far as the vertex. 4. Third occipital nerve—It is the cutaneous branch of the medial division of the posterior primary ramus of the 3rd cervical nerve. It pierces the trapezius and fascia colli and supplies the skin over the lower part of the back of the head. It lies medial to the greater occipital nerve.

Motor Nerve 1. Posterior auricular nerve—It is a branch of the facial nerve. It runs upwards between the external auditory meatus and the mastoid process and supplies the auricularis posterior and occipital belly of the occipitofrontalis.

ARTERY SUPPLY OF THE SCALP AND TEMPORAL REGION On each side of the head there are 5 superficial arteries of which 3 are distributed in front of the ear and 2 behind it.

In Front of the Ear Supratrochlear and supraorbital arteries—These are the branches of the ophthalmic artery. They accompany the nerves of the same name. Superficial temporal artery—It is the smaller terminal branch of the external carotid

Head, Neck and Face  15 artery and begins within the parotid gland behind the neck of the mandible. It ascends over the posterior root of the zygomatic process of temporal bone immediately in front of the auricle in company with the auriculotemporal nerve which lies behind it and about 2″ above the zygoma. The artery ends by dviding into two terminal branches. The anterior (frontal) branch runs in a wavy manner towards the frontal eminence and the posterior (parietal) branch to the parietal eminence.

Branches a. Transverse facial b. Anterior auricular c. Middle temporal d. Zygomatico-orbital e. Parotid f. Articular g. Muscular h. Terminal branches— i. Anterior (Frontal) ii. Posterior (Parietal).

Behind the Ear 1. Posterior auricular artery—It is a small branch of the external carotid artery. Under cover of the parotid gland it runs upwards and backwards accompanied with the posterior auricular nerve to the back of the auricle where it divides into auricular and occipital branches.

Branches

a. Stylomastoid—It enters the stylomastoid foramen and supplies tympanic cavity, tympanic (mastoid) antrum, mastoid air cells and the semicircular canals. b. Muscular. c. Parotid. d. Auricular. e. Occipital. 2. Occipital artery—It is a large posterior branch of the external carotid artery. At its origin it lies in the upper part of the carotid triangle and runs backwards and upwards deep to the posterior belly of digastric crossing in its course the internal carotid artery, internal jugular vein and the hypoglossal, vagus and accessory nerves. It then passes along the occipital groove of the temporal bonmed covered by the mastoid process and the muscles attached to it. Finally, it enters the scalp by piercing the trapezius and deep fascia at the superior nuchal line lateral to the greater occipiral nerve.

16  Mannan’s Regional Dissection and Surface Anatomy

Branches

a. Sternocleidomastoid (lower and upper) b. Mastoid c. Auricular d. Muscular e. Descending f. Meningeal g. Occipital.

Note: Besides the above mentioned superficial arteries and nerves of the temporal region, the following deep arteries and nerves are also found there.

Arteries 1. Middle temporal artery—A branch of the superficial temporal artery. It pierces the temporal fascia and runs upwards to supply the temporalis. 2. Deep temporal arteries (anterior and posterior)—These are the branches of the 2nd part of the maxillary artery. They pass upwards between the Temporalis and percranium and supply the temporalis.

Nerves 1. Deep temporal nerves (anterior and posterior)—These are the branches of the anterior trunk of the mandibular nerve. They pass upwards deep to the temporalis and supply that muscle.

VEINS OF THE SCALP AND TEMPORAL REGION Superficial Veins These form a network in the superficial fascia and are drained by the venous trunks corresponding to the arteries. They terminate as follows: a. Supratrochlear and supraorbital veins—These unite to form the facial vein (anterior facial vein). b. Superficial temporal vein—It joins the maxillary vein to form the retromandibular (posterior facial) vein. c. Posterior auricular vein—It joins the posterior division of the retromandibular vein to form the external jugular vein. d. Occipital vein—It joins the deep cervical and vertebral veins. e. Two emissary veins—One passes through the parietal foramen and connects the superior sagittal sinus; the other passes through the mostoid foramen and connects the sigmoid sinus.

Deep Veins These are of the temporal region accompany the middle and deep temporal arteries and terminate to their corresponding mother trunks.

Head, Neck and Face  17

Emissary Veins The veins which establish communication between the extracranial veins and the intracranial venous sinuses passing through the apertures in the wall of the cranium are called emissary veins.

Sites of the Emissary Veins 1. Mastoid emissary vein through the mastoid foramen of occipital bone. Connection—This is between the sigmoid sinus with the posterior auricular or occipital vein. 2. Parietal emissary vein through the parietal foramen of the parietal bone. Connection—Superior sagittal sinus with the veins of the scalp. 3. Posterior condylar emissary vein through the condylar foramen of the occipital bone. Connection—Sigmod sinus with the veins of the suboccipital triangle. 4. Venus plexus of the hypoglossal canal through the hypoglossal fora-men of the occipital bone. Connection—Sigmoid sinus to the jugular vein. 5. Emissary vein through the foramen laccrum. Connection—Cavernous sinus with the pharyngeal vein and pterygoid plexus. 6. Emissary vein through the foramen ovale. Connection—Cavernous with the pterygoid plexus. 7. Internal carotid plexus through the carotid canal of the temporal bone. Connection—Cavernous sinus to the internal jugular vein. 8. Petrosquamous sinus? Connection—Transverse sinus with the external jugular vein. 9. Emissary vein through the foramen cecum. Connection—Nose with the superior sagittal sinus. 10. Occipital emissary vein through the occipital protuberance. Connection—Confluence of the sinus with occipital vein. 11. Emissary vein through the sphenoidal foramen. Connection—Cavernous sinus with the phryngeal vein and pterygoid plexus. 12. Emissary vein around the rim of the foramen magnum (so called marginal sinus). Connection—Occipital sinus to the vertebral venus plexus. 13. Ophthalmic vein—It connects intracranial to extracranial venus channels.

Peculiarities 1. No muscular tissue in the wall but formed by endothelium 2. Devoid of valves 3. Blood can flow in both directions.

18  Mannan’s Regional Dissection and Surface Anatomy

Function 1. Intracranial venous pressure is blanched by these veins. 2. Congestion of sinuses can be relieved by applying leeches or counter irritants over the site of these veins. Surgical importance—Inflammatory sepsis may spread from the exterior into the intracranial sinuses through the emissary veins and may lead to thrombosis of the sinuses, thereby endangering life.

Applied Anatomy 1. The skin of the scalp possesses numerous sebaceous glands, their ducts are liable to infection and damage by combs. So, sebaceous cysts and seborrheic dermatitis are common. 2. Wounds of the scalp bleed profusely as the blood vessels are attached to fibrous septa and prevent to contract or retract to alow coagulation to take place. 3. Infection of the scalp spreads via the emissary vein and diploic veins, which are valveless, cause osteomyelitis and venous sinus thrombosis respectively. 4. Loose areolar tissue, that is the fourth scalp layer extends anteriorly into the eyelids. So traumatic injury in the frontal region causes blood accumulation and this extends anteriorly to the root of the nose and eyelids and cause swelling of the eyelids, known as black eye.

Diploic Veins These are wide venous spaces of the marrow cavities between the outer and inner tables of the flat bones of the skull. They communicate with the venous sinuses of the dura mater, meningeal veins and veins of the pericranium. They are devoid of values.

MUSCLES OF THE EYEBALL Extraoccular or extrinsic muscles of eyeball—Seven voluntary muscles and three involuntary muscles are listed in Table 2.1 and discussed below: a. Voluntary extraocular muscles i. 4 recti—Medial (MR) Lateral (LR) Superior (SR) Inferior (IR). ii. 2 oblique— Superior oblique (SO) Inferior oblique (IO). iii. 1 levator palpebrae superioris. b. Involuntary extraocular muscles i. Superior tarsal ii. Inferior tarsal iii. Orbitalis.

Head, Neck and Face  19 Table 2.1: Extrinsic muscles (or extraocular muscles) of the eyeball Name

Origin

Insertion

Nerve supply

Action

Levator palpebrae superioris

Lesser wing of sphenoid bone

Anterior surface and upper border of superior tarsal plate

Oculomotor nerve and sympathetic nerve

Raises upper

Superior rectus

Common tendinous ring

Sclera, 7.7 mm behind the sclerocorneal junction

Oculomotor nerve

Raises and medially rotates cornea

Inferior rectus

Common tendinous ring

Sclera, 6 mm behind the corneal margin

Oculomotor nerve

Depress and medially rotates cornea

Lareral rectus

Common tendinous ring

Sclera, 6.9 mm behind the sclerocorneal junction

Abducent nerve

Moves the cornea laterally

Medial rectus

Common tendinous ring

Sclera, 6.9 mm behind the sclerocorneal junction

Oculomotor nerve

Moves the cornea medially

Superior oblique

Body of Sphenoid bone

By way of pidley attached to the sclera, behind the equator in its supero lateral posterior quadrant between SR and LR

Trochlear nerve

Moves the cornea downwards and laterally

Inferior oblique

Anterior part of floor of orbit

Attached to sclera behind the equator in its interolateral posterior qudrant between IR and LR

Oculomotor nerve

Moves the cornea upwards and laterally

* All of the extraocular muscles are supplied by oculomotor nerve, except a. Superior oblique by trochlear nerve (SO4) b. Lateral rectus by abducent nerve (LR6).

Involuntary Muscles (Table 2.2) 1. Superior tarsal (it is the deep portion of the levator palpebrae superioris): –– Action—It elevates upper eyelid –– Nerve supply—Sympathetic nerve.

20  Mannan’s Regional Dissection and Surface Anatomy 2. Inferior tarsal: –– Action—It depresses lower eyelid –– Nerve supply—Sympathetic nerve (from superior servical ganglion). 3. Orbitalis: –– Action—Function not known –– Nerve supply—Sympathetic nerve (from superior cervical ganglion). Table 2.2: Intrinsic muscles (or Intraocular muscles) of the eyeball Origin

Nerve supply

Action

Sphincter pupillae: They are involuntary circular muscle fibers of the iris, arranged around the margin of the pupil

Supplied by parasympathetic fibers from Edinger–Westphal muscles of oculomotor nerve. Preganglionics come via nerve to inferior oblique of oculomotor after synapsing in the ciliary nerves

It constricts the pupil by its contraction in the presence of bright light and during accommodation

Dilator pupillae: These are in fact ganglion myoepithelial cells and radial muscular processes

Supplied by fibers which arise presence of light of low of the sympathetic trunk. The preganglionic fibers arise from excessive

It dilates the pupillae in the superior cervical density, by its contraction or in the presence of the lateral gray column in

from the anterior 1st layer of the epithelium, close to the posterior surface of the Iris

sympathetic and 2nd thoracic spinal segment and pass by the upper two thoracic nerves and their white communicates to the sympathetic trunk, in which they ascend to the superior cervical ganglion and synapses and the postganglionics pass to the ciliary ganglion and reach the muscle via long/short ciliary nerves

activity that occurs in night

Ciliary muscle: Radiating group arise from the deep surface of the sclera close to cornea and rediate posteriorly to the ciliary process. Circular group —They are arranged in two or three bundles

Through the short ciliary nerve. Postganglionic parasympathetic fibers which originate in the ciliary ganglia. Preganglionic layer reach the ganglia through oculomotor nerve

Contraction of ciliary muscle specially radiating fibers pull the cllliaiy body forwards. This relieves the tension in the suspensory ligament. The lens is relaxed by contraction of ciliary muscles, and it becomes more convex

Head, Neck and Face  21

FACE “The Face” extends from the roots of hair above to the chin below and from one auricle to the other auricle at the sides. The forehead stands therefore common to the face and scalp, but for the sake of convenience the incisions are made in the dissection of face excluding the forehead. Note: Before starting the dissection, see that the lips, cheeks and eyelids are distended by placing cotton wool inside the vestibule of mouth and the conjunctival sacs and the margins of the lips and eyelids are stitched up.

SKIN INCISIONS 1. A longitudinal incision in the median plane from the root of the nose to the symphysis menti. 2. A slight curved incision from the root of the nose to the upper and front part of the auricle passing along the superciliary arch. 3. An oblique incision from the symphysis menti along the lower border of the body of the mandible to its angle. 4. One semicircular incision along the mucocutaneous junction of the upper and lower lips. 5. One circular incision along the margin of the upper and lower eyelids.

Skin To be reflected as a single flap laterally over the auricle. It is not uniform all over the face; thin and lax over the eyelids but fairly thick elsewhere. On the tip and the alae of the nose the skin is fused with the underlying cartilage in such a way that some portion of the cartilage is inevitably taken away with the skin. After removal of the skin fibers of the superficial muscles of the face will come into view but as most of them are inserted into the skin, their surfaces become somewhat lacerated in appearance. Skin of the face is very vascular, so wounds bleed freely but heal quickly.

Superficial Fascia Very thin and is generally taken away with the skin. Carefully clean the subcutaneous fat and areolar tissue without injury to the vessels and nerves. Then note the position of the facial muscles and define their outlines as clearly as possible. Preserve some portion of the buccal pad of fat at about the middle of the cheek.

22  Mannan’s Regional Dissection and Surface Anatomy

Deep Fascia There is no deep fascia in the face except posteriorly over the parotid gland and the masseter where it is known as the parotido-massereric fascia. It is derived from the deep fascia of the neck and after ensheathing the parotid gland is attached above to the zygomatic arch. It has to be reflected backwards avoiding injury to the vessels and nerves.

VESSELS AND NERVES OF THE FACE A. Nerves of the face: 13 in number on each side, of which only one is motor and twelve are sensory. Motor nerve of the face is the facial nerve and the sensory nerves are all derived from the trigeminal nerve except one which is derived from the cervical plexus. a. Sensory nerves—These are as follows: 1. Supraorbital 2. Supratrochlear Derived from the ophthalmic division of 3. Infratrochlear the trigeminal nerve 4. Lacrimal 5. External nasal

}



6. Zygomaticofacial

}

Derived from the maxillary division of 7. Zygomaticotemporal the trigeminal nerve 8. Infraorbital 9. Buccal. Derived from the mandibular division of 10. Mental the trigeminal nerve 11. Auriculotemporal

}



12. Anterior branch of the great auricular nerve—It is derived from the cervial plexus. b. Motor nerve—It is facial nerve with its following terminal branches— 1. Temporal 2. Zygomatic 3. Buccal 4. Mandibular 5. Cervical. B. Arteries of the face 1. Facial artery with its branches. 2. Transverse facial artery, a branch of the superficial temporal artery. 3. Smaller arteries that usually accompany the cutaneous branches of the trigeminal nerve having identical names, such as supraorbital, infraorbital, mental, etc. being derived from the external carotid and ophthalmic arteries.

Head, Neck and Face  23 They freely anastomose with one another, so that a network of arteries is formed in the face. C. Veins of the face: They form a plexus in the superficial fascia and muscles of the face and are drained by the veins which accompany the arteries. Facial vein is important of these veins. It has no valves. Dissection note: In dissecting the vessels and nerves of the face, first of all the nerves (motor then sensory) have to be traced, then followed by the arteries and veins. Clean the outer surface and the anterior border of the parotid gland, then trace the branches of the facial nerve which emerge from its deep surface in a radiating manner to the muscles of their supply. Cervical branch of the facial nerve goes downwards behind the angle of the mandible to the neck to supply the platysma. Then trace all the twelve sensory nerves with great care as they are very delicate; of them the following nerves are more or less stronger and must be detected at their respective sites: (a) Supraorbital, (b) infraorbital, (c) zygomaticotemporal, (d) zygomaticofacial, (e) mental and (f) auriculotemporal. In the dissection of the face, only small proximal parts of the supratrochlear, supraorbital, zygomaticotemporal and auriculo-temporal nerves are exposed but their terminal parts are distributed to the scalp and temporal region, where those 4 sensory nerves and also by 3 branches have been described (Figs 2.3 and 2.4).

Other eight sensory nerves are distributed as follows and shown in Figure 2.2 and 2.5. 1. Infratrochlear nerve—It is a branch of the nasociliary, which is a branch of the ophthalmic division of trigeminal nerve. It comes out of the orbit above the medial angle of the eye and supplies the skin and conjunctiva of the medial part of the eyelids, skin of the root of the nose, lacrimal sac and caruncula lacrimalis. 2. External nasal nerve—This is the continuation of the anterior ethmoidal nerve, which is continued behind with the nasociliary. It emerges out of the nasal cavity between the lower border of the nasal bone and the upper nasal cartilage and supplies the skin of the lip and vestibule of the nose. 3. Lacrimal nerve—This is the smallest branch of the ophthalmic division of trigeminal nerve. It enters the orbit through the superior orbital fissure and supplies the lacrimal gland and conjunctiva, then piercing the orbital septum it ends by supplying the skin of the upper eyelid. Sometimes this nerve may be absent. 4. Zygomaticofacial nerve—This is a branch of the zygomatic branch of the maxillary nerve. It comes put of the zygomaticofacial foramen of the zygomatic bone and supplies the skin over the prominence of the cheek (malar prominence). 5. Infraorbital nerve—This is the continuation of the maxillary nerve. It traverses the infraorbital groove, then infraorbital canal and appears in the face through the infraorbital foramen under cover of the levator labii superioris and ends by dividing into three sets of branches— a. Palpebral branches—Supply the skin and conjunctiva of the lower eyelid. b. Nasal branches—Supply the skin of side of the nose.

24  Mannan’s Regional Dissection and Surface Anatomy

Fig. 2.3

Fig. 2.4 Figs 2.3 and 2.4: Vessels and nesves of the face

Head, Neck and Face  25

Fig. 2.5: Sensory nerves of face and front ear

c. Labial branches—Supply the skin and mucous membrane of the cheek and upper lip. These branches communicate with each other and with the zygomatic and upper deep buccal branches of the facial nerve, forming a network, called the infraorbital plexus. 6. Buccal nerve—This is a branch of the anterior trunk of the mandibular nerve. It passes between the two heads of the lateral pterygoid muscle and appears in the face from under cover of the masseter to the outer surface of the buccinator where it supplies the skin and mucous membrane of the cheek. 7. Mental nerve—This is one of the terminal branches of the inferior dental nerve. It appears in the face through the mental foraman and under cover of the depressor anguli oris divides into branches which supply the skin and mucous membrane of the lower lip and the skin over the body of the mandible. 8. Anterior branch of the great auricular nerve—It supplies the skin of the face over the parotid gland. The great auricular nerve is formed by the anterior primary rami of the 2nd and 3rd cervical spinal nerves.

Functional Significance of Sensory Supply of the Face 1. In sinusitis, meningitis, inflammation of the gum of teeth, in common cold and boils headache is the usual symptom, as these are the places which are supplied by the sensory distribution of trigeminal nerve.

26  Mannan’s Regional Dissection and Surface Anatomy 2. Trigeminal neuralgia: It may be defined as a sudden severe paroxysmal attack of burning and scalding pain along the distribution of the sensory divission of trigeminal nerve, usually affecting the maxillary branch, which can be relieved by injecting 90% alcohol in the nerve ganglion (Fig. 2.6).

Facial Nerve (Extracranial Part) After coming out of the stylomastoid foramen, the facial nerve runs forwards through the substance of the parotid gland crossing in its course the outer aspects of the styloid process, the retromandibular vein and the external carotid artery and then divides behind the ramus of the mandible into 5 terminal branches which enter the face by piercing the anteromedial surface of the parotid gland (Fig. 2.7).

Branches a. At its exit from the stylomastoid foramen: 1. Posterior auricular—(Already described) 2. Digastric—Supplies the posterior belly of the digastric muscle 3. Stylohyoid—Supplies the stylohyoid muscle. b. On the face: 1. Temporal branches—2 or 3 in number. They pass upwards and forwards by crossing the zygomatic arch to reach the side of the head and forehead and supply the following muscles— a. Auricularis anterior and superior b. Intrinsic muscles of the lateral surface of the auricle c. Upper part of the orbicularis oculi d. Frontalis e. Corrugator. 2. Zygomatic branches—2 in number. They pass forwards above the parotid duct to the lateral angle of the eye across the zygomatic bone and supply the lower part of the orbicularis oculi, muscles of the nose and muscles between the eye and mouth. 3. Buccal branches (superficial and deep)—These run forwards below the parotid duct to the angle of mouth and supply the muscles of the cheek, buccinator and orbicularis oris. Deep branches are upper and lower. 4. Marginal mandibular branch—These runs forwards along the body of the mandible; passes deep to the depressor anguli oris and supplies the risorius and the muscles of the lower lip and chin. 5. Cervical branch—These runs downwards behind the angle of the mandible to the neck and supplies the platysma. Note: Free communications are established between the branches of the facial nerve with the great auricular, lesser occipital, transvers cutaneous nerve of the neck and with the terminal cutaneous branches of the trigeminal nerve.

Head, Neck and Face  27

Fig. 2.6: Distribution of the trigeminal nerve

Fig. 2.7: Distribution of the facial nerve

28  Mannan’s Regional Dissection and Surface Anatomy

Facial Artery (in the Face) Course It arises from the external carotid artery in the carotid triangle immediately above the greater cornea of the hyoid bone and after short course in the neck it enters the face by piercing the deep cervical fascia at the anteroinferior angle of masseter about an inch in front of the angle of the mandible and runs tortuously upwards and forwards nearly to the angle of the mouth. Then it ascends along the side of the nose and ends at the medial angle of the eye by anastomosing with the dorsal nasal branch of the ophthalmic artery.

Relation At the lower part, it lies on the mandible, buccinator and levator anguli oris covered by the skin, platysma, risorius, zygomaticus major and levator labii superioris. At the termination, the artery is embedded in the substance of the Levator labii superioris alaeque nasi. The facial vein lies posterior to the artery and some branches of the facial nerve cross the artery from behind forwards. The facial artery is tortuous in the face, as it has to accommodate itself to the movements of the mandible, lips and cheeks.

Branches (in the Face) 1. Inferior labial—Arises just below the angle of the mouth and passes medially deep to the depressor anguli oris. It supplies the lower lip and anastomoses with the fellow of the opposite side and also with the mental branch of the inferior dental artery. 2. Superior labial—Arises just above the angle of the mouth under cover of the zygomaticus major. It supplies the upper lip and anastomoses with its fellow of the opposite side. Near the middle line it gives off a septal branch, which supplies the lower % front part of the nasal septum and an alar branch, which supplies the ala of the nose. Sometimes the superior and inferior labial arteries are found to arise together from a single stem. 3. Lateral nasal—Arises by the side of the nose and lies in the groove above the ala. It supplies the ala and dorsum of the nose and anastomoses with the artery of the opposite side and the neighbouring arteries. Dissection note: Trace the above mentioned big three branches as well as the terminal part of the facial artery towards the medial angle of the eye; its other smaller, unnamed, muscular branches need not be shown. Lastly clean the trnasverse facial artery and the superficial temporal vessels.

Transverse Facial Artery It is a branch of the superficial temporal artery arising within the parotid gland. It passes transversely forwards across the masseter between the parotid duct and the zygomatic arch to the superficial aspect of the buccinator. It supplies

Head, Neck and Face  29 the parotid gland, its duct and the adjacent structures and anastomoses with the neighbouring arteries (Fig. 2.8). Note: After the dissection of the nerves and arteries, clean the facial vein, the parotid duct, the accessory part of the parotid gland and the masseter.

Facial Vein (Anterior Facial Vein) Formation It is formed by the union of the supratrochlear and the supraorbital veins at the medial angle of the eye.

Course and Relation After its formation it passes downwards and backwards just behind the facial artery, at first lying superficial to the muscles, then under cover of the zygomaticus major, risorius and platysma and crossing the anteroinferior corner of the masseter, it reaches the lower border of the mandible. There it pierces the deep cervical fascia and descends into the neck, where it joins the anterior divison of the retromandibular (posterior facial) vein and a little below and in front of angle of the mandible it opens into the internal jugular vein near the greater cornea of the hyoid bone. The facial vein is less tortuous, less flaccid and has no valves. Lateral view of facial veins are shown in Figure 2.9.

Tributaries 1. Supratrochlear and supraorbital veins 2. Deep facial vein 3. Veins corresponding to the branches of the facial artery.

Communication 1. It communicates with the cavernous sinus through the superior ophthalmic vein by its connection with the supraorbital vein. 2. It communicates with the pterygoid venous plexus through the deep facial vein which in turn communicates with the cavernous sinus by the emissary veins passing through the foramen lacerum and foramen ovale.

Surgical Importance As the facial vein drains the “Dangerous area of the face” (upper lip, septum of the nose and the adjacent areas), any infection occurring in this area may cause thrombosis of this vein and a septic embolus may spread into the cavernous sinus leading to fatal life.

Buccal Pad of Fat It is also known as the ‘suctorial pad of fat’ or corpus adiposum of the cheek.

30  Mannan’s Regional Dissection and Surface Anatomy

Fig. 2.8: Facial arteries (lateral view)

Fig. 2.9: Facial veins (lateral view): (1) Frontal branch, (2) Frontalis, (3) Supraorbital vein, (4) Orbicularis oculi, (5) Corrugator supercilii, (6) Procerus, (7) Levator labii, (8) Superioris alaeque nasi, (9) Compressor naris, (10) Lateral nasal branch of facial artery, (11) Levator labii superioris, (12) Levator anguli oris, (13) Zygomaticus major (14) Mentalis, (15) Depressor, labii inferioris (16) Depressor anguli oris, (17) Superticiam temporal vessels auriculotemporal nerve, (18) Transverse facial artery parotid duct and (19) Facial vein facial artery

Head, Neck and Face  31

Definition and Situation It is a mass of encapsulated fat situated mainly in the buccinator and partly tucked in between the buccinator and masseter.

Function It helps the cheek to resist the atmospheric pressure during the act of sucking, and as such, it is relatively larger in infants than in adults. The puffiness of child’s cheek is chiefly due to this fat though they have no teeth in their early life. Pierced by—Parotid duct, buccal vessels and nerves.

Parotid Duct (Stensen’s Duct) Definition and function—It is the excretory duct of the parotid gland and carries saliva to the mouth. • Length—2 inches. • Diameter—About 1/8 inches. • Formation—It is formed by the union of two main ductules (branches) within the anterior part of the gland. Course and relation—It runs transversely forwards across the masseter below the accessory part of the gland and the transverse facial artery, lying between the upper and lower branches of the facial nerve. While crossing the masseter it receives the duct of the accessory portion and reaching at the anterior border of the muscle, it bends sharply inwards and pierces the buccal pad of fat, the buccopharyngeal fascia, the buccinator muscle and the mucous membrane. Termination—It opens on a small papilla in the oral surface of the cheek opposite the crown of the upper 2nd molar tooth. The duct can be felt in the living subject by moving the finger up and down as it dips inwards at the anterior border of the masseter by clenching the teeth.

FACIAL MUSCLES They include the muscles of the eyelids, nose, mouth and forehead which are collectively known as the “muscles of facial expression”, because of the fact that an individual can express his outward emotions with different kinds of facial movements produced by these muscles. a. Muscles of the eyelid 1. Levator palpebrae superioris 2. Orbicularis oculi 3. Corrugator supercilii. b. Muscles of the nose 1. Procerus

32  Mannan’s Regional Dissection and Surface Anatomy c. d.

2. Nasalis i. Compressor naris (transverse part) ii. Dilator naris (alar part). 3. Depressor septi. Muscles of the mouth 1. Orbicularis oris 2. Levator labii superioris 3. Levator anguli oris (caninus) 4. Levator labii superioris alacque nasi 5. Zygomaticus major 6. Zygomaticus minor 7. Depressor labii inferioris 8. Depressor angli oris (triangularis) 9. Mentalis 10. Risorius 11. Buccinator. Muscle of the forehead 1. Frontalis (frontal belly of the occipitofrontalis).

Note: Out of the total 18 muscles on each side of the face, only following three are situated deeply and others are superficial:

a. Buccinator b. Mentalis c. Levator anguli oris. Most of the facial muscles taking origin from different bones get inserted into the skin. So, when they contract, the skin also moves with them giving the emotional change of the face. All the facial muscles are supplied by the facial nerve except the levator palpebrae superioris, which is supplied by the oculomotor nerve. Action of some of the muscles are implied in their names. A few of the common facial expressions and the muscles producing them: 1. Smiling and laughing—Zygomaticus major. 2. Sadness—Levator labii superioris and levator anguli oris. 3. Anger—Dilator naris and depressor septi. 4. Grief—Depressor anguli oris. 5. Contempt—Zygomaticus minor. 6. Horor, terror and fright—Platysma. 7. Frowning—Corrugator supercilli and procerus. 8. Surprise—Frontalis. 9. Grinning—Risorius. 10. Doubt—Mentalis. 11. Lower lip depressor—Depressor labii inferioris. 12. Lip riser and naris dilator—Levator labii superioris alacque nasi. 13. Mouth closer into a circle as in whistling and lip presses against the teeth—Orbicularis oris.

Head, Neck and Face  33

Important Facial Muscles Some important facial muscles are mentioned below:

Orbicularis Oculi It is situated around the orbit and consists of orbital, palpebral and lacrimal portions: a. Orbital part—Thickest and widest. It extends upwards into the forehead, downwards into the cheek and laterally into the temple. Its fibers form complete ellipses. –– Origin— 1. From the medial palpebral ligament 2. From the frontal process of the maxilla 3. From the nasal part of the frontal bone. –– Insertion—Into the skin of eyebrow; the upper fibers blending with the Frontalis and Corrugator constitute to form the depressor supercilii. b. Palpebral part—Thinner than the orbital part. –– Origin—From the medial palpebral ligament and the adjoining bone –– Insertion—At the periphery, it is continuous with the orbital part but at the free margin of each eyelid, the muscular fibers are thickened to form the ciliary bundle. c. Lacrimal part—Very small and thin. It lies behind the lacrimal sac. –– Origin— 1. From the crest and lateral surface of the lactimal bone 2. From the fascia covering the lacrimal sac. –– Insertion—Into the tarsi of the eyelids and the palpebral part of the muscle. –– Nerve supply—The muscle is supplied by the temporal and zygomatic branches of the facial nerve. –– Action— 1. It closes the eyelids (acting as sphincter). 2. It draws the eyelids medially, so that the tears is pushed towards the puncta. 3. Palpebral part acting involuntarily closes the eyelids as in blinking or sleeping. 4. Lacrimal part helps to dilate the lacrimal sac.

Orbicularis Oris It forms the greater part of the substance of the lips and acts as a sphincter of the mouth. It has three strata or layers of fibers: 1. Superficial stratum—Consists of fibers which are prolonged from the elevators and depressors of the angles of the mouth. They extend as far as the center of the lips and without being continuous with the fellow of the opposite side, get inserted into the skin near the middle line. These are also reinforced by the fibers derived from the levator labii superioris, zygomaticus major et minor and depressor labii inferioris.

34  Mannan’s Regional Dissection and Surface Anatomy 2. Intermediate stratum—Consists of fibers which are derived from the buccinator muscles and are continuous with the fellow of the opposite side. 3. Deep stratum—Consists of fibers which arise from the incisive fossa of maxilla and mandible and from the anterior nasal spine blending with other fibers. Except the deep stratum, the superficial and intermediate strata are devoid of bony attachment. • Nerve supply—By the lower deep buccal and the marginal mandibular branches of the facial nerve. • Action— 1. It closes the mouth into a circle, as in whistling 2. It presses the lips against the teeth.

Buccinator It occupies the interval between the maxilla and mandible at the side of the face. • Origin—From the outer surfaces of the maxilla and mandible opposite the sockets of the three molar teeth. • Insertion—The fibers converge towards the angle of the mouth and arrange themselves into three sets of fibers. The central fibers decussate, so that the upper ones descending to the lower lip and the lower ones ascending to the upper lip. The highest and lowest fibers are continued forwards into the corresponding lip without decussation. • Nerve supply—By the lower deep buccal branches of the facial nerve. • Action— 1. It compresses the cheek against the teeth and gums, thus prevents the food from accumulating into the vestibule of the mouth during mastication. 2. It compresses the air as in blowing a trumpet. 3. It helps in sucking.

Buccopharyngeal Fascia It is a thin layer of fascia which covers the buccinator muscle and extends backwards over the pterygomandibular ligament to cover the outer surface of the constrictors of the pharynx. This fascia and the buccinator muscle are pierced by the parotid duct and the buccal vessels and nerves.

Risorius It consists of a few scattered fibers lying almost horizontally opposite the angle of the mouth. The most posterior fibers of the platysma are continued upwards in the face as risorius. • Origin—From the parotid fascia. • Insertion—Into the skin at the angle of the mouth.

Head, Neck and Face  35 • Nerve supply—By the buccal branches of the facial nerve. • Action— 1. It raises the angle of the mouth (i.e. it draws the angle of the mouth posteroinferiorly) giving rise to the “risus sardonicus”, a peculiar facial expression seen in the facial paralysis. 2. It helps in the expression of laughter. Figure 2.10 shows all kinds of muscles of face and Table 2.3 describes miuscles in volned in mantication.

Structures Lying over the Masseter 1. Anterior part of the parotid gland 2. Accessory parotid gland 3. Parotid duct

Fig. 2.10: Muscles of face

Nerves upply

Action

a. Temporal fossa, excluding zygomatic bone b. Temporal fascia

Converge and pass through gap deep to zygomatic arch

a. Margins and deep surface of soronoid process b. Anterior border of ramus of mandible

Contd...

It elevates the mandible and presses it against the maxilla, as in closing the lower jaw tightly

Deep temporal a. Elevates mandible branches from b. Posterior fibers retract the protroduced anterior division of mandibular nerve mandible c. Helps in side to side grinding movement

Insertion

2. Temporalis— Fan-shaped, fills the temporal fossa

Fibers Masseteric nerves, a branch of anterior division of mandibular nerve

Origin

a. Superficial layer— a. Superficial fibers a. Superficial layer— 1. Masseter— Into the angle and From anterior 2/3rd pass downwards Quadrilateral lower part of lateral and backwards at 45 Covers lateral of lower border of surface of razygomatic arch and degrees surface of armus of mandible mus of adjoining zygomatic b. Middle and deep the mandible, process of maxila. fibers pass vertically b. Middle layer—Into the lateral surface of b. Middle layer—From downwards has three Three layers the middle part of layers anterior 2/3rd of deep ramus of mandible surface and posterior c. are separated posteroinferiorly by c. Deep layer—Into the 1/3rd of lower border an artery and nerve lateral surface of the of zygomatic arch upper part ol ramus c. Deep layer—Form and coronoid process deep surface of of mandible zygomatic arch

Muscles

Table 2.3: Muscles of mastication

36  Mannan’s Regional Dissection and Surface Anatomy

Roughened area on the medial surface of angle and adjoining ramus of mandible. Below and behind the mandibular forgamen and mylohyoid groove

Insertion

4. Medial a. Superficial head small Fibers run downwards, slip—From tuberosity backwards and laterally pterygoid— Quadrilateral, of maxilla and has a small adjoining bones superficial b. Deep head (quite large)—From medial and a large deep head surface of lateral pterygoid plate and adjoining process of palatine bone

Fibers a. Pterygoid fossa on the anterior surface of neck of mandible. b. Anterior margin of articular disk and capsule of temporomandibular joint

Origin

3. Lateral a. Upper head (small)— Fibers run backwards pterygoid— From infratemporal and laterally and Short, conical, converge for insertion surface and crest has upper and of greater wing of lower heads sphenoid bone b. Lower head (larger)— From lateral surface of lateral pterygoid plate

Muscles

Contd... Nerves upply

Action

Nerve to medial pterygoid branch of the maintrunk of mendibular nerve

a. Elevates mandible b. Helps to protrude mandible c. With lateral pterygoid brings about side to side gringing (chewing) movements

A branch from a. Depress mandible anterior division of to open mouth, with mandibular nerve suprahyoid muscle b. Lateral and medial pterygoid of both sides protrude mandible c. With medial pterygoid of same side and alternating with those of opposite side bring about side to side grinding movements

Head, Neck and Face  37

38  Mannan’s Regional Dissection and Surface Anatomy 4. Transverse facial artery and vein 5. Lower part of the facial vein 6. Zygomatic, buccal and mandibular branches of the facial nerve 7. Anterior branch of the great auricular nerve 8. Risorius muscle 9. Some lymph glands. Sometimes, a thin sheet of muscle is seen covering the zygomaticus major and minor and levator labii superioris called the musculus malaris, the fibers of which being continuous with the orbicularis oculi.

Nerve Supply of the Face on Developmental Background 1. All the facial muscles are developed from the mesenchyma of the 2nd pharyngeal arch which is inervated by the facial nerve. 2. Face is developed from the first pharyngeal arch which has two parts—One is maxillary process, another is mandibular process. Maxillary process gives rise to whole of the upper lip except philtrum which is developed from the fronto-nasal process and the area from angle of the mouth upto the lateral angle of the eye i.e. up to the lower eyelids. Developmentally the maxillary process is supplied by the maxillary division of the trigeminal nerve. Similarly whole of the mandible, its musculature and the skin overlying the mandible developed from the mandibular process are supplied by the mandibular division of the trigeminal nerve. Whole of the nose developed from the fronto-nasal process is supplied or inervated by the opthalmic division of trigeminal nerve.

PAROTID GLAND Definition and Situation Of the three paired salivary glands giving secretion of saliva, the parotid glands are the largest. Each parotid gland is situated below and in front of the external ear in a space called parotid fossa which is bounded as follows and parotid regions are shown in Figure 2.11. a. Anteriorly—Ramus of the mandible and posterior border of the masseter. b. Posteriorly—Anterior border of the Sternocleidomastoid, mastoid process and external auditory meatus. c. Above—Zygomatic arch. d. Below and medially—Styloid process with the muscles attached to it. Shape—Pyramidal. Average weight—About 25 g.

Parts Apex—Directed downward reaching a little below and behind the angle of mandible. Base—Directed downward.

Head, Neck and Face  39

Fig. 2.11: Parotid region: (1) Auriculotemporal nerve, (2) Superficial temporal artery and vein, (3) Temporal branches of facial nerve, (4) Transverse facial artery, (5) Parotid duct, (6) Parotid gland, (7) Facial nerve stylomastoid branch of Posterior auricular aretry, (8) Posterior auricular nerve and artery, (9) Digastric Posterior belly, (10) Retromandibular vein, (11) Accessory vagus and hypoglossal nerves (CNS xi. x. xii), (12) Sternocleidomastoid

Surfaces There are three surfaces that are as follows: 1. Superficial or lateral surface—Covered with skin, superficial fascia containing facial branches of the great auricular nerve, superficial parotid lymph glands, parotidomasseteric fascia and the posterior border of platysma. 2. Anteromedial surface—Grooved by the ramus of the mandible with the masseter and medial pterygoid muscle. 3. Posteromedial surface—Moulded to the mastoid process. Sternocleidomastoid, posterior belly of digastric and the styloid process with its muscular attachment.

Extension Above—Up to the zygomatic arch. Below—A little beyond the level of the angle of mandible. Posteriorly—It overlaps the anterior border of Sternocleidomastoid. Anteriorly—To about the middle of the zygomatic arch passing over the masseter. Parotid duct—Already described. a. b. c. d.

40  Mannan’s Regional Dissection and Surface Anatomy Artery supply—By the external carotid and its branches in relation to the gland. Veins—These are drained into the external jugular vein. Nerve supply—By the auriculotemporal (sensory), the glossopharyngeal (secretomotor) and the sympathetic. Lymphatics—These are drained into the superficial and deep cervical lymph glands. How the gland is kept in position? It is kept in position by the parotidomasseteric fascia derived from the superficial layer of deep cervical. What is the accessory part of the gland? It is a small detached or extended portion of the gland situated above the parotid duct and over the masseter.

Structures within the Parotid Gland Nerves 1. Facial nerve and its terminal branches. 2. Small communicating branches from the great auricular and the auriculotemporal nerves to the facial nerve (the nerves generally lie on a superficial plane).

Arteries 1. External carotid artery with its terminal branches—The superficial temporal and maxillary arteries. 2. Transverse facial artery. 3. Posterior auricular artery (sometimes).

Veins 1. Retromandibular or posterior facial vein (formed by the union of the superficial temporal and the maxillary veins), lying superficial to the external carotid artery. 2. Sometimes the commencement of the external jugular vein (formed by the union of the posterior auricular vein with the posterior division of the retromandibular vein). Few small deep parotid lymph glands.

Applied anatomy 1. Blood supply of the skin of the face is profuse. So wounds in the face bleed profusely but heal rapidly. For this reason, it is rare in plastic surgery for skin flaps, to necrose in this region. Superficial temporal artery as it crosses the zygomatic arch in front of the ear and facial artery winds around the lower margin of the mandible at the antero-inferior angle of masseter, are commonly used by the anesthetist to take the patient’s pulse.

Head, Neck and Face  41 2. Facial skin is rich in sebaceous and sweat glands. Sebaceous glands that secrete sebum keep the face oily but also cause acne in the adults. Sweat glands help in regulation of temperature. 3. Laxity of the greater part of the facial skin facilitates rapid spread of edema. Renal edema first appears in the eyelids and face before spreading to other parts of the body. Also due to fixity of the skin in the nose and auricle, boils in these areas are acutely painful. 4. There are some congenital anomalies of face—such as cleft upper lip that may be associated with cleft palate. Unilateral cleft lip due to failure of fusion of maxillary process with the median nasal process. Bilateral cleft lip due to failure of fusion in both sides of maxillary process with median nasal process. Oblique cleft lip and cleft lower lip may also occur. 5. In case of lesions of facial nerve that occur in either the facial nucleus or peripheral fibers (infranuclear lesion), there is total unifacial paralysis. If the lesion in either the facial area of cortex or descending corticobulbar fibers (supranuclear lesion), only muscles below the eye will be paralyzed, since the muscle above the eye receive cortical fibers from both sides of the brain. Paralysis of muscles of facial expression leads to a lowered eyebrow, droping of the eyelid, inability to dilate nostrils, a one sided smile, inability to contain food or saliva in mouth symptoms are unilateral. 6. If the facial nerve is damaged 6 mm above the stylomastoid foramen then there will be loss of taste on anterior 2/3rd of tongue except vallate papilla, indicates involvement of chorda tympani along with ipsilateral facial paralysis. But if it is damaged less than 6 mm above the stylomastoid foramen taste sensation will be intact, only facial paralysis will occur. 7. Danger area of the face—The upper lip and lower part of the nose are common sites for infection that may cause cavernous sinus thrombosis. This area is known as danger area of the face.

Histological Structure of the Parotid Gland The parotid gland is completely invested by the parotid capsule. It is purely a serous gland and composed of a number of alveoli. The serous alveoli are lined with pyramidal epithelial cells surrounding a narrow lumen. The cells are spherical basally located nuclei with infranuclear cytoplasmic basophilia and apical secretory droplets.

Development of the Parotid Gland It is ectodermal in origin. It develops as an outgrowth from the buccal epithelium just lateral to the angle of mouth. The outgrowth branches repeatedly to form the duct system and the acini.

42  Mannan’s Regional Dissection and Surface Anatomy

ANTERIOR TRIANGLE It is a triangular area on each side of the front of the neck.

BOUNDARY a. In front—By the middle line of the neck extending from the chin to the jugular notch. b. Behind—By the anterior border of the sternocleidomastoid. c. Base—By the base of the mandible and a line from its angle to the mastoid process. d. Apex—By the upper end of the manubrium sterni (remember that the anterior and posterior traingles of the neck are named according to the anterior and posterior positions of these traingles in relation to the Sternocleidomastoid and not in relation to the neck as a whole). Note: Before the dissection is started, the head should be allowed to hang backwards as to make the part stretched by putting wooden blocks behind the body and fix it in the required position with the hook chain (Fig. 2.12).

Fig. 2.12: Anterior triangle of the neck

Head, Neck and Face  43

SKIN INCISIONS 1. A longitudinal incision from the jugular notch to the sysmphysis menti along the middle line of the neck. 2. An oblique incision from the symphysis menti to the angle of the mandible along its base, then carrying it to the tip of the mastoid process. Reflect the triangular flap of the skin downwards and laterally up to the anterior margin of the sternocleidomastoid.

Superficial Fascia It is loosely connected with the skin and contains a variable amount of fat which is seen greatly accumulated below the chin in fatty persons. Dissection note: After removal of the skin, the fibers of the platysma will be seen intimately blended with the superficial fascia at the upper part of the triangle. So, the superficial fascia has to be reflected along with the platysma as a single layer, but carefully preserve the following cutaneous structures—

1. Transverse (anterior) cutaneous nerve of the neck—It arises from the 2nd and 3rd cervical nerves. It turns round the middle of the posterior border of the sternocleidomastoid where it pierces the deep fascia and runs forwards across the muscle; then it divides into ascending and descending branches, which after piercing the platysma, supply the skin of the anterior triangle. Note: Trace this nerve and turn it backwards by detaching its terminal end.

2. Cervical branch of the facial nerve—It emerges from the lower part of the parotid gland and after piercing the deep fascia, it passes forwards below the mandible and enters into the platysma through its deep surface to supply the muscle. It communicates with the transverse (anterior) cutaneous nerve of the neck. Note: This nerve is generally taken away with the platysma in course of dissection.

3. Anterior jugular vein—It begins near the hyoid bone by the union of several small superficial veins from the submandibular region and descends through the superficial fascia lying about 2  –1 ″ from the median plane. A little above the sternum it pierces the deep fascia and bending laterally under cover of the sternocleidomastoid, it ends into the external jugular vein. At the point of its bending the vein is connected with its fellow of the opposite side by a short transverse venous arch called the jugular arch. Peculiarities of the anterior jugular vein: Size of this vein is inversely proportional to that of the external jugular vein. Sometimes, it may be absent, or the veins of the two sides may be united to form a single median vein. It has no valves. Note: Clean this vein and the jugular arch and push them aside.

44  Mannan’s Regional Dissection and Surface Anatomy 4. A few superficial lymph glands are found lying by the side of the anterior jugular vein and below the chin. These are not required to preserve.

PLATYSMA It is a broad, thin sheet of muscle which obliquely covers the lower part of the posterior triangle and the upper part of the anterior triangle and lies in the superficial fascia. Origin—From the fascia and skin covering the upper part of the pectoralis major and deltoid, below the clavicle. • Insertion— 1. The most anterior fibers decussate with their fellow of the opposite side below the chin. 2. The middle fibers are inserted into the lower border of the body of the mandible. 3. The most posterior fibers pass upwards to the face as risorius. • Nerve supply—By the cervical branch of the facial nerve. • Action— 1. It produces oblique wrinkles of the skin on the side of the neck 2. It diminishes the gap between the lower jaw and the neck 3. The anterior fibers help in depressing the mandible.

Structures Lying between the Platysma and Fascia Colli (Figs 2.13 and 2.14) 1. 2. 3. 4. 5.

External jugular vein Transverse cutaneous nerve of the neck Cervical branch of the facial nerve Great auricular nerve Supraclavicular nerve.

Note: Before proceeding with further dissection; now study the distribution and the attachments of the deep cervical fascia.

Deep Cervical Fascia (Fascia Colli) It is the deep fascia of the neck which forms a general investment for the muscles, vessels, viscera and nerves of this region and consists of the following three lamina or layers— a. Superficial or general (investing) lamina b. Pretracheal lamina c. Prevertebral lamina.

A. Superficial (Investing) Lamina It is the most superficial layer of the fascia colli and completely invests the neck in the form of a collar. It lies under cover of the platysma.

Head, Neck and Face  45

Fig. 2.13: Anterior triangle of the neck—superficial dissection (Ansa cervicalis): (1) Great auricular nerve, (2) Accessory nerve, (3) Sternocleidomastoid branch of occipital artery, (4) Retromandibular vein. Facial vein, (5) Internal jugular vein, superior root of ansa cervicalis, (6) Inferior root of ansa cervicalis, (7) Digastric, anterior belly, (8) Facial vein, facial artery. Facial nerve, cervical branch, (9) submandibular gland, (10) Thyrohyoid and (11) Superior thyroid vein, sternocleidomastoid branch of superior thyroid artery

Fig. 2.14: Ansa cervicalis

46  Mannan’s Regional Dissection and Surface Anatomy It is attached as follows: a. Above to the— 1. External occipital protuberance 2. Superior nuchal line 3. Mastoid process of the temporal bone 4. Base of the mandible. b. Below to the — 1. Manubrium sterni 2. Clavicle 3. Acromion and the spine of the scapula. c. Behind to the— 1. Ligamentum nuchae 2. Spine of the seventh cervical vertebra. d. In front to the— 1. Symphysis menti 2. Body of the hyoid bone. Distribution of the superficial (investing) lamina a. On transverse disposition—When traced forwards from its posterior attachment, it splits into two layers to enclose the trapezius and reaching its anterior border reunite to form a single layer, which roofs over the posterior triangle. At the posterior border of the sternocleidomastoid it again splits into two layers, which enclose the muscle and at its anterior border it forms a single which roofs the anterior triangle and reaching in the median plane it becomes continuous with its fellow of opposite side. b. On vertical disposition— i. When traced downwards—Below the level of the cricoid cartilage it splits into two layers, which are attached to the anterior and posterior borders of the manubrium sterni, thus enclosing a space between the two layers, called the suprasternal space or space of Burns. This space contains— 1. Sternal heads of the sternocleidomastoid of both sides. 2. Lower portions of the anterior jugular veins and the jugular arch. 3. Small quantity of fat and areolar tissue. 4. Sometimes a lymph gland. At the lower part of the posterior traingle, the investing layer splits into two layers which are attached below to the clavicle enclosing a space, called the supraclavicular space. It contains the following— 1. Supraclavicular nerves 2. Lower part of the external jugular vein 3. Cutaneous vessels. ii. When traced upwards— a. Opposite the submandibular region—It splits into two layers which ensheath the submandibular salivary gland; the superficial layer is attached to the base of the mandible and the deep layer to the mylohyoid line. In addition to the salivary gland, few

Head, Neck and Face  47 submandibular lymph glands are also contained between these two layers. b. Opposite the gap between the mandible and the mastoid process—It splits into two layers which enclose the parotid gland; the deeper of these two layers passes upwards to be attached to the base of the skull and the superficial layer after covering the parotid gland in the name of parotid fascia, is fixed to the lower border of the zygomatic arch. The portion of the deep layer which extends from the angle of the mandible to the styloid process of the temporal bone, is specially thickened to form the stylomandibular ligament. So, the superficial (investing) layer may be summarized as follows: 1. It encloses two muscles—Trapezius and sternocleidomastoid. 2. It ensheaths two salivary glands—Parotid and submandibular glands. 3. It makes two spaces—Suprasternal and supraclavicular spaces. 4. It roofs two triangles—Anterior and posterior triangles. 5. It forms the parotid fascia and stylomandibular ligament. On the deep surface of the sternocleidomastoid the superficial lamina gives off two fascial processes one passing in front of the trachea, called the pretracheal fascia or lamina and the other passing in front of the prevertebral muscles called the prevertebral fascia or lamina.

B. Pretracheal Lamina It passes medially in front of the common carotid artery, internal jugular vein and the vagus nerve lying deep to the infrahyoid muscles, then splits to ensheath the thyroid gland and after covering the front and sides of the trachea, it reaches the median plane where it becomes continuous with its fellow of the opposite side. It is attached above to the body of the hyoid bone and opposite the middle line, to the thyroid and cricoid cartilages; below, it descends in front on the trachea and vessels into the superior mediastinum where it blends with the fibrous pericardium. Note: As the thyroid gland is fixed to the laryngeal cartilage by the pretracheal lamina it moves up and down with the larynx at the time of swallowing.

C. Prevertebral Lamina a. Medially—It passes medially behind the common carotid artery, internal jugular vein, vagus nerve, the pharynx and esophagus but in front of the prevertebral muscles and reaching the median plane it is continuous with its fellow of the opposite side, being adherent to the buccopharyngeal fascia at the back of the pharynx. b. Above—It is attached above to the base of the skull on the basilar part of the occipital bone.

48  Mannan’s Regional Dissection and Surface Anatomy c. Below—It descends to the posterior wall of the superior mediastinum where it ends by blending with the anterior longitudinal ligament. d. Laterally—It extends over the scalenus anterior and medius and levator scapulae, thus forming a fascial floor in the posterior triangle of the neck. It is also continued downwards and laterally over the brachial plexus of nerves and subclavian vessels behind the clavicle as the axillary sheath. e. Anteriorly—The prevertebral lamina is separated on either side from the buccopharyngeal fascia by an interval, known as the retropharyngeal space which contains loose areolar tissue and few retropharyngeal lymph glands. This space extends as high as the base of the skull and inferiorly it becomes continuous with the superior mediastinum. It has to be noted that the following nerves lie behind the prevertebral lamina— a. Anterior primary rami of the cervical nerves b. The phrenic nerve c. Nerve to the rhomboids d. Nerve to the serratus anterior.

Surgical Importance of the Fascia Colli Beneath the investing lamina if there is any formation of pus in the anterior triangle, it may track down into the thorax as the pretracheal lamina is continued downwards into the mediastinum. Pus forming behind the prevertebral lamina in case of chronic retropharyngeal abscess (cold abscess) due to caries of the bodies of the cervical vertebra, the posterior wall of the pharynx will be pushed forwards in the median plane or the pus may extend laterally and point in the posterior triangle. Sometimes, the retropharyngeal lymph glands of one side may be infected leading to the formation of acute retropharyngeal abscess, which will push the wall of the pharynx on one side but the pus cannot go to the other side, as the prevertebral lamina and the buccopharyngeal fascia are fixed in the middle line.

Carotid Sheath Is a tubular condensation of the deep cervical fascia.

Formation a. b. c. d.

Anteriorly—By the pretracheal lamina. Posteriorly—By the prevertebral lamina. Laterally—By the fusion of the pretracheal and prevertebral lamina. Medially—By a mass of loose areolar tissue connecting the pretracheal and the prevertebral lamina.

Situation—lt is situated in the interval, bounded behind by the scaleni muscles and the transverse processes of the cervical vertebrae, laterally by the sternocleidomastoid and medially by the larynx, pharynx, upper parts of the trachea and esophagus and the lobe of the thyroid gland.

Head, Neck and Face  49 Extension—It extends roughly from the base of the skull to the root of the neck, but a clear cut limit of the upper and lower ends cannot be ascertained. Contents 1. Common and internal carotid arteries—Medially 2. Internal jugular vein—Laterally 3. Vagus nerve—Between and behind the artery and vein.

Relation a. Anteriorly—Ansa cervicalis (hypoglossi) and its constituent nerves; specially the descending branch of the hypoglossal nerve (nervus descendens hypoglossi) runs downwards being embedded in the anterior wall of the sheath or sometimes, passes within the sheath. b. Posteriorly—The sympathetic trunk. Dissection note: After a thorough study of the deep cervical fascia, reflect the investing lamina as that of the skin taking care that the cutaneous structures and the underlying nerves from the ansa cervicalis are not injured. Then define the subdivisions of the anterior triangle; for that purpose, first of all identify the superior belly of the omohyoid, which will be found as a narrow, thin, muscular strip obliquely placed from the hyoid bone to a point on the deep surface of the sternocleidomastoid about 2″ above the clavicle. Next, clean the anterior and posterior bellies of the digastric and retract the sternocleidomastoid a little backwards by the hook chain.

Subdivisions of the Anterior Triangle (Fig. 2.15) 1. 2. 3. 4.

Muscular triangle Carotid triangle Digastric triangle Submental triangle.

Fig. 2.15: Triangles of the right side of the neck

50  Mannan’s Regional Dissection and Surface Anatomy

MUSCULAR TRIANGLE It is so named as some of the muscles are contained in this triangle.

Boundaries a. In front—Middle line of the neck from the hyoid bone to the sternum b. Above and behind—Superior belly of the omohyoid c. Below and behind—Anterior margin of the sternocleidomastoid. Dissection note: Clean the triangle and show the contents as mentioned below. Carefully raise the superior belly of the omohyoid, sternohyoid and sternothyroid and secure their nerves of supply. Look for the attachment of the pretracheal lamina to the hyoid bone and larynx, then remove it while passing deep to the infra hyoid muscle. Expose the thyroid gland by pushing the sternohyoid and sterno-thyroid laterally; secure the terminal part of the superior thyroid artery and the thyroid veins. Identify the cricothyroid muscle lying in contact with the larynx and get the cricothyroid artery over the muscle. Levator glandulae when present, clean it from below upwards.

Contents of the Triangle A. Muscles— 1. Sternohyoid: Longer and lies superficial to the sternothyroid. –– Origin— a. From the posterior surface of the sternal end of the clavicle. b. From the upper part of the posterior surface of the manubrium sterni. c. From the posterior sternoclavicular ligament. –– Insertion—Into the lower border of the body of hyoid bone. –– Nerve supply—By a branch from the ansa cervicalis. –– Action—It depresses the hyoid bone. (This muscle may be added by a small clavicular slip, called cleido hyoid). 2. Sternothyroid: Shorter and lies deep to the sternohyoid. It covers the thyroid gland. –– Origin— a. From the posterior surface of the manubrium sterni below the origin of the sternohyoid. b. From the 1st costal cartilage. –– Insertion—Into the oblique line on the lamina of the thyroid cartilage. –– Nerve supply—By a branch from the ansa cervicalis. –– Action—It draws the larynx downward. 3. Cricothyroid: A small intrinsic muscle of the larynx and lies greatly under cover of the thyroid gland. –– Origin—From the anterolateral surface of the cricoid cartilage. –– Insertion—Into the lamina of the thyroid cartilage. –– Nerve supply—By the external laryngeal nerve. –– Action—It produces tension of the vocal ligaments.

Head, Neck and Face  51 4. Levator glandulae thyroideae: It is a narrow muscular band attached from the body of the hyoid bone above, to the left half of the isthmus of the thyroid gland or to its pyramidal lobe below. It draws the thyroid gland upwards, and it also helps in keeping the gland in position. Some times the muscle is replaced by a fibrous band.

B. Vessels— 1. Superior thyroid artery—It is a branch of the external carotid artery given off in the sternohyoid muscles. Its cricothyroid branch forms an arterial arch in front of the cricothyroid muscle by anastomosing with its fellow of the opposite side. 2. Superior thyroid vein—It accompanies the superior thyroid artery and opens into the internal jugular vein.

C. Nerves 1. Branches of the ansa cervicalis (hypoglossi)—To the sternohyoid and sternothyroid muscles. 2. External laryngeal nerve—This is a branch of the superior laryngeal branch of the vagus. It descends over the outer surface of the inferior constrictor of the pharynx along a line deep to the superior thyroid artery and under cover of the sternothyroid it ends by supplying the cricothyroid. It also gives a branch of supply to the inferior constrictor of the pharynx. 3. Recurrent laryngeal nerve—This is a branch of the vagus. It ascends in the groove between the trachea and the easophagus, then passing along the medial surface of the thyroid gland it enters into the larynx by pierching the cricothyroid ligament laterally. It is mainly a motor nerve and supplies the intrinsic muscles of the larynx except the cricothyroid and partly sensory as it supplies the mucous membrane of the larynx below the vocal fold. Note: Right recurrent laryngeal nerve winds round the 1st part of the right subclavian artery from before backwards and is a branch of the vagus in the neck, but the left recurrent laryngeal nerve winds round the arch of the aorta immediatly behind the ligamentum arteriosum and is a branch of the vagus in the thorax.

D. Other structures 1. Greater part of the larynx 2. Upper part of the trachea 3. Thyroid gland.

THYROID GLAND Definition and Situation It is a highly vascular ductless gland, situated at the front and sides of the larynx and trachea opposite the 5th, 6th, 7th cervical and the 1st thoracic vertebra.

52  Mannan’s Regional Dissection and Surface Anatomy

Average Weight About 1 oz. Its size slightly increases in female during pregnancy and menstruation.

Parts It consists of two lateral loves (right and left) connected by a middle portion called the isthmus. 1. Isthmus—Lies on the 2nd and 3rd tracheal ring. It measures about –1 ″ in length, 2–1 ″ in breadth; covered by the skin and fascia. It is related along 2  its upper broder by an arterial anastomosis connecting the two anterior branches of the superior thyroid arteries. Sometimes, a small third conical lobe, called the pyramidal lobe is seen to project upwards from the left of the upper broder of the isthmus and is connected with the body of the hyoid bone by levator glandualae thyroid or by a fibrous band. Rarely the isthmus may be absent, when the lobes are connected with each other in the median plane. 2. Lobes—These are conical in shape, extending from the oblique line of the thyroid cartilage to the 4th or 5th tracheal ring. Each measures about 2″ in length. 121– ″ in breadth and 43– ″ in thickness. Each lobe presents the anterior and posterior borders; the lateral or superficial, medial or deep and posterolateral surfaces and an apex and base the apex being directed upwards and the base below.

Relation of the Surfaces and Borders (Fig. 2.16) a. Lateral surface—Sternothyroid, sternohyoid and superior belly of the omohyoid and overlapped below by the sternocleidomastoid. b. Medial surface— Two tubes—Trachea and esophagus. Two muscles—Cricothyroid and Inferior constrictor of the pharynx. Two nerves—External laryngeal and recurrent laryngeal nerves. c. Posterolateral surface—Carotid sheath, the common carotid artery being overlapped by this surface. d. Anterior border—Anterior branch of the superior thyroid artery. e. Posterior border—Parathyroid glands and the inferior thyroid fascia.

Artery Supply 1. Superior thyroid artery (branch of external carotid) to the capsules. 2. Inferior thyroid artery (branch of thyrocervical trunk) to the parenchyma. 3. Arteria thyroidea ima (branch of aortic arch or brachiocephalic artery)—to the isthmus.

Head, Neck and Face  53

Fig. 2.16: Thyroid gland: (1) Nerve to thyrohyoid, (2) Internal laryngeal nerve, (3) External carotid artery, (4) External laryngeal nerve, superior thyroid artery, (5) Sternocleidomastoid branch, (6) Superior thyroid vein, (7) Middle thyroid vein, (8) Internal jugular vein, Vagus nerve, common carotid artery, (9) Subclavian artery, (10) Inferior thyroid vein, (11) Brachiocephalic trunk, (12) Sternohyoid, reflected, (13) Thyrohyoid, (14) Cricothyroid, (15) Sternothyroid, (16) Thyroid gland, (17) Sternohyoid, reflected

Venous Drainage 1. 2. 3. •

Superior thyroid vein—Opens into the internal jugular vein. Middle thyroid vein—Opens into the internal jugular vein. Inferior thyroid vein—Opens into the left brachiocephalic vein. Nerve supply—Derived from the superior, middle and inferior cervical ganglia of the sympathetic trunk.

How it is kept in position? The thyroid gland is kept in position by the pretracheal lamina and the ligament of berry, which bind the gland with the larynx; therefore the gland moves up and down with the larynx in the act of swallowing. Its internal secretion is thyroxin (an iodine compound) which passes into the circulation through veins.

54  Mannan’s Regional Dissection and Surface Anatomy Histological structure of thyroid gland The structural unit of this gland is a follicle which compose lobules. They vary greatly in size and shape. The follicles are embeded within a delicate meshwork of reticular fibers which also supports a close network of fenestrated capillaries. A follicle consists of a layer of simple epithelium enclosing a cavity which usually is filled with a gelatinous substance. The thyroid gland also contains small proportion of parafollicular cells. The cells lie adjacent to the follicles but within the basal lamina. Development of thyroid gland The thyroid gland appears in the fourth week of intrauterine life as an epithelial proliferation in the floor of the pharyngeal gut between the tuberculum impar and copula of his. Subsequenty the thyroid primordium penetrates the underlying mesoderm and decends in front of the pharyn-geal gut as a bilobed diverticulum.

LARYNX OR VOICE BOX Definition and Situation It is the upper part of the respiratory passage situated above the trachea opposite the 3rd, 4th, 5th and 6th cervical vertebra. Above it opens into the pharynx and below into the trachea. Function—It serves as an organ of phonation and conducts air passage. Growth—At birth it remains like a tube; between 3rd–12th year of age it grows very slowly but from the 12th year the growth becomes rapid which is more seen in the males than in females. Relation: a. Anteriorly—Skin, superficial and deep fascia and depressor muscles of the hyoid bone. b. Posteriorly—Pharynx. c. On either side—Sternohyoid, sternothyroid, omohyoid and thyro-hyoid muscles and the common carotid artery. Structure—It is composed of a cartilaginous framework joined together by ligaments and membranes. It is moved by extrinsic and intrinsic muscles and lined internally by the ciliated columnar epithelium.

CARTILAGES OF THE LARYNX They are 9 in number, of which three are unpaired or single such as (1) thyroid, (2) cricoid, (3) epiglottis and three paired—(a) arytenoid, (b) corniculate and (c) cuneiform. Thyroid cartilage—It is largest and consists of two flat quadrilateral plates of cartilages which from either side meet in front forming as angular prominence called the laryngeal prominence or Adam’s apple (pomun adami), more prominent in male than in female. The two plates diverge behind. Each plate has go 4 borders—Superior, inferior, anterior and posterior and 2 cornu—Superior and inferior.

Head, Neck and Face  55 Cricoid cartilage—It is like a signet ring having a narrow anterior arch and a broader posterior quadrate lamina, situated below the thyroid cartilage being connected with it by the cricothyroid membrane. Epiglottis—It is a leaf-like structure situated at the entrance of the larynx behind the tongue. It closes the superior laryngeal aperture during deglutition. Its free upper end is broad and rounded and the lower attached end (stalk) is narrow being connected to the inner surface of the thyroid angle by the thyroepiglottis ligament. Arytenoid cartilages—These are two pyramidal pieces of cartilage placed at the upper border of the quadrate lamina of the cricoid cartilage at the posterior part of the larynx. Corniculate cartilages—These are two small cone-shaped nodular pieces of cartilage situated on the apices of the arytenoid cartilages. Cuneiform cartilages—These are two small pieces of cartilage situated in front of the corniculate cartilages. Artery supply of the larynx—By the laryngeal branches from the superior and inferior thyroid arteries. Veins of the larynx—Superior and inferior laryngeal veins open into the internal jugular vein. Nerve supply—By the superior and recurrent laryngeal nerves and by the sympathetic (Fig. 2.17).

Fig. 2.17: Anterior triangle of the neck, deeper dissection: (1) External carotid artery (2) Occipital artery, (3) Hypoglossal nerve accessory vein, (4) Superior root of ansa cervicalis sternocleidomastoid artery, (5) Internal carotid artery, external carotid artery, (6) Ansa cervicalis common carotid artery, (7) Internal jugular vein sternocleidomastoid branch, (8) Sternocleidomastoid, (9) Facial carpet of posterior triangle, (10) Transverse cervical vein, (11) Omohyoid fascia, (12) Sternocleidomastoid

56  Mannan’s Regional Dissection and Surface Anatomy

CAROTID TRIANGLE It is so named as portions of all the three carotid arteries (common, external and internal) are contained in this triangle.

Boundaries of the Triangle a. b. c. d. e.

Behind—Anterior border of the sternocleidomastoid. In front and above—Posterior belly of the digastric and stylohyoid. In front and below—Superior belly of the omohyoid. Roof— Skin, superficial fascia, platysma and the deep fascia. Floor—Anteriorly : Thyrohyoid and hyoglossus and posteriorly; middle and inferior constrictors of the pharynx.

Contents of the Triangle (Fig. 2.18) a. Carotid sheath. b. Arteries: 1. Distal part of the common carotid and the proximal parts of the external carotid arteries. 2. Superior thyroid, lingual, facial, occipital and ascending pharyngeal branches of the external carotid artery. c. Veins: Internal jugular vein and its six tributaries (facial, lingual, occipital, pharyngeal, superior and middle thyroid veins).

Fig. 2.18: (1) Internal carotid artery, (2) Vagus nerve, (3) Accessory nerve, (4) Interior jugular vein, (5) Superior root ansa cervicalis, (6) Common carotid artery, (7) Sternocleidomastoid muscle

Head, Neck and Face  57 d. Nerves: Vagus nerve with its external and internal laryngeal branches; hypoglossal nerve with its descending and thyrohyoid branches; ansa cervicalis with its three branches; nervus descendens cervicalis; accessory nerve and the sympathetic trunk. e. Other structures: Part of the larynx and trachea, greater cornu of the hyoid bone carotid body, some lymph vessels and glands. Dissection note: Full the sternocleidomastoid backwards as far as possible by the hook chain, so as to widely expose the triangle for clear identification of the structures. Then clean the space by removing the remains of the fascia colli and the surrounding fat, taking care that the ansa cervicalis and its constituent nerves, which are placed in front of the carotid sheath, be not injured. At the upper part of the triangle, first secure the lower part of the facial vein terminating into the internal jugular vein. Next, proceed to display the ansa cervicalis and its constituent nerves according to the following procedure: At first, hold the hypoglossal nerve as it descends by crossing outside the internal and external carotid arteries and follow the nerve forwards till it disappears under the posterior belly of the digastric; then secure the descending branch of the hypoglossal nerve and trace it downwards, either in front or sometimes within the carotid sheath till the ansa is reached at the lower part of the triangle. Now, from this ansa (loop), the descending cervical nerve has to be traced upwards as far as possible, then secure the three branches of the ansa to the respective muscles. While tracing the nervus descendens hypoglossi, try to preserve its small branch to the superior belly of the omohyoid.

Ansa Cervicalis (Hypoglossi) Definition and Formation It is a loop of nerve formed by the union of the superior root of the ansa cervical is (nervus descendens hypoglossi) with the inferior root of the ansa cervicalis (nervus descendens cervicalis). Situation—It is situated in front of the carotid sheath, opposite the common carotid artery at the level of the cricoid cartilage. Branches—3 in number to the sternohyoid, sternothyroid and the inferior belly of the omohyoid (branches may go individually to the muscles or by one or two stems but ultimately dividing into three). Derivation of the fibers—From the anterior primary rami of the 1st, 2nd and 3rd cervical nerves; the nervus descendens hypoglossi being derived from the 1st cervical and the nervus descendens cervicalis from the 2nd and 3rd cervical spinal nerves). Dissection note: After studying the ansa and its constituent nerves, push them aside; then remove the carotid sheath and find out the contents as mentioned before. Follow the common carotid artery from below upwards and get into its two terminal branches. First clean the internal carotid artery which gives no branch in the neck and lies lateral to the external carotid artery. Then clean the external carotid artery and its five branches in this triangle.

58  Mannan’s Regional Dissection and Surface Anatomy

Common Carotid Artery Two in number, right and left. The right common carotid artery begins at the bifurcation of the branchiocephalic (innominate) artery behind the right sternoclavicular joint, whereas the left one springs from the arch of the aorta; thus it has got a thoracic and a cervical portion. Each ends by dividing into external and internal carotid arteries at the level of the upper border of the thyroid cartilage. 1. Thoracic part of the left common carotid artery: Runs upwards from the arch of the aorta to behind the left sternoclavicular joint, where it becomes continuous with the cervical part. Relation: a. In front—Manubrium sterni, sternohyoid and sternothyroid muscles, left pleura and lung, left branchiocephalic vein and the remains of thymus. b. Behind—Trachea, left subclavian artery, esophagus, left recurrent laryngeal nerve and the thoracic duct. c. To the left—Left vagus and phrenic nerves, the left pleura and lung. d. To the right—Brachiocephalic artery, trachea, inferior thyroid veins and the remains of thymus. Branch—nil. 2. Cervical part of the right and left common carotid artery: Same on both sides. Each runs from behind the sternoclavicular joint to the upper border of the thyroid cartilage. In the neck, the common carotid artery together with the internal jugular vein and vagus nerve is contained within the carotid sheath. Relation a. Anterolaterally—(At the upper part) the skin, superficial fascia, platysma, fascia colli, anterior margin of the sternocleidomastoid. (At the lower part) the inferior belly of the omohyoid, sternohyoid and sternothyroid muscles intervene between the artery and the sternocleidomastoid. Nervus descendens hypoglossi and the ansa lie in front of the artery separated by the carotid sheath. Sternocleidomastoid branch of the superior thyroid artery crosses the artery from its medial to the lateral side. Superior and middle thyroid veins cross the artery at the lower part. b. Posteriorly—Transverse processes of the lower four cervical vertebra, prevertebral muscles and lamina, sympathetic trunk, ascending cervical artery and on the left side, the thoracic duct. c. Medially—Pharynx, larynx, trachea, esophagus, inferior thyroid artery, recurrent laryngeal nerve and the thyroid gland. d. Laterally—Internal jugular vein. e. Posterolaterally—Vagus nerve. Branch—Excepting the terminal branches (external and internal carotid artery), the common carotid artery usually gives no branch in the neck or thorax.

Head, Neck and Face  59

Peculiarities of the Common Carotid Artery 1. Two carotid arteries may arise from a single trunk. 2. Right common carotid artery may arise as a separate branch from the arch of aorta and the left from the brachiocephalic artery. 3. Division of the artery may occur higher or lower than the usual site. 4. Vertebral, superior and inferior thyroid, occipital and ascending pharyngeal arteries may arise from it.

Carotid Sinus It is a slight dilatation at the point of division of the carotid artery. Here, the tunica, media is proportionately thinner than the tunica adventitia of the wall. The sinus is richly supplied with the sympathetic and the parasympathetic (9th and 10th cranial) nerves. Function—It regulates blood pressure. Distension of the sinus with blood stimulates the nerve ending in its wall, there by reflexly causes slowing of the heart rate and lowering of the blood pressure. Carotid body—It is a small oval reddish brown structure behind the point of division of the common carotid artery. Function—It acts as a reflex stimulator of the respiratory center, when the amount of carbon dioxide is increased in the blood.

External Carotid Artery It is named external as it supplies the parts outside the cranium. Course—It begins at the bifurcation of the common carotid artery opposite the upper border of the thyroid cartilage and ascends wrth a slight anteroposterior curve to a point midway between the tip of the mastoid process and the angle of mandible, where, in the substance of the parotid gland, it ends by dividing into superficial temporal and maxillary arteries. Lower two-third of the artery is contained in the carotid triangle and then leaves it being externally crossed by the posterior belly of the digastric and stylohyoid; the upper-third lies above the digastric on the postero-medial surface of the parotid gland. Relation a. Anterolaterally—Skin superficial fascia with platysma, fascia colli, anterior margin of the sternocleidomastoid and crossed by the hypoglossal nerve, lingual and facial veins. b. Posteromedially—Internal carotid artery, but separated from it by the styloid process, styloglossus and stylopharyngeus muscle, the glossopharyngeal nerve, pharyngeal branch of the vagus and a small part of the parotid gland. c. Medially—Pharynx, external and internal laryngeal nerves and the greater cornu of the hyoid bone.

60  Mannan’s Regional Dissection and Surface Anatomy Branches: 1. Superior thyroid 2. Lingual 3. Facial 4. Ascending pharyngeal 5. Occipital 6. Posterior auricular 7. Superficial temporal—Terminal branch 8. Maxillary—Terminal branch. Note: Of these eight branches no. 1–5 are contained in the carotid triangle and described below.

Superior Thyroid Artery It arises from the front of the external carotid artery just below the greater cornu of the hyoid bone. It runs downwards and forwards being covered by the skin, superficial fascia, platysma, deep fascia and the anterior edge of the sternocleidomastoid; then it passes to the thyroid gland under cover of the superior belly of the omohyoid, sternohyoid and sternothyroid muscles. Medially, it is realated to the external laryngeal nerve and the inferior constrictor of pharynx. Branches— 1. Glandular—Anterior and posterior terminal branches. 2. Infrahyoid. 3. Sternocleidomastoid. 4. Cricothyroid. 5. Superior laryngeal—It passes deep to the thyrohyoid muscle in company with the internal laryngeal nerve and enters the larynx by piercing the thyrohyoid membrane, the nerve lying above the artery. Dissection note: Superior thyroid artery is the lowest branch of the external carotid; follow it downwards to the gland. Then carefully trace the superior laryngeal branch and the accompanying nerve to the larynx.

Lingual Artery It arises from the anteromedial aspect of the external carotid artery, opposite the tip of the greater cornu of the hyoid bone, in between the origin of the superior thyroid and facial arteries. After a short course, it passes deep to the hyoglossus above the hyoid bone and finally ends in the tip of the tongue by anastomosing with its fellow of the opposite side. By the hyoglossus muscle the lingual artery is divided into 3 parts as follows: a. First part—Extends from its origin to the posterior border of the hyoglossus and lies in the carotid tingle. It is covered by the skin, superficial fascia, platysma and deep fascia.

Head, Neck and Face  61 Middle constrictor of the pharynx lies medial to the artery. At first it runs upwards and medially, then descends forming a loop, which is crossed superficially by the hypoglossal nerve. This “loop” is the characteristic of the artery and it lies above the greater cornu of the hyoid bone. b. Second part—Lies deep to the hyoglossus. It runs along the upper border of the hyoid bone, lying on the middle constrictor of the pharynx and genioglossus. It is covered by the hyoglossus, tendon of the digastric, stylohyoid, posterior part of the mylohyoid and the lower part of the submandibular gland. It is separated from the hypoglossal nerve by the hyoglossus and crossed superficially by the stylohyoid ligament. c. Third part—Extends from the anterior border of the hyoglossus to the tip of the tongue and named as the arteria profunda linguae. It runs upwards under cover of the mylohyoid, at first ascends vertically, then runs forwards to the under surface of the tongue near the frenulum accompanied by the lingual nerve. It is related medially to the genioglossus, laterally to the longitu-dinalis linguae inferior and below to the mucous membrane of the tongue. At the tip of the tongue it anastomoses with its fellow of the opposite side. Branches: 1. Suprahyoid—From the first part. 2. Dorsal lingual branches (rami dorsali linguae)—From the 2nd part. 3. Sublingual—From the 3rd part. Dissection note: Only the 1st part of the artery is exposed in the carotid triangle and it has to be traced till it disappears under the hyoglossus.

Facial Artery (in the Neck) It arises from the front of the external carotid artery, a little higher than the lingual artery and immediately above the greater cornu of the hyoid bone. At first, it passes upwards under cover of the posterior belly of the digastric and stylohyoid to the angle of the mandible, where it is lodged in a groove on the posterior part of the submandibular salivary gland, then it turns downwards and forwards between the gland, and the medial pterygoid muscle to the lower border of the mandible, from where it ascends by piercing the deep fascia and enters the face at the anteroinferior angle of the masseter. Carvical part of the facial artery is also tortuous, as it has to accommodate itself to the movements of the pharynx during deglutition. Branches (in the neck)— 1. Ascending palatine 2. Tonsillar 3. Glandular (submandibular) 4. Submental.

62  Mannan’s Regional Dissection and Surface Anatomy Dissection note: Trace the facial artery till it passes deep to the posterior belly of the digastric and stylohyoid. The remaining part of the artery will be found in the digastric triangle.

Ascending Pharyngeal Artery It arises from the medial aspect of the commencement of the external carotid artery. It passes vertically upwards between the internal carotid artery and the wall of the pharynx to the base of the skull, being crossed by styloglossus and the stylopharyngeus. It anastomoses with the ascending palatine branch of the facial artery. Branches— 1. Pharyngeal 2. Inferior tympanic 3. Meningeal. Dissection note: Carefully raise the external carotid artery, then hold the ascending pharyngeal branch and follow it upwards as far as possible.

Occipital Artery It has been already described on page 15. Only a small part of the artery is found at the upper angle of the carotid triangle.

Internal Carotid Artery Course—It begins at the bifurcation of the common carotid artery against the upper border of the thyroid cartilage. It ascends along the side of the pharynx to the base of the skull and enters the cranial cavity through the carotid canal of the petrous part of the temporal bone. Then it runs forwards through the cavernous sinus along the carotid sulcus on the side of the body of the sphenoid and after piercing the duramater, it bends backwards to end below the anterior perforated substance of the brain by dividing into anterior and middle cerebral arteries. Thus the artery may be divided into four parts— 1. Cervical 2. Petrous 3. Cavernous 4. Cerebral.

Relation of the Cervical Part It is contained in the carotid sheath along with the internal jugular vein and vagus nerve. External carotid artery lies anteromedial to it below and anterolateral to it above. i. Posteriorly—Longus capitis, intervened by the superior cervical sympathetic ganglion and the superior laryngeal nerve.

Head, Neck and Face  63 ii. Medially—Wall of the pharynx, ascending pharyngeal artery, pharyngeal veins and external and internal laryngeal nerve. iii. Anterolaterally— a. In the carotid triangle—Sternocleidomastoid, occipital artery, facial and lingual veins, hypoglossal nerve and its descending branch. b. Above the carotid triangle—Posterior belly of the digastric and stylohyoid muscles and the occipital and posterior auricular arteries. The internal carotid is separated from the external carotid artery by the styloid process, styloglossus and stylopharyngeus, glossopharyngeal nerve, pharyngeal branch of the vagus and part of the parotid gland. At the base of the skull, the 9th, 10th, 11th and 12th cranial nerves lie between the internal carotid artery and internal jugular vein. Branches— a. From the cervical part—Nil b. From the petrous part: 1. Caroticotympanic 2. Pterygoid. c. From the cavernous part: 1. Cavernous 2. Hypophyseal 3. Meningeal. d. From the cerebral part: 1. Ophthalmic 2. Anterior cerebral 3. Middle cerebral 4. Posterior communicating 5. Anterior choroid. Structures lying between the external and internal carotid arteries: 1. Glossopharyngeal nerve 2. Pharyngeal branch of the vagus 3. Stylopharyngeus muscle 4. Small part of the parotid gland 5. Styloid process.

Internal Jugular Vein Course—It begins as the direct continuation of the sigmoid sinus in the posterior compartment of the jugular foramen and terminates behind the sternal end of the clavicle by uniting with the subclavian vein to form the brachiocephalic (innominate) vein. It presents two dilatations, one at its commencement, called the superior bulb which is lodged in the jugular fossa of the temporal bone and the other near its termination, called the inferior bulb. Relation—At its origin, it lies behind the internal carotid artery separated by the last four cranial nerves, then it descends through the neck being enclosed in the carotid sheath along the lateral side of the internal and common carotid arteries, the vagus nerve intervening between and behind the two.

64  Mannan’s Regional Dissection and Surface Anatomy The vein is covered by the sternocleidomastoid, crossed superficially by the posterior belly of the digastric and the superior belly of the omohyoid muscles by the accessory and the descending cervical nerves and by the posterior auricular, occipital and sternocleidomastoid arteries. Tributaries— 1. Inferior petrosal sinus 2. Facial 3. Lingual 4. Pharyngeal 5. Superior and middle thyroid 6. Occipital (sometimes). Dissection note: Clean the internal jugular vein and its tributaries, but except the facial vein, other tributaries may be cleared off the field to show the important arteries and nerves in the triangle. Then, hold the vagus nerve which lies behind and between the common carotid artery and the internal jugular vein. Find out the internal laryngeal nerve as it emerges from under cover of the external carotid artery near the tip of the greater cornu of hyoid and trace it to the larynx along with the superior laryngeal artery passing deep to the thyrohyoid. A delicate branch of the hypoglossal nerve may now be secured to the thyrohyoid muscle. External laryngeal nerve will be found on a deeper plane almost in a line with the superior thyroid artery and runs downwards to the muscular triangle. Then follow the internal or external laryngeal nerve upwards to reach the superior laryngeal nerve which lies deep to the internal carotid artery. Clean the hyoglossus above the hyoid bone and see that the hypoglossal nerve is passing on its surface (but deep to the digastric) to the digastric triangle and the lingual artery disappearing under it’s posterior border. A small part of the accessory nerve will be found at the uppermost corner of the carotid triangle running downwards and backwards across the internal jugular vein to enter into the sternocleidomastoid. Lastly, behind the carotid sheath find out the Sympathetic trunk which can be easily identified by the fusiform shaped superior cervical ganglion lying against the 3rd and 4th cervical vertebra.

Vagus Nerve (10th Cranial) It is a mixed nerve consisting of motor and sensory fibers. The name vagus, has possibly been derived from “Vagabond”, because of its extensive course and distribution to the structures in the skull, neck, thorax and abdomen (Fig. 2.19). i. Motor fibers arise from— a. Dorsal nucleus of the vagus—It is situated in the floor of the fourth ventricle under the vagal triangle. It is a mixed nucleus. Fibers arising from it, supply the involuntary muscles of the bronchi, heart, esophagus, stomach, small and large intestines up to the right half of the transverse colon. Its secretomotor fibers supply the glands in the alimentary canal, liver, pancreas and kidney. b. Nucleus ambiguous—It is situated in the medulla oblongata. Fibers arising from it, supply the cricothyroid and the muscles of the pharynx.

Head, Neck and Face  65

Fig. 2.19: The distribution of the vagus nerve—peripheral and intermediate connections

ii. Sensory fibers arise from— a. The superior ganglion—It is situated in the jugular foramen. b. The inferior ganglion—It is situated just below the jugular foramen. Fibers arising from these two ganglia on the nerve trunk run peripherally to the organs of distribution but centrally the fibers end in the medulla oblongata to the following nuclei: 1. Dorsal nucleus—Receive afferent fibers from all the viscera to which it supplies efferent fibers and also from the larynx, pharynx and lungs. 2. Nucleus of the tractus solitarius—Receives fibers from the taste buds of the epiglottis and the vallecula through the internal laryngeal nerve. The vagus nerve is attached to the side of the medulla oblongata by about ten root below the 9th cranial nerve in the groove between the olive and the inferior cerebellar peduncle.

66  Mannan’s Regional Dissection and Surface Anatomy

Course and Relation of the Vagus Nerve (in the Neck) The vagus nerve leaves the cranial cavity through the middle compartment of the jugular foramen along with the 9th and 11th cranial nerves; while in the jugular foramen the cranial root of the accessory joins with the vagus. In the neck, it descends vertically lying at first between the internal jugular vein and the internal carotid artery, then between and behind the same vein and the common carotid artery, being enclosed in the carotid sheath, in front of the longus capitis and longus cervicis. At the root of the neck, the right vagus crosses in front of the first part of the subclavian artery, then passes downwards and medially to enter the thorax behind the right internal jugular vein. The left vagus descends in the interval between the left common carotid and the left subclavian arteries and enters the thorax behind the left innominate vein.

Branches of the Vagus Nerve a. b. c. d.

In the jugular fossa: 1. Meningeal 2. Auricular. In the neck: 1. Pharyngeal 2. Branches to the carotid body 3. Superior laryngeal 4. Right recurrent laryngeal 5. Cardiac. In the thorax: 1. Cardiac 2. Left recurrent laryngeal 3. Pulmonary 4. Esophageal. In the abdomen: 1. Gastric 2. Celiac 3. Hepatic.

Superior Laryngeal Nerve It runs downwards and forwards deep to the internal carotid artery by the side of the pharynx and ends by dividing into external and internal laryngeal nerves. a. External laryngeal nerve—It is a motor branch and supplies the cricothyroid and the inferior constrictor of pharynx (it has been already described in the muscular triangle). b. Internal laryngeal nerve—It is a mixed branch, being motor to the arytenoideus muscle and sensory to the mucous membrane of the larynx up to the vocal fold. It runs downwards and medially on the side of the pharynx deep to the external carotid artery and passing under cover of the thyrohyoid muscle, it

Head, Neck and Face  67 enters the larynx by piercing the thyrohyoid membrane just above the superior laryngeal vessels. Then, it divides into upper and lower branches which supply the mucous membrane at the base of the tongue, lower part of the pharynx, vallecula, both surfaces of the epiglottis down to the vocal fold.

Accessory Nerve (11th Cranial) It is a pure motor nerve and supplies the sternocleidomastoid and trapezius. It has two roots—cranial and spinal. Origin—The cranial root—It arises from the lower part of the nucleus ambiguous in the medulla oblongata and it is accessory to the vagus. The Spinal root—It arises from the anterior horn cells of the upper five cervical segments of the spinal cord. The fibers of this root unite to form a trunk which ascends between the ligamentum denticulatum and the posterior roots of the spinal nerves, then enters the skull through the foramen magnum behind the vertebral artery and joins the cranial root. Course and relation—The accessory nerve being thus formed by the union of these two roots, descends through the intermediate compartment of the jugular foramen and soon after its exit from the foramen, the cranial root—Separates off and unites with the vagus and is distributed through its pharyngeal, recurrent laryngeal and cardiac branches. The spinal root—It descends between the internal jugular vein and the internal carotid artery under cover of the parotid gland, styloid process and the posterior belly of the digastric, then it passes across the upper angle of the carotid triangle lying superficial (rarely deep) to the internal jugular vein and accompanied by the upper sternocleidomastoid branch of the occipital artery it enters into the sternocleidomastoid. It emerges from about the middle of the posterior border of the sternocleidomastoid and runs downwards across the posterior triangle over the levator scapulae and then disappear under the trapezius in which it ends by communicating with the branches from the 3rd and 4th cervical nerves.

Hypoglossal Nerve (12th cranial) It is purely motor and supplies all the extrinsic and intrinsic muscles of the tongue except the palatoglossus. Origin—It arises from the hypoglossal nucleus situated in the floor of the fourth ventricle opposite the hypoglossal triangle. The fibers (rootlets) emerging through the anterolateral sulcus of the medulla oblongata between the olive and the pyramid, pass laterally behind the vertebral artery and are collected into two roots. They separately pierce the duramater and leave the cranium through the anterior condyloid (hypoglossal) canal and soon after their exit the two roots unite to form the nerve trunk. Course and relation—It descends into the neck lying at first medial to the internal jugular vein, internal carotid artery, the 9th, 10th and 11th cranial nerves but soon inclines laterally and runs downwards between the internal

68  Mannan’s Regional Dissection and Surface Anatomy carotid artery and internal jugular vein, lying on the lateral side of the vagus but deep to the parotid gland and posterior belly of the digastric. It enters the carotid triangle at the lower border of the digastric and comes out between the internal carotid artery and the internal jugular vein, then curves forwards turning round the lower sternocleidomastoid branch of the occipital artery, crosses the external and internal carotid arteries, the loop of the lingual artery and enters the digastric triangle deep to the posterior belly of the digastric and the stylohyoid (Figs 2.20 and 2.21). In the digastric triangle, it runs forwards upon the hyoglossus being related above to the submandibular duct and the lingual nerve and reaches the tongue as far as its tip. It communicates with the vagus, lingual, first cervical and the sympathetic nerve.

Branches 1. Meningeal 2. Descending 3. Thyrohyoid 4. Geniohyoid 5. Muscular

}

Derived from the 1st cervical nerve

Nervus Descendens Hypoglossi (Upper Root of the Ansa Cervicalis) Arises from the hypoglossal nerve as it enters the carotid triangle at the lower border of the posterior belly of the digastric. It descends over the internal carotid and common carotid arteries lying in front or within the carotid sheath, gives a branch to the superior belly of the omohyoid and ends by joining with the nervus descendens cervicalis (from the 2nd and 3rd cervical nerves) to form a loop, called the ansa cervicalis (hypoglossi).

Cervical Sympathetic Trunk It is a ganglionated nerve trunk consisting of superior, middle and inferior ganglia. Course and relation—It extends from the base of the skull to the neck of the 1st rib and lies behind the carotid sheath but in front of the transverse process of the lower six cervical vertebra, longus capitis, longus cervicis and the prevertebral lamina. It is continued above as the cranial sympathetic (the internal carotid nerve) and below it is continuous with the thoracic sympathetic. It crosses the inferior thyroid artery opposite the 6th cervical vertebra. Cervical sympathetic send out ‘gray rami communicates’ to all the cervical spinal nerves but they do not receive any ‘white rami communi-cates’ from them. Each ganglion gives out communicating visceral and vascular branches. a. Superior cervical ganglion: Largest of the three and about an inch long fusiform in shape. Situation—It lies opposite the transverse processes of the 2nd and 3rd cervical vertebra.

Head, Neck and Face  69

Fig. 2.20: Distribution of the accessory nerves

Fig. 2.21: Distribution of the hypoglossal nerve

70  Mannan’s Regional Dissection and Surface Anatomy Branches— 1. Lateral or communicating—With the first four cervical nerves, glossopharyngeal, vagus and hypoglossal nerves. 2. Medial or visceral—Cardiac and laryngopharyngeal branches. 3. Anterior or vascular—To the walls of the common carotid, external carotid artery and its branches. b. Middle cervical ganglion: Smallest of the three, almost pin head in size. Situation—It lies opposite the transverse process of the 6th cervical vertebra in front of or just above the inferior thyroid artery. Branches— 1. Communicating—With the 5th and 6th cervical nerves 2. Visceral—Cardiac and thyroid branches 3. Vascular—To the wall of the inferior thyroid artery. c. Inferior cervical ganglion: A bit larger than the middle, i.e. pea shaped. Situation—It lies behind the vertebral artery between the neck of the 1st rib and the transverse process of the 7th cervical vertebra. Branches— 1. Communicating—With the 7th and 8th cervical nerves 2. Visceral—Cardiac branch 3. Vascular—To the wall of the subclavian artery and to its branches.

DIGASTRIC TRIANGLE It has been so named as the triangle is bounded on its two sides by the two bellies of the digastric muscle (Fig. 2.22).

Boundaries of the Triangle a. Above—Base of the mandible and a line from its angle to the mastoid process.

Fig. 2.22: Boundaries and contents of digastric triangle

Head, Neck and Face  71 b. c. d. e.

Below and in front—Anterior belly of the digastric. Below and behind—Posterior belly of the digastric and the stylohyoid. Roof— Skin, superficial fascia, platysma and the deep fascia. Floor—Mylohyoid and hyoglossus.

Dissection note: Carefully remove the deep fascia and the lymph nodes from the exposed outer surface of submandibular salivary gland, which almost fills the triangle and raise it upwards with a hook chain preserving the terminal part of the facial vein in its place. Then, clean the anterior and posterior bellies of the digastric and the fibrous pully which binds their intermediate tendon to the hyoid bone. Note here the splitting of the stylohyoid for the passage of the posterior belly of the digastric. Clean the posterior margin of the mylohyoid and see that the hypoglossal nerve is passing forwards deep to this muscle; the hyoglossus intervenes between the hypoglossal nerve and the lingual artery. Then, find out the facial artery as well as other contents of the triangle as mentioned below.

Contents of the Triangle a. Glands 1. Submandibular lymph nodes (glands)—3 or 4 in number. These are found on the surface of the submandibular salivary gland. They receive afferents from the lower part of the face, lips, floor of the mouth, tongue, teeth and gums, etc. and their efferents pass to the deep cervical lymph nodes. 2. Lower part of the submandibular salivary gland—(Its upper part lies under cover of the body of the mandible along its duct). 3. Lower part of the parotid gland—Projects downwards at the poste-rior corner of the triangle.

b. Veins 1. Lower part of the facial vein—It pierces the deep fascia at the base of the mandible and passes superficial to the submandibular gland. Here it joins with the anterior division of the retromandibular vein and a little in front and below the angle of the mandible it opens into the internal jugular vein. 2. Upper part of the internal jugular vein—lies posterolateral to both the carotid arteries.

c. Arteries 1. Facial artery—It enters this triangle deep to the posterior belly of the digastric and stylohyoid, grooves the posterior part of the submandibular gland and before it pierces the deep fascia at the base of the mandible to enter the face, it gives off its submental branch which runs forwards to the chin deep to the anterior belly of digastric. 2. Terminal part of the external carotid artery—It ascends deep to the stylohyoid and enters into the substance of the parotid gland.

72  Mannan’s Regional Dissection and Surface Anatomy 3. Small part of the internal carotid artery—It lies deep to the external carotid but separated from it by the stylopharyngeus and the glossopharyngeal nerve. 4. Mylohyoid branch of the inferior alveolar (dental) artery—It lies under cover of the body of the mandible along with the mylohyoid nerve.

d. Nerves 1. Mylohyoid nerve—A branch of the inferior alveolar (dental). It runs along with the corresponding artery and supplies the mylohyoid and the anterior belly of the digastric. 2. Hypoglossal nerve—It enters this triangle deep to the posterior belly of the digastric and stylohyoid. It runs forwards over the hyoglossus and disappears under cover of the mylohyoid. 3. Glossopharyngeal nerve—It passes downwards below the stylopharyngeus muscle between the external and internal carotid arteries, then runs forwards deep to the hyoglossus. 4. Vagus nerve—Only a small part will be found lying deep to the internal carotid artery and the internal jugular vein.

Submandibular Gland It is one of the three salivary glands and is about the size of a walnut. Situation—It is situated at the anterior part of the digastric triangle lying partly under cover of the mandible and partly between the mandible and the hyoid bone. It is enveloped by a sheath derived from the investing layer of the deep cervical fascia. Parts—It consists of a large superficial and a small deep part which are continuous with each other at the posterior border of the mylohyoid. a. Superficial part: It has got three surfaces— 1. Inferior surface—This is covered by the skin, superficial fascia, platysma and deep fascia. Facial vein and the cervical branch of the facial nerve cross this surface. 2. Lateral surface—This lies in contact with the submandibular fossa of the mandible and with the medial pterygoid muscle. 3. Medial surface—This is related with the mylohyoid, hyoglossus, stylohyoid, posterior belly of the digastric and the stylohyoid ligament. The mylohyoid vessels and nerve run forwards behind the gland and the mylohyoid muscle. Facial artery grooves the posterior and upper part of the gland. b. Deep part: It lies between the hyoglossus and styloglossus medially and the mylohyoid laterally. It is related above to the lingual nerve and below to the hypoglossal nerve and the deep lingual vein. Artery supply—By the branches from the facial and the lingual arteries. Nerve supply— By the lingual, chorda tympani and sympathetic nerves through the submandibular ganglion.

Head, Neck and Face  73

Submandibular Duct (Wharton’s Duct) It emerges from the medial surface of the superficial part of the gland and runs forwards on the hyoglossus and genioglossus but deep to the mylohyoid and sublingual gland. It opens at the floor of the mouth on the summit of the papilla by the side of the frenulum linguae. Its length is about 2″.

Glossopharyngeal Nerve (9th Cranial) It is a mixed nerve containing motor and sensory fibers. It supplies— a. Motor fibers—To the stylopharyngeus. b. Secretomotor fibers—To the parotid gland. c. Sensory fibers—To the palatine tonsil, mucous membrane of the pharynx, tympanic cavity and the posterior one third of the tongue for general and special (taste) sensation. Origin— a. Motor fibers—These arise from the nucleus ambiguous in the medulla oblongata. b. Sensory fibers—These arise from the superior and inferior ganglia of the nerve, situated just below the jugular foramen; their central processes end in the dorsal nucleus of vagus (for general sensation) and in the nucleus of the tractus solitarius (for taste); their peripheral processes run in course with the nerve. The two roots unite and appear in the groove between the olive and inferior cerebellar peduncle. Course and relation—The nerve leaves the cranial cavity through the middle compartment of the jugular foramen anterior to the vagus and accessory. In the neck—It descends between the internal jugular vein and the internal carotid artery lying deep to the styloid process and its muscles. Then passing between the external and internal carotid arteries along the posterior border of the stylopharyngeus, it curves forwards across the superficial surface of the muscle and disappears under cover of the hyoglossus, where it finally breaks up into its terminal branches.

Branches 1. Tympanic—Ganglionic 2. Carotid—Ganglionic 3. Pharyngeal—Cervical 4. Muscular—Cervical 5. Tonsilar—Terminal 6. Lingual—Terminal.

Phayngeal Plexus It is a network of nerves situated on the middle constrictor of the pharynx under cover of the carotid arteries.

74  Mannan’s Regional Dissection and Surface Anatomy It is formed by— a. The pharyngeal branch of the glossopharyngeal nerve. b. The pharyngeal branch of the vagus. c. The laryngopharyngeal branch from the superior cervical ganglion of the sympathetic trunk. It supplies— a. All the muscles of the pharynx except stylopharyngeus b. All the muscles of the soft palate except tensor palati c. Mucous membrane of the pharynx.

SUBMENTAL TRIANGLE It has been so named as the triangle is situated below the mentum (chin)limited on either side by the anterior belly of the digastric, the apex being formed by the mandible and the base by the body of the hyoid bone. But practically half of this whole triangular area falls under the subdivisions of the anterior triangle.

Boundary a. Medially—Middle line of the neck extending from the chin to the hyoid bone along the median raphe of the mylohyoid. b. Laterally—Anterior belly of the digastric. c. Below—Body of the hyoid bone. d. Floor—Mylohyoid muscle. e. Roof—Skin and fascia. f. Contents— 1. Submental lymph nodes (one or two) 2. Begining of the anterior jugular vein. Dissection note: Clean the space, show the contents and identify the mylohyoid muscle and its median fibrous raphe.

Digastric It consists of anterior and posterior bellies connected by an intermediate tendon. • Origin –– Anterior belly—From the digastric fossa at the base of the mandible. –– Posterior belly—From the digastric fossa (mastoid notch) of the temporal bone. • Insertion—Two bellies are inserted into the intermediate tendon, which is bound to the body and the greater cornu of the hyoid bone by means of a fibrous loop (pully) through which the tendon moves forwards and backwards.

Head, Neck and Face  75 • Nerve supply— –– Anterior belly—By the mylohyoid branch of the Inferior alveolar (dental) nerve. –– Posterior belly—By the facial nerve. • Action—It elevates the floor of the mouth and the hyoid bone during deglutition. It also depresses the mandible.

Mylohyoid • •

Origin—From the whole length of the mylohyoid line of the mandible. Insertion— 1. Partly into the body of the hyoid bone. 2. Mainly into the median fibrous raphe which extends from the symphysis menti to the hyoid bone. • Nerve supply—By the mylohyoid branch of the inferior alveolar (dental) nerve. • Action— 1. It raises the hyoid bone during deglutition 2. It forms with its fellow of the opposite side, the floor of the mouth.

Stylohyoid • Origin—From the posterior surface of the styloid process near its base. • Insertion—Into the junction of the body and the greater cornu of the hyoid bone (near its insertion it is perforated by the digastric tendon). • Nerve supply—By the facial nerve. • Action—It draws the hyoid bone upwards and backwards during deglutition.

Geniohyoid It lies deep to the mylohyoid. • Origin—From the inferior mental spines (genial tubercles). • Insertion—Into the anterior surface of the body of the hyoid bone. • Nerve supply—By a branch from the first cervical spinal nerve through the hypoglossal nerve. • Action—It raises the hyoid bone upwards and backwards during deglutition.

Omohyoid • •

Origin— 1. From the upper border of the scapula near the suprascapular notch  2. From the superior transverse scapular (suprascapular) ligament. Insertion­—Into the lower border of the body of the hyoid bone, lateral to the insertion of the sternohyoid.

76  Mannan’s Regional Dissection and Surface Anatomy • Nerve supply­— –– Superior belly—By a branch from the upper root of the ansa cervicalis (nervus descendens hypoglossi). –– Inferior belly—By a branch from the ansa cervicalis. • Action—It depresses the hyoid bone after it has been elevated. Note: The muscle consists of superior and inferior bellies united by an intermediate tendon. From the scapula it arises as the inferior belly which ends in the intermediate tendon; the superior belly begins from this intermediate tendon and finally gets inserted into the hyoid bone. The tendon lies on the internal jugular vein under cover of the sternocleidomastoid at the level of the cricoid arch. It is held in position by a band of the deep cervical fascia which is attached below to the clavicle and 1st rib, thus making the muscle angular in form.

Thyrohyoid • Origin—From the oblique line on the lamina of the thyroid cartilage. • Insertion—Into the lower border of the greater cornu and adjacent part of the body of the hyoid bone. • Nerve supply—By a branch from the hypoglossal nerve, the fibers being derived from the 1st cervical spinal nerve. • Action—It depresses the hyoid bone.

Hyoglossus • Origin—From the whole length of the greater cornu and lateral part of the body of the hyoid bone. • Insertion—Into the posterolateral aspect of the tongue. • Nerve supply—By the hypoglossal nerve. • Action—It depresses the tongue. The Supra- and Infrahyoid muscles are grouped as follows— a. Suprahyoid muscles: 1. Digastric 2. Mylohyoid 3. Stylohyoid 4. Geniohyoid. b. Infrahyoid muscles: 1. Sternohyoid 2. Sternothyroid 3. Omohyoid 4. Thyrohyoid.

Sternocleidomastoid • Origin (by two heads)— a. Medial or sternal head—From the upper and lateral part of the anterior surface of the manubrium sterni.

Head, Neck and Face  77 • • • •

b. Lateral or clavicular head—From the superior surface of the medial one-third of the clavicle. Insertion— 1. Into the lateral surface of the mastoid process form the apex to its upper border. 2. Into the lateral half of the superior nuchal line of the occipital bone. Nerve supply— 1. By the accessory nerve. 2. By a branch from the ventral (anterior primary) ramus of the 2nd and sometimes of the 3rd spinal nerves. Artery supply— 1. By upper and lower sternocleidomastoid branch of the occipital artery. (The lower branch enters the sternocleidomastoid in company with the accessory nerve). 2. By the sternocleidomastoid branch of the superior thyroid artery. Action— 1. When both acting together, they flex the head and neck on the trunk. 2. When one acts, it draws the head towards the shoulder of the same side and also rotates the head, so to turn the face towards the opposite side. 3. When the head is fixed, they assist in forced inspiration.

Structures Lying Deep to the Sternocleidomastoid The whole area is divided into 3 parts by the posterior belly of the digastric above and omohyoid below (Fig. 2.23). 1. Below the omohyoid—Sternoclavicular joint, sternohyoid and sternothyroid muscles, anterior jugular vein, carotid sheath and subclavian artery. 2. Between the omohyoid and the posterior belly of the digastric— a. Arteries—Common carotid, externa1 and internal carotid, transverse cervical, suprascapular and sternocleidomastoid branch of the superior thyroid artery. b. Veins—Internal jugular, facial and lingual. c. Nerves—Vagus, hypoglossal, descendens hypoglossi, descendens cervicalis, ansa hypoglossi, cervical plexus, upper part of the branchial plexus and phrenic nerve. d. Muscles—Splenius capitis, levator scapulae and scaleni muscles. e. Deep cervical lymph nodes. 3. Above the posterior belly of the digastric— a. Arteries—External and internal carotid and occipital. b. Nerves—Hypoglossal, vagus and accessory. c. Vein—Internal jugular. d. Muscles—Stylohyoid, splenius capitis and longissimus capitis. e. Bones—Mastoid process of the temporal.

Structures Lying Superficial to the Sternocleidomastoid 1. Skin 2. Superficial fascia with platysma

78  Mannan’s Regional Dissection and Surface Anatomy

Fig. 2.23: Submental triangle (lateral view)

3. 4. 5. 6. 7.

External jugular vein Great auricular nerve Transverse cutaneous nerve of the neck Investing lamina of the deep cervical fascia Small part of the parotid gland.

Constrictors of the Pharynx 1. Superior constrictor –– Origin— –– From the pterygoid hamulus. –– From the lower part of the posterior margin of the medial pterygoid plate. –– From the pterygomandibular ligament. –– From the posterior part of the mylohyoid line of the mandible. –– From the side of the tongue. –– Insertion—Into the posterior median fibrous raphe of the pharynx extending upwards to the pharyngeal tubercle. –– Nerve supply—By the pharyngeal plexus.

Head, Neck and Face  79 2. Middle constrictor –– Origin— –– From the lesser cornu of the hyoid bone. –– From the whole length of the upper border of the greater cornu of the hyoid bone. –– From the lower part of the stylohyoid ligament. –– Insertion—Into the posterior median fibrous raphe. –– Nerve supply—By the pharyngeal plexus. 3. Inferior constrictor –– Origin— –– From the side of the carotid cartilage. –– From the oblique line of the lamina and the inferior horn of the thyroid cartilage. –– Insertion—Into the posterior median fibrous raphe. –– Nerve supply— 1. By the pharyngeal plexus 2. By the external and recurrent laryngeal nerves.

Structures Passing between the Constrictors of the Pharynx a. Between the base of the skull and the superior constrictor (in the sinus of morgagni): 1. Tensor palati 2. Levator palati 3. Pharyngo tyampanic tube 4. A branch from the ascending palatine artery. b. Between the superior and middle constrictors: 1. Stylopharyngeus muscle 2. Glossopharyngeal nerve. c. Between the middle and inferior constrictors: 1. Internal laryngeal nerve 2. Superior laryngeal artery. d. Between the inferior constrictors esophagus: 1. Recurrent laryngeal nerve 2. Inferior laryngeal artery. The following structures are found in the middle line of the neck from the symphysis menti to the jugular notch— 1. Median raphe of the mylohyoid muscles 2. Suprahyoid branch of the lingual artery 3. Body of the hyoid bone 4. Levator glandulae thyroidae (occasional) 5. Infrahyoid branch of the superior thyroid artery

80  Mannan’s Regional Dissection and Surface Anatomy 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18.

Median thyrohyoid ligament with the hyoid bursa Thyroid notch Laryngeal prominence Cricothyroid ligament Cricothyroid artery Cricoid arch Cricotracheal ligament First ring of the trachea Isthmus of the thyroid gland (covering 2nd and 3rd tracheal rings) 4th–8th rings of the trachea Jugular arch Inferior thyroid vein Interclavicular ligament.

Head, Neck and Face  81

POSTERIOR TRIANGLE The posterior triangle lies behind the sternocleidomastoid by the side of the neck (Fig. 2.24).

BOUNDARIES a. b. c. d.

In front—By the posterior margin of the sternocleidomastoid. Behind—By the anterior margin of the trapezius. Base—By the upper border of the middle one-third of the clavicle. Apex—By the meeting point of the sternocleidomastoid and trapezius on the occipital bone.

Note: Before commencing the dissection, the head should be turned to the opposite side and fixed by the hook chain. When the dissection of one side is finished, do the other side with a similar position.

(It is better for the part to finish with the dissection of the posterior triangle prior to that of the anterior triangle).

Fig. 2.24: Posterior triangles of the neck: (1) Semispinalis capitis, (2) Posterior auricular, (3) Posterior branch of retromandibular vein, (4) Internal jugular vein, (5) Hypoglossal nerve, (6) Trapezius, (7) Splenius capitis, (8) Accessory nerve (9) Levator scapular, (10) Dorsal scapular nerve, (11) External jugular vein, (12) Scalenus madius, (13) Transverse cervical artery, (14) Omohyoid inferior belly, (15) Brachial plexus, (17) Nerve to thyrohyoid, (18) Superior root of ansa cervicalis

82  Mannan’s Regional Dissection and Surface Anatomy

SKIN INCISIONS 1. An oblique incision from the mastoid process of the temporal bone to the sternal end of the clavicle (the line of incision passing almost midway between the anterior and posterior margins of the sternocleidomastoid). 2. A transverse incision from the lower end of the 1st incision to the junction of the medial two-thirds and the lateral one-third of the clavicle along its upper border (This incision should be given very lightly, otherwise the supraclavicular nerves would be injured). 3. Another transverse incision from the upper end of the 1st incision backwards for about 2 inches. Skin—To be reflected backwards till the anterior margin of the trapezius is exposed.

Superficial Fascia It is thin and contains less fat. In this region the fat generally accumulates under the deep fascia. Platysma is intimately blended with the superficial fascia at the lower part of this triangle. So, the superficial fascia is to be reflected along with the platysma as a single layer without injury to the following cutaneous structures— 1. External jugular vein: It is formed by the union of the posterior division of the retromandibular vein with the posterior auricular vein below and behind the angle of the mandible. It passes over the sternocleidomastoid obliquely, pierces the deep fascia at its posterior border about an inch above the clavicle and opens into the subclavian vein. It has two pairs of valves. Note: Clean the vein from above downwards till it pierces the deep fascia. 2. Cutaneous nerves: They are the superficial branches of the cervical plexus, which emerge at the posterior border of the sternocleidomastoid about its middle and diverge from one another upwards, forwards and downwards. Trace them so far exposed in this triangle to their points of emergence from the sternocleidomastoid. a. Lesser occipital nerve—This runs upwards along the posterior border of the sternocleidomastoid and pierces the deep fascia near the apex of the posterior triangle (described). b. Great auricular nerve—This runs upwards and forwards over the sternocleidomastoid (described). c. Transverse cutaneous nerve of the neck—It runs forwards across the sternocleidomastoid deep to the external jugular vein: (described). d. Supraclavicular nerve—It arise from the ventral (anterior primary) rami of the 3rd and 4th cervical nerves by a common trunk, which emerges a little below the middle of the posterior border of the sternocleidomastoid. It then divides into lateral, intermediate and medial branches, which diverge from one another and pierce the deep fascia, a little above the clavicle, then descends over the corresponding

Head, Neck and Face  83 thirds of the clavicle to supply the skin of the upper part of the chest wall and the anterior aspect of the shoulder region down to the level of the sternal angle.

Deep Fascia It is described here in two parts— a. Deep fascia of the roof—It is that part of the investing lamina of the deep cervical fascia which stretches between the sternocleidomastoid and the trapezius and forms roof of the posterior triangle. It is pierced by— 1. External jugular vein 2. Three divisions of the Supraclavicular nerves 3. Cutaneous blood vessels 4. Laymph vessels. b. Deep fascia of the floor—It covers the muscle at the floor of the posterior triangle and is continuous medially with the prevertebral lamina of the deep cervical fascia. Dissection note: Reflect the deep fascia of the roof as that of the skin without injury to the cutaneous structures. The accessory nerve which runs in contact with the under surface of the investing lamina of the deep fascia should be carefully preserved while reflecting it. Clean the lower part of the external jugular vein into which the transverse cervical and the suprascapular veins terminate. Trace the divisions of the supraclavicular nerves from below upwards to their common trunk at the posterior border of sternocleidomastoid, where other cutaneous nerves should also be cleaned. Then, remove the remains of fat and deep fascia of the floor taking care that the contents of the triangle are not injured. At the lower part of the triangle, look for the inferior belly of the omohyoid which passes obliquely upwards and medially to the under surface of the sternocleidomastoid and secure its nerve coming from the ansa cervicalis. Note: The posterior triangle is subdivided by the inferior belly of the omohyoid into an upper larger occipital triangle and a lower smaller supraclavicular triangle.

OCCIPITAL TRIANGLE Boundaries In front—Posterior margin of the sternocleidomastoid. Behind—Anterior margin of the trapezius. Base—Inferior belly of the omohyoid. Apex—Meeting point of the sternocleidomastoid and the trapezius. Floor—(from above downwards) splenius capitis, levator scapulae, scalenus medius and posterior, covered by the prevertebral layer of the deep cervical fascia. f. Roof—Skin, superficial fascia, platysma (at the lower part) and deep fascia. a. b. c. d. e.

84  Mannan’s Regional Dissection and Surface Anatomy

Contents 1. Occipital artery—Found at the apex of the triangle, while it comes out from beneath the sternocleidomastoid. 2. Superficial cutaneous branches of the cervical plexus—It appear at about the middle of the posterior border of the sternocleidomastoid (mentioned before). 3. Muscular branches to the trapezius and levator scapulae (from the 3rd and 4th cervical nerves)—It appear near the middle of the sternocleidomastoid and enter the respective muscles. 4. Accessory nerve (spinal root)—After piercing the sternocleidomastoid it appears at the junction of the upper third and the lower two-thirds of its posterior border, passes obliquely downwards across the triangle on the levator scapulae and enters into the trapezius on its deep surface, (described). Note: Remember that this nerve though counted as one of the contents of the triangle but practically it passes in its roof.

5. Upper trunk of the brachial plexus with its following supraclavicular branches— a. Nerve to the rhomboideus major and minor—It is very delicate nerve passing downwards and backwards, disappears behind the levator scapulae. b. Nerve to the subclavius—It is also a delicate nerve. It runs downwards behind the omohyoid on the lateral side of the external jugular vein. c. Suprascapular nerve—It runs downwards and backwards lying partly under cover of the inferior belly of the omohyoid. It supplies the supra and infraspinatus muscles and the shoulder joint. 6. Transverse cervical artery—It is a branch of the thyrocervical trunk, it passes laterally crossing in front of the phrenic nerve, scalenus anterior and upper part of brachial plexus but covered by the internal jugular vein sternocleidomastoid and platysma. Then reaching the deep surface of the trapezius, it divides into superficial and deep branches. Note: This artery will be found at the lower part of the occipital triangle with its accompanying vein.

7. Few deep cervical lymph nodes—Found mostly along the posterior margin of the sternocleidomastoid.

SUPRACLAVICULAR TRIANGLE Boundaries a. Above—Inferior belly of the omohyoid. b. Below—Upper border of the middle-third of the clavicle. c. Base—Posterior border of the sternocleidomastoid.

Head, Neck and Face  85 d. Apex—Meeting point of the omohyoid and the clavicle. e. Floor—Scalenus medius, the first digitation of the serratus anterior and the 1st rib. f. Roof—Skin, superficial fascia, platysma and the deep fascia. Note: The supraclavicular triangle is usually very small but it should be made wider by cutting the clavicular head of origin of the sternocleidomastoid and reflecting it medially when all the contents of the triangle will be clearly exposed.

Contents 1. Terminal part of the external jugular vein. 2. Middle and lower trunks of the brachial plexus. 3. Nerve to the serratus anterior—Found at the back of the plexus. It arises from the roots of the 5th, 6th and 7th cervical nerves. 4. Lower part of the nerve to the subclavius—(Its upper part is already found in the occipital triangle). 5. Transverse cervical vessels—Only a small part is seen here, they pass to the occipital triangle deep to the omohyoid. 6. Suprascapular vessels—It placed transversely along the upper part of the posterior surface of the clavicle. Suprascapular artery It is a branch of the thyrocervical trunk. It runs laterally and accompanying the suprascapular nerve under cover of the trapezius, enters the supraspinous fossa by passing above the suprascapular ligament (suprascapular nerve passing below the ligament), then through the spinoglenoid notch it reaches the infraspinous fossa, where it anastomoses with the circumflex scapular artery and the deep branch of the transverse cervical artery. 7. Third part of the subclavian artery—It extends from the lateral margin of the scalenus anterior (opposite the posterior border of the sternocleidomastoid) to the outer border of the 1st rib (behind the lower border of the middle of the clavicle) from where it is continued as the axillary artery). No branch is given off from this part. Relation: i. In front—Skin, superficial fascia, platysma, supraclavicular nerves, deep fascia and clavicle suprascapular vessels, subclavian vein, subclavius muscle with its nerve of supply and the terminal part of the external jugular vein. ii. Behind—Scalenus medius, separated by the lower trunk of the brachial plexus. iii. Above—Upper and middle trunks of the brachial plexus and the inferior belly of the omohyoid. iv. Below—Upper surface of the 1st rib and the pleura. Note: In the cadaver the artery has a tendency to sink down, so it has to be pulled up from behind the clavicle at the time of dissection.

86  Mannan’s Regional Dissection and Surface Anatomy 8. Phrenic nerve—Usually it is not a content of this triangle, as it remains concealed by the sternocleidomastoid, but this nerve should be exposed here bv retracting the lower part of the sternocleidomastoid medially. It will be found descending obliquely in front of the scalenus anterior under cover of its fascia from its lateral to the medial side. It is a mixed nerve, consisting of motor and sensory fibers in the proportion of 2 : 1. It arises chiefly from the 4th cervical nerve but also receives branches from the 3rd and 5th cervical nerves. 9. Few lymph nodes.

Splenius Capitis • •

Origin— 1. From the lower half of the ligamentum nuchae. 2. From the spines of the 7th cervical and the upper four thoracic vertebra. Insertion—Into the mastoid process of the temporal bone and to the surface just below the lateral third of the superior nuchal line. • Nerve supply—By the lateral branches of the dorsal (posterior primary) rami of the 4th, 5th and 6th cervical spinal nerves. • Action—Acting from both sides, the head is drawn backwards but acting singly, it bends the head and neck to the same side with turning of the face to that side.

Levator Scapulae • Origin— 1. From the transverse processes of the atlas and the axis. 2. From the posterior tubercles of the transverse processes of the 3rd and 4th cervical vertebra. • Insertion—Into the medial border of the scapula above the insertion of the rhomboideus minor. • Nerve supply—By branches from the 3rd, 4th and 5th cervical spinal nerves. • Action— 1. It elevates the scapula. 2. It depresses the point of shoulder acting with the pactoralis minor and the Rhomboids.

Scalenus Anterior • Origin—From the anterior tubercles of the transverse processes of the 3rd, 4th, 5th and 6th cervical vertebra. • Insertion—Into the scalene tubercle and the adjoining ridge on the upper surface of the 1st rib in front of the groove for the subclavian artery. –– Nerve supply—By the branches from the ventral (anterior primary) rami of the 4th, 5th and 6th cervical spinal nerves.

Head, Neck and Face  87



–– Action— 1. It bends the neck to the same side. 2. It steadies the 1st rib during inspiration.

Scalenus Medius • Origin—From the posterior tubercles of the transverse processes of all cervical vertebra. • Insertion—Into the upper surface of the 1st rib between the groove for the subclavian artery and the tubercle of the rib. • Nerve supply—By the branches from the ventral (anterior primary) rami of the 3rd–8th cervical spinal nerves. • Action—Same as above.

Scalenus Posterior • Origin—From the posterior tubercles of the transverse processes of the 4th, 5th and 6th cervical vertebra. • Insertion—Into the supero-lateral surface of the 2nd behind the impression for the serratus anterior. • Nerve supply— By the branches from the ventral (anterior primary) rami of the lower three cervical spinal nerves. • Action— 1. It bends the neck to the same side. 2. It elevates the 2nd rib.

SUBOCCIPITAL TRIANGLE It is a small deep seated, triangular space situated just below the squamous part of the occipital bone at the upper most part of the back of the neck. Note: Before starting the dissection, the head should be clean-shaved and flexed properly by placing a block under the chest as to make the part stretched.

Skin Incision 1. A longitudinal incision along the middle line from the external occipital protuberance to a point midway between the spine of the vertebra prominens and the external occipital protuberance. 2. Two transverse incisions, one from each end of the first incision extending laterally for about three inches.

Skin Thick and fibrous. Reflect it laterally. Superficial fascia—It is tough and contains moderate amount of fat. It has to be carefully reflected without injury to the following cutaneous structures in it—

88  Mannan’s Regional Dissection and Surface Anatomy 1. Greater occipital nerve—It is the larger medial branch of the dorsal (posterior primary) ramus of the 2nd cervical nerve. It appears below the obliques capitis inferior and winding round its lower border runs upwards and medially across the suboccipital triangle under cover of the semispinalis capitis; then it pierces this muscle and running upwards for a short distance pierces the trapezius and deep fascia close to the superior nuchal line about an inch lateral to the external occipital protuberance. It supplies the skin of the back of the head as far as the vertex and also gives a muscular branch to the semispinalis capitis. 2. Third occipital nerve (described). 3. Terminal branches of the occipital artery—Supply the scalp as high as the vertex in company with the branches of the greater occipital nerve.

Deep Fascia It is here that part of the investing lamina of fascia colli, which is attached above to the external occipital protuberance and superior nuchal line and behind to the ligamentum nuchae. Dissection note: Reflect the deep fascia as that of skin preserving the cutaneous structures. Then, the following muscles will be required to separate as to expose the suboccipital triangle which is placed deep to these muscles—

a. Trapezius—Cut at its origin from the superior nuchal line and from the ligamentum nuchae, then reflect it downwards. Note that this muscle is very thin in this region, so particular care should be taken not to reflect it along with the deep fascia. b. Splenius capitis—Cut at its insertion from the occipital bone and reflect it downwards. Note that the fibers of this muscle are directed obliquely, whereas those of the semispinalis capitis are vertical. c. Semispinalis capitis—Cut at its insertion from the occipital bone and reflect it downwards. While reflecting, preserve the nerve twig that enters this muscle for syupply. d. Longissimus capitis—It is placed vertically just outside the semispinalis capitis. It shiould be retracted laterally by the hook chain. What is the guide to reach “the triangle”from the exterior? The greater occipital nerve serves as a guide to reach the triangle, as this nerve can be traced by dissecting step by step from the superficial fascia to the lower border of the obliques capitis inferior, just above which the triangle is situated. So, care should be taken to preseve this nerve while reflecting the muscles for the exposure of the triangle.

Boundaries of the Triangle a. Above and medially—Rectus capitis posterior major. b. Above and laterally—Obliques capitis superior.

Head, Neck and Face  89 c. Below and laterally—Obliques capitis inferior. d. Roof—Formed medially by the semispinalis capitis with a layer of dense fibro-fatty tissue on its deep surface and laterally by the longissimus capitis. e. Floor—Formed by the posterior arch of the atlas and the posterior atlantooccipital membrane. Dissection note: Remove the fibro-fatty tissue from the space and clean the muscles of the boundaries very carefully, so that the nerve twigs supplying them be not injured. The greater occipital nerve will now be found to pass upwards across the medial part of the triangle. Hold one of the muscular branches and follow it to the posterior arch of the atlas where the trunk of the nerve will be found to come below the vertebral artery. Then, from the trunk trace the other branches. The nerve to the rectus minor will be found to enter the muscle passing across the rectus major (Fig. 2.25).

Contents of the Triangle 1. Dorsal (posterior primary) ramus of the 1st cervical nerve or sub-occipital nerve. 2. Third part of the vertebral artery. 3. Suboccipital plexus of veins. 4. Tough fibrous tissue and fat.

Fig. 2.25: Head and neck: Median section

90  Mannan’s Regional Dissection and Surface Anatomy Dorsal (posterior primary) ramus of the 1st cervical nerve or suboccipital nerve: It emerges above the posterior arch of the atlas below the vertebral artery and enters the suboccipital triangle where it divides into— a. Five muscular branches—It radiate to supply the rectus capitis posterior major at minor, oblique capitis superior and inferior and semispinalis capitis. b. One communicating branch—To the greater occipital nerve from the nerve to the oblique capitis inferior. The dorsal (posterior) ramus of the 1st cervical nerve is larger than ventral (anterior) ramus and is usually motor but sometimes gives off a cutaneous branch which accompanies the occipital artery to the scalp. Note: With the exception of the 1st cervical, 4th and 5th sacral and the coccygeal nerves, the dorsal (posterior primary) ramus of the other spinal nerves divide into medial and lateral branches for the supply of muscles and skin.

The ventral (anterior primary) ramus of the 1st cervical nerve—Though it appears above the posterior arch of the atlas but does not fall under the contents of the suboccipital triangle, as it passes forwards winding round the lateral aspect of the lateral mass of the atlas, lying medial to the vertebral artery and then descends to join the cervical plexus. As the 1st cervical nerve emerges below the occipital bone, it is also called as the suboccipital nerve. Vertebral artery: It is a branch of the 1st part of the subclavian artery. It has four parts— a. 1st part—Extends from the origin of the artery to the foramen transfers rium of the 6th cervical vertebra and it passes in front of the anterior root of the transverse process of the 7th CV. b. 2nd part—Extends from the foramen transversarium of the 6th CV to that of the atlas (i.e. it traverses through the foramina transversarium of the upper six CV). c. 3rd part—Extends from the foramen transversarium of the atlas to the medial border of its posterior arch. d. 4th part—Extends from the atlas to the lower part of the pons, where it unites with its fellow of the opposite side to form the basilar artery. This part pierces the dura and arachnoid mater and ascends through the subarachnoid space in front of the roots of the hypoglossal nerve.

Branches a. Cervical— 1. Spinal (from the 2nd part) 2. Muscular (from the 3rd part). b. Cranial (from the 4th part)— 1. Meningeal. 2. Posterior spinal.

Head, Neck and Face  91

3. Anterior spinal. 4. Posterior inferior cerebellar. 5. Medullary—to the medulla oblongata (no branch is given off from the 1st part).

Third Part of the Vertebral Artery Course and relation—It begins as a continuation of the 2nd part of the artery from the foramen transversarium of the atlas medial to the rectus capitis lateralis and lateral to the ventral (ant. primary) ramus of the 1st cervical nerve. It curves backwards and medially behind the lateral mass of the atlas and lies in the groove on the upper surface of the posterior arch of the atlas separated by the dorsal (posterior primary) ramus of the suboccipital nerve being covered by the semispinalis capitis. It then turns medially and passes under cover of the free lateral part of the posterior atlanto-occipital membrane and becomes the 4th part (Fig. 2.26).

Fig. 2.26: Arteries of the head and neck

92  Mannan’s Regional Dissection and Surface Anatomy Branch—Few small muscular branches to the neighboring muscle. Dissection note: The free lateral part of the posterior atlantooccipital membrane and the venous plexus have to be carefully removed for thorough exposure of the 3rd part of the vertebral artery.

Suboccipital Plexus of Veins It is the network of veins which is formed by the union of (a) the occipital veins, (b) posterior condylar emissary vein, (c) small muscular veins, (d) veins from the plexus inside the vertebral canal. It is drained by the deep carvical vein and plexus of veins that surround the 2nd part ol the vertebral artery. (Remember that only the 1st part of the vertebral artery is accompanied by the vertebral vein but the other parts are surrounded by a plexus of veins).

Trapezius It is a triangular muscle, covering the back of the neck, the shoulder and the upper part of the trunk. • Origin— 1. From the external occipital protuberance. 2. From the medial 1/3 of the superior nuchal line. 3. From the ligamentum nuchae. 4. From the spine of the 7th cervical vertebra. 5. From the spines of the thoracic vertebra. 6. From the supraspinous ligament. • Insertion— a. Upper fibers—These passes downwards and laterally and inserted into the posterior border of the lateral of the clavicle, encroaching on its upper surface. b. Middle fibers—These passes transversely and inserted into the medial margin of the acromion and the upper lip of the crest of the spine of the scapula. c. Lower fibers—These passes upwards and laterally in a converging manner and inserted by a tendon into a tubercle at the apex of the smooth triangular area of the spine of the scapula. • Nerve supply— 1. Accessory nerve. 2. Branches from the ventral rami of the 3rd and 4th cervical spinal nerves. • Action— 1. It draws the scapula upwards and backwards and thus raises the point of shoulder. 2. It rotates the scapula forwards and thus enables the arm to be raised above the shoulder. 3. It draw the head backwards and laterally. 4. When both acting together, they draw the head and neck backwards.

Head, Neck and Face  93

Splenius Capitis Discussed on page 86.

Semispinalis Capitis • Origin— 1. From the tips of the transverse processes of the upper six thoracic and 7th cervical vertebra. 2. From the articular processes of the 4th, 5th and 6th cervical vertebra. 3. From the spine of the 7th cervical or 1st thoracic vertebra. • Insertion—Into the medial part of the area between the superior and inferior nuchal lines. • Nerve supply—By the dorsal (posterior primary) rami of the cervical and thoracic spinal nerves. • Action—It extends the head and turns the face to the opposite side. (The medial part of this muscle is termed as biventer cervicis which remains blended with the splenius capitis).

Longissimus Capitis • • •

Origin— 1. From the transverse processes of the upper four or five thoracic vertebra. 2. From the articular processes of the lower three or four cervical vertebra. Insertion—Into the posterior margin of the mastoid process of temporal bone. Nerve supply—By the dorsal (posterior primary) rami of the lower cervical and thoracic spinal nerves. • Action—It extends the head and turns the face to the same side.

Suboccipital Muscles (Fig. 2.27) 1. Rectus capitis posterior major –– Origin—From the spine of the axis. –– Insertion—Into the lateral part of the inferior nuchal line and to the bone below it. –– Action—It extends the head and rotates it to turn the face to the same side. 2. Rectus capitis posterior minor It lies medial to and partly under cover of the rectus major. –– Origin—From the tubercle on the posterior arch of the atlas. –– Insertion—Into the medial part of the inferior nuchal line and to the bone between it and the foramen magnum. –– Action—It extends the head backwards. 3. Obliques capitis inferior –– Origin—From the lateral surface of the spine and adjacent part of the lamina of the axis.

94  Mannan’s Regional Dissection and Surface Anatomy

Fig. 2.27: Suboccipital muscles of the head and neck

–– Insertion—Into the posteroinferior part of the transverse process of the atlas. –– Action—It turns the face to the same side by rotating the atlas on the axis. 4. Obliques capitis superior –– Origin—From the upper surface of the transverse process of the atlas. –– Insertion—Into the occipital bone between the superior and inferior nuchal lines lateral to the semispinalis capitis. –– Action—It bends the head backwards and to the same side. –– Nerve supply—All the four suboccipital muscles are supplied by the branches from the dorsal (posterior primary) ramus of the 1st cervical spinal nerve.

Lymphatic Drainage of the Head, Neck and Face Principal lymphatic vessels and nodes are discussed below and shown in Figure 2.28.

Head, Neck and Face  95

Fig. 2.28: Principal lymph node groups and drainage of head, neck and face

1. Lymphatic vessels: A. Lymphatic vessels of the scalp are drained as follows— a. Frontal area—Into anterior auricle and parotid node. b. Temporal and parietal area—Into parotid and retroauricular nodes. c. Occipital area—Into occipital and deep cervical nodes.  B. Lymphatics of external ear are drained into— a. Pre- and retro-auricular nodes b. Superficial and deep cervical nodes. C. Lymphatic vessels of the face are drained as follows— a. From eyelids and conjunctiva—Into submandibular and parotid nodes. b. From cheek—Into the parotid and submandibular node. c. From the side of nose, upper lip and lateral part of the lower lip—Into the submandibular nodes. d. From ‘the medial part of the lower lip-into the submental nodes. e. From the temporal and infratemporal fossa—Into the deep facial and deep cervical nodes. 2. Lymph nodes: A. Lymph nodes of the head— a. Occipital area: Back of the head close to the edge of trapezius. Afferent—From the scalp at the back of head. Efferent—Ends into the superior deep cervical nodes. b. Retroauricular area: At insertion of the sternocleidomastoid on mastoid process. Afferent—From the posterior temporal and parietal region. Efferent—Ends into the superior deep cervical lymph nodes.

96  Mannan’s Regional Dissection and Surface Anatomy c. Preauricular area: Infront of the tragus of the ear. Afferent—From the temporal region and pinna. Efferent—Ends into the superior deep cervical lymph node. d. Parotid area: Two sets either embeded in gland or just below it. Afferent—From the root of the nose, eyelids, anterior temporal region and external auditory meatus. Efferent— Ends into the superior deep cervical nodes. e. Facial: 3 sets : i) Infraorbital, ii) buccal and iii) mandibular. Afferent—From the eyelids, conjunctiva, skin of the nose, nasal mucosa and cheek. Efferent—Ends into the submandibular region. B. Lymph nodes of the neck— a. Submandibular: Situation: Under the body of the mandible. Afferent—From the cheek, nose, upper lip, lower lip, facial and submental nodes. Efferent—Ends into the superior deep cervical nodes. b. Submental: Situation: Between the anterior belly of the digastric. Afferent—From the central part of the lower lip, floor of the mouth. Efferent—Ends into the submandibular and deep cervical lymph nodes. c. Superficial cervical: Situation—Along the external jugular vein. Afferent—From the ear and parotid region. Efferent—Ends into the superior deep cervical node. d. Deep cervical: Situation—Along the carotid sheath. It is divided into— i. Superior deep cervical: Situation—Situated under sternocleidomastoid, along accessory nerve and internal jugular vein. Afferent—From the back of the head and neck. Tongue, larynx, thyroid gland, palate, nose, esophagus and all nodes, except inferior deep cervical. Efferent—Ends into the inferior cervical nodes and jugular trunk. ii. Inferior deep cervical: Situation—Extending below the border of the sternocleidomastoid close to the subclavian vein. Afferent—From the dorsum of the scalp and neck, superficial pectoral region, part of the arm and superior deep cervical nodes. Efferent—Joins the efferent of superior deep cervical nodes to form the jugular trunk.

Jugular Trunk Termination— a. On the right side: At the juncton of internal jugular vein and subclavian vein. b. On the left side: In the thoracic duct.

Head, Neck and Face  97

 RTICULATION OF THE HEAD, NECK AND VERTEBRAL A COLUMN 1. Temporomandibular joint Type—It is condylar variety of synovial joint but strictly speaking it is a ellipsoid variety of synovial joint (Table 2.4). Table 2.4: Types of movements and muscle involved in producing movement Movements

Muscles involved in producing Assisting muscles movement

1. Depression

1. Lateral pterygoid

2. Elevation

2. a. Temporalis b. Masseter c. Medial pterygoid

3. Protrusion

3. a. Leteral pterygoid b. Medial pterygoid

4. Retraction

4. Temporalis (Posterior fibers)

1. Digastric, mylohyoid and geniohyoid

5. Lateral movement 5. a. Lateral pterygoid b. Medial pterygoid

2. Atlantooccipital joint: Type—Ellipsoid variety of synovial joint (Table 2.5). Table 2.5: Synovial joint movement and muscles involved in it Movement 1. Flexion

Muscles involved in producing movement 1. a. Longus capitis b. Rectus capitis anterior

2. Extension

2. a. Rectus capitis posterior major and minor b. Obliques capitis superior c. Semispinalis capitis d. Splenius capitis e. Trapezius (upper part)

3. Restricted lateral flexion

3. a. Rectus capitis lateralis b. Semispinalis capitis c. Splenius capitis d. Sternocleidomastoid and trapezius (upper part)

3. Atlantoaxial joint: Type—There are 3 synovial joints a. Lateral atlantoaxial joint Type—Plane variety of synovial joint. b. Median atlantoaxial joint

98  Mannan’s Regional Dissection and Surface Anatomy Type—Pivot variety of synovial joint. Here dense (axis) is fixed and ring moves. Movement—Rotation of the atlas (and with it the skull) upon the axis. The extent being limited by the alar ligaments. 4. Joints of the vertebral column: A. Vertebral arch joint: Synovial joint B. The joints of the vertebral bodies: Symphysis type of cartilagenous joint.

Movements of the vertebral column 1. 2. 3. 4. 5.

Flexion by— a. Longus cervicis b. Scaleni c. Sternocleidomastoid d. Rectus abdominis of both sides. Extension by— a. Erector spinae b. Splenius and semispinalis capitis of both sides. Lateral flexion by— a. Longissimus b. Iliocostocervicalis. Rotation by— a. Rotatores b. Multifidus c. Splenius. Sacrococcygeal and intercoccygeal joint: Type—Symphysis types.

Curvature of the vertebral column The vertebral column possesses 4 curvatures— • Primary curvature—Formed at the thoracic and sacral region. • Secondary curvature—Formed at the cervical and lumber region. • Deformities of the vertebral column— a. Kyphosis—Forward bending of the vertebral column. b. Lordosis—Backward bending of the vertebral column. c. Scoliosis—Lateral bending of the vertebral column either on right or left side.

CRANIAL NERVES Cranial nerves, components and their points of exit in the skull are tabulated in Table 2.6.

Background of Nomenclature of the Cranial and Spinal Nerves Cranial nerves—They are attached to the brain and emerge from the skull or cranium.

Head, Neck and Face  99 Table 2.6: Cranial nerves, components and their points of exit in the skull Name

Components

Points of exit in the skull

1. Olfactory

Sensory

Opening in the cribriform plate of the ethmoid bone

2. Optic

Sensory

Optic foramen

3. Oculomotor

Motor

Superior orbital fissure

4. Trochlear

Motor

Superior orbital fissure

5. Trigeminal Ophthalmic Maxillary Mandibular

(Mixed) Sensory Sensory Motor (mixed)

Superior orbital fissure Foramen rotundum Foramen ovale

6. Abducent

Motor

Superior orbital fissure

7. Facial

Motor (mixed) Secretomotor

Internal acoustic meatus, facial canal, stylomastoid foramen

8. Vestibulocochlear Vestibular/cochlear

Sensory

Internal acoustic meatus

9. Glossopharyngeal

Motor (mixed) Secretomotor Sensory

Jugular foramen

10. Vagus

Moror (mixed) Sensory

Jugular foramen

11. Accessory

Motor

Jugular foramen

12. Hypoglossal

Motor

Hypoglossal canal

Motor → 3, 4, 6, 11, 12 Parasympathetic → 3, 5, 7, 9, 10

Mixed → 5, 7, 9, 10

Sensory → 1, 2, 8

Spinal nerves—They are attached to the spinal medulla and escape from the vertebral column through the intervertebral foramina. There are 12 pairs of cranial nerves, which leave the brain through the foramina of the skull. Distributed to head, neck except 10th which also supply thorax and abdomen.

CERVICAL PLEXUS Formation—It is formed by the ventral rami of the upper 4 cervical nerves. Situation—It is situated at the level of 1st four cervical vertebrae and lies deep to the sternocleidomastoid in front of the scalenus medius and levator scapulae.

100  Mannan’s Regional Dissection and Surface Anatomy

Branches (Fig. 2.29) A. Superficial branch: 1. Superficial ascending branch— a. Lesser occipital → 2c b. Greater occipital → 2, 3c c. Transverse cutaneous → 2, 3c. 2. Superficial descending branch— a. Supraclavicular (3, 4c) i. Medial ii. Intermediate iii. Lateral. B. Deep branch: 1. Medial series— a. Communicating branches with i. Hypoglossal → 1, 2c ii. Vagus → 1.2c iii. Sympathetic → 1, 2, 3, 4c.

Fig. 2.29: Nerves adjacent to vertebral musculature

Head, Neck and Face  101



b. Muscular branches to— i. Rectus capitis lateralis → lc ii. Rectus capitis anterior → 1, 2c iii. Longus capitis → 1, 2, 3c iv. Longus colli → 2, 3, 4c v. Inferior root of ansa cervicalis → 2, 3c vi. Phrenic → 3, 4, 5c. 2. Lateral series— a. Communicating i. Accessory → 2, 3, 4c b. Muscular branches to i. Sternocleidomastoid → 2, (3)c ii. Trapezius → 3, 4c iii. Levator scapulae → 3, 4c iv. Saleneus medius → 3, 4c.

3

Superior Extremity CLAVIPECTORAL FASCIA

It is a strong fascia that occupies the interval between the clavicle above and

the pectoralis minor below. Note: In th is dissect ion t he clavipecto ral fa scia and th be prese rved.

I SKIN INCISIONS

e it, m ust

'

1. A longitudinal incision in the median pl~ from the jugular notch to the level of the 4th costal cartilagg. 2. A transverse incision along the clavicle from the jugular notch to the tip of the acromion.

( The 2nd incision should be very carefully given, so that the supra-clavicular nerves passing over the clavicle be not cut). Skin: Reflect the triangular flap of skin downwards and laterally.

Superficial fascia: