Textbook of Anatomy: Head, Neck and Brain, Volume III, 2e (PDF)

TEXTBOOK OF ANATOMY HEAD, NECK AND BRAIN This page intentionally left blank TEXTBOOK OF ANATOMY HEAD, NECK AND BRAIN Volume III Second Edition Vishram Singh, MS, PhD Professor and Head, Departmen...

TEXTBOOK OF ANATOMY HEAD, NECK AND BRAIN This page intentionally left blank TEXTBOOK OF ANATOMY HEAD, NECK AND BRAIN Volume III Second Edition Vishram Singh, MS, PhD Professor and Head, Department of Anatomy Professor-in-Charge, Medical Education Unit Santosh Medical College, Ghaziabad Editor-in-Chief, Journal of the Anatomical Society of India Member, Academic Council and Core Committee PhD Course, Santosh University Member, Editorial Board, Indian Journal of Otology Medicolegal Advisor, ICPS, India Consulting Editor, ABI, North Carolina, USA Formerly at: GSVM Medical College, Kanpur King George’s Medical College, Lucknow Al-Arab Medical University, Benghazi (Libya) All India Institute of Medical Sciences, New Delhi ELSEVIER A division of Reed Elsevier India Private Limited Textbook of Anatomy: Head, Neck and Brain, Volume III, 2e Vishram Singh © 2014 Reed Elsevier India Private Limited First edition 2009 Second edition 2014 All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the Publisher. This book and the individual contributions contained in it are protected under copyright by the Publisher (other than as may be noted herein). ISBN: 978-81-312-3727-4 e-book ISBN: 978-81-312-3627-7 Notices Knowledge and best practice in this field are constantly changing. As new research and experience broaden our understanding, changes in research methods, professional practices, or medical treatment may become necessary. Practitioners and researchers must always rely on their own experience and knowledge in evaluating and using any information, methods, compounds, or experiments described herein. In using such information or methods they should be mindful of their own safety and the safety of others, including parties for whom they have a professional responsibility. With respect to any drug or pharmaceutical products identified, readers are advised to check the most current information provided (i) on procedures featured or (ii) by the manufacturer of each product to be administered, to verify the recommended dose or formula, the method and duration of administration, and contraindications. It is the responsibility of practitioners, relying on their own experience and knowledge of their patients, to make diagnoses, to determine dosages and the best treatment for each individual patient, and to take all appropriate safety precautions. To the fullest extent of the law, neither the Publisher nor the authors, contributors, or editors, assume any liability for any injury and/or damage to persons or property as a matter of products liability, negligence or otherwise, or from any use or operation of any methods, products, instructions, or ideas contained in the material herein. Please consult full prescribing information before issuing prescription for any product mentioned in this publication. The Publisher Published by Reed Elsevier India Private Limited Registered Office: 305, Rohit House, 3 Tolstoy Marg, New Delhi-110 001 Corporate Office: 14th Floor, Building No. 10B, DLF Cyber City, Phase II, Gurgaon-122 002, Haryana, India Senior Project Manager-Education Solutions: Shabina Nasim Content Strategist: Dr Renu Rawat Project Coordinator: Goldy Bhatnagar Copy Editor: Shrayosee Dutta Senior Operations Manager: Sunil Kumar Production Manager: NC Pant Production Executive: Ravinder Sharma Graphic Designer: Milind Majgaonkar Typeset by Chitra Computers, New Delhi Printed and bound at Thomson Press India Ltd., Faridabad, Haryana  Dedicated to My Mother Late Smt Ganga Devi Singh Rajput an ever guiding force in my life for achieving knowledge through education My Wife Mrs Manorama Rani Singh for tolerating my preoccupation happily during the preparation of this book My Children Dr Rashi Singh and Dr Gaurav Singh for helping me in preparing the manuscript My Teachers Late Professor (Dr) AC Das for inspiring me to be multifaceted and innovative in life Professor (Dr) A Halim for imparting to me the art of good teaching My Students, Past and Present for appreciating my approach to teaching anatomy and transmitting the knowledge through this book This page intentionally left blank  Preface to the Second Edition It is with great pleasure that I express my gratitude to all students and teachers who appreciated, used, and recommended the first edition of this book. It is because of their support that the book was reprinted three times since its first publication in 2009. The huge success of this book reflects appeal of its clear, unclustered presentation of the anatomical text supplemented by perfect simple line diagrams, which could be easily drawn by students in the exam and clinical correlations providing the anatomical, embryological, and genetic basis of clinical conditions seen in day-to-day life in clinical practice. Based on a large number of suggestions from students and fellow academicians, the text has been extensively revised. Many new line diagrams and halftone figures have been added and earlier diagrams have been updated. I greatly appreciate the constructive suggestions that I received from past and present students and colleagues for improvement of the content of this book. I do not claim to absolute originality of the text and figures other than the new mode of presentation and expression. Once again, I whole heartedly thank students, teachers, and fellow anatomists for inspiring me to carry out the revision. I sincerely hope that they will find this edition more interesting and useful than the previous one. I would highly appreciate comments and suggestions from students and teachers for further improvement of this book. “To learn from previous experience and change accordingly, makes you a successful man.” Vishram Singh This page intentionally left blank  Preface to the First Edition This textbook on head, neck and brain has been carefully planned for the first year MBBS and Dental students. It follows the revised anatomy curriculum of the Medical Council of India. It also meets the standards of dental curriculum of the Dental Council of India. Following the current trends of clinically-oriented study of Anatomy, I have adopted a parallel approach – that of imparting basic anatomical knowledge to students and simultaneously providing them its applied aspects. To help students score high in examinations the text is written in simple language. It is arranged in easily understandable small sections. Conforming to the anatomy curriculum and pattern of examination, major portion of the book has been devoted to head and neck anatomy while for brain only essential aspects are included; for detailed description of brain students can refer to the author’s Textbook of Clinical Neuroanatomy. While anatomical details of little clinical relevance, phylogenetic discussions and comparative analogies have been omitted, all clinically important topics are described in detail. Brief accounts of histological features and developmental aspects have been given only where they aid in understanding of gross form and function of organs and appearance of common congenital anomalies. The tables and flowcharts summarize important and complex information into digestible knowledge capsules. Multiple choice questions have been given chapter-by-chapter at the end of the book to test the level of understanding and memory recall of the students. The numerous simple 4-color illustrations further assist in fast comprehension and retention of complicated information. All the illustrations are drawn by the author himself to ensure accuracy. Throughout the preparation of this book one thing I have kept in mind is that anatomical knowledge is required by clinicians and surgeons for physical examination, diagnostic tests, and surgical procedures. Therefore, topographical anatomy relevant to diagnostic and surgical procedures is clinically correlated throughout the text. Further, Clinical Case Study is provided at the end of each chapter for problem-based learning (PBL) so that the students could use their anatomical knowledge in clinical situations. Moreover, the information is arranged regionally since while assessing lesions and performing surgical procedures, the clinicians encounter region-based anatomical features. Due to propensity of lesions of oral cavity and cranial nerves there is in-depth discussion on oral cavity and cranial nerves. As a teacher, I have tried my best to make the book easy to understand and interesting to read. For further improvement of this book I would greatly welcome comments and suggestions from the readers. Vishram Singh This page intentionally left blank  Acknowledgments At the outset, I express my gratitude to Dr P Mahalingam, CMD; Dr Sharmila Anand, DMD; and Dr Ashwyn Anand, CEO, Santosh University, Ghaziabad, for providing an appropriate academic atmosphere in the university and encouragement which helped me in preparing this book. I am also thankful to Dr Usha Dhar, Dean Santosh Medical College for her cooperation. I highly appreciate the good gesture shown by Dr Ruchira Sethi, Dr Deepa Singh, and Dr Preeti Srivastava for checking the final proofs. I sincerely thank my colleagues in the Department, especially Professor Nisha Kaul and Dr Ruchira Sethi for their assistance. I gratefully acknowledge the feedback and support of fellow colleagues in Anatomy, particularly,  Professors AK Srivastava (Head of the Department) and PK Sharma, and Dr Punita Manik, King George’s Medical College, Lucknow.  Professor NC Goel (Head of the Department), Hind Institute of Medical Sciences, Barabanki, Lucknow.  Professor Kuldeep Singh Sood (Head of the Department), SGT Medical College, Budhera, Gurgaon, Haryana.  Professor Poonam Kharb, Sharda Medical College, Greater Noida, UP.  Professor TC Singel (Head of the Department), MP Shah Medical College, Jamnagar, Gujarat.  Professor TS Roy (Head of the Department), AIIMS, New Delhi.  Professors RK Suri (Head of the Department), Gayatri Rath, and Dr Hitendra Loh, Vardhman Mahavir Medical College and Safdarjang Hospital, New Delhi.  Professor Veena Bharihoke (Head of the Department), Rama Medical College, Hapur, Ghaziabad.  Professors SL Jethani (Dean and Head of the Department), and RK Rohtagi, Dr Deepa Singh and Dr Akshya Dubey, Himalayan Institute of Medical Sciences, Jolly Grant, Dehradun.  Professors Anita Tuli (Head of the Department), Shipra Paul, and Shashi Raheja, Lady Harding Medical College, New Delhi.  Professor SD Joshi (Dean and Head of the Department), Sri Aurobindo Institute of Medical Sciences, Indore, MP. Lastly, I eulogize the patience of my wife Mrs Manorama Rani Singh, daughter Dr Rashi Singh, and son Dr Gaurav Singh for helping me in the preparation of this manuscript. I would also like to acknowledge with gratitude and pay my regards to my teachers Prof AC Das and Prof A Halim and other renowned anatomists of India, viz. Prof Shamer Singh, Prof Inderbir Singh, Prof Mahdi Hasan, Prof AK Dutta, Prof Inder Bhargava, etc. who inspired me during my student life. I gratefully acknowledge the help and cooperation received from the staff of Elsevier, a division of Reed Elsevier India Pvt. Ltd., especially Ganesh Venkatesan (Director Editorial and Publishing Operations), Shabina Nasim (Senior Project Manager- Education Solutions), Goldy Bhatnagar (Project Coordinator), and Shrayosee Dutta (Copy Editor). Vishram Singh This page intentionally left blank  Contents Preface to the Second Edition vii Preface to the First Edition ix Acknowledgments xi Chapter 1 Living Anatomy of the Head and Neck 1 Chapter 2 Osteology of the Head and Neck 12 Chapter 3 Scalp, Temple, and Face 46 Chapter 4 Skin, Superficial Fascia, and Deep Fascia of the Neck 68 Chapter 5 Side of the Neck 77 Chapter 6 Anterior Region of the Neck 86 Chapter 7 Back of the Neck and Cervical Spinal Column 96 Chapter 8 Parotid Region 111 Chapter 9 Submandibular Region 119 Chapter 10 Infratemporal Fossa, Temporomandibular Joint, and Pterygopalatine Fossa 133 Chapter 11 Thyroid and Parathyroid Glands, Trachea, and Esophagus 156 Chapter 12 Pre- and Paravertebral Regions and Root of the Neck 168 Chapter 13 Oral Cavity 180 Chapter 14 Pharynx and Palate 199 Chapter 15 Larynx 218 Chapter 16 Blood Supply and Lymphatic Drainage of the Head and Neck 231 Chapter 17 Nose and Paranasal Air Sinuses 251 Chapter 18 Ear 265 xiv Contents Chapter 19 Orbit and Eyeball 282 Chapter 20 Vertebral Canal and Its Contents 302 Chapter 21 Cranial Cavity 315 Chapter 22 Cranial Nerves 333 Chapter 23 General Plan and Membranes of the Brain 353 Chapter 24 Brainstem 363 Chapter 25 Cerebellum and Fourth Ventricle 375 Chapter 26 Diencephalon and Third Ventricle 382 Chapter 27 Cerebrum 389 Chapter 28 Basal Nuclei and Limbic System 399 Chapter 29 Blood Supply of the Brain 405 Multiple Choice Questions 413 Index 435  CHAPTER 1 Living Anatomy of the Head and Neck HEAD C F The head is the globular cranial end of the body, which contains brain and special sense organs, viz. eyes for vision, ears for hearing and equilibrium, nose for smell, and tongue Dog for taste. It also provides openings for the respiratory and digestive systems. Structurally and developmentally, the head C is divided into two parts: cranium and face. F The cranium (also known as braincase) contains the brain. The face possesses openings of eyes, nose, and mouth. A little description of comparative anatomy makes the distinction between the size of cranium and face easier to Monkey understand. The sense of smell is one of the oldest sensibilities. The C pronograde canines (e.g., dog) are guided predominantly by smell for searching food and sex. The other senses, such as F touch, hearing, and vision play an accessory role. Therefore, they have well-developed snout, and, their face is located in front of the cranium (Fig. 1.1). The arboreal mode of life of apes and monkeys favored Man the higher development of visual, acoustic, tactile, kinesthetic, and motor functions with improvement in Fig. 1.1 Change in position of face in relation to cranium their intelligence. In these animals, usefulness of the nose during evolution. The face is located in front of cranium in was lost and sense of smell became an accessory sense. dog, below and in front of cranium in monkey and below the anterior part of cranium in man. Note that the size of jaws is Consequently in orthograde monkeys, it resulted in the loss inversely proportional to the size of cranium (C = cranium, of the projecting snout, and there face is located below and F = face). in front of the cranium. The supremacy of man in animal kingdom is due to his large well-developed brain, which provides him the reduction in the size of jaws occurred due to change in eating unlimited power of thinking, reasoning, and judgement. To habits of these animals. The jaws are smallest in man because accommodate large brain, the size of cranium has also he prefers to eat soft cooked food. The size of jaws is larger in increased proportionately. Consequently, in plantigrade canines because they use it for holding, breaking, biting, man the forehead is prominent and the face is located tearing, and chewing the food. With receding jaws, the below the anterior part of the cranium. mouth is proportionately reduced in size. It is important to note that size of jaws is inversely In man, eyes are placed in more frontal plane to enable proportional to the size of cranium. Thus the pronograde stereoscopic vision. To permit freedom of mobility to the canine has larger jaws; an orthograde monkey has smaller tongue for a well-articulated speech in man, the alveolar jaws whereas plantigrade man has smallest jaws. The arches are broadened and the chin is pushed forward, making 2 Textbook of Anatomy: Head, Neck, and Brain the mouth cavity more roomy. The prominent chin is a arch. It is more prominent in adult males. The smooth non- characteristic feature of human beings. The distinctive hairy elevated area between the eyebrows is called glabella, external nose with prominent dorsum, tip, and alae is which tends to be flat in children and adult females, and characteristic of a man, although it has nothing to do with forms a rounded prominence in adult males. Indian married the sense of smell. Probably it serves to protect the eyes from Hindu females apply bindi at this site to enhance their beauty. injuries. The brow ridges are markedly reduced in man as It is important to note that the pineal gland lies about 7 cm compared to other primates due to their prominent forehead. behind the glabella. The prominence of forehead, the frontal eminence is evident on either side above the eyebrow. The LIVING ANATOMY frontal prominence is typically more pronounced in children and adult females. The living anatomy deals with the examination of surface features by visualization (inspection) and palpation of the PARIETAL REGION living individuals to get information about the deeper It is an area limited anteriorly by hair line and posteriorly by structures. It is of immense importance in clinical examination a coronal plane behind the parietal eminences and on either of the patients. The study of living anatomy (also called living side by the temporal line. The parietal eminence can be felt or surface anatomy) of head and neck begins with the division on either side in this region about 2 inches above the auricle. of the surface into regions and examining surface landmarks The parietal prominences are evident on or just in front of in each region. The students are advised to practice finding the interauricular line. these landmarks in each region on themselves or on their colleagues to develop the skill of examination. OCCIPITAL REGION REGIONS OF THE HEAD The occipital region is an area of cranium behind the parietal eminences, and above the external occipital protuberance The head is divided into the following regions: frontal, and superior nuchal lines. parietal, occipital, temporal, auricular, parotid, orbital, nasal, The most prominent point in the occipital region is zygomatic, buccal, oral, and mental (Fig. 1.2). called opisthocranion or occiput. The external occipital protuberance can be felt in the median line just above the FRONTAL REGION (FOREHEAD) nuchal furrow. The superior nuchal line, one on either side of external occipital protuberance, runs laterally with its The frontal region of the head is an area superior to the eyes convexity facing upwards. and below the hair line. Eyebrows are the raised arches of The soft tissue covering frontal, parietal, and occipital skin with short, thick hairs above the supraorbital margins. regions forms the scalp. Just deep to eyebrow is the curved bony ridge or superciliary Clinical correlation Parietal region Hair line The large area of scalp over the vault of skull is thickly Frontal region covered by terminal hair. Due to presence of hair, many lesions in this area remain unnoticed by both clinicians and patients. Hence, this area should be carefully examined by Orbital region Parietal the clinicians. Nasal region eminence Temporal Infraorbital region on region regi Auricular om atic Oral region TEMPORAL REGION (TEMPLE) Zyg region Buccal The temporal region is the area on the side of skull between region Mental region Occipital the temporal line and zygomatic arch (Fig. 1.3). It is the site region of attachment of temporalis muscle, which can be palpated Parotid when the teeth are clenched repeatedly. Try on yourself. Soft region tissue in the temporal region includes skin, subcutaneous tissue, temporal fascia, and temporalis muscle. In the anterior part of temporal region, deep to soft tissues is a small area where four bones meet the pterion (Fig. 1.3). This region is clinically important because it is the site of entrance to Fig. 1.2 Regions of the head. cranial cavity in craniotomy to remove the extradural  Living Anatomy of the Head and Neck 3 Temporal line The lobule is approximately at the level of the apex of the nose. The portion of the auricle anterior to the external auditory meatus is a small nodular flap of tissue called tragus. It projects posteriorly, partially covering and protecting the Pterion external auditory meatus. The condyle of mandible can be Asterion palpated by putting the tip of finger just in front of tragus External Zygomatic and then opening and closing the mouth. occipital Another flap of tissue opposite the tragus is the antitra- arch protuberance gus. Between the tragus and antitragus is a deep notch called Mastoid intertragic notch. process Angle of Mental A semicircular ridge anterior to the helix is called Head of protuberance antihelix. mandible mandible (gonion) The upper end of antihelix divides into two crura enclosing a triangular depression called triangular fossa. The Fig. 1.3 Surface landmarks on the lateral aspect of the head. depressed hollow of the auricle is called concha. hematoma. Pterion is described in detail on page 18. The The upper end of the helix which extends backwards to temporal region (temple) is described in detail on page 50. some extent into concha is called crux of helix. AURICULAR REGION Clinical correlation The auricular region includes fleshy oval flap of the ear The external auditory meatus and tragus are important (auricle) and external acoustic meatus. landmarks to use when taking extraoral radiographs and The auricle collects the sound waves. The external administering local anesthesia on a patient. The pulsations auditory meatus is a tube through which sound waves are of superficial temporal artery can be felt by putting the fingertip just in front and above the tragus on the root of transmitted to the middle ear within the skull. Observe the zygoma. following surface features of the auricle (Fig. 1.4). The superior and posterior free margins of the auricle forming a kind of rim are called helix, which ends inferiorly PAROTID REGION at the fleshy protuberance of the ear called ear lobule. The upper end of the helix is typically at the level of the As the name implies, it is region around the ear (para = eyebrows and the glabella. around; otic = ear). It is limited in front by anterior border Crura of antihelix Scaphoid fossa Triangular fossa Darwin’s tubercle Crus of helix Helix Cymba External acoustic conchae meatus Antihelix Tragus Concha Lobule Intertragic notch Antitragus A B Fig. 1.4 Lateral view of right auricle: A, schematic figure; B, actual picture. 4 Textbook of Anatomy: Head, Neck, and Brain of masseter, behind by mastoid process and below by line Glabella Frontal extending from angle of mandible to the tip of mastoid prominence process. This region is occupied by parotid gland. The Superciliary Eyebrow mastoid process lies behind the lower part of the ear. Its arch Supraorbital anterior border, tip and posterior border can be easily felt. Frontozygomatic notch suture The masseter overlies the ramus of the mandible. It can be Nasion felt when the teeth are clenched. Bridge of nose Infraorbital Infraorbital foramen Clinical correlation margin Nostril (or nare) Ala of nose Angle of mouth The parotid gland is often enlarged following infection by Tip of nose Mental foramen mumps virus. This produces a painful swelling in the parotid region elevating the ear lobule. The parotid gland is also the site of slow growing painless tumor called mixed parotid tumor. Fig. 1.6 Surface landmarks on frontal aspect of the head. ORBITAL (OCULAR) REGION The outer corner where the upper and lower eyelids meet is called lateral (outer) canthus. The inner corner where the The ocular region includes the eyeball and associated struc- two eyelids meet is called medial canthus. A fleshy pinkish tures. Most of the surface features of the ocular region pro- elevation in the medial angle of the eye is called lacrimal tect the eye (Fig. 1.5). Eyebrow is a ridge of hair along the caruncle. superciliary arch above the orbit, which protects the eyes Palpate the following landmarks in this region (Fig. 1.6) against sunlight and mechanical blow. The two movable eye- in yourself: lids reflexly close to protect eyes from foreign particles and bright sunlight (for details on eyelids see Chapter 3). The 1. Supraorbital notch on the highest point of supraorbital eyelashes are a row of hair at the margins of eyelids. The eye- margin about 2.5 cm from the midline. lashes prevent airborne objects from contacting the eyeball. 2. Frontozygomatic suture, which is marked by a slight Behind the lateral part of the upper eyelid and within the irregular depression on the lateral orbital margin. orbit is the lacrimal gland, which produces lacrimal fluid or tears. The tears wash away chemical and foreign particles and Clinical correlation lubricate the front of the eye to prevent the surface of the eyeball, particularly the all-important cornea from drying. The condition of the eyes profoundly affects the facial The conjunctiva is a delicate thin mucous membrane appearance. Lesions affecting the eye and its associated structures are enormous. A few easily recognizable and which lines the inner surface of the eyelids and the front of surgically relevant conditions are as follows: the eyeball. It aids in reducing friction during blinking. Arcus senilis, a white rim around the outer edge of the iris, The sclera, the ‘white’ of the eye is seen on either side of is commonly seen in elderly people. It occurs due to cornea. sclerosis and deposition of cholesterol in the edge of the The cornea is the circular transparent anterior portion of cornea. the eyeball. Xanthelasma are fatty plaques in the skin of the eyelids. They look like masses of yellow opaque fat. If multiple and Eyebrow growing, they indicate underlying abnormality of choles- Upper eyelid terol metabolism, diabetes, or arterial disease. Exophthalmos is a forward protrusion of the eyeball from its normal position in the orbit. The commonest cause of both bilateral and unilateral exophthalmos is thyrotoxico- Lacrimal gland sis (hyperthyroidism). Cilia Ectropion is the eversion of the lower eyelid. Lateral canthus Medial canthus NASAL REGION Sclera Lacrimal Pupil The main feature of nasal region is the external nose. It is a caruncle Iris Lower eyelid pyramidal projection in the middle third of the face with its root up and base downwards (Fig. 1.6). The root of the nose Fig. 1.5 Frontal view of the left eye. is located between the eyes inferior to glabella. The firm  Living Anatomy of the Head and Neck 5 narrow bony portion below the nasion is the bridge of the The zygomatic arch extends from just inferior to lateral nose. The nose below this level has pliable cartilaginous margin of the eye towards the upper portion of the auricle. framework that maintains the openings of the nose. The tip Inferior to the zygomatic arch and just anterior to the tragus of the nose is called apex. It is flexible when palpated because of the ear is the temporomandibular joint. The zygomatic it is made up of cartilage. Inferolateral to the apex on either arch is bony bridge that spans the interval between the ear side is a nostril (or nare). The nostrils are separated from and the eye. The zygomatic bone forms the bony prominence each other by a midline nasal septum. The nares are bounded of the cheek below and lateral to the orbit. laterally by wing-like alae of the nose. The alae of nose forms The movements of the temporomandibular joint can be the flared outer margin of each nostril. felt by opening and closing the mouth or moving the lower The distinctive external nose with exuberant growth of jaw from side to side. One way to feel the movements of head cartilages forming prominent dorsum, tip, and alae is a of mandible is to gently place a finger into the outer portion characteristic feature of human beings. of the external auditory meatus. A well-marked depression at the root of the nose is called nasion. BUCCAL REGION The buccal region of face is a broad area of the face between Clinical correlation the nose, mouth, and parotid region. It overlies the buccina- Saddle nose: A nose whose bridge is depressed and tor muscle. It is made of soft tissues of the cheek. widened. The pulsations of facial artery can be felt about 1.25 cm Rhinophyma: The nasal skin covering the alar cartilages lateral to the angle of the mouth. is thick and adherent, and contains many sebaceous glands. The hypertrophy and adenomatous changes of ORAL REGION these glands gives rise to a lobulated tumor called rhinophyma. The structures of the oral region include fleshy upper and lower lips, and the structures of oral cavity that can be observed when the mouth is widely open. INFRAORBITAL REGION The lips are chiefly composed of muscles covered exter- The infraorbital region of head is located below the orbital nally by skin and internally by mucous membrane. Each lip region and corresponds to the upper part of the anterior has a pinkish zone called vermillion zone. The lips are out- surface of the maxilla. The infraorbital foramen is located in lined from the surrounding skin by a transition zone called this region about 1 cm below the infraorbital margin in line vermillion border. The small triangular median depression in with the supraorbital notch or foramen (Fig. 1.6). The the upper lip is called philtrum. The apex of philtrum is knowledge of its location is important for giving infraorbital towards the nasal septum and the base downwards where it nerve block. terminates in a thicker area called tubercle of the upper lip. The corners of mouth where upper and lower lips meet are called labial commissure. The groove running upward ZYGOMATIC REGION between the labial commissure and the alae of nose is called The zygomatic region overlies the zygomatic (cheek) bone nasolabial sulcus. The lower lip is separated from the chin by and zygomatic arch. a horizontal groove called labiomental groove (Fig. 1.7). Nasolabial sulcus Vermillion border Philtrum Vermillion zone Upper lip Labial Lower lip commissure Tubercle of upper lip Mental protuberance (mentum) Labiomental A groove B Fig. 1.7 Frontal view of the lips: A, schematic figure; B, actual picture. 6 Textbook of Anatomy: Head, Neck, and Brain Clinical correlation The color of the lips and the mucus membrane of the oral cavity are clinically important; lips may appear pale in patients with severe anemia or bluish in people suffering Uvula from lack of oxygenation of blood (cyanosis). A lemon yellow tint of lips may indicate jaundice. The lips are a common site for carcinoma, mostly affecting Palatopharyngeal arch individuals above 60 years of age. Carcinoma of the lip usually occurs in lower lip (93%) as compared to the upper Palatoglossal arch lip (5%). Palatine tonsil The bone underlying the upper lip is the alveolar process of the maxilla, whereas the bone underlying the lower lip is Posterior wall of the alveolar process of the mandible. The alveolar processes pharynx contain teeth and are called maxillary and mandibular teeth. Tongue MENTAL REGION The mental region is an area of face below the lower lip and is characterized by the presence of mental protuberance or mentum, a privileged feature of human beings (Fig. 1.7). Fig. 1.8 Features of the oral cavity and oropharynx. Important bony landmarks in the region of the head are summarized in Table 1.1.  The part of oral cavity inside the alveolar arches is called Examine the following structures of oral cavity by asking oral cavity proper. It contains a mobile muscular organ, your friend to open his mouth widely (Fig. 1.8). the tongue. Table 1.1 Bony landmarks in the region of head Landmark Location Mental protuberance/ Protuberance of the chin mentum Nasion Depression at the root of nose at the junction of frontonasal and internasal sutures Glabella Smooth non-hairy area between the eyebrows above nasion Vertex Highest point on the top of head in the midline External occipital Knob-like bony projection at the upper end of nuchal furrow protuberance Inion Apex of external occipital protuberance Gonion Angle of mandible Head of mandible In front of lower part of the tragus Preauricular point In front of upper part of the tragus Mastoid process Behind the lower part of the auricle Pterion 4 cm above the midpoint of zygomatic arch/3.5 cm behind and 1.5 cm above the frontozygomatic suture Asterion Depression—2.5 cm behind the upper part of the root of ear Supraorbital notch/foramen On the supraorbital margin 2.5 cm from midline Infraorbital foramen 1 cm below infraorbital margin and 1.25 cm lateral to the side of nose Mental foramen 2.5 cm lateral to symphysis menti and 1.25 cm above the lower border of mandible Frontal prominence Area of maximum convexity on either side of forehead where top, front and side of head meet Parietal prominence Area of maximum convexity on either side in the parietal region where back, top and side of head meet (Area of maximum transverse diameter of the skull)  Living Anatomy of the Head and Neck 7  The oral cavity is lined by a mucus membrane or mucosa. Skin The inner aspects of the lips are lined by pink and thick Superficial fascia Trachea labial mucosa. The labial mucosa is continuous with the Investing layer of equally pink and thick buccal mucosa that lines the inner Esophagus deep cervical fascia cheek. Common Pretracheal  The space between cheek/lip and gum is called vestibule. fascia carotid artery  On the inner aspect of buccal mucosa opposite the upper Internal Sternocleido- mastoid second molar tooth is a small elevation called parotid jugular vein papilla on which opens the parotid duct. Anterior Prevertebral  The gingiva is a part of oral mucosa that covers the fascia compartment alveolar processes of the jaws. (visceral compartment) Trapezius  The roof of oral cavity which presents two portions: (a) a firm anterior portion is called hard palate and a flexible Posterior compartment posterior portion is called soft palate. A cone-shaped projection hanging down from the middle of the posterior free margin is called uvula of the palate, which is Fig. 1.9 The basic plan of the neck in cross section. continuous with palatopharyngeal arch on each side. Note the location of anterior and posterior compartments.  A dense pad of soft tissue behind the last molar tooth is called retromolar pad. trapezius muscles in its course around the neck. The two  The floor of mouth is located inferior to the ventral fascial layers (called pretracheal and prevertebral fasciae) surface of the tongue. extending from the investing layer of deep fascia across the structures within the neck divide the neck into anterior and N.B. The oral cavity provides entrance into the throat or the posterior compartments (Fig. 1.9). pharynx. Topographically, the structures of the neck are organized One can easily examine the following features in the into anterior and posterior compartments. oropharynx (Fig. 1.8): 1. A curved, leaf-like flap of cartilage is located behind the ANTERIOR COMPARTMENT base of tongue and in front of oropharynx. It is epiglottis, the cartilage of the larynx. The basic topography of the anterior compartment is simple 2. Mass of lymphoid tissue projecting on either side into the (Fig. 1.10). In the midline there are two tubes: the respiratory lateral wall of the oropharynx is called palatine tonsil tract (larynx and trachea) in front and digestive tract (Fig. 1.8). The palatine tonsils are generally called tonsils (pharynx and esophagus) behind. The thyroid gland clasps by the patients. The tonsil lies in triangular fossa called the front and sides of the larynx and trachea and overlaps the tonsillar fossa located between the palatoglossal and carotid tree on either side. These structures are bounded palatopharyngeal arches. Note that the tonsils lie anteriorly by pretracheal fascia, which extends on either side opposite the angle of mandible between the back of to merge with the investing layer of deep cervical fascia deep tongue and soft palate. to sternocleidomastoid. On either side of the midline tubes are several ascending and descending neurovascular structures, such as carotid NECK tree consisting of common carotid, internal carotid and external carotid arteries, internal jugular vein and last four The neck is approximately a cylindrical region of the body cranial nerves. At the upper end these structures enter or that connects the head to the trunk. It supports and permit leave the skull through various foramina in the base of the the movements of the head. skull, viz. foramen ovale, foramen spinosum, carotid canal, and jugular foramen. TOPOGRAPHICAL ORGANIZATION OF THE NECK The neck is flexible and provides passage to several POSTERIOR COMPARTMENT structures such as spinal cord, trachea, esophagus, blood The posterior compartment of neck consists of cervical part vessels supplying the brain, the last four cranial nerves, etc. of vertebral column and its surrounding musculature All these structures are essential for the sustenance of life. (Fig. 1.10). This musculoskeletal block is bounded by The investing layer of deep cervical fascia encloses the prevertebral fascia, which merges behind on either side with neck like a collar. It splits to enclose sternocleidomastoid and the deep fascia enclosing the trapezius muscle. The 8 Textbook of Anatomy: Head, Neck, and Brain Thyroid gland Respiratory tract Sternocleidomastoid Anterior compartment Digestive tract Parathyroid gland Common carotid artery Internal jugular vein C Vagus nerve Cervical sympathetic chain Prevertebral muscles Posterior S Scalene muscles compartment Root of cervical nerve Muscles of back Trapezius Fig. 1.10 Cross section of the neck showing anatomical details (S = spinal cord, C = cervical vertebra). musculature includes: (a) prevertebral muscles located in front of the cervical column, (b) scalene muscles extending between the neck and upper two ribs, and (c) muscles of the back of the neck. The vertebral canal within the cervical vertebral column provides passage to the spinal cord. The roots of cervical spinal nerves come out through intervertebral foramina in Hyoid bone this region. The ventral rami of the first four cervical nerves form the cervical plexus and ventral rami of the lower four Ventral rami cervical nerves along with ventral ramus of T1 form the of cervical brachial plexus. Midline tubes plexus The neck, therefore, is a complex region of the body. The Neurovascular spinal cord, digestive and respiratory tracts, and major blood structures vessels traverse this highly flexible area. The neural structures present in the region include: last four cranial nerves and Brachial plexus cervical and brachial plexuses. Several organs are also located here. The musculature of neck produces an array of move- Thyroid gland ments in this area. The layout of these structures is depicted in Figure 1.11 to understand the typography of the neck. Fig. 1.11 Basic layout of structures of the neck. N.B. A newborn baby has no visible neck because his or her lower jaw and chin touches the shoulders and thorax. and trachea) tracts, vessels to and from the head, last four cranial nerves, and thyroid and parathyroid glands. REGIONS OF THE NECK The following structures can be easily palpated in the anterior region of the neck. The neck is divided into the four regions: In the midline (Fig. 1.12): 1. Anterior region. 1. Hyoid bone: It is situated in a depression behind and 2. Right lateral region. slightly below the chin and can be easily felt if the neck is 3. Left lateral region. slightly extended. The hyoid bone can be gripped 4. Posterior region (nucha). between the thumb and index finger and moved from side to side. ANTERIOR REGION (CERVIX) 2. Thyroid cartilage: It is the most prominent feature in The anterior region of the neck contains strap muscles, the anterior region of the neck, particularly the anterior digestive (pharynx and esophagus) and respiratory (larynx angle formed by the fusion of its two laminae which  Living Anatomy of the Head and Neck 9 form the laryngeal prominence. It is prominent in males and called Adam’s apple whereas in females it is not usually apparent. The thyroid notch, the curved upper Transverse process of atlas vertebra border of the thyroid cartilage can be easily palpated. Angle of mandible 3. Cricoid cartilage: It can be easily palpated below the Mastoid process thyroid cartilage. 4. Tracheal rings: These can be palpated below the cricoid Hyoid bone cartilage by pressing gently backwards above the jugular Sternocleido- notch. mastoid Thyroid cartilage 5. Isthmus of the thyroid gland: It lies on the front of the Trapezius Cricoid cartilage 2nd, 3rd, and 4th tracheal rings and can be palpated. 6. Suprasternal (jugular) notch: It is a depression just Isthmus of superior to sternum between the medial expanded ends thyroid gland of the clavicle and can be easily palpated. Tracheal rings The vertebral levels of some of the structures that can be Clavicle Suprasternal notch palpated in the anterior midline of the neck are given in Table 1.2. Fig. 1.12 Surface landmarks in the anterior median and lateral regions of the neck. Table 1.2 Vertebral levels of structures in the anterior midline of the neck 2. Clavicle: It is easily visible in thin people and palpable Structure Vertebral level along its entire extent except in morbidly obese persons Hyoid bone C3 because it is subcutaneous throughout. 3. Sternocleidomastoid: It can be palpated along its entire Upper border and notch of C3/C4 length. When the head is turned to the opposite side it thyroid cartilage forms a prominent raised ridge that extends diagonally Thyroid cartilage C4–C5 from mastoid process to sternum. The tendon of this Cricoid cartilage C6 muscle becomes especially prominent to the side of the Suprasternal notch T2/T3 jugular notch. 4. Trapezius: The anterior border of trapezius becomes prominent when the person is asked to shrug his On either side of the midline (Fig. 1.12): shoulder against the resistance. 1. Thyroid lobe: It can be palpated on either side just below 5. External jugular vein: It can be seen as it crosses the level of cricoid cartilage. obliquely across the sternocleidomastoid muscle, 2. Common carotid artery: It can be observed and particularly if a person is angry or if the collar of his palpated on either side at the level of junction between shirt is too tight. the larynx and trachea along the anterior border of 6. Transverse process of the atlas vertebra: It can be felt on sternocleido-mastoid muscle. deep pressure midway between the angle of the mandible The common carotid artery can be compressed against and the mastoid process. the prominent anterior tubercle of transverse process of the 6th cervical vertebra called carotid tubercle (Chassaignac’s Clinical correlation tubercle). Cervical lymph nodes in the lateral region of the neck often become swollen and painful from infections of the oral and RIGHT AND LEFT LATERAL REGIONS pharyngeal regions. (RIGHT AND LEFT SIDES OF THE NECK) The lateral regions on either side are composed of two large POSTERIOR REGION (OR NUCHA) superficial muscles of the neck and cervical lymph nodes. The following structures can be palpated in the lateral The posterior region of neck includes cervical vertebral region: column, spinal cord, and associated structures. 1. Mastoid process: It can be easily felt behind the lower The following structures can be palpated in the posterior part of the auricle. region of the neck (Fig. 1.13). 10 Textbook of Anatomy: Head, Neck, and Brain Sternocleidomastoid muscle External occipital protuberance Posterior cervical triangle Anterior Superior cervical triangle nuchal line Inion Nuchal furrow Fig. 1.14 Location of the anterior and posterior cervical triangles of the neck. Spine of 7th cervical vertebra 4. Ligamentum nuchae: It is raised when the neck is flexed and extends from spine of C7 vertebra below to the external occipital protuberance above. Fig. 1.13 Surface landmarks in the posterior region of the neck. Clinical correlation Clinically, the posterior region of neck is extremely important 1. External occipital protuberance: It can be easily because of the debilitating damage it sustains from whiplash palpated with inion at its summit at the upper end of injury or a broken neck. nuchal furrow in the posterior midline of the neck. 2. Superior nuchal line: It can sometimes be palpated as a curved bony line with concavity below extending TRIANGLES OF THE NECK from external occipital protuberance to the mastoid process. The neck is conventionally divided into various triangles. 3. Spine of 7th cervical vertebra (vertebra prominence): It The sternocleidomastoid muscle transects the side of neck can be felt at the lower end of nuchal furrow especially obliquely on each side and divides it into anterior and when the neck is flexed. posterior cervical triangles (Fig. 1.14).  Living Anatomy of the Head and Neck 11 Golden Facts to Remember " Most expressive feature of the face Eyes " Most projecting part of the face Nose " Most important surface landmark of head which Pterion can neither be seen nor palpated " Stiles’ method of locating pterion Place the thumb behind the frontal process of zygomatic bone and two fingers above the zygomatic arch. The angle between the thumb and upper finger lies on pterion " Most important surface landmark in the region of Cricoid cartilage neck " Most prominent feature on the front of neck in Laryngeal prominence/Adam’s apple the midline " Chief characterizing facial feature of man Nose Clinical Case Study A 20-year-old medical student went to a hill station on every case of head injury, and gives a good initial his motorbike to enjoy his summer vacation. After indication of the degree of brain damage. enjoying his holidays, while returning home his bike hit a rock and overturned. He became unconscious. He was Table C1 Glasgow coma scale (GCS) rescued and taken to a nearby hospital by some tourists. Function tested Response Score The attending physician first assessed the level of his consciousness using Glasgow coma scale. He regained Eye opening Spontaneous 4 To verbal command 3 consciousness by the time he was examined in the hos- To pain 2 pital. He had superficial wounds in the temporal region No response 1 of his head but had no other obvious injures. Radiographs of his skull were taken, which did not Best verbal Oriented and converses 5 reveal any fracture or hematoma. He was discharged response Disoriented and converses 4 from the hospital one hour after being given first-aid. Inappropriate words 3 Incomprehensible sounds 2 Questions No response 1 1. Enumerate any four regions in cranial part of the Best motor Obeys verbal commands 6 head? response Localizes pain 5 2. What is ‘Glasgow coma scale’? Flexes normally 4 3. What are the boundaries of temporal region? Flexes abnormally 3 Extends 2 Answers No response 1 1. (a) Frontal region, (b) parietal region, (c) temporal region, and (d) occipital region. Total score ranges from 3 to 15 when the full 2. It is a scale used to record the level of consciousness scale is used. by testing certain functions and seeing their 3. The temporal region is bounded above by temporal response. The baseline observation of this sort line and below by zygomatic arch. form an important first step in the assessment of  CHAPTER 2 Osteology of the Head and Neck The study of osteology (bony skeleton) of head and neck Parts of the Skull (Fig. 2.1) forms the basis to understand this region. The skeleton of The skull is subdivided into two parts: head and neck consists of skull, cervical vertebrae, and hyoid 1 An upper dome-shaped part which covers the cranial bone. The students should study the skull and cervical cavity containing brain is called cranial vault/calvaria/ vertebrae thoroughly relating their main features to the bony brain box. It is attached to the skull base below. The points which can be felt in a living individual. The calvaria along with skull base is called cranial skeleton/ prominences and depressions on the bony surface are cranium. landmarks for attachments of the muscles, tendons, and ligaments. The openings in the bone are also landmarks 2. A lower anterior part is called facial skeleton, which where various nerves and blood vessels enter or exit. includes mandible. The cranium (cranial skeleton) is a strong and rigid SKULL container for the brain, while the facial skeleton is a rather fragile and light basis for face. The facial skeleton The bony skeleton of the head is termed skull. It consists of lies below the anterior part of the cranium in human 22 bones excluding ear ossicles. Except mandible (bone of beings. lower jaw), all the bones of skull, joined together by sutures, Many anatomists use alternative terms, neurocranium for are immobile and form the cranium. However, the two terms the cranial skeleton and viscerocranium for the facial skull and cranium are generally used synonymously. skeleton. Cranial skeleton Cranial skeleton Facial skeleton Facial skeleton A B Fig. 2.1 Skull showing cranial skeleton (orange color) and facial skeleton (yellow color): A, lateral view; B, frontal view.  Osteology of the Head and Neck 13 Functions of the Skull meatuses lie in the same horizontal plane (Frankfurt’s The functions of the skull are: plane). 1. Provides case for protection of the brain and its N.B. A horizontal line formed by joining the infraorbital coverings (meninges). margin and the center of external auditory meatus is called 2. Provides cavities for accommodation of organs of special Reid’s baseline. senses such as sight, hearing, equilibration, smell, and taste. 3. Provides openings for the passage of air and food. 4. Accommodates teeth and jaws for mastication. STUDY OF SKULL AS A WHOLE The study of skull as a whole is of greater importance to N.B. The term cranium (Gk. cranium = skull) is sometimes most health professionals than the study of unnecessary used to mean the skull without mandible. details of the individual bones. The skull can be studied from outside or from inside BONES OF THE SKULL (after removing the calvaria or skull cap). The skull is made up of 22 bones, excluding ear ossicles. EXTERIOR OF THE SKULL 1. Cranial skeleton, consisting of 8 bones, out of which two are paired and four unpaired The external features of the skull are studied from five Paired bones Unpaired bones different aspects, viz. Parietal Frontal 1. Superior aspect (norma verticalis). Temporal Occipital 2. Posterior aspect (norma occipitalis). Sphenoid 3. Anterior aspect (norma frontalis). Ethmoid 4. Lateral aspect (norma lateralis). 2. Facial skeleton, consisting of 14 bones, out of which six 5. Inferior aspect (norma basalis). are paired and two unpaired: When the skull is viewed from superior aspect it is called Paired bones Unpaired bones norma verticalis; when from posterior view, norma Maxilla Mandible occipitalis; when from anterior aspect, norma frontalis; Zygomatic Vomer when from lateral aspect, norma lateralis; and when from Nasal inferior aspect, norma basalis. Lacrimal Palatine Norma Verticalis (Fig. 2.3) Inferior nasal concha When the skull is viewed from above, it appears oval, being wider posteriorly than anteriorly. JOINTS OF THE SKULL It presents the following features: The bones of the skull are united at immovable joints called sutures. The connective tissue uniting the bones is called sutural ligament. Exception to this rule is mandible for it is Upper margin of connected to the cranium by synovial temporomandibular external joints, which are freely movable joints. auditory Reid’s meatus baseline N.B. All the bones of the skull are immovable except for the mandible which permits free movements. The ear ossicles within the middle ear are also mobile, but conventionally Frankfurt’s plane they are not included in the skeleton of the head. Lower Center of external margin of ANATOMICAL POSITION OF THE SKULL auditory meatus orbit (auricular point) (infraorbital It is the position of skull (Fig. 2.2) in which the orbital margin) cavities are directed forwards, and lower margins (infraorbital margins) of the orbits and upper margins of external acoustic Fig. 2.2 Anatomical position of the skull. 14 Textbook of Anatomy: Head, Neck, and Brain N.B. Metopic suture The metopic suture is occasionally present in the median Frontal bone plane of the frontal bone in 3–8% cases. It represents the Coronal suture remnants of suture between the two halves of the frontal Bregma bone in fetal skull, which develops by separate centres of ossification. Parietal bone Temporal line Isolated sutural bones, ossified from separate centres are Obelion often seen along the lambdoidal suture. Parietal foramen Other Features These are as follows: Lambda 1. Bregma: It is a point at which coronal and sagittal Wormian bone sutures meet. Occipital Lambdoid suture 2. Parietal eminence/tuber: It is an area of maximum bone convexity of parietal bone. 3. Vertex: It is the highest point on the skull. It lies on the sagittal suture near its middle and is situated a few Fig. 2.3 Norma verticalis. centimeters behind the bregma. 4. Parietal foramen: It is a small foramen in parietal bone near sagittal suture, 2.5–4 cm in front of lambda. Bones and Sutures 5. Obelion: It is a point on sagittal suture between the two The bones are frontal, parietal, and occipital. They are parietal foramina. located as follows: Norma Occipitalis (Fig. 2.4) 1. Frontal bone (squamous part) anteriorly. 2. Parietal bones (paired) on each side of midline. When the skull is viewed from behind, it appears convex 3. Occipital bone (squamous part) posteriorly. upwards and on sides but flattened below. It presents the following features: These bones are united by the following three sutures. 1. Coronal suture (L. = a crown), between frontal and two Bones and Sutures parietal bones. It crosses the cranial vault from side-to- The bones seen in this view are posterior portions of pari- side. etal bones, the upper part of occipital bone, and mastoid 2. Sagittal suture (L. = an arrow), between two parietal parts of temporal bones. They are located as follows: bones. It lies in the median plane. 1. Parietal bones, superiorly one on each side. 3. Lambdoid suture, between occipital and two parietal 2. Occipital bone (squamous part), inferiorly. bones. It is shaped like the letter lambda, hence its 3. Mastoid part of temporal bone, inferolaterally on each name. side. Sagittal suture Lambdoid suture Parietal bone Parietomastoid suture Occipital bone Occipitomastoid Mastoid foramen suture Mastoid process External occipital protuberance Highest Posterior margin of External Superior Nuchal lines foramen magnum occipital crest Inferior Fig. 2.4 Norma occipitalis.  Osteology of the Head and Neck 15 The sutures which unite these bones are as follows: Norma Frontalis (Fig. 2.5) 1. Lambdoid suture, between occipital and two parietal In frontal view, the skull appears oval, being wider above bones. and narrower below. 2. Occipitomastoid suture, between occipital and mastoid The anterior aspect of the skull presents the following part of temporal bone. features: 3. Parietomastoid suture, between parietal and mastoid 1. Frontal region formed by frontal bone. part of temporal bone. 2. Orbital openings. 3. Prominences of the cheek formed by zygomatic bones. Other Features 4. Bony external nose and anterior nasal aperture. The other features to be noted on the posterior aspect of the 5. Upper and lower jaws bearing teeth. skull are: 1. Lambda: It is the point at which sagittal and lambdoid Frontal region formed by frontal bone: The frontal region sutures meet. or the forehead is formed by the squamous part of the 2. External occipital protuberance: It is a median bony frontal bone. Below on each side of median plane, it projection about midway between the lambda and the articulates with the nasal bones. Frontal region presents the foramen magnum. The most prominent point of the following features: superciliary arches, glabella, and frontal external occipital protuberance is called inion. eminences. They are already described in Chapter 1. 3. Superior nuchal lines: These are curved bony ridges Orbital openings: These are the openings of two orbital passing laterally on each side from external occipital cavities on the face. Each opening is present above and lateral protuberance. In some cases curved faint bony ridges are to the anterior nasal aperture. It is quadrangular in shape seen 1 cm above the superior nuchal lines. They are and presents four margins, viz. supraorbital, lateral, called highest nuchal lines. infraorbital, and medial. 4. External occipital crest: It is a vertical ridge between the 1. The supraorbital margin is formed entirely by the external occipital protuberance and posterior margin of frontal bone. At the junction of its lateral two-third and the foramen magnum. medial one-third, there is a notch called supraorbital 5. Inferior nuchal lines: These are curved bony ridges notch (or foramen in some skulls), through which passes passing laterally on each side from middle of the external the supraorbital nerve and vessels. occipital crest. 2. The lateral orbital margin is formed by the frontal process 6. Mastoid foramen: It is present near the occipitomastoid of zygomatic bone and zygomatic process of frontal bone. suture. Frontal bone Glabella Frontal prominence Nasion Superciliary arch Frontozygomatic suture Supraorbital notch Whitnall’s tubercle Zygomatic bone Zygomaticofacial foramen Orbital opening Infraorbital foramen Middle nasal Anterior nasal spine concha Inferior nasal Alveolar process concha of maxilla Alveolar process Anterior nasal of mandible aperture Mental foramen Mentum (mental protuberance) Fig. 2.5 Norma frontalis. 16 Textbook of Anatomy: Head, Neck, and Brain 3. The infraorbital margin is formed by the zygomatic The sutures seen in this view are as follows: bone laterally and the maxilla medially. 1. Frontonasal. Below this margin the maxilla presents an opening 2. Internasal. called infraorbital foramen through which passes the 3. Frontomaxillary. infraorbital nerve and vessels. 4. Zygomaticomaxillary. 4. The medial orbital margin is ill-defined as compared to other margins. It is formed by the frontal bone above Other Features and the anterior lacrimal crest of the maxilla below. In addition to the above, the following features should be Prominences of the cheek formed by zygomatic bones (malar noted in the median plane and lateral regions of the anterior bones): Each prominence is situated on the lower and lateral aspect of the skull: side of the orbit and rests on the maxilla. It is marked by a 1. In the median plane: foramen called zygomaticofacial foramen. (a) Glabella, a median elevation above the nasion and Bony external nose and anterior nasal aperture: The bony between the superciliary arches. external nose is formed by the nasal bones and maxillae. It (b) Nasion, a median point at the root of the nose where terminates in front and below as piriform aperture of the the internasal and frontonasal sutures meet. nose called anterior nasal aperture which is bounded above (c) Anterior nasal spine, a sharp bony projection in the by the nasal bones, and laterally and below on each side by median plane, in the lower boundary of the piriform the nasal notches of the maxillae. aperture. The two nasal bones articulate in the midline with each (d) Symphysis menti, a median ridge joining two halves other at internasal suture, posteriorly with frontal process of of the mandible. maxilla and superiorly with frontal bone at the frontonasal (e) Mental protuberance, a triangular elevation at the suture. Anterior nasal spine is a sharp bony projection which lower end of symphysis menti. marks the meeting of the two maxillae in the lower boundary (f) Mental point (gnathion), middle point of the base of of the anterior nasal aperture. the mandible. Upper and lower jaws: The upper jaw is formed by two 2. In the lateral region (from above downwards): maxillae. On the anterior aspect each maxilla presents: (a) Frontal prominence, a low rounded elevation above (a) a zygomatic process, which extends laterally and articulate the superciliary arch. with the zygomatic bone, (b) Three foramina lying in same vertical plane, viz. (b) a frontal process, which projects upwards and articulates (i) Supraorbital notch or foramen, at the junction with the frontal bone, of medial one-third and lateral two-third of the (c) an alveolar process, which carries the upper teeth, and superior orbital margin. (d) the anterior surface of the maxilla, which presents: nasal (ii) Infraorbital foramen, 1 cm below the infra- notch medially; infraorbital foramen 1 cm below the orbital margin. infraorbital margin; incisive fossa above the incisor (iii) Mental foramen, below the interval between teeth; canine fossa lateral to canine eminence produced two premolar teeth. by the root of canine tooth. (c) An oblique line on the body of the mandible, extending between mental tubercle and lower end of anterior The lower jaw is formed by the m