Musculoskeletal III System Integrated Book PDF

1 2  MUSCULOSKELETAL III SYSTEM INTEGRATED BOOK PREFACE Head and neck is a special region of the body where the proximal alimentary and respiratory tracts exist in close proximity. The anatomical relationships of these or...

1 2  MUSCULOSKELETAL III SYSTEM INTEGRATED BOOK PREFACE Head and neck is a special region of the body where the proximal alimentary and respiratory tracts exist in close proximity. The anatomical relationships of these organs to each other are important to understand as often diseases afflicting one of these also affect other organs by contiguity. These interdisciplinary integrated books provides an introduction to the basic sciences pertaining to musculoskeletal III system as well as to the clinical practice of the wide variety of disorders as Injuries to the region of head; face & neck are associated with high mortality & morbidity. A firm understanding of the musculoskeletal III system will enable the student to prevent such life- style diseases through spreading relevant health education messages. We hope this book for our medical students of the fifth semester will be a guide to facilitate their study with comprehensive knowledge in a relevant context so you do not have to resort to rote memorization to acquire the competencies for your profession. THE AUTHORS 3 4  MUSCULOSKELETAL III Integrated Book Contributors Professor Dr. Hoda ElAasar Professor Dr. Maged Haroun Professor Dr.Hala Kheidr Professor Dr. Ghada Farouk Professor Dr. Marwa Matboli Assistant Professor Dr. Nagwa Mahmoud Assistant Professor Dr. Fatima Zahran Assistant Professor Dr. Salwa Morsi Assistant Professor Dr. Hanan Mahmoud Dr. Marmar Ahmed 5 6  LIST OF CONTENTS ANATOMY Skull And Mandible 11 Hyoid bone 18 Cervical Vertebrae 19 The Scalp 20 The Face 22 The Parotid gland 24 Temporal and Infratemporal fossae 26 Cervical Fascia 39 Posterior Triangle 40 Anterior Triangle 44 Submandibular Region 51 The Cranial Nerves 54 The Oral Cavity 60 The Pharynx 63 Lymphatic Drainage of the Head and Neck 65 Joints of Atlas and Axis 67 Development of Head and Neck 68 Development of the Face 70 HISTOLOGY Oral cavity 76 Salivary glands 81 Integumentary system 85 Eye: outer coat 94 Lens 97 Eye; inner coat 99 Ear: vestibular apparatus 104 Ear: auditory apparatus 106 PHYSIOLOGY Aqueous humor 112 The cornea 114 The Iris 115 Light reflex 116 The Lens 118 The Retina 122 Photopic and Scotopic vision 124 Color vision 126 Binocular and stereoscopic vision 128 Visual pathway & its lesions 130 Hearing and the Cochlea 133 Mechanism of hearing 136 Perception of sounds by cerebral cortex 140 Smell sensation and its pathway 142 Taste sensation and mechanism of stimulation 144  BIOCHEMISTRY Classification of muscle diseases 150 MICROBIOLOGY Bacterial infections of the skin and soft tissue 160 Viral infections of the skin 172 Fungal infections of the skin 181 PARASITOLOGY Nematodes affecting skin and subcutaneous tissue 193 Filarial worms 193 A. Loa loa 193 B. Onchocerca volvulus 195 Dracanculus medinensis 197 Protozoa affecting skin and subcutaneous tissue 197 Cutaneous and mucocutaneous Leishmaniasis (cl) 197 Medical entomology 200 Class: Insecta 201 Diptera 201 1) mosquitoes 201 2) pseudo-mosquitoes 202 3) flies 202 Siphonaptera (fleas) 205 Hemiptera (bugs) 207 Anoplura (lice) 208 Class: arachnida 210 Ticks (ioxididae and argasidae) 210 Mites 212 I. Sarcoptes scabiei 212 Ii. House dust mites 213 III. Follicular mites 214 Class: crustacea 214 Cyclops (water flea) 214 PATHOLOGY Basal Cell Carcinoma 218 Melanocytic Lesions 220 Naevus 221 Melanoma 224 Non Melanocytic lesions 226 Seborrheic keratosis 226 Epidermal cyst 228 Salivary gland lesions 230 Sialadenitis 230 Tumours 231 Oral cavity lesions 235 Musculoskeletal III module MUS III 325 Anatomy BY PROF. DR. HODA ELAASAR PROFESSOR & HEAD OF ANATOMY DEPARTMENT FACULTY OF MEDICINE - MTI PROFESSOR OF ANATOMY FACULTY OF MEDICINE - CAIRO UNIVERSITY 9 10  The Skull& Mandible The Skull Norma Verticalis (Superior View of Skull) - Four bones: Frontal bone anteriorly, 2 parietal bones in the middle and occipital bone posteriorly - Three sutures: Coronal, sagittal and lambdoid suture: Coronal suture: separates the frontal from the two parietal bones, anteriorly. Sagittal suture: separates the two parietal bones in the middle. Lambdoid suture: separates the occipital from the two parietal bones, posteriorly. - Norma verticalis shows the following features: 1. Parietal eminences: They are the most convex areas on the parietal bones and are present posterolaterally. 2. Parietal emissary foramen: (It may be absent): It lies in each parietal bone close to the sagittal suture and anterior to the lambda and transmits emissary vein. 3. Bregma: The point of meeting of the coronal and sagittal sutures. It is the site of the anterior fontanelle in the fetus. It is filled with diamond-shaped membrane which ossifies about one and half years after birth. 4. Lambda: The point of meeting of the sagittal & lamboid sutures. It is the site of posterior fontanelle in the fetus which ossifies at about three months after birth. Norma Frontalis (Anterior View of Skull I. Vertical part of frontal bone: consists of the following parts: 1. Frontal eminences: A slightly elevated areas above the superciliary arches. 2. Superciliary arches: They lie just above the medial parts of the superior margins of the orbits. They are more marked in males. 3. Glabella: A median elevation between the two superciliary arches. 4. Nasion: A depression below the glabella at the root of the nose where the frontal bone meets the two nasal bones. 5. The supraorbital margins: They show the supraorbital foramina or notches at the junction of the lateral 2/3 with the medial 1/3 of each margin. 6. Frontal bone projects inferiorly forming the upper part of the medial and lateral margins of the orbits. II. The Maxillary bones: They form a part of norma frontalis extending from the orbit till the upper jaw and from the nose (medially) to the zygomatic bone (laterally). The two maxillary bones unite together in the midline anteriorly. The anterior surface of the body of maxilla shows the following features: a. Canine eminence: An elevated ridge produced by the root of the canine tooth. b. Canine fossa: A deep fossa which lies lateral to the canine eminence. c. Incisive fossa: A shallow fossa which lies medial to the canine eminence. d. Infraorbital foramen: Lies above the canine fossa, about 1 cm below the infraorbital margin. It transmits the infraorbital nerve and vessels. Three processes extend from the anterior surface of body of maxilla. They are: a. Frontal process of maxilla: articulates with the frontal bone. b. Zygomatic process of maxilla: articulates with the zygomatic bone. c. Alveolar process of maxilla: forms the upper jaw containing the sockets of the upper teeth. 11  III. Nasal Bones and Anterior Nasal Aperture: Superiorly, the paired nasal bones articulate with each other in the midline, and with the frontal bone above. The central depression at the frontonasal suture is termed the nasion. Laterally, the nasal bone articulates with the frontal process of each maxilla. Below the nasal bones, there is a large piriform opening called the anterior nasal aperture through which the lower part of the bony nasal septum ending anteriorly as the anterior nasal spine and the paired inferior and middle nasal conchae are visible. IV. Zygomatic Bones (The cheek bones): Each zygomatic bone forms the lateral part of the inferior margin of the orbit as well as the lower part of the lateral margin of the orbit. Its anterolateral surface is convex and is pierced by the zygomaticofacial foramen, which may be doubled or absent and transmits zygomaticofacial nerve and vessels. V. Orbital Opening: is nearly quadrangular. It is bounded by: Supraorbital margin: formed entirely by the frontal bone. Infraorbital margin: formed by maxilla medially and zygomatic bone laterally. Lateral margin: formed mainly by the frontal process of zygomatic bone and completed above by the zygomatic process of the frontal bone. Medial margin: formed above by the frontal bone and below by the frontal process of maxilla. Norma Occipitali (Posterior View of Skull It is convex and consists of posterior parts of the parietal and occipital bones. The occipital bone in this norma presents the following features: a. External occipital protuberance: A median tubercle present midway between the lambda and foramen magnum. b. Superior nuchal lines: Two curved lines pass laterally from the protuberance to the mastoid processes. c. External occipital crest: A vertical ridge extends downwards from the external occipital protuberance to the foramen magnum. d. Highest nuchal lines: Poorly marked lines present one cm above the superior nuchal lines. e. Inion:The summit and the most prominent point of the external occipital protuberance. Norma Lateralis (Side View of Skull) It includes the following bones: 1. Parietal. 5. Nasal bone. 2. Temporal bone (All its parts except the petrous). 6. Maxillary bone. 3. Lateral surface of greater wing of sphenoid. 7.Parts of frontal and 4. Zygomatic bone. occipital bones. The norma lateralis shows the following features: 1. Two Temporal lines: Begin at the zygomatic process of frontal bone arching upward and backwards across the coronal suture and the parietal bone. They end at the posterior end of zygomatic arch to become continuous with the supramastoid crest. 2. Squamous part of temporal bone: It articulates with the parietal bone above and with the greater wing sphenoid bone in front. It gives the zygomatic process of 12  temporal bone which articulates with the temporal process of zygomatic bone to form the zygomatic arch. 3. Zygomatic Arch: Posteriorly the lower border of the zygomatic arch forms the articular tubercle and mandibular fossa while its upper border continuous with supramastoid crest. 4. External Acoustic (Auditory) Meatus: It lies below the root of the zygomatic arch. Its posterosuperior part is formed by the squamous part of temporal bone while its anteroinferior part is formed by the tympanic plate. 5. Suprameatal Triangle: A small triangular depression lies posterosuperior to the external acoustic meatus. It forms the lateral wall of the mastoid antrum which lies 1.5 cm deep to it. 6. Mastoid Part of Temporal Bone: The posterior part of the temporal bone which lies posterior to the external auditory meatus. The point of meeting of the parietal, occipital and mastoid bones is called Asterion; At birth it is the site of the mastoid (or posterolateral) fontanelle which ossifies and closes at the end of the 1 st year. 7. The mastoid process is a nipple-like downward extension from the mastoid part of temporal bone. It lies posteroinferior to the external auditory meatus. 8. The Styloid Process: A slender pointed projection of variable length extends from the lower part of the temporal bone. It lies anterior and medial to the mastoid process and is directed downwards, forwards and medially. ❖ Fossae in the Norma Lateralis 1. Temporal fossa. 2. Infratemporal fossa. 3. Pterygopalatine fossa. 1. Temporal Fossa: The space between the temporal lines and the zygomatic arch. -Boundaries: a. Above: Temporal lines. b. In front: Zygomatic bone and frontal process of zygomatic bone containing the zygomaticotemporal foramen for zygomaticotemporal nerve and vessels. c. Behind: Supramastoid crest. d. Below: Zygomatic arch (deep to it the temporal and infratemporal fossae communicate together). e. Medially: The floor of the fossa is formed by four bones (parietal, frontal, squamous part of temporal and temporal surfaced of greater wing of sphenoid bone) (G.WI) articulate together at irregular H-shaped suture. NB. Pterion: The small circular area at the site of articulation of the previous 4 bones is called pterion. It lies 4 cm above the zygomatic arch and 3.5 cm behind the frontozygomatic suture. It marks the anterior division of the middle meningeal artery which is liable to be torn in fracture of this area, resulting in extradural hematoma. Pterion is the site of the sphenoidal fontanelle which ossifies at about 3 months after birth. 2. Infratemporal Fossa: An irregular post maxillary space that lies below the zygomatic arch and medial to the ramus of mandible. - Boundaries: a. In front: Back of body of maxilla containing posterior superior alveolar foramen. b. Behind: Tympanic plate and styloid process. c. Medially: Lateral pterygoid plate. d. Laterally: Ramus of mandible. e. Above: Infratemporal surface of greater wing of sphenoid (G.WII). 13  3. Pterygopalatine Fossa A small pyramidal space lying below the apex of the orbit and behind the maxilla. - Boundaries: a. Anteriorly: Posterior surface of the maxilla. b. Posteriorly: The root of the pterygoid process and greater wing of sphenoid. c. Medially: The perpendicular plate of the palatine bone. d. Laterally: The pterygomaxillary fissure. - Contents: a. Maxillary nerve. b. Pterygopalatine (sphenopalatine) ganglion. b. Third part of maxillary artery. Norma Basalis Externa (Inferior View of Skull) A.The anterior part: It consists of the alveolar arch and hard palate. 1. Alveolar arch (margin): carrying the sockets of 16 teeth. 2. Hard (bony) palate: showing the following features: a. Median palatine suture: A vertical midline suture which divides the hard palate into 2 equal halves. The anterior part of this suture is called intermaxillary suture and the posterior part is called interpalatine suture. b. Palatomaxillary suture: A horizontal suture which divides the hard palate into 2 parts, the anterior ¾ is called palatine process of maxilla and the posterior ¼ is called horizontal plate of palatine bone. c. Incisive fossa: It is a deep pit in the anterior end of the median palatine suture containing 2 lateral incisive foramina in most of cases, occasionally it contains 4 foramina (2 lateral and 2 median). d. Posterior nasal spine: A projecting spine in the posterior end of the median palatine suture. It gives attachment for the muscles of the uvula. e. Palatine crest: A slightly curved crest which lies in front of the posterior edge of the palate separating the greater palatine foramen in front and the 2 lesser palatine foramina behind. The greater and lesser palatine foramina, lead to the greater and lesser palatine canals, that communicate the palate with the pterygopalatine fossa superiorly. f. Vascular groove formed by the greater palatine vessels extending forwards from the greater palatine foramen close to the alveolar margin. B. The middle part: It lies between the posterior border of hard palate and a line passing just in front of foramen magnum. The middle part is divided into 3 areas (median and two laterals): I. The median area: consists of three bones present in the median plane: 1. Vomer: Is a small vertical bone that lies between the two choana (the posterior nasal openings) and forms the posteroinferior part of nasal septum. Two canals are present on either side of vomer. They are: a. Vomerovaginal canal medially. b. Palatovaginal canal laterally, it opens anteriorly into the pterygopalatine fossa. 2. Basisphenoid (the body of sphenoid) articulating with the vomer anteriorly and basilar part of occipital bone (posteriorly). 3. basilar part of occipital bone: It shows small tubercle called pharyngeal tubercle in front of foramen magnum. II. The lateral area: consists of: a. Two bones (anteriorly): 1. Pterygoid process (medially). 14  2. Greater wing of sphenoid (laterally). b. Two bones (posteriorly): 1. Petrous part (medially). 2. Squamous part (laterally). - The lateral area shows the following features: a. Pterygoid process: It extends downwards behind the 3rd molar tooth lateral to the choana. It consists of a narrow medial plate and a broader lateral one separated by the pterygoid fossa. The medial pterygoid plate ends below by a hook-like projection called the pterygoid hamulus. Superiorly each medial plate divides to form a small shallow scaphoid fossa. At the root of the medial pterygoid plate, Superior to the scaphoid fossa, lies the opening of the pterygoid canal which passes forwards to the pterygopalatine fossa. b. Greater wing: Lies lateral to the pterygoid process, it contains foramen ovale and foramen spinosum. Spine of sphenoid projects downwards posterolateral to foramen spinosum. c. Petrous temporal bone: A wedge-shaped bone that lies between the greater wing of sphenoid anterolaterally and the basilar part of occipital bone medially. The apex of the petrous part lies anteromedially behind the foramen lacerum, which is an irregular opening filled in life with cartilage. The petrous part contains the opening of the carotid canal for the passage of the internal carotid artery. Between the petrous part and the greater wing of sphenoid is a groove for the cartilaginous part of the auditory tube (the pharyngotympanic tube). d. Squamous part of temporal bone: It lies just lateral to the greater wing of sphenoid and contains the mandibular fossa and the articular tubercle. e. Squamotympanic fissure: It runs posterolaterally between the mandibular fossa and the tympanic plate. It transmits the chorda tympani nerve. C. The posterior part: It lies between the anterior edge of the foramen magnum anteriorly and the superior nuchal lines posteriorly. It consists of central part a two lateral parts. The central part consists of two parts of the occipital bone; they are: a. The lateral parts of the occipital bone: Lie just lateral to the foramen magnum and show the following features: Occipital condyles: Oval or kidney-shaped convex masses that slightly overlap the margins of foramen magnum anteriorly. They articulate with the atlas vertebrae to form the atlanto-occipital joints. Anteriorly, above each condyle is the anterior condylar canal (Hypoglossal canal). Posterior to each condyle is the condylar fossa. Jugular foramen: A large irregular foramen that lies lateral to the occipital condyle, medial to the styloid process and behind the carotid canal. b. The squamous part of the occipital bone: It lies behind and above the foramen magnum and shows the following features: 1. External occipital protuberance with superior nuchal lines. 2. External occipital crest. 3. Inferior nuchal lines: Two arched lines that extend laterally from the midpoint of the external occipital crest. The lateral parts: consist of two parts of the temporal bone, they are: a. Medial surface of the mastoid process showing the mastoid notch (digastric fossa) and occipital groove, medial to the notch. b. Styloid process lies anteromedial to the mastoid process with the stylomastoid foramen present between the 2 processes. 15  The structures passing through the foramina of norma basalis externa Foramen Structures passing through it Incisive fossa a. Greater palatine vessels b. Nasopalatine nerves Greater palatine Greater palatine nerve and vessels Lesser palatine Lesser palatine nerves and vessels Carotid canal a. Internal carotid artery and the sympathetic plexus around it b. Emissary vein Stylomastoid Facial nerve and stylomastoid artery Skull of Newly Born The bones of face are small forming ⅛ of cranium (1/3 of cranium in adult) due to small sized maxilla and maxillary sinus, non-eruption of teeth and small nasal cavity. The vault of skull contains 6 fontanelles at the angles of the parietal bones. They are (Figs. 9,10): a. Anterior fontanelle: Diamond shaped, 4 x 2.5 cm in diameter. Obliterated at about 1½ year after birth. b. Posterior fontanelle: Triangular in shape.Closed about 3 months after birth. c. & d. Two sphenoidal and two mastoid fontanelles: Small and irregular in shape and lie at sphenoidal & mastoid angles of the parietal bone. The sphenoidal fontanelle is closed at the 3rd month while the mastoid fontanelle is closed at the end of the first year after birth. The frontal and parietal eminences are prominent. The glabella, superciliary arches and mastoid processes are not developed. Internal and middle ear and mastoid antrum are almost adult in size. Mandible at birth: it consists of 2 halves, mental foramen lies near the lower border and the angle is obtuse. The Sex Differences in the Skull 1. The female skull is smaller as a whole with small paranasal sinuses than that of the male skull. 2. The female skull is lighter than that of male and its surface is smoother with less marked muscular ridges. 3. In female skull the mastoid process is small, the glabella and superciliary arches are less prominent than that of skull in male. 4. The squamous part of occipital bone is smooth in female and rough in male. The occipital condyles are smaller in female than male. ❖ Clinical importance of the fontanelles: 1. Delayed closure of fontanelles indicates retarded growth as in rickets. 2. Bulging fontanelles occur if the intracranial pressure increases. 3. Depressed fontanelles occur in dehydration. 4. Anterior fontanelle used for injection of blood or fluids into superior sagittal sinus which lies immediately deep to it. The Mandible It is the skeleton of the lower jaw which is formed of a body and 2 rami. A. The Body: It is horseshoe-shaped which is convex forwards, it has: 16  I. Two borders: a. Upper border: Carries the teeth and is called alveolar margin. b. Lower border (Base): Shows two depressions one on either side of the middle line extending upwards in the inner surface of the body called digastric fossae. II. Two Surfaces: a. Outer surface: Shows the following features: 1. Bony ridge in the middle line called symphysis menti ending below in a mental protuberance. 2. Mental foramen: It lies opposite the 2nd pre molar or the interval between the two premolar teeth, from which emerge the mental nerve and vessels. 3. Oblique line: It is a faint ridge extending from the anterior border of the ramus downwards and forwards. b. Inner surface: Shows the following features: 1. Two genial tubercles (mental spines) upper and lower on either side of the middle line. 2. Mylohyoid line: Prominent ridge of bone which extends downwards and forwards dividing the inner surface of the body into: a. Sublingual fossa: Above and in front for the sublingual salivary gland. b. Submandibular fossa: Below and behind for the submandibular salivary gland. 3. A shallow curved groove for lingual nerve lies below and behind the last molar tooth (above the posterior end of the mylohyoid line). B. The Ramus: The ramus has: 1. Two borders: a. Anterior border: Continuous with the posterior end of the oblique line. b. Posterior border: Joins the lower border of the body at the angle of the mandible. 2. Two surfaces: a. Outer surface: Flat, related to masseter muscle and parotid gland. b. Inner surface: Shows the following features: Mandibular foramen: It is an oblique opening which lies in the centre of this surface and leads to mandibular canal, which ends at mental foramen. Lingula: A tongue-like process which lies anterosuperior to the mandibular foramen overlapping it. Mylohyoid groove: Begins behind the lingula and descends downwards and forwards below the posterior part of the mylohyoid line. 3. Tw ends: a. Upper end: which has: Coronoid process: in front. Condyloid process: behind and consists of head and neck. On the anteromedial surface of the neck there is a small depression called the pterygoid fovea. Mandibular notch separates these 2 processes and transmits the masseteric nerve and vessels. b. Lower end: Continuous with the body. The Age of the Mandible ❖ At birth: 1. The mandible consists of 2 halves united together at the symphysis menti by fibrous tissue. The 2 halves fuse together by bony tissue by the end of the 1st year. 17  2. The mandibular canal and the mental foramen are present near the lower border of the mandible. 3. The coronoid process projects above the condyloid process. 4. The angle of mandible is obtuse (140° or more). ❖ The mandible of adult: 1. The mandible increases in thickness due to deposition of bone along the lower border of the body. 2. The mandibular canal and the mental foramen lie midway between the upper and the lower borders of the body. 3. The coronoid process lies at the same horizontal line of the condyloid process. 4. The angle of the mandible becomes 110-120° because the ramus becomes nearly vertical. ❖ The mandible of old age: 1. The mandible becomes reduced in size and thickness due to loss of teeth and absorption of the alveolar margin. 2. The mandibular canal and the mental foramen shift upwards and lie near to the upper (alveolar) margin. 3. The neck is bent backwards, so the coronoid process becomes at higher level than the condyloid process. 4. The angle of the mandible returns towards the infantile condition and becomes obtuse about 140°. Sex of Mandible ❖ Male mandible: 1. Thick and heavy. 2. The angle of mandible is rough and everted. 3. The mental spines and protuberance are more prominent. ❖ Female mandible: 1. Thin and light. 2. The angle of mandible is smooth and inverted. 3. The mental spines and protuberance are less marked. ❖ Applied Anatomy of the Mandible: 1. The common sites of fractures of the mandible are: a. The region of the canine tooth. b. The region of the neck of the mandible. c. The angle of the mandible. 2. The lingula of the mandible is a landmark for injection of the inferior alveolar nerve at the mandibular foramen. HYOID BONE A small U-shaped bone which lies in the upper anterior part of the neck below the mandible and is suspended from the tips of both styloid processes by the stylohyoid ligaments. It consists of body, 2 lesser horns and 2 greater horns (Fig. 14). The body: Irregular, quadrilateral in shape; it has rough, slightly convex anterior surface and smooth concave posterior surface. Lesser horns: They are 2 small conical projections at the junction of the body with the greater horns. They receive the attachments of the stylohyoid ligaments. Greater horns: They project backwards from the lateral ends of the body. Each horn has 2 surfaces (upper & lower) and 2 borders (medial & lateral). 18  Hyoid bone gives attachment to 20 muscles (14 muscles insertion and 4 muscles origin and 2 tendons of digastric muscles attached to it by fibrous loops). Hyoid bone gives attachment to stylohyoid ligaments and thyrohyoid membrane. CERVICAL VERTEBRAE I. Typical cervical vertebrae: they are the from 3rd to the 6th vertebrae and they are characterized by: The body is small and has 2 lateral lips above, and anterior and posterior lips below. The vertebral canal is large and triangular. The transverse process contains foramen transversarium for vertebral vessels. The transverse process ends in two tubercles (anterior and posterior). The spine is short and bifid. II. Atypical cervical vertebrae: They are 1st, 2nd and 7th vertebrae. A.The 1st cervical vertebra (Atlas): it is characterized by: Has no body and spine. There is transverse process and foramen transversarium. The small anterior arch has an anterior tubercle and a posterior facet for the dens (odontoid process) of the axis (2nd vertebra). The long posterior arch has a posterior tubercle and a groove for the vertebral artery on its upper surface. Two lateral masses, each mass has an upper facet (concave and kidney-shaped) and a lower facet (flat and circular). A tubercle on the medial aspect of each lateral mass for the attachment of the transverse ligament of atlanto-axial joint.The upper facet articulates with the occipital condyle forming the atlanto-occipital joint. The lower facet articulates with the upper facet of the axis vertebra. B. The second cervical vertebra (Axis): characterized by: 1.It has odontoid process (dens) which projects from the upper aspect of its body. This process articulates with the posterior surface of the anterior arch of Atlas to form atlantoaxial joint. 2. The spine is strong and bifi 3. Transverse process is very small and contains foramen transversarium. 4. The superior articular processes lie on the upper surface of the body. They are oval and flat surfaces for the articulation with the inferior articular facets of the atlas vertebra. C. The 7th cervical vertebra (Vertebra Prominens): characterized by: 1.The spine is not bifid, long and prominent. It can be felt at the lower part of the back of the neck and accordingly this vertebra is named the vertebra prominens. 2.The transverse process is large. 3. The foramen transversarium is small or even absent or may be doubled on one or both sides. If present, it transmits the vertebral vein only. 19  THE SCALP ILOs By the end of the lectures, the student should be able to: Describe the layers of the scalp. Describe the blood supply, nerve supply and lymph drainage of the scalp. Interpret some related clinical problems on the anatomical basis. - Layers of the scalp: From superficial to deep, the scalp consists of 5 layers: 1. (S) Skin: Which contains numerous hair follicles, sebaceous glands and is firmly adherent to the underlying layer. 2. (C) Connective tissue: Formed of dense fibrous connective tissue which binds the skin to the third layer. It contains the vessels and nerves of scalp & is rich in fat and fibrous septa. 3. (A) Epicranial aponeurosis: Wide tendon which connects the frontal and occipital bellies of the occipitofrontalis muscle. It is attached: a. Anteriorly: To frontal bellies. b. Posteriorly: To occipital bellies, external occipital protuberance and highest nuchal lines. c. On each side: To superior temporal lines. 4. (L) Loose areolar tissue (sub-aponeurotic layer): It facilitates movements of epicranial aponeurosis. 5. (P) Pericranium: Is the periosteum which covers the vault of skull, and is adherent to its suture lines. - Applied anatomy of the scalp: a. Infection of connective tissue layer is usually limited due to the presence of the fibrous septa. On other hand cut wound in the scalp in this layer leads to severe bleeding due to its rich blood supply as well as the wall of the arteries are unable to contract due to its attachment to the surrounding fibrous septa. b. The loose areolar tissue layer is the dangerous area of the scalp because infection can pass into the cranial cavity via the emissary veins present in it. Hemorrhage from these emissary veins is usually large and separates the scalp from the skull bones. ❖ Occipito-Frontalis Muscle: It consists of two bellies connected together by the epicranial aponeurosis. a. Frontal belly: Large muscle which arises from epicranial aponeurosis and is inserted into the skin of eye brow and root of nose. - Action: It raises the eye brow. b. Occipital belly: small muscle arises from the lateral 2/3 of the highest nuchal line and is inserted into the epicranial aponeurosis. - Action: it pulls the posterior part of scalp. - Nerve supply: Facial nerve (through its temporal branch for the frontal belly and through its posterior auricular branch for the occipital belly). - Nerve Supply of the Scalp: Each half of the scalp is supplied by 10 nerves, 5 nerves in front of the auricle and 5 nerves behind it. A.Nerves in front of the auricle: (4 sensory and one motor) 20  a. Sensory nerves: they are four sensory nerves derived from the trigeminal nerve: 1. Branches from the ophthalmic division of the trigeminal nerve. they are: ▪ Supratrochlear: supplies the skin of the forehead near the median plane. ▪ Supraorbital nerve: It supplies the skin of the scalp till its middle. 2. Zygomaticotemporal nerve: It arises from the zygomatic nerve which is a branch from the maxillary nerve. and supplies the anterior part of side of the scalp. 3. Auriculotemporal nerve: It arises from the mandibular division of the trigeminal nerve. It supplies the skin of the posterior part of the temple and the upper 2/3 of the lateral surface of auricle. b. Motor nerve: it is the temporal branch of facial nerve supplying frontal belly B. Nerves behind the auricle (4 sensory and one motor) a. Sensory nerves: 1. Greater occipital nerve (C2): Supplies the upper part of back of scalp. 2. Lesser occipital nerve (C2): Supplies a small area of back of scalp. 3. Third occipital nerve (C3): Supplies the lower part of back of scalp. 4. Great auricular nerve (C2-C3): Supplies a small area of back of scalp near the lower part of auricle. b. Motor nerve: It is the posterior auricular branch of facial nerve. It supplies the occipital belly of occipitofrontalis muscle. - Arterial Supply of Scalp: Two arteries supply its anterior part: a- The supraorbital artery. b- The supratrochlear artery. They both arise from the ophthalmic artery of the internal carotid artery. They supply the anterior part of scalp. Two arteries supply its posterior part: a- The posterior auricular artery. b- The occipital artery. They both arise from the external carotid artery. They supply the back of scalp. One artery supplies the side of the scalp: The superficial temporal artery: It is one of the two terminal branches of the external carotid artery. It leaves the upper end of parotid gland and ascends in front of the auricle. It crosses the root of the zygoma, accompanied by the auriculotemporal nerve. It ends by dividing into parietal and frontal branches; they are tortuous branches supplying the side of the scalp. - Venous Drainage of Scalp: a. The supraorbital vein. b. The supratrochlear vein: They drain the anterior part of the scalp and then unite together at the medial angle of the eye to form the anterior facial vein. c. The superficial temporal vein: It drains the lateral part of the scalp and unites with the maxillary vein to form the posterior facial vein (retromandibular vein). d. The posterior auricular vein: It drains the back of the auricle and scalp. It unites with the posterior division of the retromandibular vein to form the external jugular vein. e. The occipital vein: It drains the back of scalp into the suboccipital venous plexus present in the suboccipital triangle or it may end in internal jugular vein. - Lymph drainage of the scalp: a. Anterior part is drained into submandibular lymph nodes. b. Lateral part is drained into parotid lymph nodes. c. Posterior part is drained into mastoid and occipital lymph nodes. 21  THE FACE ❖ Muscles of the Face: They have a bony origin from the skull and are inserted into the skin. They are called muscles of facial expression and are supplied by branches from facial nerve. The most important facial muscles are: 1. Orbicularis oculi muscle: It is formed of 3 parts: a. Orbital part (around the orbital margin): It closes the eye firmly and suddenly in danger. b. Palpebral part (in the eye lids): It closes the eye gently as in sleep. c. Lacrimal part: It stretches and dilates the lacrimal sac to help in drainage of tears. - Nerve supply: From temporal and zygomatic branches of facial nerve. 2. Buccinator muscle: It is the muscle of the cheek. It consists of 3 parts: - Origin: a. Upper part: From alveolar process of maxilla opposite the upper 3 molars. b. Lower part: From oblique line of mandible opposite the lower 3 molars. c. Middle part: From pterygomandibular ligament which extends from pterygoid hamulus till the posterior end of the mylohyoid line. - Insertion: a. Upper part: Inserted into the upper lip. b. Lower part: Inserted into the lower lip. c. Middle part: Decussates at the angle of mouth so that the upper fibers enter the lower lip, and the lower fibers enter the upper lip acting as a sphincter. - Nerve supply: buccal branch of facial nerve. - Action: 1. It prevents accumulation of food in the vestibule of the mouth and prevents the dribbling of saliva from the angle of mouth. 2. It is the muscle of blowing and whistling. 3. Orbicularis oris muscle: It consists of extrinsic and intrinsic parts: The intrinsic part surrounds the mouth in the upper and lower lips. The extrinsic part is formed as extensions from the surrounding muscles as the buccinator muscle. Nerve supply: Buccal and mandibular branches of facial nerve. Action: It is responsible for the movements of the lips and act as a sphincter for the mouth to close it. ❖ Nerve Supply of Face: I. Motor Supply (from the facial nerve): The facial nerve enters the parotid gland where it ends by dividing into its 5 terminal branches which are: 1. Temporal branch: It leaves the upper end of the anterior border of parotid gland to supply frontal belly of occipito-frontalis and orbicularis oculi muscles. 2. Zygomatic branches (upper and lower): Emerge from the anterior border of the parotid gland to supply the orbicularis oculi, the muscles present between eye and mouth and the muscles of the nose. 3. Buccal branch: Supplies the buccinator and orbicularis oris. 4. Mandibular branch: Supplies orbicularis oris and muscles of lower lip. 5. Cervical branch: Emerges from the lower end of the parotid gland to supply the platysma. 22  II. Sensory Supply (from the trigeminal nerve): The face is supplied by the 3 divisions of the trigeminal nerve (ophthalmic, maxillary, mandibular), except for a small area of skin covering the angle of the mandible and the parotid gland which is supplied by the great auricular nerve (C2-C3). ❖ Blood Supply of Face - Arterial supply of face: 1. Facial artery: It arises from external carotid artery in the neck. It has 2 parts; cervical and facial. - Course of the Facial part: It enters the face at the anteroinferior angle of the masseter muscle; it follows a tortuous course to a point 1 cm lateral to the angle of the mouth, then it passes vertically upwards to reach the medial angle of the eye. It ends as an angular branch, which anastomoses with the supraorbital and supratrochlear branches of ophthalmic artery. - Branches of the facial part: i. Inferior labial artery: Supplies the lower lip. ii. Superior labial artery: Supplies the upper lip iii. Nasal branch: Supplies the side of the nose. 2. Transverse facial artery: It arises from the superficial temporal artery inside the parotid gland. It ends by anastomosing with other arteries which supply the face. 3. Infraorbital artery: the termination of the maxillary artery. It is divides into 3 branches: a. Palpebral branch for the lower eye lid. b. Nasal branch for the side of nose. c. Labial branch for the upper lip. 4. Buccal artery: It arises from the maxillary artery and lies over the buccinator muscle. 5. Mental artery: It arises from the inferior alveolar artery (from maxillary artery) and supplies the chin and the lower lip. 6. Supra-orbital and supra-trochlear arteries: They arise from the ophthalmic artery and supply the upper eye lids and the forehead. 7. Dorsal nasal artery: It arises from the ophthalmic artery and supplies the dorsum of the nose. Applied anatomy: Facial nerve injury (Facial palsy) is characterized by: 1. Dribbling of saliva from the angle of the mouth in the affected side. 2. Accumulation of food in the vestibule of mouth in the affected side. 3. The patient can not close his eye in the affected side. 4. Deviation of the angle of the mouth to the opposite side (healthy side). Trigeminal neuralgia: - It is a disease affecting the sensory root of the trigeminal nerve and caused by compression of the nerve by large blood vessel or by tumour. - Trigeminal neuralgia is characterised by severe episodic pains restricted to the areas supplied by maxillary and/or mandibular nerves. - Venous Drainage of Face: 1. Anterior facial vein (facial vein): It is formed at the medial angle of the eye by the union of supratrochlear and supra- orbital veins. It runs a straight course downwards and backwards in the face behind the facial artery. It leaves the face at the anteroinferior angle of masseter muscle, crosses the body of mandible and the submandibular gland to enter the neck. It unites 23  with the anterior division of the retromandibular vein to form the common facial vein which ends in the internal jugular vein. - Tributaries: b. Supratrochlear and supraorbital veins which form it. c. In the face it receives the following veins: nasal, superior labial, inferior labial vein, deep facial vein and veins from buccinator, parotid and masseter muscle. d. In the neck: it receives submental, tonsillar, external palatine (paratonsillar) and submandibular veins from submandibular gland. 2. Retromandibular vein: It is formed inside the parotid gland by union of maxillary and superficial temporal veins. It lies superficial to the external carotid artery and deep to the facial nerve. It ends by dividing into anterior and posterior divisions, which leave the lower end of the parotid gland. a. Anterior division unites with anterior facial vein to form the common facial vein. b. Posterior division unites with posterior auricular vein to form the external jugular vein. Other veins of the face: Transverse facial, infraorbital and mental veins which end in the pterygoid venous plexus. - Applied anatomy: Dangerous area of the face: Triangular area in the middle part of the face around the nose and upper lip. It is dangerous because infection in this area can spread and reach the cavernous sinus by this way: facial vein → deep facial vein → pterygoid venous plexus → emissary vein through foramen ovale → cavernous sinus. ❖ Lymph nodes of the face: a. Buccal nodes drain the cheek. b. Parotid nodes drain the upper and lateral part of the face. c. Submandibular nodes drain the nose, upper lip, and lower lip. THE PAROTID GLAND - Shape, Position and Extent: Wedge-shaped gland which lies in the depression between the ramus of the mandible and the mastoid process. It projects forwards over the masseter muscle, and backwards to cover a part of the sternomastoid muscle. The gland lies below the external auditory meatus and extends downwards to reach a point 2 cm below and behind the angle of the mandible where it forms its lower end. - Parotid fascia: The gland is enclosed within a capsule of the deep cervical fascia. - Parts of parotid gland: A main superficial part: It is wedge-shaped, lies between the ramus of the mandible anteriorly and the mastoid process and sternomastoid muscle posteriorly. A deep part: It lies deep to the mandible. A small accessory part: It lies above the parotid duct on the masseter muscle. - Relations of Parotid Gland: The parotid gland has 2 ends, 2 borders and 3 surfaces. Relations of borders and ends of parotid gland: Upper end: It is concave and related to external auditory meatus. The superficial temporal artery and vein and auriculo-temporal nerve appear at this end. Lower end: It lies 2 cm below and behind the angle of mandible, overlapping the posterior belly of digastric muscle. Three structures leave this end: cervical branch of facial nerve and anterior and posterior divisions of retromandibular vein. 24  Anterior border: Many structures leave this border: a. Parotid duct with the accessory part of the gland above it. b. Transverse facial artery (above the duct). c. Four branches of facial nerve: ▪ Temporal (T) and zygomatic (Z) branches above the duct. ▪ Buccal (B) and mandibular (M) branches below the duct. Relations of the surfaces of the parotid gland: 1. Lateral surface: Related to skin, fascia, superficial lymph nodes, and great auricular nerve. 2. Anteromedial surface: Extremely concave surface, clasping the posterior border of the ramus of mandible. It is related to ramus, masseter muscle (laterally) and medial pterygoid muscle (medially). 3. Posteromedial surface related to: a. Two processes: Mastoid and styloid processes. b. Two muscles attached to mastoid process: Sternomastoid muscle (superficially) and posterior belly of digastric muscle (deeply). c. Three styloid muscles and 2 ligaments attached to the styloid process. d. Two blood vessels: Internal carotid artery and internal jugular vein with the last 4 cranial nerves in between. e. Two structures enter this surface: Facial nerve and external carotid artery. - Surface Anatomy of the Gland: a. Upper end: Is represented by a concave line which is drawn upwards from the tragus of the auricle (head of mandible) to the middle of mastoid process, around the external auditory meatus. b. Anterior border: Is represented by a line drawn from the tragus and passes downwards and forwards till a point in the middle of masseter muscle, then downwards and backwards to a point 2 cm below and behind the angle of mandible (lower end). c. Posterior border: Straight line drawn from the mastoid process to a point 2 cm below and behind the angle of mandible (lower end), it runs along the anterior border of sternomastoid muscle. ❖ Parotid duct: It is thick-walled, narrow lumen, 5 cm long. It begins at the anterior border of the gland, passes horizontally with its accessory part over masseter muscle, one finger breadth below zygomatic arch. At the anterior border of masseter, it pierces 4 structures: buccal pad of fat, bucco- pharyngeal fascia, buccinator muscle and buccal mucous membrane. It opens in the vestibule of mouth opposite the upper 2nd molar tooth. - Surface anatomy of the duct: it is represented by the middle 1/3 of a line extending from the tragus of auricle to a mid point between the ala of nose and red margin of the upper lip. - Structures within the parotid gland: 1. Facial nerve: Enters the upper part of the posteromedial surface of the gland close to stylomastoid foramen. It passes forwards superficial to the retromandibular vein and divides into five branches: T.Z.B.M.C. 2. Retromandibular vein: It is formed within the gland behind the neck of mandible by the union of superficial temporal and maxillary veins. It descends vertically superficial to external carotid artery and leaves the lower end of the gland as two divisions (anterior and posterior). 3. External carotid artery: It passes deep to the lower end of the gland then it enters its posteromedial surface. It ascends vertically deep to the retromandibular 25  vein and divides opposite the neck of the mandible into 2 terminal branches: maxillary and superficial temporal arteries. 4. Deep parotid lymph nodes: They are embedded in the substance of the gland around the blood vessels. - Nerve supply of the parotid gland: 1. Parasympathetic: The parotid gland receives parasympathetic secretomotor fibers from the glossopharyngeal nerve. They have the following course: a. The preganglionic fibers arise from the inferior salivary nucleus in the medulla and pass with the glossopharyngeal nerve. Then, the fibers pass in the tympanic branch of the glossopharyngeal nerve which enters the middle ear cavity to form the tympanic plexus. b. The tympanic plexus gives the lesser superficial petrosal nerve, which passes through the foramen ovale to relay in the otic ganglion. c. Postganglionic fibers join the auriculotemporal nerve which carries them to the parotid gland. 2. Sympathetic: From the sympathetic plexus around the external carotid and middle meningeal arteries. 3. Sensory: From the auriculotemporal nerve. - Blood vessels: Arteries: from superficial temporal artery. Veins: The retromandibular and external jugular veins. - Lymphatic drainage: The gland is drained into the superficial and deep parotid lymph nodes which finally drain into the deep cervical lymph nodes. - Applied Anatomy: 1. Inflammation of the parotid gland (parotitis): (bacterial or viral). The infection reaches the gland from the mouth through the duct of the gland or via the blood stream. The cardinal clinical picture of parotitis is severe pain and swelling of the parotid gland with raised or everted lobule of the auricle. The pain in the gland is due to its enlargement causing stretching of the tight parotid capsule. Parotitis causes pain during mastication due to close relation of the gland to the temporo-mandibular joint. 2. Parotid tumours usually arise from the part of the gland superficial to the branches of the facial nerve. Benign tumours do not affect the facial nerve but malignant ones compress and invade the nerve leading to facial nerve paralysis. TEMPORAL AND INFRATEMPORAL FOSSAE ❖ Temporal Fossa (or Temple): It is the region on the side of the head which lies below the temporal lines and above the zygomatic arch. - Contents: temporalis muscle and deep temporal vessels and nerves ascend upward deep to the muscle. ❖ Infratemporal Fossa: It is the region which lies below and medial to the zygomatic arch, behind the maxilla and deep to the ramus of the mandible. - Contents: 1. Muscles of mastication: insertion of temporalis, medial and lateral pterygoid muscles. 2. Blood vessels: 26  a. First and second parts of maxillary artery and their corresponding branches. b. Pterygoid venous plexus. 3. Nerves: Mandibular nerve and its branches, otic ganglion and chorda tympani. 4. Ligaments: Sphenomandibular ligament. 27  ❖ Muscles of Mastication: Nerve Muscle Origin Insertion Action supply 1. Temporalis a. Temporal a. Tip and medial 1. Elevation of Fan-shaped muscle has fossa surface of mandible by three sets of fibers: b. Temporal coronoid anterior fibers a. Anterior: vertical fascia process 2. Retraction by b. Middle: oblique c. Inferior b. Anterior border posterior fibers c. Posterior: horizontal temporal line of ramus of mandible 2. Masseter a. Superficial Both fibers are 1. Protrusion of Has two sets of fibers fibers: from inserted into the the mandible by Anterior division of mandibular nerve a. Superficial: oblique lower border lateral surface of superficial fibers b. Deep: vertical of zygomatic ramus of mandible 2. Elevation by arch deep fibers b. Deep fibers: from deep surface of zygomatic arch 3. Lateral pterygoid a. Upper head: The 2 heads of the 1. Both ms. It has 2 heads, upper from infra- muscle unite produce and lower temporal together at a depression of surface and tendon which mandible crest of GW of enters TM joint 2. Lateral and sphenoid and inserted into: medial pterygoid b. Lower head: 1. Pterygoid fovea of one side from lateral of neck of protrude surface of mandible mandible to the lateral 2. Articular disc opposite side pterygoid 3. Capsule of TM 3. Lateral and plate joint medial pterygoid ms of both sides produce side to side movement during their alternate action 4.Medial a- Superficial Medial surface of 1. Both muscles pterygoid head: small angle and ramus elevate the mandibular nerve It has 2 heads; slip from of mandible below mandible a- Superficial maxillary the mandibular 2. As 2 in lateral Trunk of b- Deep tuberosity foramen pterygoid b- Deep head: 3. As 3 in lateral from medial pterygoid surface of lateral pterygoid plate 28 - Nerve Supply of Muscles of Mastication: All muscles of mastication are supplied by branches from the anterior division of mandibular nerve except the medial pterygoid supplied by branch from main trunk. ❖ Temporomandibular Joint - Type and articular surfaces: It is a biaxial condylar synovial joint present between the head of mandible below, and mandibular fossa and articular tubercle above. - Fibrous capsule: It is attached as follows: Above: To the margins of the mandibular fossa and articular eminence. It is thickened laterally forming temporomandibular ligament. Below: It is attached around the neck of mandible. The capsule is also attached to the margins of the articular disc. - Articular disc: An oval plate of avascular dense fibrocartilagenous tissue which separates the joint cavity into an upper and lower compartment. Its upper surface is concavo-convex while its lower surface is concave. Its periphery is attached to the fibrous capsule all around and it receives the insertion of lateral pterygoid muscle. - Ligaments: There are 3 ligaments: 1. Temporomandibular ligament: Triangular thickened band of the lateral part of the capsule. Above, it is attached to the tubercle at the root of zygomatic arch. Below, it is attached to the lateral and posterior surfaces of the neck of mandible. It is the only proper ligament which supports the joint. 2. Stylomandibular ligament: From the adjacent anterior surface of the styloid process near its tip to the angle and posterior border of the ramus of mandible. 3. Sphenomandibular ligament: It lies on the medial side extending from spine of sphenoid to lingula of mandible. - Movements of mandible (movements of TM joint): 1. Depression (opening the mouth): It consists of two combined movements; simple hinge movement of the head (rotating downwards around a horizontal axis) followed by gliding movement of the head with the articular disc forwards and downwards to lie below the articular tubercle. Opening the mouth is produced mainly by lateral pterygoid muscles assisted by gravity. Digastric, mylohyoid and geniohyoid muscles help lateral pterygoids if the movement occurs against resistance. 2. Elevation (closing the mouth, occlusal position): Produced by reversed movements to the depression. It occurs by medial pterygoid, temporalis and masseter muscles of both sides. 3. Protrusion (forward movement): The lower teeth are drawn forwards over the upper teeth by the lateral and medial pterygoids of both sides. The superficial fibers of masseter muscle has a small effect in protraction. 4. Retraction (backwards movement): The mandible is drawn backwards to the position of rest by the posterior fibers of temporalis muscle. 29  5. Side to side movement (for grinding and chewing): Produced by medial and lateral pterygoid muscles of both sides acting alternately. - Nerve supply: Fine branches from the auriculo-temporal nerve and nerve to masseter. - Blood supply: 1. Maxillary artery. 2. Superficial temporal artery. - Applied Anatomy: The mandible is dislocated only forwards. With the mouth open, the condyles are present below the articular tubercle and sudden violence, even muscular spasm may displace one or both condyles into the infratemporal fossa in front of the articular tubercle. ❖ Trigeminal Nerve (5th Cranial Nerve) It arises from the lateral surface of the pons by 2 roots (sensory and motor roots) A- Sensory root: The largest root, it has a ganglion called trigeminal ganglion. The ganglion and its covering fold of dura, lying in a special depression in the anterior surface of petrous bone near its apex. The nerve divides into 3 sensory branches; ophthalmic, maxillary, and mandibular supplying the skin of face, scalp and the anterior 2/3 of the tongue. B- Motor root: The smallest root which joins the mandibular nerve and supplies 8 muscles: 4 muscles of mastication, 2 tensor muscles (tensor palati and tensor tympani), and 2 other muscles: mylohyoid and anterior belly of digastric. I. Ophthalmic Nerve (Discussed later) II. Maxillary Nerve It arises from the trigeminal ganglion, and it is purely sensory nerve. - Course: It passes forwards along the lower part of lateral wall of cavernous sinus, and then it leaves the middle cranial fossa through foramen rotundum to enter the pterygo- palatine fossa. It inclines laterally to reach the back of maxilla and enters the orbit through the inferior orbital fissure, where it continues as infra-orbital nerve. It passes in the infra-orbital groove, infra-orbital canal and finally passes through the infra-orbital foramen to reach the face and terminates by dividing into 3 branches: Palpebral, nasal and labial. - Branches of Maxillary Nerve 1. In cranial cavity: it gives meningeal branch to dura mater of middle cranial fossa. 2. In the pterygo-palatine fossa: Gives 3 types of branches: a. Two ganglionic branches: Connect maxillary nerve to spheno-palatine ganglion. b. Posterior superior alveolar nerve: It supplies the upper molar teeth, gum and maxillary sinus. c. Zygomatic nerve: It enters the orbit through the inferior orbital fissure and divides into two branches: Zygomatico-temporal nerve: supplies the skin of anterior part of temple. Zygomatico-facial nerve: supplies the skin over the body of zygomatic bone. 3. In the orbit: It gives the following branches: 30  a. Middle superior alveolar nerve: supplies the upper premolars and gum and maxillary sinus. b. Anterior superior alveolar nerve: supplies the upper incisors and canine. It supplies also the gum and maxillary sinus. 4. In the face: The infra-orbital nerve terminates by dividing into 3 branches: 1. Palpebral (P): Supplies the skin of lower eyelid. 2. Nasal (N): Supplies the skin of side of nose. 3. Labial branch (L): Supplies the skin of upper lip. ❖ Sphenopalatine Ganglion: Small flattened parasympathetic ganglion that lies in the depth of the pterygopalatine fossa, suspended by 2 roots from maxillary nerve. - Roots of the ganglion: A. Parasympathetic root: Greater superficial petrosal nerve. it arises from facial nerve in the petrous bone, it traverses the pterygoid canal to reach and relays in the ganglion. The postganglionic fibers supply the lacrimal gland in the orbit and the mucosal glands of nose, palate and pharynx. B. Sympathetic root: Deep petrosal nerve. It arises from sympathetic plexus around internal carotid artery. It traverses the pterygoid canal to reach and traverses the ganglion without relay. C. Sensory root: Two ganglionic branches which connect the ganglion to the maxillary nerve. They contain sensory fibers from the orbit, nose, palate and nasopharynx which traverse the ganglion without relay. - Branches of Spheno-Palatine Ganglion: 1. Orbital branches: supply the periosteum of orbit. 2. Nasal branches: They reach the nose through the spheno-palatine foramen (SPF) and divide into 2 groups lateral (L) and medial (M): Lateral nasal (short spheno-palatine) branches (2L): They supply the postero-superior part of lateral wall of nose. Medial nasal (long spheno-palatine) branches (2M): They supply the nasal septum, the floor of the nose and the anterior part of hard palate. 3. Palatine branches: a. Greater palatine nerve: It descends in the greater palatine canal to reach the hard plate and supply its mucosa and glands. It supplies also the lower posterior part of the lateral wall of nasal cavity. b. Lesser palatine nerves: They descend in the greater palatine canal, then they pass through the lesser palatine foramina to supply the soft palate and palatine tonsils. 4. Pharyngeal branches: They run posteriorly to supply the nasopharynx and the auditory (Eustachian) tube. III. Mandibular Nerve - Origin: by two roots (large sensory and small motor) 1. Motor: The motor root of the trigeminal nerve arises from pons. 2. Sensory: Arises from the trigeminal ganglion. - Course: The two roots leave the skull through the foramen ovale where they unite together just beyond the foramen forming mandibular nerve trunk. 31 - Branches: I. From the trunk: (one motor and one sensory branches): They are: A. Motor: Nerve to medial pterygoid, it gives 3 branches for 3 muscles: a. Medial pterygoid muscle. b. Tensor palati muscle. c. Tensor tympani muscle. B. Sensory: Nervus spinosus: It reaches the middle cranial fossa through foramen spinosum to supply its dura mater. II. From the anterior division: All its branches are motor except one sensory branch, they are: A. Motor branches: a. Two branches for temporalis, called deep temporal nerves. b. Branch for masseter, passes through mandibular notch. c. Branch for lateral pterygoid. B. Sensory branch: (Buccal nerve): It is the continuation of the anterior division of the mandibular nerve. It supplies the skin covering and the mucosa lining the buccinator muscle. III. From the posterior division: A. Auriculotemporal nerve: It arises by 2 roots around the middle meningeal artery. It passes backwards deep to the neck of mandible, then it ascends behind TM joint within the parotid gland. It leaves the upper end of the gland crossing the zygomatic arch to reach the scalp where it divides into many branches. - Branches: a. Sensory branches: To skin of posterior ½ of temple, upper 2/3 of lateral surface of auricle, external auditory meatus and ear drum. b. Parotid branches: It receives the postganglionic parasympathetic and sympathetic fibers from otic ganglion to the parotid gland. c. Articular branches: To the temporo-mandibular joint. B. Inferior alveolar nerve: It is the largest branch of posterior division of mandibular nerve. It passes vertically downwards on medial pterygoid muscle, posterior to the lingual nerve to enter the mandibular foramen. It runs in the mandibular canal giving the inferior dental branches and divides at the mental foramen into two terminal branches: mental and incisive. - Branches: a. Nerve to mylohyoid: (motor nerve from posterior division). It supplies the mylohyoid and anterior belly of digastric muscles. b. Dental branches: They arise in the mandibular canal supplying the lower teeth, gums, and alveolar bone. c. Mental nerve: It comes out from the mental foramen to supply the skin of chin and lower lip. C. Lingual nerve: - Course: It is related to 3 parts, in this order: 1. Deep to the ramus of mandible: It passes downwards on the medial pterygoid muscle in front of inferior alveolar nerve. 2. Deep to the body of mandible: It passes downwards and forwards in a faint groove below the last molar tooth, covered with oral mucosa. 3. At the side of the tongue: It crosses styloglossus muscle, upper part of hyoglossus muscle hooking around the submandibular duct, passes forwards deep to sublingual gland to reach the tongue. On hyoglossus muscle, the 32  submandibular ganglion is suspended from lingual nerve by two roots. Near its origin it is joined by chorda tympani which distributed with its branches, to supply: a. General sensation: For the anterior 2/3 of tongue, mucosa of the floor of the mouth and gums and for submandibular and sublingual glands. b. Taste sensation of anterior 2/3 of tongue. c. Parasympathetic fibers: They relay in the submandibular ganglion and the postganglionic fibers to supply two glands: submandibular and sublingual glands. N.B.: (branches b and c from the chorda tympani nerve). ❖ Otic Ganglion: It is small parasympathetic ganglion lying in the infra-temporal fossa just below the foramen ovale. It lies deep to the trunk of mandibular nerve suspended from it by the nerve to medial pterygoid. - Roots and branches of the ganglion: A. Parasympathetic root (Lesser superficial petrosal nerve): It arises from tympanic plexus in middle ear as a continuation of the tympanic branch of the glossopharyngeal nerve. It passes through foramen ovale to reach and relay in otic ganglion. The postganglionic fibers join the auriculo-temporal nerve to reach and supply the parotid gland. B. Sympathetic root: It arises from sympathetic plexus around middle meningeal artery, then traverses the ganglion without relay to join the auriculo-temporal nerve which supplies the parotid gland. C. Motor root: Two fibers arise from nerve to medial pterygoid. They traverse the ganglion without relay to supply 2 muscles: tensor palati and tensor tympani. Maxillary Artery - Origin: The larger of the two terminal branches of external carotid artery. - Course: It begins opposite the neck of the mandible inside the parotid gland. It passes forwards, medially and slightly upwards and enters the pterygomaxillary fissure to reach the pterygo-palatine fossa where it ends by dividing into many branches. It has 3 parts: a. 1st part: It lies deep to the neck of mandible within parotid gland. It passes nearly horizontal from its origin till the lower border of lateral pterygoid muscle. b. 2nd part: It passes obliquely upwards and forwards superficial to the lateral pterygoid muscle, in some cases the artery may pass deep to it. c. 3rd part: It dips between the two heads of lateral pterygoid muscle, passes through the pterygo-maxillary fissure to reach and end in the pterygo-palatine fossa. - Branches of 1st part: 1. Middle meningeal artery 2. Accessory meningeal artery: It enters the foramen ovale to reach the middle cranial fossa where it supplies the trigeminal ganglion and the dura mater. 3. Inferior alveolar artery: It descends with its nerve through the mandibular foramen and canal to supply the bone of mandible and the lower teeth. It gives the mylohyoid artery, which descends in its groove with its nerve. 4. Anterior tympanic artery: It supplies the middle ear and the tympanic membrane. 5. Deep auricular artery: Supplies the external auditory meatus and ear drum. 33 ❖ Middle Meningeal Artery - Beginning and course: It arises from the 1st part of maxillary artery. It runs upwards and medially deep to lateral pterygoid muscle surrounded by the two roots of auriculo- temporal nerve. It passes through foramen spinosum to reach the middle cranial fossa. where it divides into two terminal branches: anterior and posterior: a. Anterior branch: A line drawn upwards and forwards towards the pterion, then passing obliquely upwards and backwards towards a point midway between the nasion and inion. b. Posterior branch: A line drawn backwards and upwards towards the lambda. - Branches of middle meningeal artery: All the branches arise inside the cranial cavity. They are: a. Meningeal branches for the dura mater. b. Small branches to the bones of skull and the covering periosteum. c. Branches to trigeminal ganglion and its roots. d. Tympanic branches: They enter the tympanic cavity to supply it. e. Branch enters the superior orbital fissure to supply the orbit. - Applied Anatomy: The middle meningeal artery may be torn in temporal fractures or by injuries separating the dura mater from the bone, followed by haemorrahge between them (extradural haemorrhage). Trephine operation is necessary to reduce cerebral compression. - Branches of the 2nd part: The artery gives muscular branches for the muscles of mastication and buccal artery which accompanies the buccal nerve to reach the face. - Branches of the 3rd part: 1. Greater palatine artery (GPA): supplies the hard palate, the nasal septum. It gives 2 lesser palatine arteries for the soft palate and palatine tonsils. 2. Spheno-palatine artery: It passes through spheno-palatine foramen to enter the nasal cavity supplying it. 3. Posterior superior alveolar artery: Supplies the upper molars, premolars and maxillary sinus (like the corresponding nerve). 4. Infra orbital artery: It emerges from the infra-orbital foramen to reach the face where it divides into 3 branches: palpebral, nasal and labial. In infra-orbital canal it gives off the anterior superior alveolar artery supplying the anterior teeth. 5. Pharyngeal artery and 6- Artery of pterygoid canal: They supply the nasopharynx. Pterygoid Venous Plexus - Beginning, end and tributaries: It is a rich plexus of veins, lying superficial and deep to the lateral pterygoid muscle. It receives the veins corresponding to the branches of the maxillary artery. It ends posteriorly by forming maxillary vein which passes backwards through the parotid gland to join the superficial temporal vein forming the retromandibular vein. - Communications: a. In front: It communicates with anterior facial vein by deep facial vein. b. Above: It communicates with cavernous sinus by emissary veins passing through the foramen ovale and foramen lacerum. c. In front and above: It communicates with inferior ophthalmic vein by a vein that passes through the inferior orbital fissure. 34  THE ORBIT - Bony orbit: It is pyramidal in shape narrow from behind forming the apex containing the optic canal, and wide from in front forming the orbital opening in the face. Bony orbit has 4 walls. Each wall is formed of many bones as follows: Roof Floor Medial wall Lateral wall 1. Orbital plate of 1. Orbital surface of 1. Frontal process 1. Greater frontal bone (the maxilla (the main of maxilla wing of main part) part) 2. Lacrimal bone sphenoid 2. Lesser wing of 2. Orbital surface of 3. Orbital surface (posteriorly sphenoid (the most zygomatic bone of ethmoid ) posterior part) (the anterolateral bone 2. Frontal It contains the lacrimal part) 4. Body of process of fossa in its It contains infraorbital sphenoid from zygomatic anterolateral part for groove and canal before bone the lacrimal gland backwards (anteriorly) - Orbital fissures: Superior orbital fissure Inferior orbital fissure It lies between the lesser wing of It lies between the maxilla (in the floor) sphenoid (in the roof) and the greater and the greater wing of sphenoid (in the wing of sphenoid (in the lateral wall). lateral wall). It communicates the orbit with the It communicates the orbit with the middle cranial fossa. infratemporal and pterygopalatine fossae. - Contents of the Orbit: 1. The eyeball. 2. The extraocular muscles. 3. Nerves: a. Optic nerve: For vision. b. Ophthalmic nerve: For general sensations. c. Oculomotor, trochlear and abducent nerves: Motor to the muscles of the eyeball. d. Sympathetic fibers: From the superior cervical ganglion. e. Parasympathetic (ciliary) ganglion: Attached to the nasociliary branch of the ophthalmic nerve. 4. Vessels: Ophthalmic artery and veins. 5. Lacrimal apparatus. 6. Pad of fat. Extraocular Muscles These are 7 muscles (4 recti, 2 obliques and one levator palpebrae superioris). A. The Recti Muscles: - Common origin: From a common tendinous ring that surrounds the optic foramen and the medial part of the superior orbital fissure. The superior rectus from above, inferior rectus from below, medial rectus from the medial and the lateral rectus from the lateral part of the ring. Lateral rectus has another head from the margin of the superior orbital fissure. 35  - Insertion: Each muscle is inserted into the sclera a short distance behind the corneoscleral junction. - Actions: a. Lateral rectus: It rotates the eyeball laterally (abduction). b. Medial rectus: It rotates the eyeball medially (adduction). c. Superior rectus: It rotates the eyeball upwards and medially with slight intorsion. d. Inferior rectus: It rotates the eyeball downwards and medially with slight extorsion. B. Superior Oblique: - Origin: From the roof of the orbit, above and medial to the optic foramen. It lies just above and medial to the origin of the superior rectus. - Insertion: by tendon that passes forwards through the trochlea, then curves backwards, downwards, and laterally to become inserted into the sclera, behind the equator of the eyeball. C. Inferior Oblique: - Origin: From the floor of the orbit just lateral to nasolacrimal groove. - Insertion: The muscle is directed backwards, upwards, and laterally below the eyeball to be inserted into the sclera, behind the equator of the eyeball. D. Levator Palpebrae Superioris: - Origin: From the roof of the orbit, in front of the optic foramen. - Insertion: It is inserted into the tarsus and skin of the upper eyelid and the superior fornix of the conjunctiva. The deep part of the levator is formed by smooth muscle called Muller’s muscle and supplied by sympathetic fibers. - Action: Superior oblique: It rotates the eyeball downwards, laterally with intorsion. Inferior oblique: It rotates the eyeball upwards, laterally with extorsion. Levator palpebrae superioris: Elevates the upper eyelid. ❖ Nerve Supply of the Extraocular Muscles: All extraocular muscles are supplied by the oculomotor nerve (3rd cranial nerve) except two muscles: Superior oblique: by the trochlear nerve (4th cranial nerve). Lateral rectus: by the abducent nerve (6th cranial nerve). Lacrimal Apparatus It is formed of:: 1. Lacrimal gland: Formed of two parts; large orbital part which lies in the lacrimal fossa at the anterolateral part of the roof of the orbit, above the levator palpebrae superioris muscle and a small palpebral part, that lies below the muscle. The gland has 10-12 short ducts that open in the lateral part of the upper fornix of the conjunctiva. It is innervated by the greater superficial petrosal nerve, which relays in the sphenopalatine ganglion. The postganglionic fibers join the maxillary nerve, pass in its zygomatic nerve, then into zygomaticotemporal nerve, then through a communicating ramus to lacrimal nerve supplying the lacrimal gland. 2. Lacrimal canaliculi: They are two canaliculi one for each eyelid. Each one runs in the edge of corresponding eyelid, for a short distance about 1 cm long, extending from the lacrimal punctum at the top of lacrimal papilla, and draining the tears into the lacrimal sac. 36 3. Lacrimal sac: Lies in the lacrimal groove present in the anterior part of the medial wall of the orbit. The upper blind end of the sac is called the fundus. While its lower end is continuous with the nasolacrimal duct. 4. Nasolacrimal duct: About 18 mm long, starts from the lacrimal sac and is directed downwards inside the nasolacrimal canal to open at the anterior part of the inferior meatus of the nose. Vessels of the Orbit I. Ophthalmic artery: - Course: It arises from the internal carotid artery as it leaves the cavernous sinus and enters the optic foramen inferolateral to the optic nerve, and then becomes lateral to it. In the orbit: The artery crosses the optic nerve, from lateral to medial, then passes forwards along the medial wall of the orbit between 2 muscles: superior oblique and medial rectus. It ends by dividing into two terminal branches: supratrochlear and dorsal nasal arteries. - Branches: 1. Central artery of the retina: It is an end artery supplies the retina. 2. Lacrimal artery: It supplies the lacrimal gland and upper lid. 3. Ciliary arteries: a. Posterior ciliary arteries pierce the sclera. b. Anterior ciliary arteries: arise from the muscular branches and supply the iris. 4. Muscular branches of the ophthalmic artery: Supply the orbital muscles. 5. Supraorbital artery: It supplies the upper lid and the forehead. 6. Anterior and posterior ethmoidal arteries: to supply the ethmoidal air cells. 7. Medial palpebral arteries: Two arteries supplying the upper and lower eyelid. 8. Supratrochlear artery: One of the two terminal branches of the ophthalmic artery. It supplies the upper lid and the forehead. 9. Dorsal nasal artery: The other terminal branch, supplying the dorsum of the nose. II. Ophthalmic veins: They are the superior and inferior ophthalmic, formed by union of veins accompanying branches of ophthalmic artery. They leave the orbit through the superior orbital fissure to end in the anterior end of the cavernous sinus. The central retinal vein ends in the cavernous sinus or superior ophthalmic vein. Nerves of the Orbit I. Sensory Nerves: A. Ophthalmic Division of the Trigeminal Nerve: It divides into three branches before it enters the orbit through SOF: 1. Nasociliary nerve: It carries the ciliary ganglion. It enters the orbit through the medial part of S.O.F. It passes medially crossing the optic nerve, to reach the medial wall of the orbit giving the following branches: a. Two long ciliary nerves: Run along the optic nerve to pierce the back of the eyeball. They carry also sympathetic fibers to the dilator pupillae muscle. b. Anterior ethmoidal nerve: It passes to the nasal cavity supplying it. It then leaves it as the external nasal nerve. c. Posterior ethmoidal nerve: supplies the ethmoidal air cells. d. Infratrochlear nerve: supplies the medial parts of the eyelids & the root of nose. 37  2. Frontal nerve: passes forwards below the roof of the orbit, and above the levator palpebrae muscle, where it divides into two terminal branches; supraorbital and supratrochlear nerves which supply the skin of the anterior part of the scalp and upper eye lid. 3. Lacrimal nerve: passes forwards above the lateral rectus to end in the lacrimal gland. It gives palpebral branch supplying the lateral 1/3 of the upper lid. It receives a twig from the zygomaticotemporal branch of maxillary nerve which contains the secretomotor fibers to the lacrimal gland. B. Optic Nerve (the 2nd cranial nerve): It is the axons of the ganglionic cells of the retina. The optic nerve is surrounded by extension of meninges, so it differs from the other cranial nerves. This means that the optic nerve is surrounded by subarachnoid space and CSF. So, any increase in intracranial pressure is reflected on the optic nerve and causes edema of the optic disc (papilledema). The optic nerve leaves the orbit and enters the cranial cavity through the optic foramen where it partially decussates with the optic nerve of the opposite side, to form the optic chiasma. II. Motor Nerves of the Orbit: A. Oculomotor Nerve (the 3rd cranial nerve): - Deep origin: It arises from the midbrain by 2 nuclei: a. Motor nucleus: Lateral cell mass and central nucleus. b. Parasympathetic nucleus: Edinger Westphal nucleus. - Superficial attachment and exit from the brain: From the anterior surface of the midbrain in the interpeduncular fossa. - Course & branches: The nerve then passes forwards in the upper part of the lateral wall of the cavernous sinus and enters the orbit through the SOF by two divisions: superior and inferior. In the orbit: The superior division supplies two muscles: superior rectus and levator palpebrae superioris. The inferior division passes forwards supplying the medial rectus, inferior rectus and ends in the inferior oblique supplying it. It contains the parasympathetic fibers to the ciliary and the sphincter pupillae muscles. ❖ Ciliary ganglion: A small parasympathetic ganglion lies between the optic nerve and the lateral rectus. It is suspended from the nasociliary nerve. - Roots: It has 3 roots: 1. Sensory root: Nasociliary nerve. 2. Parasympathetic root: Oculomotor nerve through the nerve to inferior oblique. 3. Sympathetic root: From the sympathetic plexus around the internal carotid artery. - Branches: 12-15 short ciliary nerves which pierce the back of eyeball around the entrance of optic nerve. They contain the following fibers: a- Parasympathetic postganglionic fibers which supply the ciliary and the sphincter pupillae muscles. b- Sympathetic fibers supply the dilator pupillae and the blood vessels of the eyeball. c- Sensory fibers: carry the sensation from the eyeball. - Applied Anatomy: Injury of the oculomotor nerve produces the following features: 1. Ptosis (drop of upper eyelid) due to paralysis of the levator palpebrae superioris. 2. Lateral squint due to paralysis of the medial rectus and unopposed action of the lateral rectus. 38  3. Dilatation of the pupil due to paralysis of the sphincter pupillae. 4. Loss of accommodation due to paralysis of the ciliary muscle. B. Trochlear Nerve (the 4th cranial nerve): - Deep origin: From the trochlear motor nucleus in the lower part of the midbrain. - Superficial attachment and exit from brain: The nerve appears on the back of midbrain (the right nerve comes from the left nucleus and vice versa). - Course: The nerve curves forwards round the side of the midbrain (cerebral peduncle), then it passes between the posterior cerebral and the superior cerebellar arteries. It pierces the dura at the point of crossing of the free and the attached borders of tentorium cerebelli, runs in the lateral wall of the cavernous sinus. It enters the orbit through the superior orbital fissure to supply one muscle (superior oblique). C. Abducent Nerve (the 6th cranial nerve): - Deep origin: Abducent motor nucleus in the pons. - Superficial attachment and exit from brain: At the lower border of pons near the midline. - Course: It pierces the dura mater at the apex of the petrous bone, to enter the cavity of the cavernous sinus and passes forwards lateral to the internal carotid artery, then it enters the orbit through the superior orbital fissure to supply lateral rectus muscle. - Applied anatomy: Injury of the abducent nerveLeads to medial squint due to paralysis of the lateral rectus. CERVICAL FASCIA A. Superficial Cervical Fascia It is a thin layer of fascia embedded in it the following structures: I. Platysma: It is a broad sheet of muscle fibers. - Origin: Deep fascia covering deltoid and pectoralis major muscles. - Insertion: a. Lower border of the body of mandible. b. Blends with the muscles at the angle of the mouth. c. The muscle fibers interlace with that of the opposite side below the symphysis menti. - Nerve supply: Cervical branch of facial nerve. - Action: a. Wrinkles the skin of neck. b. Depresses the angle of the mouth. c. Assists in depression of the mandible. II. Superficial veins: External jugular vein and its tributaries. III. Cutaneous nerves: They are the cutaneous branches of cervical plexus: 1. Lesser occipital nerve. 2. Great auricular nerve. 3. Transverse cutaneous nerve of neck. 4. Supraclavicular nerves. IV. Superficial cervical lymph nodes: They lie superficial to the sternomastoid muscle along the external jugular vein. They receive lymph from occipital and mastoid lymph nodes and drain it to the deep cervical lymph nodes. 39  B. The Deep Cervical Fascia (The Deep Fascia of the Neck) I. The Investing Layer of the Deep Fascia: It surrounds the whole neck and splits to envelop, trapezius and sternomastoid muscles. - Structures that pierce the general investing fascia: 1. External jugular vein pierces the fascia one inch above the clavicle. 2. Anterior facial vein pierces it one finger below the mandible. 3. All cutaneous branches of cervical plexus II. Prevertebral Fascia: It covers the prevertebral muscles. It covers the scalenus anterior muscle and the muscles forming the floor of the posterior triangle. As the subclavian artery and the trunks of the brachial plexus emerge from beneath the lateral border of the scalenus anterior muscle, they take a tube of prevertebral fascia with them, behind the clavicle, which is called axillary fascia. III. Pretracheal Fascia: A deep fascia lies in front and sides of trachea, it splits to invest the thyroid gland connecting it to the oblique line of thyroid and to the arch of cricoid cartilages (the larynx). That is why the thyroid gland moves up and down with larynx during swallowing. Laterally it blends with carotid sheath; inferiorly it invests the inferior thyroid veins and is continuous inside the thoracic cavity with the fibrous pericardium. IV. Carotid Sheath: A tube of deep fascia that invests the big vessels and nerves of the neck except external carotid artery. - Attachments: Above: It is attached to tympanic plate and petrous part of temporal bone. Anteriorly: It is connected to pretracheal fascia. Posteriorly: It is continuous with prevertebral fascia. - Contents: 1. Common and internal carotid arteries medially. 2. Internal jugular vein laterally. 3. Vagus in between and slightly posteriorly. 4. Sympathetic chain is embedded in its posterior wall and ansa cervicalis is embedded in its anterior wall. 5. The upper part of the sheath, above the posterior belly of digastric muscle, contains the lower 4 cranial nerves while the lower part of the sheath contains the vagus nerve only. V. Buccopharyngeal Fascia: VI. Pharyngeobasilar Fascia POSTERIOR TRIANGLE OF THE NECK - Boundaries: In front: Posterior border of sternomastoid. Behind: Anterior border of trapezius. Below (base): Middle 1/3 of clavicle. Above (apex): The attachment of the sternomastoid and trapezius muscles to the superior nuchal line of the occipital bone. 40  Roof: Is formed by the following structures: 1. Skin, superficial fascia including platysma and external jugular vein. 2. Deep investing fascia of the roof: It is pierced by the external jugular vein , the supraclavicular nerves and by the cutaneous branches of cervical plexus. The spinal root of accessory nerve is embedded in the deep fascia of the roof. Floor: 1. Deep fascia of the floor (prevertebral fascia): It covers the muscles of the floor. 2. Muscles of the floor (arranged from below upwards): Scalene muscles mainly scalenus medius, levator scapulae and splenius capitis. - Contents: A. Inferior belly of omohyoid muscle B. Nerves: 1. Trunks of brachial plexus 2. Cutaneous branches of cervical plexus: They appear at the middle of posterior border of sternomastoid muscle, They are: a. Lesser occipital nerve (C2): supplies the skin of the back of scalp and upper 1/3 of the back of auricle. b. Great auricular nerve (C2,3): supplies the skin over the parotid gland, angle of mandible, mastoid process and lower part of auricle. c. Transverse cutaneous nerve of neck (C2,3): supplies the skin of the anterior