Anatomy Of The Head And Neck PDF

ANATOMY OF THE HEAD AND NECK 1  THE SCALP Scalp is the soft tissue covering skull vault, it is composed of 5 layers: S Skin (scalp skin is thick rich in hair & sebaceous glands) C Connective tissue (it is dense, it contains blood vessels & nerve...

ANATOMY OF THE HEAD AND NECK 1  THE SCALP Scalp is the soft tissue covering skull vault, it is composed of 5 layers: S Skin (scalp skin is thick rich in hair & sebaceous glands) C Connective tissue (it is dense, it contains blood vessels & nerves) A Aponeurosis of occipito-frontalis muscle L Loose areolar connective tissue P Pericranium (periosteum) Occipito-frontalis muscle: Attachment: -Occipital bellies: Arises from nuchal lines of the occipital bone & is attached in front into the aponeurosis. -Frontal bellies (part): Arises from the aponeurosis & is attached in front into the skin of the forehead. Nerve supply: Facial N (occipital bellies are supplied by its posterior auricular branch and frontal bellies are supplied by its temporal branch) Action: Elevate eye brows and wrinkles the skin of the forehead 2 Arterial supply of the scalp: 5 arteries on each side: -Supratrochlear A (branch from ophthalmic A which is a branch of internal carotid A) -Supraorbital A (branch from ophthalmic A which is a branch of internal carotid A) -Superficial temporal A (branch from external carotid A) -Posterior auricular A (branch from external carotid A) -Occipital A (branch from external carotid A) Venous drainage of the scalp: 5 veins on each side: Supratrochlear V; Supraorbital V; Superficial temporal V; Posterior auricular V; Occipital V Nerve supply of the scalp: 10 nerves on each side Motor nerve supply: - Facial N supply occipito-frontalis muscle Sensory nerve supply: - Trigeminal nerve supplies the anterior half of the scalp through its 3 divisions (Ophthalmic N; Maxillary N; Mandibular N) - Cervical nerves supply the posterior half of the scalp through Great occipital N; Lesser occipital N; Third occipital N) 3  THE FACE Skin of the face is elastic and very vascular. Superficial Fascia contains in addition to fat; muscles, vessels and nerves. Deep Fascia is absent in the face except over buccinator and parotid gland. MUSCLES OF THE FACE: They are called muscles of expression, they are attached to the skin of the face & are supplied by the facial nerve. There are around twenty muscles on each side, including muscles of forehead, eye lids, auricles, nose, cheecks & mouth. The most important muscles are: BUCCINATOR: -Origin: -Alveolar margin of the maxilla opposite to the upper 3 molar teeth -Alveolar margin of the mandible opposite to the lower 3 molar teeth -Pterygomandibular ligament in between -Insertion: -The upper fiber into the upper lip -The lower fibers into lower lip -The middle fibers decussate so the upper one pass to lower lip and the lower fibers to the upper lip -Nerve supply: Facial nerve through its buccal branch -Action: -Prevent accumulation of food in the vestibule of the mouth by keeping the cheeks applied to the gums. -Blowing and whistling. 4  ORBICULARIS ORIS: -It consists of extrinsic and intrinsic fibers: -Extrinsic fibers derived from other facial muscles as buccinator inserted into lips -Intrinsic fibers which are present inside the lips -Nerve supply: Facial nerve -Action: Closes the mouth ARTERIAL SUPPLY OF THE FACE: -FACIAL ARTERY: It is the main artery of the face Beginning: In the neck as a branch of the external carotid A Course: -It ascends on the submandibular salivary gland. -It then curves around the lower border of mandible just anterior to masseter to enter the face -In the face it has a tortuous course, ascends upwards till the angle of the mouth then upwards on the side of the nose till the medial angle of the eye End: At the medial angle of the eye by becoming angular artery Branches: Inferior labial A; Superior labial A; Nasal A & Angular A NB: Other arteries supplying the face: -Supratrochlear A, -Supraorbital A, -Infraorbital A, -Transverse facial A VENOUS DRAINAGE OF THE FACE: 1-ANTERIOR FACIAL VEIN: Begins at the angle of the eye by union of supratrochlear and supraorbital veins. It accompanies facial artery lying behind the artery. It ends by joining the anterior division of retromandibular vein to form common facial vein which drains into internal jugular vein 2-RETROMANDIBULAR VEIN: Formed by union of superficial temporal and maxillary veins inside the parotid gland, it ends by dividing into anterior and posterior divisions: The anterior division joins the anterior facial vein form common facial vein which drain into internal jugular vein The posterior division joins the posterior auricular vein into the external jugular vein 5 6 NERVE SUPPLY OF THE FACE: MOTOR: -FACIAL NERVE: It is the 7th cranial nerve. It leaves the skull through the stylomastoid foramen, passes along lateral side of styloid process, then enters the parotid gland where it ends by dividing into five terminal branches that supply the muscles of the face. Branches: -2 branches after it emerges from the skull through stylomastoid foramen: Branch to supply occipital belly of occipitofrontalis & branch to supply posterior belly of digastric -5 terminal branches within the parotid gland: Temporal N, Zygomatic N, Buccal N, Marginal mandibular N, Cervical N SENSORY: -TRIGEMINAL NERVE: It is the 5th cranial nerve. It divides into three divisions Ophthalmic N, Maxillary N & Mandibular N, that supply the face as follows: Ophthalmic nerve: supply the skin of the forehead, upper eye lid & front of nose; through its following branches: Supratrochlear, Supraorbital, Lacrimal, Infratrochlear and External nasal N Maxillary nerve: supply skin of lower eye lid; side of nose & over maxilla through its following branches: Zygomaticotemporal N; Zygomaticofacial N & Infraorbital N Mandibular nerve: supply the skin over the mandible through its following branches: Auriculotemporal N, Buccal N & Mental N NB: A small area of the skin of the face which lies over the angle of the mandible is supplied by Great auricular N, which arises from cervical nerves (it is not a branch of trigeminal N) 7 8  PAROTID GLAND It is the largest salivary gland in the body. Parts: -Main part (consists of a superficial and a deep parts) -Accessory part (lies over parotid duct) Extensions: -Above: to the zygomatic arch & external auditory meatus -Below: to the angle of the mandible -Anteriorly: overlap masseter muscle -Posteriorly: overlap sternomastoid muscle Shape: It is wedge shape having 2 ends (upper end, lower end), 3 surfaces (lateral surface, anteromedial surface, posteromedial surface). It is surrounded by a capsule derived from the deep fascia. Relations: Lateral surface: related to skin and fascia containing great auricular nerve and superficial parotid lymph node. Anteromedial surface: related to masseter, ramus of mandible and medial pterygoid muscle. Posteromedial surface: related to sternomastoid muscle, mastoid process, posterior belly of digastric, styloid process and carotid sheath. Structures inside the parotid gland: 1- Facial N: the most superficial structure, enters through posteromedial surface divide into 5 terminal branches which are: Temporal (exit through upper pole of the gland); Zygomatic, Buccal & Marginal mandibular (exit through anterior border of the gland); Cervical (exit through lower pole of the gland) 2- Retromandibular vein: the middle structure, formed inside the gland by union of superficial temporal & maxillary veins. It exits through lower pole of the gland where it divides into anterior & posterior divisions 3- External carotid artery: the deepest structure, it enters through lower pole of the gland & divide into superficial temporal artery (which exit through the upper pole of the gland) & maxillary artery (which exit through the anteromedial surface of the gland) 4- Auriculotemporal nerve pierce the upper end of the gland 5- Deep parotid lymph nodes 9 Parotid duct (Stensen's duct): It is 5 cm long. It begins at the anterior border of the gland, runs forwards on the masseter, then turns medially at the anterior border of the masseter and pierces buccal pad of fat, buccopharyngeal fascia, buccinator muscle & mucous membrane to open in the vestibule of mouth opposite to the upper 2nd molar teeth. Blood supply: -Arterial supply: branches from ECA -Venous drainage: into retromandibular vein Nerve supply: -Sensory: Great auricular N supply the capsule & Auriculotemporal N supply the parenchyma of the gland -Sympathetic: From the sympathetic nerve plexus around the external carotid artery -Parasympathetic: From Glossopharyngeal N → Lesser superficial petrosal N → Otic ganglion → Postganglionic fibers pass with Auriculotemporal N to the parotid gland 10  MUSCLES OF MASTICATION Nerve Muscle Origin Insertion Action supply Temporalis a- Inferior temporal Into the tip, anterior 1. Elevation of mandible line border and medial 2. Retraction of mandible Anterior division of mandibular nerve b- Temporal fossa surface of coronoid by its posterior fibers process NB: The muscle is covered by temporal fascia that is attached to the superior temporal line Masseter a- Superficial fibers: Lateral surface of 1. Elevation of mandible from lower border of ramus of mandible 2. Protraction of Anterior division of mandibular nerve zygomatic arch mandible by its b- Deep fibers: from superficial fibers deep surface of zygomatic arch Lateral pterygoid a- Upper head: from -Capsule & articular 1. Depress mandible infra-temporal disc of TMJ 2. Both muscles (Rt & Anterior division of mandibular nerve surface of greater -Pterygoid fossa Lt) protrude the wing of sphenoid (fovea) of the neck mandible b- Lower head: from of mandible 3. One muscle lateral surface of alternating with lateral pterygoid muscle of opposite plate side produce side to side movement Medial pterygoid a- Superficial head: Medial surface of 1. Elevate mandible from maxillary angle of mandible 2. Both muscles (Rt & tuberosity Lt) protrude mandibular nerve Main trunk of b- Deep head: from mandible medial surface of 3. One muscle lateral pterygoid alternating with plate muscle of the opposite side produce side to side movement 11 Temporalis Masseter Lateral & Medial pterygoid 12  Relations of Lateral Pterygoid Muscle 1- Above: nerves to temporalis (called the deep temporal nerves) and nerve to masseter. 2- Below: lingual nerve and inferior alveolar nerve. 3- Superficial relations: maxillary artery, pterygoid venous plexus, buccal nerve, temporalis, masseter. 4- Deep relations: ▪ Muscles: Deep head of medial pterygoid. ▪ Nerves: Mandibular nerve and chorda tympani nerve. ▪ Arteries: Middle meningeal artery and accessory meningeal artery. 5- Between its two heads: Maxillary artery and buccal nerve. 13  TEMPOROMANDIBULAR JOINT (TMJ) Joint type: Synovial, condylar joint Articulating bones: Above: Articular fossa & articular eminence of the temporal bone Below: Head of the mandible Joint cavity: The joint cavity is surrounded by a capsule lined by a synovial membrane. An articular disc of fibrocartilage divides the joint cavity into upper and lower compartments. Ligaments: -Lateral temporomandibular ligament: is the main ligament, it is triangular in shape extending from root of zygomatic arch to the neck of mandible -Sphenomandibular ligament: extends from spine of sphenoid to lingula of mandible -Stylomandibular ligament: extends from the styloid process to angle of mandible Arterial supply: Superficial temporal A mainly (a branch from external carotid A) Nerve supply: Auriculotemporal N (a branch from mandibular N) Movements of the joint & muscles producing them: -Elevation: Temporalis, masseter, medial pterygoid -Depression: Lateral pterygoid, digastric, mylohyoid, geniohyoid, platysma -Protraction: Superficial fibers of masseter, lateral and medial pterygoid -Retraction: Posterior fibers temporalis -Side to side movement: Lateral and medial pterygoid 14  MAXILLARY ARTERY Beginning: It begins within the parotid gland as one of the two terminal branches of the external carotid artery, (the other terminal branch is the superficial temporal artery) Course and relations: The course of the maxillary artery is divided into 3 parts: -First part: runs forward deep to the neck of the mandible along the lower border of the lateral pterygoid muscle -Second part: runs upward & forward along the lateral surface of the lateral pterygoid muscle -Third part: passes between the 2 head of the lateral pterygoid muscle to enter pterygopalatine fossa, where it passes through the pterygomaxillary fissure to enter pterygopalatine fossa Termination: Maxillary artery passes through the inferior orbital fissure to enter the orbit where it becomes termed INFRAORBITAL ARTERY which runs in the infra orbital canal then passes through infraorbital foramen to reach the face where it ends by dividing into three terminal branches: Palpebral, Nasal & Labial Branches of the Maxillary A: From the 1st part: (5 branches → MAADI) -Middle meningeal A (passes through foramen spinosum to supply the dura) -Accessory meningeal A (passes through foramen ovale to supply the dura) -Anterior tympanic A (supply the middle ear) -Deep auricular A (supply ear drum) -Inferior alveolar A (pass with the inferior alveolar nerve through the mandibular foramen and mandibular canal to supply the lower jaw, it ends by dividing into incisor branch to canines and incisors teeth and mental branch that leaves mental foramen) From the 2nd part: (5 branches to the following 5 muscles) -Temporalis -Masseter -Lateral pterygoid -Medial pterygoid -Buccinator From the 3rd part: -Post superior alveolar A (to upper molar and premolar teeth) -Greater palatine A (passes through greater palatine foramen to supply hard palate) -Lesser palatine A (are two in number, pass through lesser palatine foramina to supply soft palate) -Shenopalatine A (passes through sphenopalatine foramen to supply the nose) -Pharyngeal A (to the pharynx) Branches of the Infraorbital A: -Anterior superior alveolar A (to upper canine and incisor teeth) -Terminal branches in face: Palpebral, Nasal & Labial 15 16  PTERYGOID PLEXUS OF VEIN It is a network of veins present around and inside the lateral pterygoid muscle. It drains into the maxillary vein which drains into the retromandibular vein. Communications: -With anterior facial vein through deep facial vein -With cavernous sinus through an emissary vein which pass through foramen ovale Clinical importance: Infection from the dangerous area of the face may pass along deep facial vein to the pterygoid plexus of veins then along emissary vein which pass through the foramen ovale to reach the cavernous sinus causing cavernous sinus thrombosis. 17  CRANIAL CAVITY Cranial cavity contains the brain and the cranial nerves. The brain is enveloped by meninges (pia matter, arachnoid matter and dura matter). DURAL FOLDS: They are duplications (two layers) from the inner layer of the dura, acting as septa separating different parts of the brain to stabilize them. The most important are: -Falx cerebri: between the two cerebral hemisphere -Falx cerebelli: between the two cerebellar hemisphere -Tentorium cerebelli: between the cerebrum & cerebellum 18 DURAL VENOUS SINUSES: They are spaces between the outer and inner layers of dura mater, lined with endothelial cells and have no valves. They receive venous blood from the brain. They are connected to veins outside the skull through emissary veins. Single: -Superior sagittal sinus -Inferior sagittal sinus -Straight sinus -Occipital sinus -Basilar sinus Paired: -Sphenoparietal sinus -Cavernous sinus -Superior petrosal sinus -Inferior petrosal sinus -Transverse sinus -Sigmoid sinus 19  CAVERNOUS SINUS Site: It lies on the side of the body of sphenoid. Size: it is about 2 cm long & 1 cm wide. Structure inside the cavernous sinus: They include: 1-Structures in the lumen of the cavernous sinus: -Internal carotid artery -Abducent nerve 2-Structures in the lateral wall of the cavernous sinus: -Oculomotor N -Trochlear N -Ophthalmic N -Maxillary N Tributaries: -Ophthalmic veins -Superficial middle cerebral vein -Pterygoid venous plexus through emissary veins passing through foramen ovale Clinical importance: Infection from the dangerous area of the face may pass along deep facial vein to the pterygoid plexus of veins then along emissary vein which pass through the foramen ovale to reach the cavernous sinus causing cavernous sinus thrombosis. 20