Face lec.pptx
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Gross Anatomy: Face and Scalp Dr. Michael O Ibiwoye, MD, DTM &H, MPH, PhD E-mail: [email protected] Office Hours: By Appointment Thursday, 9 November 2023 Reading Assignment • Moore KL, Dalley AF and Agur AMR: Clinically Oriented Anatomy, 9th Edition (2023). Chapter 8: Head (Section on Face and Sc...
Gross Anatomy: Face and Scalp Dr. Michael O Ibiwoye, MD, DTM &H, MPH, PhD E-mail: [email protected] Office Hours: By Appointment Thursday, 9 November 2023 Reading Assignment • Moore KL, Dalley AF and Agur AMR: Clinically Oriented Anatomy, 9th Edition (2023). Chapter 8: Head (Section on Face and Scalp) • Drake RL, Vogl AW and Mitchell AWM: Gray’s Anatomy for Students, 5th Edition (2023). Chapter 8: Head and Neck • Frank H:Netter’s Atlas of Human Anatomy, 8th Edition (2022) Learning Objectives • Describe the boundaries of the face and how facial bones articulate with each other. • Know major foramina, bony landmarks and muscles of the face, orbit and scalp. • Know which cranial nerves supply cutaneous innervation to the face. • Identify the muscles of facial expression, their functions, and motor innervation. • Describe the arterial supply, venous and lymphatic drainage of the face. • Know some examples of clinical applications associated with this region of the body Face: Introduction FACE: • Anterior aspect of the head bounded superiorly by the superciliary arches, inferiorly by the lower edge of the mandible and posteriorly by the right and left ears. • Shape of face reflects identity of individual human beings. • Trauma, scarring, etc., could have consequences beyond their physical effects. • The underlying bones determine the basic shape of the face • Plays a key role in communication – e.g., interactions with one another and with your Note positions of the 3 foramina (red rectangles) and how they are named based on location on the face! Nasal Nasal Nasal Nasal Nasion Bones of the Face Bones of the Orbit (See Your Bone Box) Seven bones comprise the orbital walls (blue circles): 1. Ethmoid 2. Lacrimal 3. Palatine 4. Maxilla 5. Zygomatic 6. Sphenoid 7. Frontal (Can you identify them?) SCALP: • Consists of hair-bearing skin and subcutaneous tissue covering the neurocranium from the superior nuchal lines on the occipital bone to the supra-orbital margins of the frontal bone • Extends laterally over the temporal fascia to the zygomatic arches. • Composed of FIVE LAYERS, the first three of which are connected intimately and move as a unit (e.g., as in wrinkling the forehead). • Each letter in the word “SCALP” serves as a mnemonic for each of its five layers (annotated in red): Scalp: Five Layers Scalp in Coronal Plane Depicting the Five Layers • • • Skin; thin, except in the occipital region; has sweat and sebaceous glands and hair follicles, rich arterial supply, venous and lymphatic drainage. Connective tissue (thick, dense, attaches the skin to third layer; highly vascularized; rich supply of cutaneous nerves); Aponeurosis (aka epicranial aponeurosis/galea aponeurotica): firmly attached to the skin by the dense connective tissue of the second layer. Scalp: Five Layers (Contd.) • Loose areolar tissue: sponge-like layer, includes potential spaces that may distend with fluid due to injury or infection; allows free movement of the scalp proper (i.e., first 3 layers - skin, connective tissue & epicranial aponeurosis) over the underlying calvaria; • Pericranium (periosteum of the outer table of bone). the occipitofrontalis muscle is attached to this layer Scalp: Five Layers (Contd.) Scalp Layers: Illustrative Summary Skin Connective tissue Aponeurosis Loose connective tissue Pericranium SCALP Muscles Attached to Aponeurotic Layer Aponeurosis (epicranial aponeurosis): • Broad, strong, tendinous sheet that covers the calvaria; serves as the attachment for muscle bellies converging from the forehead, occiput (occipitofrontalis muscle) & temporal bones on each side (temporalis and superior auricular muscles). • The frontal belly of the occipitofrontalis pulls the scalp anteriorly, wrinkles the forehead, and elevates the eyebrows while The occipital belly pulls the scalp posteriorly, smoothing the skin of the forehead. • The superior auricular muscle elevates the auricle of the external ear. • All parts of the above epicranial muscles and aponeurosis are Other Muscles Innervated by Facial Nerve • • • Stapedius Posterior belly of digastric Stylohyoid • • • All muscles of facial expression develop from mesoderm in the second pharyngeal arches, carrying branches of the nerve of the arch (the facial nerve, CN VII) with it to supply all the muscles formed from the arch The muscular sheet differentiates into muscles that surround the facial orifices (mouth, eyes, and nose), serving as sphincter and dilator mechanisms that also produce many facial expressions Due to their common embryological origin, the platysma and facial muscles are often fused, and their fibers are Innervation of Facial Muscles Identifying Muscles of Face and Scalp Muscles of the Face 3 Groups: Orbital Nasal Oral 1. Anterior nasal spine 2. Body of mandible 3. Frontal bone 4. Frontal notch 5. Frontal process of maxilla 6. Glabella 7. Greater wing of sphenoid bone 8. Infra-orbital foramen 9. Infra-orbital margin 10. Inferior nasal concha 11. Inferior orbital fissure 12. Lacrimal bone 13. Lesser wing of sphenoid bone 14. Maxilla 15. Mental foramen 16. Mental protuberance 17. Middle nasal concha 18. Nasal bone 19. Nasal septum 20. Nasion 21. Orbit (orbital cavity) 22. Ramus of mandible 23. Superior orbital fissure 24. Supra-orbital foramen 25. Supra-orbital margin Facial Muscle Attachments: Useful Landmarks I. The orbicularis oculi: • Large muscle that surrounds each orbital orifice and extends into each eyelid • Outer orbital part is a broad ring that encircles the orbital orifice and extends outward beyond the orbital rim. • Inner palpebral part is in the eyelids and consists of muscle fibers originating in the medial corner of the eye that arch across each lid to attach laterally. II. Corrugator supercili: • Smaller, deep to the eyebrows and the orbicularis oculi muscle and is active when frowning. • Arises from the medial end of the superciliary arch, passing upward and laterally to insert into the skin of the medial half of the eyebrow. • Draws the eyebrows toward the midline, causing vertical wrinkles above the nose. Group I: Orbital Group (2 Muscles) Two Parts of Orbicularis Oculi: Actions Orbital part closes eyelids forcefully Palpebral part closes eyelids gently Facial Muscles: I. Orbital Group (Summary) Facial Muscles: II. Nasal Group (3 Muscles) I. Nasalis • Largest and best developed of the muscles of the nasal group • Active when the nares are flared. • Consists of a transverse part (the compressor naris) and an alar part (the dilator naris): • Transverse part compresses the nares, originates from the maxilla and its fibers pass upward and medially to insert, along with fibers from the same muscle on the opposite side, into an aponeurosis across the dorsum of the nose. • Alar part draws the alar cartilages downward and laterally, so opening the nares and, • Originates from the maxilla, below and medial to the transverse part, and inserts into the alar cartilage. Facial Muscles: II. Nasal Group (3 Muscles) (Contd.) II. Procerus • Small muscle superficial to the nasal bone and is active when an individual frowns. • Arises from the nasal bone and the upper part of the lateral nasal cartilage and inserts into the skin over the lower part of the forehead between the eyebrows. • Draws the medial border of the eyebrows downward to produce transverse wrinkles over the bridge of the nose. III. Depressor septi nasi • Assists in widening the nares. Arises from the maxilla above the central incisor tooth and ascend to insert into the lower part of the nasal septum. • Pulls the nose inferiorly, so assisting the alar part of the nasalis in opening the nares. Facial Muscles: II. Nasal Group (Summary) The Orbicularis Oris • Complex muscle consisting of fibers that completely encircle the mouth. • Its function is apparent when pursing the lips, as occurs during whistling. • Some of its fibers originate from the maxilla superiorly and the mandible inferiorly, whereas other fibers are derived from both the buccinator, in the cheek, and the numerous other muscles acting on the lips. • Inserts into the skin and mucous membrane of the lips. Facial Muscles: III. Oral Group Facial Muscles: III. Oral Group (Contd.) Buccinator: • • • • Arises from posterior part of maxilla & mandible; Inserted into orbicularis oris around the mouth Resists distension of the cheeks when blowing Protects by keeping inner cheek walls away from molars during chewing Levator Labii Superioris Alaeque Nasi (LLSAN) in Action Functions of LLSAN: • Snarled or angry appearance, with • Elevation and external rotation of the lateral ala, Acute nasolabial angle, enhanced nasolabial folds, and • Prominent lateral bunny lines Facial Muscles: III. Oral Group (Summary) Other Muscles Derived from 2nd Pharyngeal Arch Specific Facial Expressions by Individual Facial Muscles Trigeminal Nerve: 3 Paired Divisions (V1, V2, V3) and 3 Corresponding Pairs of Foramina 3 Trigeminal Nerve Divisions 3 Foramina V1 Ophthalmic Supraorbit al V2 Maxillary Infraorbit al V3 Mandibular Menta l Review Your Understanding: Summary of Objectives So Far! • Describe the boundaries of the face and how facial bones articulate with each other. • Know major foramina and bony landmarks of the face and scalp. • Identify the muscles of facial expression, their functions, and motor innervation. Sensory Innervation of Face and Scalp Derived From V1, V2 and V3 Innervation of the scalp: • Anterior to the auricles of the external ears is through branches of all three divisions of CN V, the trigeminal nerve (V1, V2 and V3). • Posterior to the auricles, the nerve supply is from spinal cutaneous nerves (C2 and C3) (see next slide Innervation of Face and Scalp Derived From V1, V2 and V3 (Contd.) Course and Distribution of CNV Branches (V1, V2 and V3) Course and Distribution of CNV Branches - V1, V2 and V3 (Contd.) Distribution of CNV Branches - V1, V2 and V3 Trigeminal Nerve (CNV): (Contd.) Type: Mixed sensory and motor • Originates from the lateral surface of the pons by two roots: motor and sensory (analogous motor (anterior) and sensory (posterior) roots of spinal nerves. • Sensory root of CN V consists of the central processes of neurons located in a sensory ganglion (trigeminal ganglion). • Motor root is the motor nerve that supplies the muscles of mastication (temporalis, lateral and medial pterygoid and Branches From the 3 Divisions of Trigeminal Nerve: Summary Facial Nerve (CNVII): Origin and Course Facial nerve (CN VII) finally exits skull via the stylomastoid foramen and branches to supply facial expression muscles (next slide) Facial Nerve (CNVII): Branches of Facial Terminal branches (6 branches) arise from Nerve the parotid plexus (CN VII). within the parotid gland. The branches emerge from the gland under cover of its lateral surface and radiate anteriorly across the face • Temporal • Zygomatic P: Parotid Gland • Buccal • Marginal mandibular • Cervical Useful Mnemonic: Two Zebras Bit My Clavicle Painfully • Posterior auricular • • • • Blood Supply of the Face & Scalp Facial artery (a branch of the external carotid) Source from internal carotid artery (in asterisks provides most of the arterial supply to the face Winds around the mandible anterior to masseter crosses the mandible, buccinator, and maxilla and courses over the face to the Other derivatives of the external medial angle of the eye, carotid: superficial temporal and where the superior and transverse facial (from superficial inferior eyelids meet temporal) arteries; mental artery is a Gives off superior and direct branch of the maxillary artery. inferior labial arteries The supratrochlear and supraorbital and lateral nasal arteries arteries are branches of the Finally becomes angular ophthalmic artery, a branch of the artery just distal to the internal carotid artery. lateral nasal artery Blood Supply of Face & Scalp: Summary Blood Supply of Face & Scalp: Summary (Contd.) Source from internal carotid artery (asterisks) Blood Supply of Face & Scalp: Diagrammatic Illustration Facial Veins: • Provide the main superficial drainage of the face. • Supratrochlear and supraorbital veins unite to form the ANGULAR VEIN. • Angular vein becomes the facial vein and lies just posterior to the facial artery; • Facial vein drains eyelids, external nose, lips, cheek, and chin; • Communicates with ophthalmic veins (via supratrochlear and supraorbital veins) and the deep facial vein that drains the pterygoid venous plexus in the deeper regions of the head and neck. Venous Drainage of Face and Scalp Lymphatic Drainage of the FaceNodes: 3 Groups of Superficial Lymph I. Submental: drain medial part of lower lip and chin bilaterally II. Submandibular: drain medial corner of orbit, most of external nose, medial cheek, upper lip III. Pre-auricular and parotid: drain most of eyelids, part of external nose and lateral part of the cheek. Note: Arrows indicate direction of lymph flow to lymph nodes Lymphatic Drainage of the Face (Contd.) All lymphatic vessels from the face: • Directly or indirectly into the deep cervical lymph nodes a chain of nodes mainly located along the internal jugular vein (IJV) in the neck. • Lymph from these deep nodes passes to the jugular lymphatic trunk, which joins the thoracic duct on the left side and the IJV or brachiocephalic vein on the right side. Review Your Understanding: Summary of Objectives So Far! • • Know which cranial nerves supply cutaneous innervation to the face. Describe the arterial supply, venous and lymphatic drainage of the face. • Know some examples of clinical applications associated with this region of the body: Final Objective Clinical Application: I. Trigeminal Neuralgia Trigeminal Neuralgia: • Chronic pain (a.k.a. “tic douloureux”) • Mild sensory stimulation (e.g., brushing teeth) of your face can result in severe, excruciating pain • Usually on one side (unilateral) • Usually more common in women (older than 50 years) • Multiple causes (e.g., contact between a vessel and the trigeminal nerve, multiple sclerosis, etc.) • Treatment starts with medications, may become so severe as to require surgery Clinical Application: II. Inferior Alveolar Nerve Block Most Vulnerable Parts of the Face (Danger Triangle!!!) • • • • • • Blood from the medial angle of the eye, nose, and lips usually drains inferiorly through the facial vein. Facial vein is valveless and so, Blood may pass through facial vein in the opposite direction. Therefore, venous blood from the face may enter the cavernous sinus. Thrombophlebitis of the facial vein may spread into the intracranial venous system and produce thrombophlebitis of the cavernous sinus. Infection of the facial veins spreading to the dural venous sinuses may result from lacerations of the nose or be initiated by squeezing pustules (pimples) on the side of the nose and upper lip. Triangular area (danger zone): Extends from the upper lip to the bridge of the nose Facial Nerve Lesions The complexity of the facial nerve [VII] is demonstrated by the different pathological processes and sites at which these processes occur (Print out slide 36 above, and use it as reference guide for slides 47-50) The Facial Nerve [VII] Origin and Course: • Formed from the nuclei within the brainstem emerging at the junction of the pons and the medulla. • Enters the internal acoustic meatus, passes to the geniculate ganglion, and emerges from the skull base after a complex course within the temporal bone, leaving through the stylomastoid foramen (see slide #11 above). • Enters the parotid gland and gives rise to terminal branches that supply muscles in the face and deeper or more posterior muscles (see slide #11 above). • Series of lesions may affect the nerve along its course, and it is possible to clinically determine the site of the lesion in relation to the course of the nerve (use slide #34 as a guide to possible lesion site). Facial Nerve Lesions (Contd.) I. Central lesions of Facial Nerve • Primary brainstem lesion affecting the facial [VII] motor nucleus would lead to ipsilateral (same side) weakness of the whole face. • Because the upper part of the nucleus receives motor input from the left and right cerebral hemispheres a lesion occurring above the nucleus leads to contralateral lower facial weakness. Therefore, • Motor innervation to the upper face is spared because the upper part of the nucleus receives input from both hemispheres. Preservation and loss of the special functions are determined by the extent of the lesion. II. Lesions at and around the geniculate ganglion • Lesions around the geniculate ganglion are accompanied by loss of motor function on the whole of the ipsilateral (same) side of the face. • Taste to the anterior two-thirds of the tongue, lacrimation, and some salivation also are likely to be affected because the lesion is proximal to the greater petrosal and chorda tympani branches of the nerve. Facial Nerve Lesions (Contd.) Lesions at and around the stylomastoid foramen • Lesions the level of the stylomastoid foramen are the commonest abnormality of the facial nerve and usually result from a viral inflammation of the nerve within the bony canal before exiting through the stylomastoid foramen. • Typically, the patient has an ipsilateral loss of motor function of the whole side of the face (see next slide). • Not only does this produce an unusual appearance, but it also prevents chewing of food. • Lacrimation and taste may not be affected if the lesion remains distal to the greater petrosal and chorda tympani branches that originate deep in the temporal bone.
