BMS100_Face, Skull and Neck.docx

BMS100 – MSK4 FACE, SCALP, CRANIUM, NECK, MUSCLES OF MASTICATION AND CRANIAL NERVES Scalp Skin – physical barrier from trauma and potential pathogens Dense CT – hair follicles, vessels, nerves and lymph Aponeurosis – galea aponeurotica; continuous with muscle Loose CT – mobility of the scalp Peri...

BMS100 – MSK4 FACE, SCALP, CRANIUM, NECK, MUSCLES OF MASTICATION AND CRANIAL NERVES Scalp Skin – physical barrier from trauma and potential pathogens Dense CT – hair follicles, vessels, nerves and lymph Aponeurosis – galea aponeurotica; continuous with muscle Loose CT – mobility of the scalp Pericranium – dense irregular CT; tightly adhered to cranium bone MUSCLES OF SCALP AND FOREHEAD MUSCLE ATTACHMENT/LOCATION INNERVATION ACTION Occipitofrontalis Origin: galea aponeurotica layer of skull Insertion: Frontalis – skin over eyebrows Occipitalis – superior nuchal line Temporal branch of facial nerve (CN VII) Posterior auricular branch of facial nerve (CN VII) Elevate eyebrows and wrinkle forehead skin (frontal part) Retract scalp (occipital part) MUSCLES OF ORBIT MUSCLE ATTACHMENT/LOCATION INNERVATION ACTION Orbicularis Oculi Sphincter muscle arranged in concentric bands around the upper and lower eyelids Close eyelids (when muscle contracts) Levator palpebrae superioris Triangular-shaped muscle located in each upper eyelid Elevation and retraction of upper eyelid MUSCLES OF MOUTH, LIPS AND CHEEKS MUSCLE ATTACHMENT/LOCATION INNERVATION ACTION Levator labii superioris Maxilla to upper lip skin Cranial nerve VII – facial nerve Elevator, retractors and evertors of upper lip Move upper lip towards eye Zygomaticus major and minor Lateral surface of zygomatic bone to the angle of the mouth Elevator, retractors and evertors of upper lip Smiling (true smile) Risorius Superficial layer of facial muscles overlying the buccinator muscle Elevator, retractors and evertors of upper lip Moving corner of lip (fake smile) Orbicularis oris Sphincter around the mouth Closes and protrudes lips = kissing Helps keep food in mouth Buccinator Wide band of muscle on cheek Presses cheeks against teeth and lips = whistling Helps to keep food in mouth Resists distention of the mouth Several dilator muscles Radiate from lips and angles of the mouth like spokes of a wheel Retracting the various borders of the oral fissure collectively, in groups or individually Pull lips down = grimace and frowning MUSCLES OF MASTICATION MUSCLE ATTACHMENT/LOCATION INNERVATION ACTION Temporalis Origin: temporal fossa and fascia Insertion: coronoid process and anterior border of ramus of mandible Mandibular nerve (V3) Elevation and retraction of the mandible (close jaw) Masseter Origin: zygomatic arch Insertion: lateral surface of ramus of mandible Elevation and protraction of the mandible (pulling lower jaw to upper jaw; forward sliding of jaw) Medial pterygoid Origin: pterygoid process of sphenoid bone Insertion: medial surface of angle of mandible Elevation, protrusion, and contralateral deviation of mandible Lateral pterygoid Origin: pterygoid process of sphenoid bone Insertion: articular disc and neck of the mandible Protrusion and contralateral deviation of mandible; depression Temporomandibular joint (TMJ): the two joints that connect lower jaw to your skull Movements of TMJ Opening of the mouth – anterior movement of the head of the mandible and the articular disc on the articular surface of the mandibular fossa When mouth is fully opened – head of the mandible lies inferior to the articular tubercle Rocking and sliding movement Initial movement – rock of condyle against the disc Second movement – sliding of the condyle against the disc Articular surfaces – lined with hyaline Disc Condylar process of mandible Articular tubercle of temporal bone Mandibular fossa of temporal bone Synovial joint – combined hinge and planar type TMJ-articular disc (meniscus): fibrocartilaginous disc that separates the joint cavity into superior and inferior compartments each with its own synovial membrane Superior and inferior compartments are separate both structurally and functionally Articular capsule: loose covering around the circumference of the joint Attaches the margins of articular area on temporal bone and around the mandible; lined by synovial membrane Ligaments of TMJ TMJ-lateral ligament: consists of two short bands on the lateral surface of the articular capsule Extends inferiorly and posteriorly from inferior border and tubercle of the zygomatic process of the temporal bone to the lateral and posterior aspect of the neck of mandible (from mandible to zygomatic arch) Covered by parotid gland and strengthens the TMJ laterally Helps prevent posterior dislocation of the mandible TMJ-sphenomandibular ligament: supporting, extrinsic ligament Extends from spine of sphenoid to the medial surface of the ramus of the mandible (sphenoid to mandible) Does not contribute significantly to the strength of TMJ (tethers mandible to skull) TMJ-stylomandibular ligament: supporting, extrinsic ligament Extends from the styloid process of the temporal bone to the inferior and posterior borders of ramus of mandible (styloid process to the angle of the mandible) Separates the parotid gland from the submandibular gland and limits movement of the mandible at the TMJ Limits swinging open motion; prevents further opening Dislocation of TMJ Can happen during yawning, taking a large bite to sideways blow to the chin when mouth is open – mandible dislocates anterior to the articular tubercle Movements of Mandible Muscle(s) Elevation (close mouth) Temporalis, masseter, medial pterygoid Depression (open mouth) Lateral pterygoid, suprahyoid, infrahyoid muscles Protrusion (protrude chin) Lateral pterygoid, masseter, medial pterygoid Retrusion (retrude chin) Temporalis (posterior oblique and near horizontal fibers) Lateral movements (grinding and chewing) Temporalis of same side, pterygoids of opposite side and masseter BLOOD SUPPLY TO THE FACE, HEAD AND NECK Blood supply From aorta – ascending and arch of aorta Brachiocephalic artery (head and neck) Left common carotid artery (brain) Left subclavian artery (upper limb) Descending aorta (rest of body) Subclavian artery branches Pre-scalene part: Vertebral artery brain supply Internal thoracic artery anterior thoracic wall and breast tissue Thyrocervical trunk larynx, trachea, esophagus, thyroid Post-scalene part: Dorsal scapular artery – back of scapula Carotid artery branches Left and right common carotid arteries supply the head and neck with oxygenated blood; divides at level of C3 or C4 cervical vertebrae to form external and internal carotid External common carotid arteries supplies blood to the face and neck Internal common carotid arteries brain, eyes Ophthalmic artery Anterior cerebral artery Middle cerebral artery Posterior communicating artery Posterior cerebral artery Carotid body – sensory to give feedback about blood pressure, blood content, ion concentration VENOUS DRAINAGE FROM THE FACE, HEAD AND NECK Venous drainage of the head and neck begins from three main venous systems: Intracranial – cerebral veins (sinuses) Superficial veins Deep veins Three sources form the two main veins of the neck internal and external jugular veins = drain all blood from head and neck External veins of the face Cavernous sinus Superficial temporal Posterior auricular Retromandibular (posterior and anterior divisions) External jugular Internal jugular Subclavian Superior and inferior ophthalmic Angular Facial NERVES OF THE FACE, HEAD AND NECK Main facial nerves: Cranial nerve 5 – trigeminal nerve Three branches: V1 – ophthalmic (sensory) V2 – maxillary (sensory) V3 – mandibular Cranial nerve 7 – facial nerve Five branches (can use fingers to remember starting with thumb): Temporal Zygomatic Buccal Mandibular Cervical Peripheral nerves: travels through intervertebral foramen and extends everywhere in the body that is not your spinal cord or brain; two subsystems: Autonomic – automatic functions vs. somatic – purposeful functions All of these are routes by which all signals travel from the brain and spinal cord to the body structures - sensory and motor signals can be conscious or unconscious Spinal nerves: 31 pairs that attach to the spine and serve the upper limb, trunk and lower limb Cranial nerves: 12 pairs that connect directly to the brain and serve the head and neck Olfactory Optic Oculomotor Trochlear Trigeminal Abducent (abducens) Facial Vestibulocochlear Glossopharyngeal Vagus Spinal accessory Hypoglossal BONES OF SKULL (CRANIUM) Skull (cranium): complex structure composed of two distinct regions – neurocranium and viscerocranium Viscerocranium: bones that make of the face skeleton [14 bones – 6 paired and 2 unpaired*] Lacrimal bone Nasal bone Zygomatic bone Maxilla Inferior nasal concha Mandible* Vomer* Neurocranium: brain case; bones that accommodate the human brain [8 bones – 2 paired and 4 unpaired*] Parietal bone Temporal bone Frontal bone* Occipital bone* Sphenoid bone* Ethmoid bone* Important landmarks of the skull: Temporal fossa – above midpoint of zygomatic arch Pterion – joining of 4 bones (temporal, parietal, frontal and sphenoid bones) Lambda – posterior marker; two parietal bones and occipital bone meet Lambdoid suture – dense fibrous connective tissue joint on posterior aspect of skull; connects the two parietal bones with occipital bone Bregma – anterior marker; two parietal bones and frontal bone meet Skull of a newborn: Posterior fontanelle – closes 2-3 months Lateral fontanelle – closes 6 months Anterior fontanelle – 12-18 months Choanae – opening of nasal cavity; posterior nasal aperture separated by the vomer (opening between nasal cavity and nasopharynx) Floor of the cranial cavity is divided into three distinct depressions Anterior cranial fossa Ethmoid bone Crista galli – attachment for dura matter Cribiform plate – openings for cranial nerves Middle cranial fossa Sphenoid bone Body of sphenoid bone Sella turcica Hypophyseal fossa Dorsum sellae Temporal bone Groove for superior petrosal sinus Foramina of cranial base: Optic canal Superior orbital fissure Foramen rotundum Foramen ovale Foramen spinosum Foramen lacerum Carotid canal Posterior cranial fossa Temporal bone – groove for sigmoid sinus Occipital bone – groove for transverse sinus Foramina of cranial base: Internal acoustic meatus Jugular foramen Hypoglossal canal Foramen magnum