--- module: 080-01 language: en chapter: 80 title: "Head, Neck, Cranial Nerves, Pharynx, and Larynx Anatomy" module_title: "Skull, scalp, face, orbit, nasal cavity, and oral cavity" source_sha256: b46c557427a59f195e2cae51633c74fa39b78c992a63dc1bc43f0c2f0a166fbe --- # Skull, scalp, face, orbit, nose, and mouth ## Skull and cranial base ### Neurocranium surrounds brain, viscerocranium forms face ### Calvaria: outer and inner tables with diploic veins ### Sutures permit growth, then interdigitate ### Fontanelles allow moulding and assessment #### Palpation also reflects position, hydration, crying ### Anterior fossa: cribriform plate and optic canals #### Fracture: anosmia and CSF rhinorrhoea ### Middle fossa: orbital fissure, rotundum, ovale, spinosum ### Posterior fossa: acoustic meatus, jugular, hypoglossal ### Foramen magnum: medulla and vertebral arteries ## Scalp and meninges ### Five scalp layers #### Dense tissue holds cut vessels open ##### Profuse bleeding #### Loose layer connects via emissary veins ##### Historical dangerous area ### Aponeurosis links frontal and occipital bellies #### Subaponeurotic blood spreads widely #### Cephalohaematoma limited by sutures ### Dura: periosteal and meningeal layers #### Separation forms venous sinuses #### Folds: falx, tentorium, diaphragma sellae #### Tentorial notch: pressure boundary in herniation ### Pterion fracture tears middle meningeal artery #### Epidural haematoma ### Acceleration tears bridging veins #### Subdural bleeding ## Face ### Expression muscles: second arch, facial nerve ### Mastication muscles: first arch, mandibular nerve ### Trigeminal territories meet and overlap #### Angle of mandible: upper cervical nerve ### Facial artery crosses mandible anterior to masseter ### Valveless facial vein links to cavernous sinus #### Central face infection can spread, rarely severe ### Parotid duct pierces buccinator at upper second molar ### Facial nerve traverses parotid, not secretomotor ### Parotid fascia limits swelling, causing pain ## Temporomandibular joint and chewing ### Synovial joint divided by articular disc #### Lower compartment rotates, upper translates #### Wide opening: condyle-disc onto eminence ### Masseter, temporalis, medial pterygoid elevate ### Lateral pterygoid protrudes and assists opening #### Unilateral action moves jaw contralaterally ### Auriculotemporal nerve: joint sensation, parotid fibres ### Disc, muscle, arthritis, referred pain look alike ## Orbit ### Pyramid: base anterior, apex posterior ### Thin floor and medial wall #### Vulnerable in blowout fracture ### Apex joins cranium via canal and fissure ### Orbital septum limits anterior infection #### Postseptal infection threatens vision and sinus ### Oculomotor supplies most extraocular muscles #### Lateral rectus abducens, superior oblique trochlear ### Tears drain via nasolacrimal duct to inferior meatus ### Secretomotor: facial, pterygopalatine, trigeminal ## Nasal cavity and sinuses ### Septum: cartilage, ethmoid plate, vomer ### Conchae warm, humidify, direct airflow ### Meatal drainage #### Middle meatus: frontal, maxillary, anterior ethmoid #### Inferior meatus: nasolacrimal duct ### High maxillary ostium limits gravity drainage ### Sphenoid sinus near pituitary, optic nerves, carotids ### Kiesselbach region: common anterior bleeding ### Posterior bleeding near sphenopalatine, hard to see ## Ear ### External canal: cartilaginous lateral, bony medial ### Tympanic membrane: malleus handle, umbo, light reflex ### Middle ear: air space with ossicles, chorda tympani #### Tube to nasopharynx, back to mastoid cells #### Infection reaches mastoid, facial nerve, dura, sinus ### Tensor tympani trigeminal, stapedius facial ### Inner ear: endolymph within perilymph #### Vestibule senses acceleration, cochlea vibration ## Oral cavity, palate, tongue, and teeth ### Soft palate separates nasopharynx in swallowing ### Tensor veli palatini mandibular, others vagal ### Intrinsic muscles shape, extrinsic position tongue ### Hypoglossal supplies all but palatoglossus #### Weakness deviates tongue toward weak side ### Anterior two-thirds: lingual nerve, chorda tympani ### Posterior third: glossopharyngeal for both ### Dental infection follows roots and muscle attachments ## Clinical localisation ### Rigid compartments linked by foramina ### Trace symptoms through bone, space, nerve, vessel