Lecture 37: Gross Anatomy - Scalp & Skull PDF

Lecture 37: Gross Anatomy - Scalp & Skull Overview of head: 1 cranial cavity + 2 ears + 2 orbits + 2 nasal cavities + 1 oral cavity Major functions: protecting brain & receptor systems associated w/ special senses, senses environment (vision, olfaction, taste, hearing, balance), start of respirator...

Lecture 37: Gross Anatomy - Scalp & Skull Overview of head: 1 cranial cavity + 2 ears + 2 orbits + 2 nasal cavities + 1 oral cavity Major functions: protecting brain & receptor systems associated w/ special senses, senses environment (vision, olfaction, taste, hearing, balance), start of respiratory & GI systems, communication (sound & facial) Face: anterior aspect of head; extends from area b/w superciliary arches (superior), lower edge of the mandible (inferior) & as far back as the ears (lateral/posterior) Skull: covers the superior, posterior, & lateral regions of the head; extends from superciliary arches (anterior) to external occipital protuberance & superior nuchal lines (posterior) & zygomatic arch (lateral) Scalp: 5 layers: Skin, dense Connective tissue (anchors skin to aponeurotic layer, contains NVBs), Aponeurotic layer (consists of occipitofrontalis m. & aponeurotic tendon, which make up the epicranial aponeurosis), Loose connective tissue (facilitates movement of the scalp proper over the calvaria), Pericranium (periosteum on outer surface of calvaria) Scalp lacerations (CC): often bleed profusely due to rich blood supply & DCT holding cut vessels open Dangerous area of scalp (CC): LCT layer can transmit infection from scalp to cranial cavity via emissary vv. (no valves, connect scalp vv. to diploic vv. & intracranial venous sinuses) Sensory innervation: major sources are CN V & cervical nerves C2 & C3 Trigeminal branches (CN V): ophthalmic division (V1) = supratrochlear & supraorbital nn., maxillary division (V2) = zygomaticotemporal n., mandibular division (V3) = auriculotemporal n. Cervical nerves (C2 & C3): ventral rami = great auricular n. (C2/C3), lesser occipital n. (C2); dorsal rami = greater occipital n. (C2) & third occipital n. (C3) Arteries: major sources are ophthalmic a. from internal carotid (branches = supraorbital a. & supratrochlear a.) & branches of external carotid (superficial temporal, posterior auricular, & occipital aa.) Veins: supraorbital & supratrochlear vv. → ophthalmic v.; superficial temporal & posterior auricular v. → retromandibular v. → external jugular; occipital v. → internal jugular CC: scalp bleeding is predominantly arterial due to low venous pressure in erect position Lymphatic drainage: occipital region → occipital nodes → upper deep cervical nodes; upper scalp posterior to vertex → mastoid nodes (retro/posterior auricular) → upper deep cervical nodes; upper scalp anterior to vertex → pre-auricular & parotid nodes; all eventually drain into jugular trunk in root of neck Skull: houses & protects the brain & special sensory organs & serves as attachments for head mm. Components of skull: 22 bones arranged into a cranium & mandible Cranium: neurocranium (calvaria/domed part + base/floor) + viscerocranium (facial skeleton) Calvaria: superior view = anterior frontal bone + lateral parietal bones (paired) + posterior occipital bone Parietal foramen: emissary vv. pass through them Lateral view: reveals paired sphenoid bones (posterior to eyes) & temporal bones (deep to ears) Posterior view: shows temporal, parietal, sphenoid, & occipital bones Pterion: junction where the frontal, parietal, sphenoid, and temporal bones are in close proximity CC: the bone in the pterion area is particularly thin & overlies the anterior division of the middle meningeal a., which can be torn by a skull fx in this area, resulting in an extradural hematoma Sutures: immovable fibrous joints which connect the bones of the cranium; major sutures = coronal, sagittal, lambdoid, squamous, sphenosquamous, sphenoparietal, occipitomastoid, parietomastoid Fontanelles: membranous & un-ossified gaps b/w the bones of the skull which allow the head to deform during birth; anterior, posterior, sphenoidal, & mastoid; most close during 1st year of life, full ossification begins in late 20s & finishes in 5th decade of life Base of cranium: formed by frontal, ethmoidal, sphenoid, temporal, & occipital bones Facial skeleton: formed by mostly paired bones (nasal, maxilla, zygomatic, lacrimal, inferior nasal conchae, & palatine bones) & unpaired vomer External foramina in frontal view: External foramina in ant/mid inferior view: —---------—→ Sphenoid bone: articulates w/ vomer (inferiorly) & perpendicular plate of ethmoid bone (ant.) Features on temporal bone: mastoid process, styloid process, carotid canal (posterolateral from foramen lacerum), pharyngotympanic (auditory) tube (in groove b/w petrous part of temporal & greater wing of sphenoid), mandibular fossa (concavity where mandible articulates w/ base of skull) Features on occipital bone: pharyngeal tubercle (bone protuberance for attachment of parts of pharynx to base of skull) External foramina in post. inferior view: —--------—----→ Other features in post. inferior view: occipital condyles (articulate w/ atlas), external occipital crest, external occipital protuberance, inferior nuchal line, superior nuchal line Cranial cavity: the space w/in the calvarium that contains the brain, meninges, proximal parts of the CN’s & blood vessels & cranial venous sinuses Anterior cranial fossa: filled by frontal lobes of the cerebral hemispheres; has midline frontal crest (in frontal bone) & cribriform plate (in ethmoid) Internal foramina: —--------—--------------------------→ Middle cranial fossa: contains temporal lobe of brain & pituitary gland Internal foramina: —-------------------------------------→ Posterior cranial fossa: contains brainstem (midbrain, pons, medulla) & cerebellum Internal foramina: —-------------------------------------→