Intro to head and neck anatomy (gross lab 1) Flashcards Preview

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Cranial cavity

-Divided into 3 parts (fossa)
-Anterior cranial fossa
-Middle cranial fossa
-Posterior cranial fossa


Anterior cranial fossa (CN I)

-Frontal bone, ethmoid bone (cribiform plate and crista galli), lesser wing of sphenoid bone
-Cribiform plate + olfactory fibers
-Olfactory bulb and tract (CN I)
-Crista galli: anterior connection of falx cerebri


Middle cranial fossa (CN II-VI)

-Sphenoid bone (body, greater wing, groove for middle meningeal artery)
-Optic canal: CN II and opthalmic artery
-Superior orbital fissue: III, IV, V1, VI, opthalmic vein
-Foramen rotundum: V2
-Foramen ovale: V3
-Foramen spinosum: middle meningeal artery
-Carotid canal: internal carotid artery
-Cavernous sinuse, containing VI and internal carotid w/in sinus, and III, IV, V1 and V2 as lateral walls
-Temporal bone (squamous and petrous parts): hiatus for greater petrosal nerve, greater petrosal nerve


Posterior cranial fossa (CN VII-XII)

-Temporal bone (petrous part)
-Internal acoustic meatus: VII, VIII
-Jugular foramen: IX, X, XI
-Occipital bone (basilar part, condyle)
-Hypoglossal canal: XII
-Foramen magnum: XI, vertebral artery
-Posterior cranial fossa houses the internal jugular, sigmoid and transfers sinuses


Cranial nerves I, II, and VIII

-Special senses only
-CN I: olfactory, only sense of smell
-CN II: optic, only sense of vision
-CN VIII: vestibulocochlear, only sense of hearing and balance


Cranial nerves III, IV, VI

-Cell body origins: III and IV from midbrain, VI from medulla
-III (para/pre, SM): oculomotor, innervates extraocular muscles (except superior oblique and lateral rectus muscles) and provides parasympathetics to the eye
-IV (SM): trochlear (pulley), innervates the superior oblique muscle
-VI (SM): abducent (abducts), innervates the lateral rectus muscle


Cranial nerves XI and XII

-Both only innervate skeletal muscle
-Cell body origins: XI from spinal cord C5-6, XII from medulla
-XI (SM): accessory, innervates SCM/trapezius
-XII (SM): hypoglassal, innervates all tongue muscles (glossal=tongue)


Cranial nerve V

-Trigeminal nerve, originating from and innervating the 1st pharyngeal arch
-Has 3 subdivisions: V1 (opthalmic, SS only), V2 (maxillary, SS only), V3 (mandibular, SS and SM)
-Cell bodies of SS for all divisions in trigeminal ganglia, where the trigeminal nerve breaks off into its subdivisions
-Cell bodies of SM (V3 only) in pons
-Provides SS innervation to all ectodermally derived structures, including face, teeth, cornea, nasal, and oral mucosa (general sensory to anterior 2/3rds of tongue)
-V3 SM innervates: masseter, temporalis, medial and lateral pterygoid, anterior diagastric, mylohyoid, and others


Cranial nerve VII

-Facial nerve, originating from and innervating the 2nd pharyngeal arch
-Provides taste to tongue (anterior 2/3rds), parasympathetics to all but one gland of the head
-Also contains SS and SM to many facial muscles (those originating from the 2nd arch): facial expression, posterior diagastric, stylohyoid, stapedius
-Cell bodies in the medulla


Cranial nerve IX

-Glossopharyngeal nerve, originating from and innervating the 3rd pharyngeal arch
-Provides taste to tongue (posterior 1/3rd, along w/ vagus), general sensation (SS) to external auditory meatus and tympanic membrane, and provides parasympathetic to parotid gland
-Also contains SM (innervating the muscle originating from the 3rd arch: stylopharngeus), and VS (pain/reflex to endodermally-derived structures: middle ear, eustachian tube, oropharynx, nasopharynx, carotid body/sinus)
-Cell bodies in medulla


Cranial nerve X

-Vagus nerve, originating from and innervating 4th and 6th pharyngeal arches
-Provides taste to epiglottis, also VS to laryngopharynx, larynx
-Provides parasympathetics to larynx, foregut and midgut, heart, trachea, and lungs
-Also contains SM (muscles from arches 4 and 6) and VS (pain/reflex to endoderm-derived structures)
-Muscles of arch 4: pharyngeal constrictors, other muscles of the posterior mouth/throat
-Muscles of arch 6 (recurrent laryngeal nerve, a branch of vagus): muscles of larynx


Hemifacial microsomia

-Birth defect characterized by underdeveloped mandible, weak or absent jaw muscles, malformations of external/middle ear, and abnormal temporomandibular joint (TMJ)
-All of these are from the 1st pharyngeal arch, and it is believed this is caused by interrupted blood flow to the developing 1st pharyngeal arch


Buccopharyngeal membrane

-Demarcates the separation btwn endoderm and ectoderm in development
-Is useful for identifying which parts are endoderm (VS) and which are ectoderm (SS)
-Approximate area in adults: back of throat just anterior to where the nasal cavity meets the oral cavity


Sinuses of the brain

-The superior sagittal sinus (SSS) runs along the top of the falx cerebri, and the inferior sagittal sinus (ISS) runs along the bottom
-The straight sinus comes off the ISS when the falx breaks into the R and L tentorium cerebelli
-The straight sinus meets w/ the SSS and the transverse sinuses (R and L) at the confluence of sinuses
-Blood flows anteriorly->posteriorly, to eventually end up in the confluence
-From the confluence blood runs into either the R or L transverse sinus, then down the R or L sigmoid sinus
-The sigmoid sinus receives blood from the cavernous sinus
-The sigmoid sinus then becomes the internal jugular vein


Anatomy of the SSS

-Scalp: skin, connective tissue (dense subcutaneous), aponeurotic layer, loose connective tissue, periosteum
-Under the skull is 2 layers of dura, with space btwn them
-This space is the SSS, and there are emissary veins (draining good from skull into SSS), cerebral veins (draining blood from brain), and arachnoid granulations (draining CSF from subarachnoid space) draining into SSS
-The arachnoid granulations leave pits in the skull (arachnoid granulation pits)


Epidural hematoma

-Due to laceration of the middle meningeal artery
-B/c the artery is under high pressure, there can be lots of blood accumulating outside of the dura (where the artery runs)
-This can cause a mass effect and compress the brain
-Can often be caused by trauma


Subdural hematoma

-Due to rupture of a cerebral veins (thin-walled) just before they enter the SSS
-The blood accumulates in the subdural space (btwn the dura and arachnoid membrane), which did not exist prior to the hemorrhage
-Blood accumulates slowly due to low pressure from venous system, but can also cause mass effect
-Can be due to trauma


Subarachnoid hematomas

-Due to rupture of a cerebral artery, which courses within the subarachnoid space
-This leads to rapid loss of blood into the CSF that flows w/in the subarachnoid space (hemorrhagic stroke)
-Usually does not cause mass effect


Cavernous sinus

-Straddles the sphenoid bone in the middle cranial fossa
-Contains numerous trabecular that slow down the flow of blood
-This makes the cavernous sinus vulnerable to infection, and possibly lead to thrombus formation
-The internal carotid artery and abducent (VI) nerve run through the sinus
-The pituitary sits on top (superior) of the middle of the sinus
-The CNs III (oculomotor), IV (trochlear), V1 (opthalmic) and V2 (maxillary) all course along the two lateral walls of the sinus (imbedded w/in the dura that surrounds the sinus)

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