Cranial Fossae and Cranial Nerves Flashcards
Anterior Fossa
Middle Fossa
Posterior Fossa
Internal Auditory (acoustic) Meatus
Cranial Nerves
Cranial Nerves Exiting the Skull
CN I - Olfactory
Outgrowth of telencephalon
Travels from olfactory mucosa through cribriform plate to synapse in olfactory bulb
Olfactory tracts to prepiriform area of amygdala (primary olfactory cortex)
Only sensory system not relayed through thalamus
CN II - Optic
Extension of Diencephalon
From retina through optic canal, forms chiasm then optic tracts
90% fibres to lateral geniculate body (thalamus) then striate area (visual cortex). 10% along medial root (non-geniculate) unconscious regulation
CN III - Oculomotor
Midbrain though superior orbital fissue to orbit
Runs interal wall of cavernous dural venous sinus. Through annular ring.
Somatic motor and parasympathetic (visceral efferent)
Motor to inferior oblique, superior rectus, inferior recuts and medial rectus, levator palpabra
Parasympathetic to sphincter pupillae and ciliary muscle
Superior division = levator palpabrae and superior rectus
CN IV - Trochlear
Midbrain through superior orbital fissue to orbit
Run in latera wall of cavernous dural venous sinus
Outside annular ring
Only cranial nere in which all fibres cross to opposite side
Only cranial nerve from posterior surface of midbrain - longers intra cranial (dural) route of any of the cranial nerves
Motor fibres to superior oblique
CN V - Trigeminal
Orignates form pons - forms a ganglion and divides into 3
CN V1 - Opthalmic enters orbit through superior orbital fissure
CN V2 - Maxillary enters pterygopalatine fossa through foramen rotundum
CN V3 - Mandibular through forament ovale to inferior surface of base of skull
Motor and sensory
Lacrimal (V1), Zygomatic (V2), Lingual and Auriculotemporal(V3) allow passage of parasympathetic fibres from other CN’s
CN V - Trigeminal Nerve Divisions
CN VI - Abducent
Orignates from pons and passes through superior orbital fissure to reach orbit
Long extradural pathway
Passes through cavernous dural venous sinus with ICA
Through annular ring
Motor to lateral rectus
Nerve and Artery entrance points
CN VII - Facial
Orignates from pons, through internal acoustic meatus into temporal bone
Greater petrosal, stapedial and chorda tympani
Motor to muscles of facial expression - leave through stylomastoid foramen (temporal, zygomatic, buccal, mandibular and cervical posterior auricular)
Stapedius, stylohyoid and posterior belly of digastric
Facial Nerve
CN VIII - Vestibulocochlear
Special somatic afferent
Vestibular apparatus and auditory apparatus through internal auditory meatus to pons/medulla oblongata
Vestibular - cerebellum, CN III, IV, VI, and spinal tracts
Cochlear - Inferior colliculi, medial geniculate nucleus of thalamus to auditory cortex
CN IX - Glossopharyngeal
Orignates from medulla oblongata and passes through jugular foramen
Parasympathetic to parotid, buccal and labial glands
Tase from posterior 1/3rd tongue
Motor to pharyngeal plexus and stylopharyngeus
Sensory to posterior 1/3 of tongue, soft palate, pharynx, tympanic cavity, membrane, pharyngotympanic tube, external ear and auditory canal
Carotid Artery, Body and Sinus
CN X - Vagus
Originates from the medulla oblongata and passes through the jugular foramen
Cranial, cervial, thoracic and abdominal distribution
Motor to pharyngeal plexus, soft palate, larynx
Parasympathetic to throracic and abdominal viscera
Sensory to dura (post cranial fossa), ear, external auditory canal, lower pharynx, laryngeal mucosa, thoracic and abdominal viscera
Laryngeal
CN XI - Accessory
Originate in spinal cord, enter foramen magnum and join “cranial root” then pass through jugular foramen
Motor to trapezius and sternocleidomastoid
“Cranial root” now considered part of vagus nerve (soft palate)
CN XII - Hypoglossal
Originates from the medula oblongata (anterior to olive) passes through hypoglossal canal
Enters root of tongue above hyoid bone
Motor to all intrinsic muscles of the tongue and all extrinsic except palatoglossus
