Cranial fossa and cranial nerves

Question 1

Anterior fossa

Answer 1

cribriform plate
crista galli
optic canal

Question 2

Middle fossa

Answer 2

foramen rontundum
foramen ovale
foramen spinosum -middle meningeal artery
foramen lacerum
carotid canal - internal carotid artery goes into foramen lacerum

Question 3

Posterior fossa

Answer 3

groove for sigmoid dural venous sinus
jugular foramen
foramen magnum
hypoglossal canal

Question 4

CN I

Answer 4

Olfactory

Question 5

Olfactory

Answer 5

outgrowth of telencephalon
olfactory mucosa through cribiform plate to synapse with olfactory bulb
olfactory tracts to prepiriform area of amygdala - primary olfactory cortex
only sensory system not relayed through thalamus

Question 6

CN II

Answer 6

Optic

Question 7

Optic

Answer 7

Extension of diencephalon
From retina through the optic canal, form chiasm then optic tracts.
90% fibres to lateral geniculate body (thalamus) then striate area (visual cortex), 10% along medial root (non-geniculate) unconscious regulation.

Question 8

CN III

Answer 8

Oculomotor

Question 9

Oculomotor

Answer 9

Midbrain through superior orbital fissure to orbit
Run in lateral wall of cavernous dural venous sinus
Through annular ring
Somatic motor and parasympathetic (visceral efferent)
Motor to inferior oblique, superior rectus, inferior rectus and medial rectus, levator palpabrae
Parasympathetic to sphincter pupillae and ciliary muscle
Superior division = levator palpabrae and superior rectus

Question 10

CN IV

Answer 10

Trochlear

Question 11

Trochlear

Answer 11

Midbrain through superior orbital fissure to orbit
Run in lateral wall of cavernous dural venous sinus
Outside annular ring
Only cranial nerve in which all fibres cross to opposite sides.
Only cranial nerve from the posterior surface of the midbrain - longest intracranial (dural) route of cranial nerves
Motor fibres to superior oblique

Question 12

CN V

Answer 12

Trigeminal

Question 13

Trigeminal

Answer 13

Originates from the pons, forms a ganglion and divides into 3 divisions:

CN V1 = ophthalmic enter orbit through superior orbital fissure

CN V2= maxillary enters pterygopalentine fossa through foramen rotundum

CN V3= mandibular through foraman ovale to inferior surface of the base of the skull

Motor and sensory

Lacrimal (CN V1), Zygomatic ( CN V2), lingual and auriculotemporal (CN V3) allow passage of parasympathetic fibres from other cranial nerves

Question 14

Opthalmic division CN V1

Answer 14

general sensory for eye, lacrimal gland, eyebrow, skin of forehead, nose etc.
Runs in lateral wall of cavernous dural venous sinus

Question 15

Maxillary division CN V2

Answer 15

general sensory for skin of cheek, lower lid, upper jaw (and teeth), side of nose, mucosa of mouth etc

Runs in lateral wall of cavernous dural venous sinus

Question 16

Mandibular division CN V3

Answer 16

Sensory to ear canal, parotid gland, lower jaw and teeth etc.
Motor muscles of mastication, anterior belly of digastric, mylohyoid, tensor tympani, veli tensor palatini

Question 17

CN VI

Answer 17

Abducent

Question 18

Abducent

Answer 18

Originates from pons and passes through the superior orbital fissure to reach the orbit.
Long extradural pathway
Passes through cavernous dural venous sinus with internal carotid artery.
Through annular ring
Motor to lateral rectus

Question 19

CN VII

Answer 19

Facial

Question 20

Facial nerve

Answer 20

Originates from the pons, through internal acoustic meatus into temporal bone

Greater petrosal, stapedial and chorda tympani

Motor fibres to muscles of facial expression leaves via stylomastoid foramen= temporal, zygomatic, buccal, mandibular, and cervical posterior auricular

Stapedius, stylohyoid and posterior belly of digastric

Question 21

CN VIII

Answer 21

Vestibulocochlear

Question 22

Vestibulocochlear

Answer 22

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 (area 41 temporal)

Question 23

CN VIX

Answer 23

Glossopharyngeal

Question 24

Glossopharyngeal

Answer 24

Originates from the medulla oblongata and passes through jugular foramen

Parasympathetic to parotid, buccal and labial glands

Taste from posterior 1/3rd tongue
Motor to pharyngeal plexus and stylopharyngeus
Sensory to posterior 1/3 rd tongue, soft palate, pharynx, tympanic cavity, membrane pharyngotympanic tube, external ear and auditory canal.

Question 25

CN X

Answer 25

Vagus

Question 26

Vagus

Answer 26

Originates from the medulla oblongata and passes through the jugular foramen

Cranial, cervical, thoracic and abdominal distribution
Motor to pharyngeal plexus, soft palate, larynx

Parasympathetic to thoracic and abdominal viscera

Sensory to dura (post cranial fossa), ear, external auditory canal, laryngeal mucosa, thoracic and abdominal viscera

Question 27

CN XI

Answer 27

Accessory

Question 28

Accessory

Answer 28

Originate in the 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

Question 29

CN XII

Answer 29

Hypoglossal

Question 30

Hypoglossal

Answer 30

Originates from the medulla oblongata (ant. 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