Cranial Fossae and Cranial Nerves

Question 1

what are the notable features of the anterior fossa?

Answer 1

cribiform plate

crista galli

Question 2

what are the notable features of the middle fossa?

Answer 2

foramen rotundum
foramen ovale
foramen lacerum
foramen spinosum
optic canal

Question 3

what are the notable features of the posterior fossa?

Answer 3

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

Question 4

what is the route of the internal carotid artery?

Answer 4

through carotid canal in base of skull, crosses superior to the foramen lacerum as it exits the carotid canal

Question 5

what passes through the foramen ovale?

Answer 5

O = otic ganglion
V = trigeminal nerve
A = accessory meningeal artery
L = lesser petrosal nerve
E = emissary vein
--> OVALE

Question 6

what passes through the cavernous sinus?

Answer 6

internal carotid artery
occulomotor (CN III)
trochlear (CN IV)
opthalmic (CN V1)
maxillary (CN V2)
abducent (CN VI)

Question 7

what is CN I?

Answer 7

olfactory nerve

Question 8

what is the origin and route of CN I?

Answer 8

outgrowth of telencephalon
olfactory mucosa –> cribiform plate (ethmoid bone) –> synapse in olfactory bulb –> olfactory tracts –> pre-piriformis area of amygdala (primary olfactory cortex)

Question 9

what is CN II?

Answer 9

optic nerve

Question 10

what is the origin and route of CN II?

Answer 10

extension of diencephalon
retina –> optic canal –> form optic chiasm –> optic tracts –> geniculate body (thalamus) –> stritate area (visual cortex) (90% fibres) or medial root (non-geniculate) (10% fibres)

Question 11

what is CN III?

Answer 11

oculomotor

Question 12

what is the route of CN III?

Answer 12

midbrain –> superior orbital fissure –> orbit

runs in lateral wall of cavernous dural venous sinus, through annular ring

Question 13

what does CN III innervate?

Answer 13

motor: inferior oblique, superior, inferior and middle rectus and levator palpabrae
parasympathetic: sphincter pupillae and ciliary muscle
superior division: levator palpabrae and superior rectus

Question 14

what is CN IV?

Answer 14

trochlear

Question 15

what is the route of CN IV?

Answer 15

midbrain –> superior orbital fissure –> orbit

runs in lateral wall of cavernous DVS, outside annular ring

Question 16

which is the only CN from the posterior surface of the midbrain, has the longest intercranial (dural) root of all CNs and who’s fibres all cross to the opposite side?

Answer 16

CN IV

Question 17

what does CN IV give motor fibres to?

Answer 17

superior oblique

Question 18

what is CN V?

Answer 18

trigeminal

Question 19

what are the 3 divisions of CN V?

Answer 19

CN V1 = opthalmic
CN V2 = maxillary
CN V3 = mandibular

Question 20

what is the roue of CN V?

Answer 20

originates from pons

forms a ganglion and divides into it’s 3 divisions

Question 21

what is the route of CN V1?

Answer 21

enters orbit through superior fissure

runs in lateral wall of cavernous DVS

Question 22

what does CN V1 supply?

Answer 22

general sensory to eye, lacrimal gland, eyebrow, forehead skin, nose etc.

Question 23

what is the route of CN V2?

Answer 23

enters pterygopalatine fossa through foramen rotundum

runs in lateral wall of cavernous DVS

Question 24

what does CN V2 supply?

Answer 24

general sensroy to skin of cheek, lower lid, upper jaw and teeth, side of nose, mucosa of mouth etc.

Question 25

what is the route of CN V3?

Answer 25

through foramen ovale to inferior surface of the base of skull

Question 26

what does CN V3 supply?

Answer 26

sensory: ear canal, parotid gland, lower jaw and teeth motor: muscles of mastication, anterior belly of digastric, mylohyoid, tensor tympani, veli tensor palatini

Question 27

what is CN VI?

Answer 27

abducens

Question 28

what is the route of CN VI?

Answer 28

pons --> superior orbital fissure --> orbit | passes through cavernous DVS w/ICA, through annular ring

Question 29

what does CN VI innervate?

Answer 29

motor to lateral rectus

Question 30

what is CN VII?

Answer 30

facial

Question 31

what is the route of CN VII?

Answer 31

pons --> internal acoustic meatus --> temporal bone | motor fibres of facial expression exit via stylomastoid foramen

Question 32

what does CN VII give rise to?

Answer 32

major branches before parotid: greater petrosal nerve, stapedial nerve and chorda tympani branches in parotid gland: temporal, zygomatic, buccal, mandibular and cervical + posterior auricular nerve (before parotid) (to muscles of facial expression)

Question 33

what does CN VII supply?

Answer 33

muscles of facial expression stapedius stylohyoid posterior belly of digastric

Question 34

what is CN VIII?

Answer 34

vestibulocochlear

Question 35

what is the route of CN VIII?

Answer 35

pons/medulla oblongata --> internal auditory meatus --> vestibular/auditory apparatus vestibular part: cerebellum, CN III, IV, VI and spinal tracts cochlear part: inferior colliculi, medial geniculate nucleus of thalamus to auditory cortex

Question 36

what is CN IX?

Answer 36

glossopharyngeal

Question 37

what is the route of CN IX?

Answer 37

medulla oblongata --> jugular foramen

Question 38

what does CN IX supply?

Answer 38

parasympathetic: parotid, buccal and labial glands motor: pharyngeal plexus and stylopharyngeus sensory: post. 1/3rd tongue (incl. taste), soft palate, pharynx, tympanic cavity and membrane, pharyngotympanic tube, external ear and auditory canal

Question 39

what is CN X?

Answer 39

vagus

Question 40

what is the route of CN X?

Answer 40

medulla oblongata --> jugular foramen | cranial, cervical, thoracic and abdominal distribution

Question 41

what does CN X supply?

Answer 41

motor: pharyngeal plexus, soft palate and larynx parasympathetic: thoracic and abdominal viscera sensory: dura (post-cranial fossa), ear, external auditory canal, lower pharynx, laryngeal mucosa, thoracic and abdominal viscera

Question 42

what is CN XI?

Answer 42

(spinal) accessory

Question 43

what is the route of CN XI?

Answer 43

spinal cord --> foramen magnum --> joins 'cranial root' (part of CN X) --> jugular foramen

Question 44

what does CN XI supply?

Answer 44

motor to trapezius and sternocleidomastoid

Question 45

what is CN XII?

Answer 45

hypoglossal

Question 46

what is the route of CN XII?

Answer 46

medulla oblongata (ant. to olive) --> hypoglossal canal --> root of tongue above hyoid bone

Question 47

what does CN XII supply?

Answer 47

motor to all intrinsic muscles of the tongue and all extrinsic except palatoglossus