Cranial nerves 6 Flashcards
where is the olfactory tract and bulb found
on the inferior surface of the frontal lobe
where does cranial nerve 8 emerge
with cn7 between the cerebellum and the pons
where do olfactory nerves arise from
the olfactory bulb and pass through the cribriform plate of the ethmoid to the upper aspect of the nasal cavity
what structures pass through the optic foramen
optic nerve, opthalmic branch of the internal carotid to the orbit
what structures lie in the internal accoustic meatus
vestibulocochlear nerve, facial nerve and labyrinthine artery (from basilar)
passes from inside the skull to structures of the inner ear
what can cause narrowing of the internal accoustic meatus
acoustic neuroma (most common)
mastoiditis
Paget’s disease
where do cn 7 and 8 go after emerging from the internal accoustic meatus
pierce the dura to run in the subarachnoid space to reach the medulla in the angle between the cerebellum and the pons
where is the internal accoustic meatus
petrous part of the temporal bone of the skull between the posterior cranial fossa and the inner ear
close to the foramen magnum
where is the external accoustic meatus
posterior to the condylar process, superior to the styloid process and anterior to the mastoid process
what is the effect of tumours in the internal accoustic meatus and cerebello pontine angle
impingement on cn 7 and 8 giving ipsilateral facial signs
what is the choroid plexus
a group of cells that produces CSF in the ventricles
ependymal cells
one in each ventricle
what structures make up the external ear
auricle, external accousic meatus
what structures make up the middle ear
ossicles, tympanic membrane
connection to pharynx via eustacian/auditory/ pharyngotympanic tube
what structures make up the inner ear
semi circular canals,
cochlear
what structure passes through the stylomastoid foramen
facial
what are the three semicircular canals called
anterior, lateral and posterior, at right angles
where can the vestibulocochlear apparatus be found on the petrous bone
middle cranial fossa, petrous temporal bone, on a slight elevation on the bone surface caused by the anterior semicircular canal
what is the tympanic plate
part of the temporal bone in front of the mastoid process, surrounds the external part of the ear canal
forms the anterior wall, floor and part of the posterior wall of the bony ear canal
what is the function of the cochlear and vestibular aqueducts
allows the membranous labyrintheto connect with the subarachnoid space
for reabsorption of peri and endolymph
what is the function of the auricle
catch and funnel sound into the EAM
name the main parts of the auricle
helix, antihelix, concha, tragus, antitragus, lobule
what nerve supplies muscles that can move the position of the auricle
cn 7, facial
how long is the EAM
2.5cm
what tissue makes up the lateral third of the EAM
cartilage
what tissue makes up the medial third of the EAM
bone
what tissues line the EAM
skin, hairs, ceruminous glands that secrete ear wax
how can the EAM be straightened to facilitate examination of the tympanic membrane
by pulling the ear superiorly, posteriorly and slightly laterally
what is the sensory supply to the auricle
greater auricular nerve (C2 and 3)
facial nerve
lesser occipital (c2 and 3)
auriculotemporal nerve (cnV3)
what is the sensory supply of the EAM
auricular branch of vagus
auriculotemporal branch of V3
what is the sensory supply to the tympanic membrane and the middle ear
glossopharyngeal 9
how is the tympanic membrane held within the temporal bone
by a fibrocartilaginous ring
lies facing downwars and anteriorly
what tissues make up the tympanic membrane
skin, facia, mucous membrane
cn9
what is the umbo
a rounded protruberance on the tympanic membrane caused by attachment of the tip of the malleus
what is the function of the round window
pressure release from the cochlear
where is sound tranmitted to after the ossicles
oval window of the cochlear which converts the mechanical impulses to electrical signals
which ossicle is in contact with the oval window
stapes
in what order do the ossicles lie in
malleus, incus, stapes
what is hyperacusis
intolerance to everyday sounds that causes distress
