Flashcards in Ear and Auditory Tube Deck (23):
function of auricle in the outer ear?
localization of sound
which cranial nerve innervates the outer ear?
vagus nerve (3rd branch: auriculotemporal nerve) innervates the anterosuperior and external surface of tympanic membrane
in cases of normal middle ear pressure, shining a light into the external auditory meatus would produce a cone of light in which quadrant of tympanic membrane?
Anteroinferior-quadrant. Deviation from here suggests increase or decrease in middle ear pressure.
describe concavity of the tympanic membrane?
concave outwards/laterally. and convex inwards/medially
which component of the middle ear permits communication with the nasopharynx? whats the purpose?
auditory/eustachian tube. allows for equalization of middle ear pressure with atm pressure.
where are ear infections more common in infants than adults?
in adults, the downward gradient of the eustachian tube into the nasopharynx makes it difficult for bacteria to get into middle ear.
In children, the eustachian tube takes a much straighter path.
whats the arrangement of the ossicles from the tympanic membrane
tympanic membrane-->malleus-->incus-->stapes-->oval window
how are environmental sounds interpreted by the ear?
incoming sounds will vibrate the occicles (malleus is attached to tympanic membrane and so on) at a rate proportional to the pitch of the incoming sound.
why is increased sensitivity to loud sounds a symptom of Bell's palsy?
because facial nerve innervates stapedius muscle (attaches to stapes ossicle and functions along with tensor tympani to dampening incoming sound.)
which two muscles in the middle ear are involved in dampening incoming loud sounds? what are their associated Cranial nerves?
-tensor tympani (inserts on malleolus, attached to anterior wall of middle ear, innervated by CN V)
-stapedius muscles (inserts on stapes, attached to posterior wall of middle ear, innervated by CN VII)
-both these muscles constrict to pull on the ossicles to dampen the vibrations
large swelling on medial wall of middle ear, formed by basal turn of the cochlea
some patients with middle ear infection may hear and feel throbbing , why might this be?
internal carotid artery runs in carotid canal through the middle ear. fluid/infection/swelling would put pressure on this canal.
through which foramen does the facial nerve exit from the facial canal?
location and structures of the inner ear?
imbedded in petrous part of temporal bone behind the oval window.
structures are found within the bony labyrinth (filled with perilymph).
membranous labyrinth is a continuous sac suspended in the bony labyrinth. sac is filled with endolymph.
which part of bony labyrinth contains membranous labyrinth with sensory receptors for hearing
which part of bony labyrinth contains membranous labyrinth with sensory receptors for static equilibrium
utricle location and function (inner ear)?
inside bony vestibule, contains sensory receptors for static equilibrium (some dynamic equilibrium)
3 orientations of semicircular ducts?
horizontal, anterior and posterior
Ampulla location and function?
within bony vestibule, contains sensory receptors for Dynamic equilibrium
where does the vestibulocochlear nerve (CN VIII) exit the inner ear?
internal acoustic meatus
in which duct are sensory receptors for hearing located?
how are high pitched and low pitched sounds relayed from environment to the cochlear duct receptors?
sounds are collected as vibrations in the auricle, transmitted through the tympanic membrane to the ossicles, high pitched sounds cause high frequency vibrations of the ossicles (opposite for low pitch sounds)
--> through to oval window where high frequency sound receptors are at the base (proximal) of the cochlear duct and low pitch receptors are at the apex of the cochlear duct (distal).