osseous and membranous cochlea

exam 3

parts of the inner ear

cochlea, vestibule and semicircular canals

subdivisions of the inner ear

osseous labyrinth and membranous labyrinth

cochlea is more posterior/anterior than the other inner ear parts

anterior

are the semicircular canals anterior/posterior to inner ear structures

posterior

shape of cochlea, length, # of turns, # of chambers

cone shape, 35 mm long, 2.5-2.75 turns, 3 chambers

what are the 3 chambers of the cochlea

scala vestibuli, scala tympani and scala media

the base of the cochlea is ___ and the apex is ___

base is wide, apex is narrow

osseous labyrinth houses what

scala tympani and scala vestibuli

what fluid fills the osseous labyrinth

perilymph (similar to CSF)

how do the scala tympani and vestibuli communicate?

helicotrema

core of the cochlea

modiolus

what combines in the modiolus?

the auditory nerve fibers from the organ of corti

what surrounds the modiolus

osseous spiral lamina

what is the osseous spiral lamina?

bony shelf-like structure wrapping around modiolus, BM attached to it

which end of cochlea is better for high frequency sounds

base, wider

which end of the cochlea is better for low frequency?

apex, narrow

diagram of bony and membranous labyrinth

purple = perilymph

blue = endolymph

what does the membranous labyrinth house?

scala media

what does the scala media house?

organ of corti, inner and outer hair cells, supporting cells and tectorial membrane

what are the walls of the scala media

reissner’s membrance (roof), basilar membrane (floor), spiral ligament (lateral), stria vascularis

reissner’s membrane

roof of scala media, connects to the spiral limbus and spiral ligament

basilar membrane

floor of scala media, connects to osseous spiral lamina and spiral ligament

spiral ligament

lateral wall of scala media

stria vascularis

attaches to spiral ligament and produced endolymph

three chambers of cochlea and fluids within

scala vestibuli = perilymph

scala media = endolymph

• organ of corti = cortilymph

scala tympani = perilymph

describe perilymph

low potassium (K+), high sodium (Na+), neutral at 0 mV

similar to CSF

describe endolymph

high potassium (K+), low sodium (Na+), positive at 80 mV

describe cortilymph

Organi of corti. low potassium (K+), high sodium (Na+), similar to perilymph

meniere’s disease

inner ear disorder with no known cause, but overproduction of endolymph is common - causes balance issues and damage to structures

perilymph fistula

abnormal communication between fluids - inner ear fluid leaking to middle ear at oval window

diagram of cochlea