The Ear Flashcards
what does the helicotrema connect?
the scala vestibuli to the scala tympani
what is the ductus reuniens?
small duct connecting the saccule to the cochlear duct
what is the vestibular membrane (reissner’s membrane)
roof of the cochlear duct that is composed of two simple squamous epithelial sheets separated by a basal lamina
What is the organ of corti responsible for?
hearing
do the bases of the hair cells in the organ of corti rest on the basilar membrane?
NO
what membrane are the stereocilia embedded in in the sensory maculae?
otolithic membrane
where does blood supply to the inner ear arise from?
the labyrinthine artery
what is the cupula? how does it function in sensation?
it is a gelatinous membrane that encapsulates the stereocilia and kinocilia. Acts like a sail: if the head rotates, the endolymph moves within the semicircular duct to push against and deviate the cupula resulting in deflection of the stereoclila; direction of deviation determines the polarity of the receptor potential
what does the tectorial membrane of the organ of corti contain?
keratin like protein
can hypothyroidism lead to hearing loss?
yes
what is the spiral ligament
outside wall of the cochlea that is made of dense CT
How does the kinocilium location determine functional polarity?
if the stereocilia are tilted TOWARD the kinocilium = depolarization; if the stereocilia are tilted AWAY from the kinocilium = hyperpolarization
what is the function of the otoliths?
increase the mass of the membrane surface to augment the effect of accelerating forces on the membrane and thus on the stereocilia
what compartments are part of the osseous labyrinth? what compartments of the cochlear are part of the membranous labyrinth?
scala vestibuli + scala tympani = osseous scala media = membranous
what causes K+ channels in the stereocilia to open?
mechanoreception via connection of stereocilia to the adjacent stereocilia
what supports the hair cells bases in the organ of corti?
phalangeal cell and a process of the phalangeal cell surrounding the apex of the hair cell
what inserts on the oval window of the vestibule?
stappes
what is located on one end of each semicircular canal?
the ampulla (swelling)
what is the boney central axis of the cochlea?
modiolus (towards modiolus = inner, away from modiolus = outer)
what is the stria vascularis?
pseudostratified, vascularized, epithelium that secretes endolymp
what is the structure of kinocilum
9 doublet microtubules; immotile; longest stereocilia is adjacent to the kinocilium
pendred syndome
genetic disorder causing hearing loss in children (SLC26A4 = carrier gene
what is the osseous spiral lamina?
spiraling shelf off of the modiolus that indents the inner edge of the cochlea
what are the sensory areas of the inner ear?
- crista ampullaris (of semicircular ducts) 2. sensory maculae (of utricle and saccule) 3. organ of corti (of cochlear duct)
what are the two types of hearing loss? what are the main differences?
- conductive losses = disruption in the conductive pathway of soundwaves traveling (ie: disruption of tympanic membrane) 2. sensorineural loss = loss of hair cells of VIII nerve fibers
what is motion sickness caused by?
over stimulation of the utricle/saccule
what forms the floor the cochlear duct?
the basilar membrane; the organ of corti is located on it
How does the organ of corti transmit sound?
the cohclear duct hair cells transduce mechanical energy into sound frequency, and the frequency response is represented as a continuous gradient along the organ of corti.
what is the function of the organ of corti:
to transduce auditory signals
what type of cells are found in the spiral ganglion?
bipolar
what is perilymph high in? low in? vs endolymph
peri = high in Na low in K+ endo = high in K+ low in Na
what are the two types of cells on the crita ampularis?
both columnar epithelium: 1. supporting cells = have secretory granules; tall columnar 2. sensory hair cells = stereocilia and kinocilia are embedded in gelatinous membrane (cupula) which acts like a sail
what happens if sensory cell of the ear is depolarized
it will release more neurotransmitter on VIII afferent processes and cause an increase in signal to the vestibular or auditory centers of the brain
where are neurotransmitters released from in the inner tunnel (of organ of corti)
spiral ganglion cells
what is the function of the utricle and saccule?
detection of linear acceleration (tripping over something)
what is the vestibular aqueduct
small boney channel that connects to the vestibule
what keeps the endolymph and perilymph from mixing?
the occluding zonules of the cells lining the membranous labyrinth
what is the crista ampullaris? where is it found?
a sensory structure in the ampulla (swelling at end of semicircular canal); detects rotational movements of the head
what is vertigo? what is it caused by
dizziness; caused by disturbances of vestibular function such as infection of the vestibule or lesions of the central or peripheral nervous system
the modiolus contains fibers for what nerves?
VIII + peripheral ganglion (spiral ganglion) for auditory system
what is menieres disease?
swelling of the membranous labyrinth leading to dizziness (vertigo) tinitus (ringing of ears) and low frequency hearing loss
what is the membranous labyrinth? what is it derived from?
it is a continuous series of epithelially lined membrane channels derived from the otocyst containing endolymph
presbyacusis
poor high frequency perception due to age related loss of hair cells at the basal turn of the cochlea
what is the membranous labyrinth composed of?
1.semicircular ducts 2. utricle 3. saccule 4. endolymphatic duct and sac 5. cochlear duct
what does the otolithic membrane contain?
crystalline includes (otoliths) in its surface
what cells line the inner tunnel of the organ of corti?
pillar cells
where is perilymph secreted from?
the blood vessels in the CT of the ossesous labyrinth
what does the vestibule connect anteriorly? posteriorly?
anteriorly: cochlea posteriorly: semicircular canals
where is the sensory maculae located?
in the utricle and saccule
how do the hair cells at the base of the organ of corti transduce sound vs those at the apex of the cochlea?
base = transduce highest frequencies apex = transduce lowest frequencies
what does the scala vestibuli connect with?
oval window ( to cochlea)
what does the scala tympani connect with?
round window ( to cochlea)
what is prominent in the pillar cells and the phalangeal cells? what is the significance of their structure?
microtubules and intermediate filaments; This allows for the pillar and phalangeal cells to form a rigid RETICULAR LAMINA in which the apical portions of the hair cells are locked via zonular adherens and zonula occludens junctions
why is it important that the basilar membrane upon which the organ of corti rests is collagenous and not rigid?
because sound causes compression of waves in the perilymph which shifts the two rigid plates to the deviate the stereocilia and produce receptor potntials in the sensory cells
what is unique to the hair cells of the organ or corti
don’t have a kinocilium, have a basal body instead
What do all of the sensory areas of the inner ear contain?
- sensory hair cells with sterocilia an single kinocilum (or basal body in the auditory cells)
