Exam 3 ear Flashcards
Hearing (audition) definition
detecting sound waves and converting them into nerve impulses
What are the components of the external ear
auricle
External auditory meatus
Tympanic membrane (eardrum)
What are the components of the middle ear
auditory tube Auditory ossicles -malleus -incus -stapes
What are the components of the inner ear
bony labyrinth
Membranous labyrinth
What is the auricle and its function
outer mass of tissue
Function: Collect sound waves and direct them into auditory canal
What is the External auditory meatus and its function
between auricle and tympanic membrane
Function: Directs sound waves to tympanic membrane (eardrum)
What is the function of the tympanic membrane
move/vibrate auditory ossicles when sounds vibrate the tympanic membrane
-sound waves into physical vibrations
What are the auditory ossicles and their function
ear bones: - malleus - incus - stapes Function: Transmit and amplify vibrations from the eardrum to inner ear
what is the auditory (eustachian) tube and its function
connects middle ear with the nasopharynx
function: equalizes air pressure in the middle ear
what is ottis media
middle ear infection
- fills up with fluid/ puss
- eardrum bulges outward
- infection can travel via the auditory tube
what is the bony labyrinth
spaces/cavities inside temporal bone
what is membranous labyrinth
membranous sacs/tubes that rest inside the bony labyrinth
what is perilymph
fluid in between bony and membranous labyrinths
- inside bony part and outside membranous
- make it “float”
- chemically similar to CSF
what is endolymph
fluid inside membranous labyrinth
- low sodium and high potassium conc
- helps conduct sound vibrations and detect changes in position/balance
describe the structure of the bony labyrinth components:
vestibule
semicircular canals
cochlea
vestibule: oval central portion
semicircular canals: 3 circular spaces/canals
cochlea: spiral chamber
describe the structure of the membranous labyrinth components: utricle saccule semicircular ducts cochlear duct (scala media)
utricle: sac inside vestibule
saccule: another sac inside vestibule
semicircular ducts: 3 membranous tubes in semicircular canals
cochlear duct: membranous tube inside cochlea
what is the scala vestibuli
above cochlear duct
- connects to oval window
- filled with perilymph
- continuous with apex
what is the vestibular membrane
thin membrane that separates the scala vestibuli from the cochlear duct
what is the scala tympani
below cochlear duct
- connects to round window
- filled with perilymph
- continuous with apex
what is the basilar membrane
separates scala tympani from cochlear duct
which structure responds to the highest sound frequencies
basilar membrane, closest to the oval window
which structure responds to the lower sound frequencies
basilar membrane, furthest away from the oval window
what happens when sound waves enter the scala vestibuli
vibrate a small portion of the basilar membrane
explain the process of hearing
- sound waves are collected by auricle, travel to external acoustic meatus, then tympanic membrane
- vibrations travel from tympanic membrane, to auditory ossicles, to oval window
- sound waves travel through the scala vestibuli and vibrate basilar membrane
- stereocilia bend against tectorial membrane, nerve impulse generated
- CN VIII takes impulse to brain
- remaining impulses leave through round window
