Middle ear flashcards |

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boundary bw outer and middle ear

tympanic membrane

tympanic membrane has _____ shape

circular

lateral layer of tympanic membrane, closest to the side of head has

epithelial cells

lateral layer of tympanic membrane closest to side of the head is continuous with skin of

external auditory canal

medial layer of tympanic membrane is continous with

mucosal lining of middle ear space

core layer is

sandwiched bw lateral and medial layer

the core layer has tough _______ ____ tissue

fibrous connective

tympanic membrane slightly coned ______

inward

tympanic memrane has _____ ____ color

pearly gray

TM orientation in adults is

perpendicular to EAC

TM orientation in infants is

parallel to EAC

TM is attache to bony wall of ear canal by ____

annulus

pars flaccida

15% of surface area; fibers are missing

pars tensa

85% of surface area has all 3 layrs

tympanic membrane landmarks

pars flaccida
pars tensa
malleus (lateral process & manubrium)
cone of light
annulus
umbo
long process of incus

Middle ear cavity aka

tympanic cavity

tympanic cavity has air filled cavity bw

outer ear and inner ear

tympanic cavity is

irregularly shaped, tall and narro

epitympatic recess

attic
-extends beyond superior border of TM

epitympanic recess is filled by

malleus head and incus

posterior to tympanic cavity is

mastoid air cells

tinniest bones in the body

ossicles
-malleus
-incus
-stapes

ossicular chain

provide connection bw tympanic membrane and oval window

ossicles are suspended from middle ear walls by

ligaments

malleus is shaped like

primitive club/mallet

malleus' handle is called

maniubrum

end of the manubrium is embedded in tympanic membrane at the _____

umbo

middle bone bw malleus and stapes

incus

incus

provides pivot point during bibration

incus' short process fits into depression on posterior wall of ____ ____ ___

middle ear space

incus' end of long process is attached to ___ head

stapes

stapes resembles a

stirrum

base of stapes is called

footplate

area of foot plate

3.2 smm

footplate sits in _____ _____

oval window

footplate and oval window are attached by

annular ligament

stapes seals ___ in inner ear

fluid

eustachian tube

connects middle ear to nasopharyngeal cavity

eustachian tube is about ____ long

1.5 in

osseous portion of eustachian tube is always open on ____ wall of middle ear

anterior

the ____ portio towards nasopharynx is normally

closed

cartilaginous portion opens during

yawning, swallowing, chewing

cartilaginous portion opens by

tensor veli paletini

function of eustachain tube

-equalizes air pressure in middle ear to outer ear pressure
-ventilation of middle ear cavity
-oxygen is absorbed by mucous and blood vessels
-drainage of middle ear secretions to prevent reflux of fluid back/up into middle ear space

Oval window

boundary bw middle and inner ear; holds footplate of stapes

round window

below oval window; covered by flexible membrane

promontory

located bw windows
-bony ridge

promontory is opposite to

basal turn of cochlea

chorda tympani is branch of

facial nerve

function of chorda tympani

carries special sensory fibers for taste for anteriro 2/3 of tongue

chorda tympani passes through middle ear space from _____ part of ______ wall to _____ wall, and crosses _____ TM

lateral part; posterior wall; anterior; behind

middel ear muscles

stapedius
tensor tympani

smallest muscle in the body

stapedius

stapedius is attached to

head of staps

stapedius contracts _____ to loud sounds

reflexively

upon contraction of stapedius

it pullls footplate of stapes out of oval window, and draws stapes toward posterior wall of the middle ear

stapedius is innervated by

CN7 facial nerve

tensor tympani's orgins

above eustachian tube opening

tensor tympani attaches to

upper end of malleus handle

tensor tympani contracts to

tactile stimulation

tensor tympani draws manubrium ____ which _____ ____ to TM

medially; applies tension

tensory tympani is innervated by

CN V trigeminal

contraction of tensor tympani and stapedius

stiffens ossicular chain and tympanic membrane

stiffening ossicular chain and tympanic membrane

decreases amount of sound passed to inner ear

decreasing amount of sound passed to inner ear

attenuates low frequencies

reasons decrease force of low frequencies

-protect inner ear from loud sounds
-tune ear to respond to speech frequencies
-dampen internal headsounds (chewing, person's own voice)

middle ear function

-impedence matching function
-protection of inner ear structures

impedence matching function

amplification of sound to comepnsate for loss of sound energy when going from air to fluid medium

amplification in middle ear occurs fro frequencies bw

100 Hz and 2000 Hz to 2500 Hz

describe impedeance matching function

sound traveling from medium of low impedance (air of outer ear canal) to medium of high impedance (cochlear fluid) gets amplified thanks to lvl of action of ossicles and difference in area bw tympanic membane and oval window

primary source of sound amplification

areal ratio of tympanic membrane to stapes footplate

two thirds of tympanic membrane that is effective in vibration

pars tensa

the area of the footplate is ____ times smaller than pars tensa

17

describe the areal ratio of tympanic membrane to stapes footplate

force cancelled at relatively large tempanic membrane, then concentrated on small area of oval window (stapes footplate), results in increased sound pressure into inner ear

what is the recovery of sound of the aerial ratio of tympanic membrane to stapes footplate?

25 dB of sound

manubrium of malleus connected toTM acts like a

pump handle

_____ pivots around its short process

incus

what's the recovery from the increase of pressure of the stapes pushing into the oval window?

2 dB

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