A&P Test 3 (copy)

bones temporal bone shares a border with

sphenoid

parietal

occipital

structures in temporal bone

middle and inner ear structures

external auditory meatus description

bony part of ear canal

internal auditory meatus description

opening for auditory nerve to pass through

petrous portion description

contains inner ear structures

red

external auditory meatus

blue

petrous portion

purple

internal auditory meatus

purpose of outer ear

sound gathering deice

pinna/auricle function

sound gathering

concha function

collects sound and directs to the external auditory meatus

external auditory meatus contains

cilia and cerumen glands

external auditory meatus function

pathway to tympanic membrane

purpose of cerumen

lubricate ear canal
trap debris

purpose of cilia

vibrate
move ear wax out

maximally resonates sounds around

3300 Hz

how much amplified will sounds be at end of canal vs start

2-4x louder

pink

concha

purple

external acoustic meatus

tympanic membrane is

boundary between outer and middle ear

properties of tympanic membrane

fibrous membrane attached to bony wall of canal by annulus

tympanic membrane shape

slightly cone shaped (conical) curved towards inner ear

tympanic membrane appearance

somewhat translucent (can see parts of ossicles through membrane)

steps to transform vibrating air (sound wave energy) into fluid waves in cochlea

tympanic membrane vibrates when sound waves strike it
vibration is transmitted to ossicles
stapes pushes into fluid of cochlea

middle ear is

conductive mechanism

middle ear description

air filled cavity within temporal bone

middle ear is between

tympanic membrane and membrane covering the oval window

what is in the middle ear

ossicles

where does the Eustachian tube open into

middle ear

ossicles are

three smallest bones in the body

malleus purpose

handle/manubrium attaches to tympanic membrane

incus description

anvil shaped with long and short limbs

stapes description

stirrup shaped

stapes purpose

footplate fits into oval window of cochlea

how is stapes held in place in oval

annular ligament

what do the ossicles do

transmit vibrations from tympanic membrane to inner ear

one

malleus

two

incus

three

stapes

tensor tympani muscle

originates in bony canal/temporal tube in front wall of middle ear cavity and inserts into handle of malleus

tensor tympani contraction

pulls handle of malleus inward to stiffen tympanic membrane and ossicular chain

what does tensor tympani contraction help with

provide protection for extremely loud noises

pink

tensor tympani

purple

stapedius

stapedius muscle description

originates in a hole in the back wall of the cavity and inserts into the stapes

contraction of stapedius muscle

draws stapes away from oval window and stiffens ossicular chain

eustachian tube runs from

middle ear to nasopharynx

eustachian tube provides

means of pressure equalization

tensor palatini contraction

opens lip of eustachian tube

where does pressure go when it is equalized

flows into middle ear space

why does the tympanic membrane vibrate freely

equal air pressure on either side

impedance mismatch

sound goes from air to fluid which causes an impedance mismatched

ways impedance is combated

• tympanic membrane is 20x larger than footplate of the stapes and all energy is focused on that one spot

• fulcrum arrangement of ossicles

• resonating characteristics of ear canal and ossicular chain combine to amplify sounds between 1000-3500 Hz

structures in bony labyrinth

oval window and round window

oval window

hole in bony labyrinth where footplate of stapes is embedded

round window

covered with membrane that displaces to accommodate fluid waves

how many canals in inner ear

three semicircular canals at various angles

what are canals of inner ear filled with

perilymph

what is in the canals of inner ear

inner duct system

what kind of fluid is in the inner duct system

endolymph

_______ _________ displace endolymph which bends hair cells (encodes movements)

head movement

vestibule contains

utricle and saccule

what is in the utricle and saccule

hair cells that sense movement of the head

purple

cochlea

blue

oval window

green

semi circular canals

pink

round window

what chambers in cochlea contain perilymph

scala vestibuli/vestibular canal

scala tympani/tympanic canal

what chamber in cochlea has endolymph

scala media (cochlear duct)

how are chambers separated

reissner’s membrane

basilar membrane

pink

vestibular canal

orange

cochlea duct

yellow

tympanic canal

green

auditory nerve

blue

basilar membrane

purple

organ of corti

basilar membrane description

stretches between bony wall and bony core

organ of corti function

converts fluid waves into bioelectric energy

hair cell function

convert hydraulic motion into electrical impulses that are sent to brain via auditory pathway

how are hair cells moved

tectorial membrane and fluid waves traveling through scala media

____ of inner hair cells and ___ rows of outer hair cells

one row inner hair cells

three rows outer hair cells

purple

outer hair cells

blue

tectorial membrane

green

inner hair cells

orange

basilar membrane

hair cells are located _________ of basilar membrane

entire length

where hair cell is located along membrane determines its __________

frequency sensitivity

base end of basilar membrane description

narrow and stiff

base end of basilar membrane is responsive to ______

high frequencies

apex end of basilar membrane description

wide and lax

apex of basilar membrane is receptive to _________

lower frequencies

middle portion of basilar membrane description

intermediate width and stiffness

middle portion of basilar membrane is responsive to _______

mid frequencies

fluid in cochlea moves

in phase with footplate of stapes

waves develop

over time

waves build to a crest where

most of its energy is spent

waves do what after crest

quickly dissipate

place on basilar membrane where wave crests is

where membrane is tuned/most sensitive to a particular frequency

displacement of basilar membrane does what

drags tectorial membrane across top of organ of corti

hair cell cilia are_____

sheared