Lecture #4 - anatomy to hearing Flashcards
define hearing :
sense through which spoken langueage or non-speech sounds are received, transmitted and processed by auditory system
what are the two systems o fthe auditory system ?
peripheral and central auditory system
what is the peripheral auditory system ?
outer ear to auditory nerve
what is the central auditory system ?
beyond the auditory nerve to cerebral cortex
what are the four parts of the peripheral auditory system ?
- outer ear
- middle ear
- inner ear
- auditory nerve
what are the two key components of the outer ear ?
pinna & external ear canal
what are the four key components of the middle ear?
- middle ear cavity
- tympanic membrane (eardrum)
- ossicles
- eustacian tube
what is another word for “ossicles” ?
bones
where are the ossicles found ? (which part of ear)
contained within the middle ear cavity
what are the ossicles connected to ?
the eardrum
how many ossicle bones are there ?
3
what are the three ossicle bones ?
- malleus
- incus
- stapes
which bone can also be called “hammer” ?
malleus
what do the ossicles bones work together to create ?
a chain
FILL IN THE BLANK
the malleus, incus and stapes bridge between the ____________ & ___________
eardrum and inner ear
what is the malleus attached to ?
the tympanic membrane
what is the smallest bone in the body ?
the stapes
what could damage to the stapes do ?
damage to this bone may cause partial or complete hearing loss
out of all ossicles bones which is the biggest ?
malleus
how big is the malleus ?
around 9 mm
what do the malleus and incus work together to create ?
a lever to tranfer force (soundwaves) to the inner ear
what bone attaches to the tympanic membrane ?
the malleus
what do the ossicles transmit ?
sound vibrations from the eardrum to the inner ear
where specifically in the inner ear do the ossicles bridge between ? (from the eardrum to the ______ )
oval window
what is another term of the incus ?
anvil
how big is the incus ?
around 7 mm
what is the incus attached to ?
the head of the malleus
how is the incus attached to the malleus ?
via tissue (saddle joint)
how does the incus move ?
moves together with the malleus a lever
what is another term for the stapes ?
stirrup
what does the stapes do ?
takes soundwaves and converts it to mechanical energy
how big is the stapes ?
around 3 mm long and 1 mm wide
where does the stapes attaches ?
to the incus
what is the stapes footplate ?
- is the flat, bottom part of the stapes bone
what does the stapes footplate connect ?
connects to the oval window, a membrane-covered opening that leads to the inner ear
how are the ossicles held in place ?
by muscles and ligaments
what specific muscles help hold the ossicles in place ?
- tensory tympani muscles
- stapedius muscle
where does the tensory tympani muscles attach ?
attached to malleus from the front wall
where does the stapedius muscle attach ?
attached to stapes from the back wall
what do muscles protec the inner ear from ?
damage
what is “accoustic reflex” ?
involuntary muscle contractin that occurs in the middle ear in response to loud sounds
an accoustic reflex involves the contraction of what two muscles ?
tensory tympani muscles and stapedius muscles
the tensory tympani muscles and stapedius muscles act on what ?
the ossicles
what does an accoustic reflex protect us from ?
really loud sounds
what is the ear’s way of protecting themselves ?
an accoustic reflex
how does an accoustic reflex work ?
1) when a loud noise hits your ear, it triggers tiny muscles in your middle ear to tighten
2) these muscles pull on the small bones (ossicles) that help transmit sound, making them less able to move
3) by stiffening these bones, the reflex reduces the amount of sound sent to your inner ear, helping protect it by damage
physiologically, what does the middle ear function as ?
functions as transformer
what does the middle ear do ?
converts sound energy to mechanical energy
what are the 5 steps that allow the middle ear to convert sound energy to mechanical energy ?
1) siund waves vibrate tympanic membrane
2) tymoanic membrane moves malleus
3) malleus transmits vibrations via incus to stapes
4) stapes movement vibrates oval window
what is the “oval window” ?
its the middle ear’s openinig to the inner ear
what does the middle ear do in regards to pressure ?
boosts pressure from tympanic membrane to oval window
why does the middle ear boost pressure from tympanic membrane to oval window ?
- the middle ear boosts pressure to make sure sound vibrations can move from the air (in the ear) to the fluid (in the inner ear)
if the middle ear didn’t boost pressue going into the inner ear, what would happen ?
without this boost, sound would lose strength when moving from air to fluid, making it harder to hear
where is the pressure higher ? stapes or eardrum ?
pressure at stapes is 20X that at the eardrum
where is the eustachian tube located ?
between the middle ear cavity and the pharynx
describe an adults eustachian tube :
- 35 mm
- 45 degree downwards
- less prone to infections
describe a young childs’ eustachian tube :
- around 17 mm
- nearly horizontal
- prone to infections
describe an infants eustachian tube :
- shorter
- wider
- most prone to infections
when does the eustrachian tube open ?
when pressure is applied
what are some examples of when pressure may be applied to the eustrachian tube ?
- yawning
- swallowing
- sneezing
is the eustrachian tube usually open or closed ?
normally closed
when does the eustrachian tube open ?
1x/minute while awake
1x/5 minutes while asleep
what tube runs from your middle ear to your throat ?
eustachian tube
what are the 3 main functions of the eustrachian tube ?
- protects middle ear
- aerates middle ear
- drains middle ear
how does the eustachian tube protect the middle ear ?
- equalizes pressure with the outside and within
- keeps the tympanic membrane flexible
how does the eustachian tube aerates the middle ear ?
air from pharynx to middle ear
how does the eustachian tube drain the middle ear ?
fluid from middle ear infections
what happens if the eustachian tube is blocked ?
air can’t move between the middle ear and the throat, which causes pressure to build up in the ear (negative pressure)
what might you feel if your eustachian tube is blocked ?
- discomfort
- muffled hearing
- ear pain
- even infections because fluid can get trapped in the middle ear
what happens anatomically if the eustachian tube is blocked (negative air pressure) ?
negative air pressure → eardrum retracts → eardrum becomes stiff → decreased hearing of low frequency sounds
what happens anatomically if the eustachian tube is blocked (persistent negative air pressure) ?
middle ear cavity fills with fluid → eardrum bulges → increased eardrum stiffness → decreased hearing of low and high frequency