Ear Anatomy


Hello everyone! In this video we’re going
to talk about the structure and function of the ear. There are three major areas
of the ear. The external ear, the middle ear, and the internal ear. Keep in mind
that these are areas, they’re not specific structures. So external ear is
everything here. Basically everything outside of the ear drum. The middle ear
is going to be this cavity over here. You’re going to see three little
ossicles (three little bones) here. This is the middle ear area. And then we also
have the internal ear, which contains this complicated and small organ called
the labyrinth. Ok. same thing right here. You can see external ear. Let’s see if I could
color it. So everything out here is considered the outer ear. In this
area you have the middle ear, it’s sort of like a cavity here. And we also have the
inner ear area, where you find this organ here called the labyrinth.
So outer ear, middle ear, and inner ear. Let’s start with the external ear. Some
of the structures of the external ear. We have the auricle. This
is what we see on the outside. The external auditory canal. You could
also call it the external acoustic meatus, or external auditory meatus. All of
those terms are correct. You also have the tympanic membrane. Which is the
eardrum. And the cerumen glands, these are the glands that produce that waxy
substance in your ears. So first, let’s start with the auricle. The auricle
actually has two parts. there’s the helix, and that’s the
cartilaginous part of your ear. And the lobule which is the fleshy dangling part
of the ear. We could see it right here. So all of this whole outer ear portion. this
is called the auricle. And this top part here the helix. And this bottom portion
that’s hanging is called the lobule. And here we have the canal right here,
the external acoustic meatus. Next structure is the tympanic membrane (or the
eardrum). The tympanic membrane actually creates the boundary between the
external ear and the middle ear. It looks like a flattened comb. The sound
waves that come into your ear, makes the eardrum vibrate. The eardrum
transfers this vibration to the middle ear by the ossicles.
so let’s take a look at that. This is an actual picture of an eardrum. So here’s
the auricle over here. It’s shaped the way that it is because it helps collect
sound waves. So when sound waves are collected, they move into this
external auditory canal (or meatus). They travel this way.
They’re going to hit the tympanic membrane right here, causing the tympanic
membrane to vibrate. And this vibration is going to be carried to the middle ear. The external acoustic meatus is a short,
curved, tube that extends from the auricle to the eardrum. The entire canal
is lined with skin bearing hairs. There’s going to be the sebaceous glands here
and modified sweat glands called to serumenous. These are the glands that
are going to produce the waxy yellow substance in your ear to repel
insects and trap foreign bodies. okay. again. it’s right here. it’s really
important to remember these structures for your lab practical. Next we have the
middle ear, so this is going to be a small airfield cavity in the temporal
bone. I’m not going to ask you to identify the bones
on an actual picture, on a real picture, I might use a model. But these are the
three ossicles. The little bones called malleus, incus, and stapes. They
receive vibrations from the eardrum and carry them to the inner ear
area. okay. let’s look at it on a picture right
here. you have the middle ear area, behind the tympanic membrane. should also
include this tube here. These are called the ossicles. These are three little
bones that work as a lever system. This is the auditory tube, formerly known
as the eustachian tube. so this is an older name here. okay I want to make
sure we could also identify this on a model. So this area over here is the
middle ear area. And these are gonna be the three little bones. We’ll take you
closer look at them. and this right here this is the auditory
tube or the eustachian tube. Another pharyngotympaic tube. In the middle
ear, we’re gonna find the ossicles. these are the three little bones. really
important to remember these. they’re called the malleus, incus, and stapes. this
is the order from the tympanic membrane. so tympanic membrane is going to touch
the malleus, incus is going to be the middle bone, and stapes is actually
the last one and this is the one that’s going to touch the labyrinth. Labyrinth is that organ in the inner ear area. the purpose of the ossicles is to work as a
lever system to transmit the vibration are coming from the eardrum to the
inner ear, where basically action potentials could happen so that we could
hear. In the middle ear area, you also have the auditory tube, formerly known as
the eustachian tube. The purpose of this tube is stabilizing pressure in the
middle ear, and I’ll talk about it more in just a second.
so here are the ossicles, as you can see they look very tiny right here. this is
the actual size. But we actually have a model that’s much bigger. you should be
able to identify these bones. This is malleus, incus, stapes.
Again, their purpose is to work as a lever system, to transmit sound waves
into the inner ear. so basically transmitting sound waves, that’s their
function. okay we can see it right here. Here’s the tympanic membrane. this is going to vibrate, causing these three little bones to vibrate. And that vibration is
going to be carried to the inner ear area. Okay. again, I’m not gonna
ask you to identify them on a picture, like this like a real image. But I do
want you guys to know what they are on the actual model. This one right here is
the malleus, this is the incus, this one right here is the stapes. the pharyngotympanic or auditory tube (another name is the eustachian tube) is a
tube that runs down obliquely from the middle ear to the nasal pharynx area.
so right here, it’s highlighted in green. this is going to be the auditory tube.
please don’t mix that up with this tube over here, this is the external auditory
canal or external acoustic canal. this is going to be the auditory tube. so
remember tube and canal. They are two different structures. The auditory tube or pharngotympanic tube is part of the middle ear. so let’s look at the function.
normally this tube is going to be flattened and closed; however, things like
yawning or swallowing can briefly open it to stabilize pressure in the
middle ear cavity. and this is important. let’s look at another slide. this is
important if the pressure on both sides of the tympanic membrane is
not equal. here’s a tympanic membrane. that will affect how this tympanic
membrane vibrates, therefore it is going to distort hearing. it’s also going to affect
a way that your hearing sound waves so it’s important that we have the same
amount of pressure on your outer ear area and your inner ear area. if
you’ve ever been on an airplane, when you reach high altitude, you’ll notice that your
ears are kind of hurting and you’re having a hard time hearing. so you start
chewing gum or eating some peanuts and then your ears will pop. well
that popping sound is this for pharngotympanic or auditory auditory tube
opening to relieve pressure in here, so that both sides of the tympanic membrane
have the same pressure. now let’s get to the inner ear area. and this is where
things are gonna get complicated. we’re going to talk about some physiology. so
first I want to talk about the anatomy the inner ear. so if you look at the
inner ear, you’re gonna find this organ over here this is called the labyrinth.
they call it the labyrinth because it has such a complicated shape. it’s going to
be found deep in the temporal bone and it is a site of delicate receptor
machinery. and it’s important to remember that this inner ear organ, this labyrinth,
isn’t only for hearing. it’s also for balance. so part of
this labyrinth is for hearing and interpretation of sound, and
the other part of it is to help with balance. Both static balance and kinetic balance. it
monitors the rotation of your head .the movement of your head in space. so first
let’s talk about two layers of the labyrinth. if we take out the labyrinth
it looks something like this over here. there are two layers to it. there is a
bony labyrinth and also a membranous labyrinth.
so here’s bony labyrinth right here. this is going to be this white layer that you
see here. the white layer covering this whole labyrinth is called the bony
labyrinth. and if we peel off this layer we’ll see that there’s this gray layer
right here. If you guys pay attention to this, you’ll see that there’s a gray
layer underneath it. so the gray layer is called the membranous
labyrinth. So this is like having a container inside another container. we
could think about it this way. there is one container and another container and
that’s what it’s like. The bony labyrinth is going to contain a fluid
called perilymph It is important to remember. and the membranous labyrinth contains a
fluid called the endolymph. The perilymph actually similar to your cerebrospinal
fluid, and the endolymph inside the membranous labyrinth is similar to
intracellular fluid. so think about it this way, you have a container you pour a
little bit of water in it, and then you also put another container in it and
then you pour more water in that container.
so that’s kind of what it’s like. so you have this bony labyrinth here, just white
layer, this pink area that you see this is supposed to represent the space that
contains perilymph. and then here we have the membranous
labyrinth, and inside the membranous labyrinth you’re gonna find endolymph. Here’s a picture I found on the internet.
it might help you a little bit. so the blue (the dark blue) here is supposed to
represent the bony labyrinth. and the pink (light purple) here is supposed to
represent the membranous labyrinth. so you have one layer inside of another
layer and each layer is going to contain some fluids. Bony labyrinth. This is a model we commonly use in lab. commonly use in lab bony labyrinth right
here the white layer the pink layer right here you can see this pink layer this is supposed to represent perilymph
inside the bony labyrinth and you could also see this gray area over here all of
this gray area this is the membranous labyrinth and inside of that you’re
gonna have the end ellipse okay here’s another picture you could see bony
labyrinth here membranous labyrinth the gray and here’s a little bit of space in
between them that’s gonna be filtered for it so those were the layers of the
labyrinth now let’s talk about structures we could divide the labyrinth
into three main parts the vestibule this is gonna be like a middle portion
the semicircular canals and the cochlear this right here this area right here
that basically looks like a snail this is the cochlea and by the way this part
of the labyrinth is going to be involved with hearing this middle portion this is
the vestibule this part is actually involved with static balance so things
like acceleration and these structures over here these are called the
semicircular canals so very important to remember these three structures this is
the cochlea vestibule and these are the semicircular canals okay let’s look at
the next slide I want to be able to identify these on the model right here
this is the cochlea so here’s the cochlea right here and this is the part
that’s going to be involved with hearing this area over here this is the
vestibule and these right here are these semicircular canals and as you could see
there’s three of them they basically respond to the XYZ
coordinates and I’ll talk about it more in a second if you pay attention here
you’ll see that when the tympanic membrane vibrates it’s going to here’s
the tympanic membrane it’s going to carry sound waves into the middle ear
and they’re going to be transferred so to speak by the ossicles
here’s a piece as you can see it’s going to touch the labyrinth right here so
basically the vibration is going to come into this inner ear area this is the
vestibular cochlear nerve you learned about the a and P one and there’s going
to be two branches to it when it comes to this inner ear area it’s going to
branch so there’s going to be a vestibular branch right here which goes
to the vestibule and it’s good but cut on this model and this is the cochlear
branch right here we’ll talk about the cochlea so from the Latin it means snail
and it does look like a snail it’s gonna be very small it’s the size of a split
pea the cochlea is going to house a receptor organ for hearing called the
spiral organ or organ of Corti very important to remember
basically the organ the receptor organ for hearing is called the organ of Corti
sometimes I call it spiral organ of Corti but that’s not really correct I
like to use organ of Corti so the cochlea is going to contain an outer
bony labyrinth and an inner membrane is labyrinth the bony labyrinth a
membranous labyrinth together form three duct and the cochlea the scale of
vestibuli skaila media and skeleton pani also called vestibular duct cochlear
duct and tympanic duct the terms that we usually use in lab I use scale Avista
Buell I I don’t typically use scale a media I use cochlear duct and scale
ten pani it’s important to remember these three ducts that are formed in the
cochlea what I’m going to do is show you what this cochlea looks like if we cut
it open as you could see this model here it could be open and we could see what
the cochlea looks like on the inside so this is what it looks like on the inside
this is the cochlea we cut it open and this Redux that I talked about right
here look at this right here here you could see the three ducts here you could
see the three ducts here here and here so the pink is supposed to represent
this gala vestibuli the blue is supposed to represent skaila media or the
cochlear duct and the green is supposed to represent skeleton panic these are
the three deaths that I was talking about now we’re going to use a much
larger model to talk about these things here’s the cochlea so basically these
are the three ducks we basically took what was in the previous slide right
here and blew it up so it looks like this up here label this really quickly this air
here this duct over here this is this gala vestibuli and the scale of
vestibuli is basically going to be filled with perilymph this is the scale
of media right here this duct over here another name for it is going to be scale
a media or cochlear duct right here and this is going to contain endolymph and
down here we have skeleton panty which is going to be filled with perilymph
so these are the three deaths that we need to remember this is the picture on
an actual microscope slide I’m not gonna ask you to identify it up on a
microscope slide but I do want you to know how to identify the structures on a
model this is just for your information okay let’s go for each one scale of
vestibuli duck that is continuous with the oval window important to pay
attention step the oval window this duck is part of the bony labyrinth and
contains perilymph remember that here’s the bony labyrinth
out here and we talked about right below the bony labyrinth you have
perilymph so it makes sense this stuff over here scale of the stimuli this is
continuous with the oval window this means that when vibrations come in today
inner ear area they’re first gonna going to enter the scale of vestibular so this
is the first point of contact and the inner ear with vibrations of sound a
good way by the way to remember the scale of vestibuli is to pay attention
to where you have the vestibular membrane this right here
diagonal line that you see diagonal membrane this is the vestibular membrane
so above that you always have the scale of its debut line next you have scale of media or the
cochlear duct that’s going to be right here it is part of the membranous
labyrinth so we talked about membranous labyrinth containing endolymph so again
because it’s part of the membranous labyrinth it is going to contain
indolence right here this is very important because this organ right here
this part that of the duct that you see right here this is going to be most
directly involved with hearing next you have skeleton panty right down here this
is going to be part of the bony labyrinth again this right here is the
bony labyrinth so skeleton panty is a duct that is part
of the bony labyrinth and as you remember the bony labyrinth contains and
excuse me contains perilous this was a typo right here I need to fix that but
it does contain peri lip so perilymph here scale of the stimuli
perilymph scale attempt Annie and endolymph is going to be in the cochlear
duct okay the organ of Corti located in the cochlear duct and contains receptor
cells for hearing what is the organ of Corti this is the organ that’s directly
involved with hearing here’s all of this by the way students always get confused
this whole duct right here this is called the cochlear duct or the skaila
media now this organ here just this part of it this is called the org
korte so again this is the scale of media or cochlear duct and just this
part over here is called the organ of Corti now we need to talk about the
organ of Corti in detail because this is involved with hearing this is what
allows hearing to happen the origin of Corti is going to rest on the basilar
membrane that the solar membrane plays a very important role in hearing here’s
the bacilli membrane right here this blue part over here and the organ of
Corti also has these receptor cells called hair cells it looks like they
have hair on top that’s why they’re called hair cells so right here these
cells over here these are called the hair cells and the
that are gonna be on the inside these are called inner hair cells the ones
towards the outside are called outer hair cells you also have a Ferrand
fibers of the vestibulocochlear nerve they’re supposed to be nerve another
typo here coil the base of hair cells and run from the organ of Corti to the
brain so you’re gonna have the fibers of the vestibulocochlear nerve coming here
and they’re going to come up all the way here so what’s gonna happen I’m talked
about fluids being in here what vibration comes into this part of
the inner ear the fluids are going to shake and when they shake they basically
shape the basilar membrane so the basilar membrane kind of vibrates and
activates these hair cells these hair cells are going to move and when they
move these hair like extensions over here rub against the tectorial membrane
over here this is called the tectorial membrane and when these hair cells rub
against the tectorial membrane action potentials are going to be generated
which are going to be carried through the vestibular cochlear nerve so here
you’re going to have action potentials happening and they’re going to be
transmitted through the vestibular cochlear nerve and go to brain basically
for hearing here’s a closer right here here’s the basilar membrane
an important structure to remember this is the tectorial membrane right here here the hair cells over here fitzy on
top they do have these little fibers on top that looks like hair cells are not
really hair so again when this vibration enters the
inner ear area the fluid they’re gonna move or it’s kind of like a gel shaking
it’s going to move the basilar membrane when this pasilla membrane move moves
it’s going to activate the hair cells that are sitting on top of it so these
hair cells over here they’re going to move they’re going to vibrate and rub
against this tectorial membrane generating action potentials that are
going to be carried into these nerve fibers over here nerve fibers of the
vestibular cochlear nerve cochlear nerve to be specific and they’re going to be
transmitted to the brain for hearing to happen helico tree mom this is the part
of the bony labyrinth for this gala vestibuli and the scala tympani meet
therefore the ducts are continuous by the helical tree map so if we look at
the model here here’s the cochlea right here and the helices Rima is going to be
on the center portion so the helices Rima is going to be right here and this
is actually an area where does scale attempt any and the scale of vestibuli
to meet so the two outer ducts and meet in that area and it’s important to keep
just in mind and you’ll see why in just a second so if we take this cochlea
right here and stretch it out stretch it out so it’s a straight line it would
look something like this over here here’s the scale of vestibuli skeleton
panty and in between you have the cochlear duct you’ll see why in just a
second but it’s really important to remember it remember this structure
here’s the outer ears this is your ear collecting sound waves coming in here
this is the external auditory canal hitting the ear drum sound waves are
going to hit the eardrum they’re going to vibrate the ossicles right here the
ossicles are going to transmit the vibration here to the scale of vestibuli
here’s the stay piece over here and the area where a piece is going to touch the
labyrinth this is called the oval window so it’s kind of touching right here and
the vibration is going to be carried here to the scale of vestibuli first this is another picture it’s not perfect
but I found it on the internet I thought it was interesting here’s the eardrum
here are the obstacles right here and basically transmitting sound wave into
the scale of the stimuli right here and as you can see here here’s the helical
terima let’s go back to the previous slide you can see right here through the
helical terima there’s this duct here when we stretch stretch out the cochlea
that connect connects the scale of a stimuli and the skeleton patty now one
step at a time we’re going to talk about how hearing
happens transmission of sound to the inner ear so first tympanic the sound
are going to enter the external acoustic meatus and cause the tympanic membrane
to vibrate so sound waves right here are going to enter this canal over here the
external acoustic canal or me ADIS and they’re going to hit the eardrum causing
this eardrum to vibrate next as this eardrum vibrates this vibration is going
to move to the ossicles right here the obstacles are going to vibrate and
they’re gonna carry this vibration right here to the oval window this is the oval
window remember this is where the stay piece is going to touch the labyrinth so
the sound waves are carried from the eardrum through the to the inner ear by
the ossicles as stay piece rocks back and forth
against the oval window it’s since it sets the perilymph in the scale of
vestibular into motion so right here we’re gonna have sound waves coming in
hitting the sand panic membrane then the obstacle then it’s gonna come here to
the inner ear area this is the cochlea stretched out so what’s going to happen
is that the first thought that it comes into contact with which is the scale of
a stimuli and the perilymph here in the scale of a stimuli is basically going to
shake it’s going to shake this fluid in here one of two things are gonna happen
if the frequency is low the frequency of sound coming into your ear is low the
waves will move from the scale of vestibuli to the scale of tympani by the
helices rima and move toward the round window so basically the sound waves are
gonna come in you’re going to hit the tympanic membrane move – hasta khals and
vibrate these ossicles the obstacles are going to carry the vibration –
oval window and the fluid in the scale of vestibuli is basically going to start
to shake we’re gonna shake this fluid but if the frequency is low what’s gonna
happen is this this frequency is gonna come in but it’s just gonna go around
here’s it’s gonna come all the way here to where the hello Katrina is remember
hello Katrina is where the scale of this tibula and the skeleton penny are
connected and it’s going to come into the skeleton penny come to the round
window right here and if this happens the hearing doesn’t happen you don’t
hear sound waves it’s basically like it comes in and it goes around and a reason
for that is because it doesn’t affect the cochlear duct it has to basically
hit the cochlear duct the frequency has to be high enough to hit the cochlear
duct for hearing to happen because the cochlear duct is going to contain the
organ of Corti that is necessary for hearing now another
could happen if the frequency is high if the frequency is high enough it is
transmitted through the cochlear duct into the skeleton patty so it’s gonna
come in here its frequency is high so instead of going around to the hello cut
Rima it’s gonna come and hit the cochlear duct and step and basically
shake the fluid that’s in the cochlear duct and in the skeleton patty and at
this point hearing can happen so if it hits the cochlear duct the basilar
membrane will vibrate remember the cochlear duct contains this organ of
Corti the organ of Corti is going to contain this bacilli membrane the
bacilli rain is going to vibrate first the vibration of the basilar membrane
activates hair cells right here these cells are going to become activated so
these hair cells are so also going to start moving you’re going to start
shaking or vibrating causing action potentials to be sent to the brain so
when these hair cells start to move the hairs on top will brush against this
tectorial membrane when they vibrate causing action potentials and as you can
see here you look right here you can see that there’s nerve fibers right here
attached to hair cells when action potentials are generated they’re gonna
move into this using these nerve fibers of the vestibular cochlear nerve and be
carried to the brain if we stretch out the cochlea we could see that different
parts of the cochlea basically different parts of the organ of Corti or the hair
cells to be exact respond to different frequency of waves
so high-pitched frequencies are going to be closer to the base so this is where
the oval window would be and low pitch sounds are going to be towards the end
right here so as you age or when people start to lose their hearing the first
hair cells that are degenerated so to speak are the ones at the base right
here because these are the ones that are the closest to the state these these are
gonna be far away so that’s why when people start to lose their hearing it’s
harder for them to hear women because women have high pitched sounds and the
reason for that is these hair cells right here respond to high pitched
sounds so these are the first ones that you began to lose okay next we’re gonna
talk about the vestibule of the ear that’s gonna be this middle point we
talked about the cochlea we talked about the organ of Corti and that was involved
with hearing this is the middle portion this is called the vestibule and that
we’re going to talk about if we remove the bony labyrinth of the vestibule
you’re gonna see these two structures right here called the saccule and the
utricle these two structures over here it kind of look like eggs two eggs in
this area these are actually two important structures involved with
balance both the cycle and the utica are going to contain something called macula
this organ this receptor organ called the macula right here these are sensory receptor
organs that monitor the position of the head and space in each cycle wall and
each utricle wall there’s going to be a macula they respond to linear
acceleration but not rotation they play a key role in posture and this is
important the macula is the organ of static balance like the organ of Corti
they contain hair cells however theatre functions are different let’s look at
this really quick clean so here right here this is the vestibule portion
you’re going to contain inside of it the utricle and the saccule two
structures of look like eggs and endometrial and the saccule you’re gonna
have the macula and the macula also contains supporting cells and hair cells
like the organ of Corti however the function of these hair cells is
different when these hair cells move and Bend they send information to your brain
regarding the position of your head and space again this is the organ that’s
involved with static balance or acceleration so think about it this way
if you are sitting in a car you’re in the passenger seat your friend is
driving and you decide to close your eyes so taking that now even after
you’ve closed your eyes you still know that the car is moving forward you would
still know that the car is accelerating or slowing down even if you can’t see
and that’s because of these hair cells over here the way they Bend and respond
to movement they inform your brain of your the position of your head and space
they basically inform your brain that you’re moving forward
you’re decelerating or accelerating this is just the close-up look what hair
cells look like once you have this the nice circular canal now the semicircular
canals have a function similar to the vestibule but slightly different they
respond to rotational movement so the vestibule had more to do with its static
balance with acceleration but not rotation the semicircular canal have to
do with angular movement and rotation of heaven space these organs they have
organs that detect rotational movement and these organs are called Krista
Krista ampule iris the Krista am pilaris are found in the ampulla of semicircular
canals they are excited by angular movements of the head these are the
organs of kinetic balance and they also have hair cells and supporting cells so
we can see that these hair cells are in different parts of the labyrinth and the
cochlea and the festival and the ampulla however their functions are different here here the semicircular canals this
is going to be the anterior one this is lateral and the one back here this is
going to be posterior and in the ampulla of the semicircular canals this is the
enlarged area over here this is called the ampulla and the ampulla you’re gonna
have the organ called the crista and Belarus right here we could see that
there’s going to be hair cells into crista ampule eres
and when the hair cells move the hairs of the hair cells move they basically
inform your brain of the rotational movement of your head in space and these
there’s three of them in each ear they correspond to the XYZ coordinates here
here you can see the Krista and Polaris right here you’re standing straight and
then when you’re rotating your head or bending your head the way that these
hair cells move will inform your brain of where your head is in space so if
you’ve been on a roller coaster let’s say you get on a roller coaster and you
regret your decision and it’s too late so you decide to close your eyes now
even though your eyes are closed you will have a good idea of when you’re
upside down when you’re turned sideways and that’s because of these Krista
ampule airs because of these hair cells in your inner ear area informing your
brain of where your head is in space okay everyone that is it for the year

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