Full transcript
0:07All right, engineers. In this video,
0:08we're going to talk about the structure
0:09of the inner ear. All right. So, what
0:12we're going to take a look at just so
0:13that before because what we're going to
0:14do is we're going to have an individual
0:16video on different sections of the inner
0:20ear. So, what we're going to do is we're
0:21going to talk about the anatomy of the
0:22inner ear. And then again, we're going
0:24to separate each component into
0:27individual videos where we'll talk about
0:28them in great detail. So, let's go ahead
0:30and get some anatomy down. All right.
0:32So, first off, what is this big old
0:35structure right here called? This big
0:37old like snail-like looking structure.
0:39This big old beast right here is called
0:43the cookia.
0:45Okay? So this big old structure right
0:47here that's nice and windy and twirl
0:49swirly and stuff like that, that's
0:50called the cookia. Now the cookia is
0:53actually broken up into three different
0:55chambers that we'll look into great
0:57detail. Okay, so there's three different
1:00chambers of it. Okay, one of the
1:02chambers is called the scala
1:07vestibuli.
1:08Okay,
1:10the one in the middle, so this is going
1:12to be the upper chamber. Okay, so this
1:14is the upper chamber.
1:16In the middle is going to be what's
1:18called the scala
1:21media. And the scala media is really
1:24important because this is actually going
1:25to be a nice little indolymphike
1:27structure. Okay? You know they also call
1:29the scala media the cclear duct. So
1:31another name for the scala media is
1:33called the coclear
1:36duct. This is the middle layer. Okay. So
1:39this is the middle layer.
1:42Then the lower layer, the bottommost
1:45layer of the cookia is what's called the
1:47scala
1:50tempani.
1:52Okay, the scala tempani and this is the
1:54lower chamber.
1:56What's really important about this
1:59is that on the scale of vestibuli,
2:02you're going to have a really important
2:03structure that we talked about within
2:04the middle ear. We said it was called
2:05the oval
2:08window.
2:10It's called the oval window. Remember
2:11the stapes? The stapes is tapping on the
2:13oval window. And when it's tapping on
2:15the oval window, because of uh sound
2:17waves, right? The sound waves were
2:19actually creating vibrations that were
2:21compressing and decompressing the tanic
2:22membrane that was moving malus, incis.
2:25And stapes is tapping on this oval
2:27window. Well, really, when it's tapping
2:29on the oval window, it's tapping on the
2:30scale of vestibuli. Why is this
2:32important? Because the scale of
2:34vestibuli is filled with a specific type
2:37of chemical.
2:39Okay? a specific type of fluid which we
2:41call
2:44perilymph.
2:46Okay, it's called perilymph. Okay, which
2:48is more of a harder like fluid
2:50substance.
2:52The other one there was a structure that
2:54was right inferior to the oval window.
2:56Remember that one? It was called the
2:57round window. What was it called? It was
2:59called the round window.
3:02And if you remember
3:06we said that the round window was
3:08important because if you remember some
3:09of the sound waves are going to come
3:10through the different parts of the scale
3:11of vestibuli the scale of media and the
3:13skeleton pani. What happens is some of
3:15those sound waves will actually can get
3:17lost or scattered throughout the inner
3:19ear. We don't want that because that can
3:20interrupt the actual action potentials
3:21going to the brain. So what we want to
3:23do is we want the round window to
3:25prevent the actual scattering of those
3:27sound waves to prevent the the actual
3:29scattering of those sound waves into the
3:30different parts of the inner ear. Okay.
3:32So again the round window is really
3:33important and that's actually located
3:36within the scala tempani and again we'll
3:38look at this in a more deeper view when
3:40we get to this individual uh coia and
3:43we'll talk about the spiral organ of
3:44cordi and a whole bunch of other stuff.
3:46Okay. But another important thing is the
3:48skeleton pani is made up of what's
3:50called
3:52perilymph
3:54you which is more of like a harder
3:56fluid-like substance with a little bit
3:57of calcium and stuff in it. Okay.
4:00Then the scala media which is really
4:02really important. The scala media or the
4:04cclear duct which is the middle layer is
4:06rich with a fluid called endolymph. And
4:09we're going to talk about endolymph a
4:11lot. We're gonna talk about what kind of
4:13structures are making the endolymph. But
4:14what I want you to remember about the
4:16endolymph is that it is a potassium rich
4:18fluid. It is a potassiumrich fluid
4:22located within the scala media or the
4:24cclear duct. So what you're able to
4:26notice here is that the scala media
4:30which is filled with endolymph is
4:32surrounded. Above it it has a scala
4:34vestibuli which is filled with
4:36perilymph. Below it has the skeleton
4:38pani which is filled with perilymph.
4:41Perilymph is what's called the outer
4:43bony labyrinth. Okay? So if something is
4:46made of perilymph, it's a part of what's
4:49called the outer
4:52bony
4:54labyrinth.
4:56So again, this one's made of perilymph
4:58also. So this would be made of this is
4:59actually called the outer bony
5:03labyrinth.
5:06And then the structure that's actually
5:07made up of endolymph,
5:09the structure that consists of endolymph
5:11is actually going to be consisted to be
5:13called the inner membranous labyrinth.
5:16So it's called the inner
5:20membranous
5:24labyrinth.
5:26So the outer bony labyrinth which is the
5:28scale of vestibular and the skeleton
5:29pani consist inside of it with an inner
5:32membranous labyrinth which is made up of
5:34indolymph. Okay.
5:37All right. Sweet deal. So that covers
5:38that part of the cookia. We'll talk
5:40about a little bit more detail. But if
5:41you see right here, you see this little
5:43ending point here. You can see that the
5:45coclear duct is this nice little blue
5:47structure here. So we can definitely
5:49clearly see here this part there which
5:52is called the cclear duct.
5:56Okay. And then we're going to have again
5:58two different components. We're going to
5:59have what's called the oval window and
6:01then we're going to have what's called
6:03the round window. And remember, we can
6:05have two chambers. Now, this isn't a
6:07perfectly uh formed here, but we're
6:09going to say that this part up here,
6:10let's say above the cclear duct, this is
6:13going to be what's called the scala,
6:15what vestibuli
6:17below this is going to be the scala
6:19tempani. And in between is going to be
6:21the cclear duct. Okay? And again if you
6:25remember we could say here would be the
6:27oval window which would be where the
6:29stapes is tapping on and below could
6:31actually be the round window and the
6:33round window is where the actual
6:35preventing of the sc the sound waves
6:36from being scattered.
6:39Sweet deal. And if you want to know one
6:40more thing this point here at the end if
6:43we follow the coar duct kind of makes
6:44this nice little spiral here and it
6:46comes to this end point here. You see
6:48this end point here right there. I'm
6:52going to write it here. this point here
6:55where the actual scala vestibuli. So
6:57again what would this one be? Scala
6:58vestibuli. Scala tempani. You see that
7:01part where the scala vestibuli and the
7:02scala tempanana actually come together
7:04and their perilymph combines. That's an
7:07important structure there. And that
7:08structure is actually called the
7:11helilico
7:14trema. Okay. So it's where the scala
7:17vestibuli
7:21and tempani
7:25perilymph
7:28mixes.
7:30All right. Sweet deal. That's the
7:31helicotrema.
7:34Now another thing that we'll talk about
7:35in great details. You see this like duty
7:36brown kind of like structure here. That
7:38duty brown like kind of structure is
7:39actually called the cclear branch of the
7:42vestibular cclear nerve. Okay. So if you
7:45see this part right here, this part
7:48right here, imagine there's actually
7:49nerve fibers coming through here and
7:51they actually come through a ganglion
7:52which is called the spiral gangleion.
7:54We'll talk about this in detail, but
7:57these axons are actually going to be a
7:58very very important component of the
8:01vestibular cclear nerve. So if you see
8:04these fibers that are coming out here,
8:05it's actually going to be an important
8:06component of the vestibular cclear
8:08nerve. Okay. But this branch here which
8:10is coming from the cookia is what
8:12branch? It's the cclear branch
8:16of the vestibular cclear nerve. So what
8:18branch is it? It's the cclear branch
8:25of cranial nerve 8. Okay? And cranial
8:29nerve 8 is going to be called the
8:31vestibular cclear nerve.
8:35Okay. Sweet deal. So that covers that
8:37part. That covers the cookia. Now we're
8:41going to talk about the next one which
8:42is going to be the vestibule. So what is
8:43this next part here? The vestibule is
8:45really important because the vestibule
8:47is a pretty decently sized structure
8:48here. Let's actually write it right
8:50here.
8:53This part here is the vestibule. Okay,
8:56it's a very kind of like vestibial is
8:58kind of like the body. Okay, so this big
9:00whole part here I'm going to kind of
9:01like encircle it here like this.
9:04Okay, if you kind of see I'm kind of
9:05encircling around it here. All of this
9:08part here is actually going to be the
9:11vestibule. Okay? All that part that I
9:13moved around with the purple, that's all
9:14the vestibule. What's important about
9:16the vestibial? The vestibial is actually
9:18going to consist of two important
9:21structures.
9:23It's going to consist of what's called
9:24the utricle,
9:26okay, internally. So the vestibial is
9:28going to consist of a structure called
9:29the utricle. And it it's going to
9:31consist of another structure called the
9:33sacule. Okay? And again, we'll look at
9:35these in more detail. I just want to get
9:36you guys introduced to them. But what's
9:38important to remember is the vestibule
9:41is the outer bony part. So it's called
9:43the outer bony labyrinth. So the
9:46vestibule, which is this whole big
9:47structure here, it is a outer bony
9:50labyrinth. So what does that mean? That
9:52means it's filled with perilymph.
9:57Okay, it's filled with perilymph. So
9:59therefore since it's filled with
10:00perilymph it is the outer
10:03bony
10:05labyrinth
10:07and again inside of the vestibule which
10:10is the outer bony labyrinth it consists
10:13of the utricle and the utricle is filled
10:15with indolymph okay so this is filled
10:18with indolymph which is potassium rich
10:22okay this is potassium rich and this is
10:25going to be the what inner
10:30membranous
10:32labyrinth.
10:36Okay, sweet deal. Same thing with the
10:38sacul. The saculle is a little bit
10:39smaller. See the utricle is actually
10:41going to be, if you want to see where
10:42it's placed here, I'll show you where
10:44it's placed. So, let's say that this one
10:46right here, but I'm going to point on
10:48with red. I'm going to bring him down
10:50here. That one right there is the
10:52utricle. Okay. So, this upper one. So,
10:55if you come here for the vestibule,
10:56let's say that this is the inferior
10:57portion. This the superior portion. The
10:59superior portion here is going to be the
11:01utricle. The inferior portion here is
11:02going to be the sacule. So what is this
11:04structure here called? This one here.
11:07This is the sacle.
11:11Okay. So we have the sacule which is the
11:14inferior part. And then over here we're
11:16going to have the utricle. And again the
11:18saculle what's important about the
11:20saculle he's going to consist of
11:22indolymph
11:25which is a potassium rich fluid
11:28and he's going to be a part of the inner
11:32membranous
11:35labyrinth.
11:38Okay. Now, why am I mentioning all this
11:39stuff? And the reason why is because the
11:41saculle and the utricle, just like the
11:43cclear duct, this endolymph is important
11:46because these structures, we'll talk
11:48about in way more detail when we get
11:49there, but they consist of things called
11:51hair cells. Okay? They consist of things
11:54called hair cells. Okay? And these hair
11:58cells are really important because the
12:00utricle and the saculle are a part of a
12:03larger structure. Okay? So really when
12:05we say vestibial, vestibial is the outer
12:07bony labyrinth. And if we really really
12:09wanted to be super super picky, the
12:12vestibule actually consists of this
12:15structure here. Now let's actually come
12:16back to this. It actually consists of a
12:18structure called the utricle and the
12:19sacule. But inside of the utricle and
12:21the sacule, they have a special
12:23structure called the macula. So they
12:26have a special structure here called the
12:28macula. And we'll talk about this in
12:31great detail because the macula is
12:32important for static equilibrium, which
12:35is like whenever you are linearly
12:37accelerating. So if I'm actually going
12:39and I'm in a car and I hit the gas,
12:40boom, I my head moves back or when I hit
12:44the brake, my head moves forward. So
12:46when I linearly accelerate and I
12:48decelerate, or when I tilt my head to
12:51the side, so if I tilt my head to the
12:54right side, I can activate these guys.
12:55If I tilt my head to the left side, I
12:56can activate these guys. Or let's say
12:58that I'm falling. I'm in an elevator and
13:01some terrible thing happens and the
13:02freaking cord breaks and I'm flying
13:03down. Ah, you know I'm flying down. That
13:05can also activate that. So a vertical
13:08deceleration could also activate these
13:10structures. Okay, so sweet deal. So
13:13again the vestibial is the outer bony
13:14labyrinth filled with perilymph
13:16consisting of the utricle and the sacula
13:18which are filled with indolymph. These
13:20are the inner membranous labyrinth. They
13:22cons contain a special structure which
13:24are consisting of these hair cells. But
13:26these hair cells as well with other
13:28structures here, you'll see them later.
13:29They're called an oolithic membrane with
13:31odiconia. Okay, little calcium carbonate
13:34crystals. They make up what's called the
13:35macula, which is a special detector for
13:38what type of equilibrium? We said that
13:40this is for static
13:43equilibrium. Okay, like I said, we'll go
13:45into this in more detail when we get
13:46there. And if since we covered this part
13:49over here, the scala media or the cclear
13:51duct, it has a special detector. So, it
13:54has special hair cells
13:57covered with what's called a tectoral
13:59membrane. And these hair cells with the
14:02tectoral membrane make up another really
14:04important structure called the spiral
14:07organ
14:10of corti. Okay? And this is interesting
14:13for sound. Okay? So, whenever you
14:16actually I'm talking to you guys right
14:17now, the sound waves that you guys are
14:20hearing is carried out by the spiral
14:22organ of cordi. Okay? So auditory
14:24information is going to be picked up by
14:26the spiral organ of corti. All right,
14:28sweet deal. We did that.
14:30Next thing, you see these these suckers
14:33here, these canals. These canals, we
14:35have three of them. Okay, we have three
14:37canals.
14:39This one right here is called the
14:41anterior
14:44semic-ircular canal.
14:47I always put a U there for some reason.
14:48Circular
14:51canal. this one in the back. So, it's
14:54coming here and it's moving posteriorly.
14:57This one right here is called the
14:58posterior
15:01semic-ircular canal.
15:06And then you have one, imagine it coming
15:08out at me like it's punching me in the
15:10face. Okay? So, imagine this bad boy is
15:12coming at me to punch me in the face.
15:14This is coming out laterally. Okay?
15:17Because remember this is an internal
15:18structure. So when this is poking out,
15:20remember we said that this was actually
15:21a little depression within the middle
15:22ear cavity or the tempanic cavity, the
15:24medial wall. So this guy is trying to
15:27come outwards is trying to go outwards
15:29towards the ear. So this is actually
15:30going to be lateral
15:34semic-ircular canal.
15:39Okay. So now that we got that, the
15:41semic-ircular canals, what's important
15:42about these guys? The semi-ircular
15:44canals
15:48are going to be the outer bony
15:50labyrinth. So outside of this, again,
15:53imagine kind of like I'm kind of
15:54highlighting it right here. You see all
15:56this stuff that I'm trying to like move
15:57in with like little lines. That part
15:59there is the outer bony labyrinth which
16:01is made up of perilymph. Okay.
16:05Now, why am I telling you that? So the
16:07outer bony labyrinth here which is made
16:10up of perilymph. So it's consisting of
16:12perilymph.
16:13So this is the outer bony
16:17labyrinth. Inside of it, there's this
16:21nice little blue structure there. What
16:22is that blue structure there called? The
16:24blue structure inside of this is called
16:28the semi-ircular
16:30ducts.
16:32Semi-ircular
16:35ducts.
16:36Another important thing is the
16:38semic-ircular ducks. So, this is a whole
16:40semic-ircular dock here. This is a
16:42semic-ircular dock coming back. And this
16:44is a semic-ircular dock going this way.
16:46All right. But these semic-ircular docks
16:48dump into a nice dilated region, which
16:50I'm going to kind of highlight here in
16:53pink. Let's say that this one right here
16:55kind of dilates right here. This kind of
16:58dilates. This kind of dilates. And that
17:01kind of dilates. Those little dilations
17:03at the end part of the semic-ircular
17:06canals here as it's getting getting
17:07ready to go into the vestibular area.
17:09These little dilated regions are called
17:10the ampula of the semic-ircular canals.
17:14So what is this part right here called?
17:15What do we say this was? This little
17:17dilated regions here. These dilated
17:19regions here are called the ampula
17:24of semi
17:27circular
17:30canals. Right? So it's the ampula.
17:34So that dilated region there is
17:37consisting of a very very special
17:40structure. So at the ampula of the
17:42semic-ircular canals that dilated region
17:44right there's semic-ircular duct right
17:47there that so the semic-ircular ducts
17:49are moving all the way around but they
17:50have little dilated regions right there.
17:52That dilated region which is in the
17:53ampula is a very very special detector.
17:57that special detector which is in the
17:59ampula.
18:00It consists of these hair cells
18:03that are covered with like a collagenous
18:06uh gelatinous membrane called the
18:08kupula. Okay. And that basically makes
18:11up a very very special detector called
18:13the christe
18:16ampularis.
18:19And the christ ampularis is important
18:21for what's called dynamic
18:23equilibrium. Okay. What do I mean?
18:27If I decide to turn my head to the
18:29right, turn my head to the left, or I
18:32decide to do circles,
18:34this guy is really important because
18:35he's helping to maintain my balance, my
18:38posture, my equilibrium whenever I'm
18:40doing head rotations or angular
18:43acceleration. So he is good for
18:46cristulus is important for angular
18:48acceleration. Whereas the macula which
18:51is consisting of the utricle and the
18:53sacule that's important for static
18:55equilibrium or linear acceleration.
18:58Okay, whether it be horizontal or
18:59vertical. And then the last one which
19:02was the cookia which is consisting of
19:04the cclear duct. These hair cells are
19:07important because the spiral organic
19:09cordi is detecting sound waves,
19:11vibrations in the air, okay, and turning
19:14that into electrical potentials for us
19:15to perceive.
19:18Okay. So in this video we covered that.
19:20Now what? Oh one other part here. Let's
19:23do this one in this color here. You see
19:26this part here? This is actually another
19:30branch of the vestibular clay nerve
19:32cranial nerve eight. But this branch is
19:34coming from the vestibule and it's
19:36coming from the what? It's coming from
19:38the actual semic-ircular canals. But I
19:41guess maybe they don't have much love
19:42for the semic-ircular canals but they
19:44are coming off the vestibule. But they
19:46call this branch that's moving with the
19:48vestibular cclear nerve. They call it
19:50the vestibular branch of the vestibular
19:52cclear nerve. So what is this branch
19:54here called? Holy crap. Get rid of that
19:56one. This is called the vestibular
20:00branch.
20:03Vestibular branch
20:07of cranial nerve eight or the vestibular
20:11cclear nerve. And just like I said, this
20:13had spiral ganglion. Okay, these also
20:17have a ganglion along the way. It's
20:18actually part of what's called scarpas
20:20ganglion. Okay, so these are the sudi
20:22pseudouiolar cell bodies which have
20:25their peripheral processes coming out
20:26here to the vestibial and the
20:27semic-ircular canals and their central
20:29processes going into the central nervous
20:30system. Same thing here. Spiral ganglion
20:33have their peripheral processes coming
20:34out to the coar duct and they have their
20:36central processes going into the central
20:37nervous system. All right and they'll
20:39take these informations into the cclear
20:41nuclei and we'll have that p we'll talk
20:43about that in the actual uh auditory
20:45pathway. Okay. Whereas the vestibular
20:47branch will take it to other structures
20:48called the vestibular nuclei. And again,
20:51we'll have another video on that. All
20:52right. So, engineers, we covered
20:54basically the anatomy of the inner ear.
20:56What we're going to do is we're actually
20:57going to have individual videos where
20:59we're going to focus on the vestibule
21:01and it's the structures inside. We're
21:03going to have another video on the
21:04semic-ircular canals and the structures
21:06that are inside those special detectors.
21:08And then we're gonna have another video
21:10on the cookia and the structures that
21:12are inside. and we're going to talk
21:13about how static equilibrium is being
21:15affected, how dynamic equilibrium is
21:17going to be affected, and how sound
21:18waves or sound is actually going to be
21:20affected. So, if you guys need any extra
21:22help with a little bit more of the
21:24actual ear anatomy, we're going to have
21:26another video that you guys can click
21:27out on the the corner of the video. It's
21:30going to be talking going over the
21:31external ear, the middle ear, and the
21:33inner ear. And I'm actually taking a
21:35model, an anatomy model, and you guys
21:37can see that in a little bit more depth
21:38if you guys need a little bit more help
21:39with that. All right, but ninja.
21:42I really do hope that you guys enjoyed.
21:44If you guys did, please hit the like
21:45button, comment down in the comment
21:46section, and please subscribe.