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AnatomySpecialSensesEarTasteSmellnew — Transcript

by Dr. Naveen Jalota, M.D. · 9,066 words · 1,572 segments · language en · Watch on YouTube

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0:00Hello and welcome. Let's talk
0:04chemical senses. Let's talk chemical
0:06senses now. Let's go through and we're
0:08going to look at a couple of different
0:10senses.
0:11And here when we go through and we talk
0:13chemical senses, chemical senses we're
0:16going to look at are going to include
0:18the senses
0:19uh in relation to smell and uh the sense
0:22taste. So, let's go through and let's
0:24look at both of these senses there.
0:26Again, this is the anatomy, so we're
0:27going to go through and we'll check out
0:28the anatomy. Uh I'll hit at a little bit
0:30of the physio there, but it's nothing uh
0:32uh
0:33that you have to know or you're going to
0:34be responsible for knowing about or
0:36um you'll have to know in great detail.
0:38Um
0:38when you get to physio, then obviously
0:40you'll see that in greater detail when
0:41you get there.
0:42So, here let's move through. Let's get
0:45slideshow opened up. Let's play this
0:47from the current slide.
0:49All right. So, here we're going to go
0:51through and what uh talk about uh this
0:53first chemical sense, this first
0:54chemical sense will be uh the chemical
0:57senses of smell. Uh the the sense of
1:00smell.
1:01Now, when we go through and we talk
1:02about uh
1:03the sense of smell, the sense of smell
1:05is going to be elicited thanks to you'll
1:06see our olfactory epithelium. Thanks to
1:09our olfactory epithelium. Now, when we
1:11go through and we talk olfactory
1:12epithelium, this olfactory epithelium is
1:15going to be found occupying basically
1:18the olfactory mucosa. So, when we talk
1:20olfactory mucosa, the olfactory mucosa
1:22itself is going to be found now lining
1:25you'll see the roof. It says the roof of
1:27the nasal cavity here in your guys'
1:28slides. Um again now when we go through
1:31and we talk uh nasal cavity, we're going
1:33to talk specifically specifically
1:34speaking, we're going to see it's going
1:35to be found lining the superior nasal
1:37conchae on both sides. Lining the
1:39superior nasal conchae on both sides.
1:42So, here when we go through and we talk,
1:45you can see that there in greater detail
1:47now.
1:49Here you got the superior nasal conchae.
1:50We've talked about these nasal conchae
1:52when we talked bones. We referred to
1:54them as scroll-like structures. Okay?
1:57And then they've got meatuses, little uh
2:00canal-like uh passageways underneath and
2:02they're going to be involved with
2:03helping to create turbulence in the air
2:05that we breathe. So, here when we talk
2:07uh
2:08uh conchae, you can see all three
2:10conchae and we've got the superior
2:13our reference point for the sense of
2:15smell now.
2:17So, again, here we've got what we call
2:20our olfactory mucosa. The olfactory
2:21mucosa contains this olfactory
2:23epithelium. Let's look at this now in
2:25greater detail. Now, while we're here in
2:27this image, I want to point out to you
2:29as well um we're not going to just look
2:31at this one part and just talk about
2:32this and just you know leave this alone.
2:34I want you to look at everything, right?
2:35There's a picture, so I want you to go
2:36through the picture and look at
2:37everything there. Now, the sense of
2:38smell, the sense of smell is going to
2:41take place inside the nasal cavity. But
2:43now here you can see the nerve that's
2:45making its way to that nasal cavity is
2:48coming from you can see the cranial
2:49cavity. So, you've got a cranial cavity
2:52you can appreciate right in here.
2:54You've got then the nasal cavity. And
2:56then here you've got oral cavity. So,
2:58you got three different cavities I want
2:59you to be able to uh
3:01put together there as well. And then
3:02we're going to go through and we're
3:03going to look at uh all these other
3:05structures uh throughout the semester as
3:06well, but here you can appreciate one
3:09bone. You should know this bone here.
3:11Not only that, you should know this bone
3:12that you have here and you should see
3:14and be able to identify this bone you
3:15have here as well. So, not only that,
3:18but then we've got these bones down
3:19here. So, these are all going to be
3:21creating different boundaries. You could
3:23think of borders from one cavity to
3:25another. So, here we've got the sphenoid
3:27bone. Okay, here we've got the frontal
3:29bone. Between the two you've got the
3:31ethmoid bone. If you recall, we had the
3:35name of that
3:36structure uh that has the openings.
3:40Very good. I know you're all guessing it
3:42right. Cribriform plate with the
3:45olfactory foramina or cribriform
3:46foramina, right? Now, here you can see
3:50we've got
3:52which bone?
3:53Okay, we all know what bone that is. Uh
3:55it's got a specific name to it. Okay? Uh
3:59you would have want to know the name to
4:00that and then here we're going to have
4:01another bone that's going to help make
4:04up then the posterior 1/3 you could
4:06think of of that hard palate and that's
4:09going to be I'm 100% sure we all know
4:11the name of that bone there as well. But
4:14again, more specifically speaking,
4:15what's the name of that specific spot of
4:18that bone?
4:19Okay? So, here you can see then you've
4:22got basically that nasal cavity and
4:25we'll discuss the nasal cavity and its
4:26boundaries, borders, and all of that in
4:27greater detail when we get to
4:30uh respiratory system. So, looking here
4:33now, you can appreciate that olfactory
4:34epithelium. Now, this olfactory nerve
4:38we've got there, we've talked about that
4:39nerve there as well. We said this is
4:40cranial nerve number one. Here you can
4:42see it's got two parts to it. It's got a
4:44tract and then you can see the bulb
4:46part. I told you guys before, we'll look
4:48at the inside and we'll see what that
4:51is what that create what basically is
4:53helping to create that bulging part uh
4:56that bulb part of that nerve there as
4:58well when we move through
4:59excuse me through here.
5:01So, let's zoom in on that. When we zoom
5:03in on that region there, this is what
5:04you see.
5:06So, higher power
5:08this is what you've got there. Again
5:10now, let me reorient you to where we're
5:11at. You've got cranial cavity up in
5:14here.
5:15Cribriform plate of the ethmoid bone.
5:18And then right down here you've got
5:19nasal cavity.
5:22So, you can see here
5:23those tiny openings you've seen them
5:25when we talked bones and we went through
5:26all of that at the beginning of the
5:28semester.
5:29Let's talk then this olfactory
5:30epithelium. Now, when we talk olfactory
5:32epithelium, this olfactory epithelium
5:34you can see it's made up of a couple of
5:36different a few different cells. Now,
5:38the major cell type that we have here
5:40that we're going to talk about we're
5:41going to check out is going to be the
5:42olfactory sensory neurons or you can
5:45refer to them as the olfactory receptor
5:48cells. Now, when we talk about these
5:50olfactory receptor cells or these
5:52olfactory sensory neurons, you can see
5:55those cells here very nicely in yellow.
5:58These cells they're described they're
6:01described as being bowling pin-shaped
6:05cells. Bowling pin-shaped cells.
6:10They're found in that olfactory
6:12epithelium.
6:13This olfactory epithelium
6:17we said is found located high up in that
6:21nasal cavity in the roof of the nasal
6:23cavity covering the superior nasal
6:25conchae on each side of that nasal
6:26septum.
6:28So, that epithelium has got one major
6:30cell type here that we can see and
6:32that's the olfactory sensory neurons.
6:35Now, these olfactory sensory neurons
6:39So again, they're going to be found
6:40making up that epithelium
6:41which covers the superior nasal conchae.
6:44Now, these olfactory receptor cells,
6:46these olfactory receptor cells
6:48these cells you'll see they are number
6:50one, they're unusual bipolar neurons. If
6:53you recall, we talked about having
6:55bipolar neurons in a couple of different
6:57places. A couple of main places where
6:59I'd like you to know about and we've hit
7:01that now both of those.
7:04Next thing you can see each of these
7:05cells, each
7:07of these olfactory sensory neurons,
7:09these receptor cells, they have a thin
7:13apical dendrite. Here you can appreciate
7:16that thin apical dendrite. You can see
7:19that here for this neuron. Same thing
7:21same thing here for this one. Same thing
7:23here for this one. Here, here, and here
7:26as well.
7:27Now, these
7:29apical dendrites, these apical dendrites
7:31they're going to terminate. They
7:33terminate.
7:35They terminate as these widened-out
7:38knob-like structures.
7:41The dendrites, these thin apical
7:42dendrites, they're going to terminate as
7:44these
7:45widened-out
7:47knob-like structures you can see right
7:48here at the end.
7:50From which you're going to see several
7:52cilia radiate. From which you can see
7:55several cilia radiate. Now, this cilia,
7:59this cilia you'll see is going to be a
8:02little different from the cilia that
8:03we've talked about we've mentioned
8:04throughout the semester. Normally
8:06speaking, we've seen cilia to be erect.
8:08Here you see it's not erect. It's found
8:10lying flat against the epithelium.
8:13And also epithelia you can see there and
8:16when we talk cilia, we said cilia is
8:17going to help to move things along. So,
8:19here you see it's not helping to move
8:20things along. Here it's going to serve
8:22as we'll see here in a few seconds as a
8:24as basically the receptive area. So,
8:27let's talk olfactory cilia. That's next
8:29up on your note taker. Now, when we talk
8:31olfactory cilia, this olfactory cilia,
8:34what it does is it increases
8:37it increases the receptive surface area.
8:41It increases the receptive surface area.
8:45And again, like I said, you can see it's
8:46going to be found lying flat against
8:49it's found lying flat against that nasal
8:52epithelium.
8:57Against those epithelial cells.
9:00Against that olfactory epithelium.
9:08Now, here when we go through and we talk
9:11this cilia, you can see the cilia is
9:13also coated. It's also covered by a thin
9:15coat. It's covered by a thin coat of
9:18mucus.
9:20This mucus
9:22is a solvent.
9:24The mucus is a solvent and what this
9:26mucus does, it's going to capture it
9:29captures and it dissolves airborne
9:32irritants.
9:33It will capture and it will help
9:35dissolve airborne irritants.
9:43Now, when we go through and we talk
9:45mucus, this mucus is going to come from
9:48we can see these glands. Here we've got
9:51olfactory glands. These olfactory
9:53glands, they're They're to help produce
9:56the mucus
9:58along with the supporting cells.
10:00So, they'll produce the mucus along with
10:02the supporting cells.
10:04And these glands, they're found, as you
10:07can see, in the underlying connective
10:10tissue.
10:13They're found,
10:14excuse me, in the underlying
10:16connective tissue.
10:18So, you can see that right underneath
10:20here. Again, remember we talked
10:21epithelium, we said epithelium has got
10:23all these different characteristics. So,
10:25one of those characteristics is it's
10:26supported by connective tissue, and
10:28that's what you got right there.
10:31Now, here you can appreciate the gland.
10:34And here you got the the duct of the
10:37gland.
10:38And so, allow it to
10:41introduce its secretions to the surface
10:43or into a cavity. So, what type of a
10:45gland are we talking about here?
10:50Very good. That duct gave it away.
10:54You're talking about exocrine glands.
10:56Exocrine glands.
10:58So, next then let's move and let's talk
11:01then. The filaments, here you can see
11:03the filaments of olfactory nerve,
11:05cranial nerve number one. Here you can
11:07see now the filaments of cranial nerve
11:09number one. They're basically these
11:12slender
11:13unmyelinated
11:15axons. They are slender, unmyelinated
11:19axons
11:20of the olfactory receptor cells.
11:24Of the olfactory receptor cells.
11:28That are going to collect
11:30that are going to collect.
11:34You can see here and gather
11:38before they penetrate
11:42through the foramina. So, we talk
11:43filaments, filaments of cranial nerve
11:46number one, they're slender unmyelinated
11:49axons of the olfactory receptor cells
11:54that are going to collect and gather
12:00right before they penetrate
12:03through this cribriform plate via those
12:06olfactory foramina or cribriform
12:08foramina.
12:13Now, you can see these fascicles are
12:15going to these filaments basically,
12:16they're going to project superiorly.
12:19So, they project superiorly through
12:22the openings, through the foramina,
12:25cribriform foramina on the ethmoid bone.
12:30Now, I told you that olfactory
12:34nerve is going to have some subdivisions
12:36to it. We saw the tract, and then here
12:37we can see the bulb. Now, the bulb, you
12:39can see the inside. Now, the bulb is a
12:41widened out region, and you can see why
12:42it's widened out. It's widened out
12:44because you can see here we've got a
12:46junction.
12:47We've got a junction between
12:50the axon of one cell
12:52and the dendrites of another cell, from
12:55one neuron to another neuron. So, here
12:57what we have is we have these
12:59axodendritic
13:01synapses.
13:04Okay? Synapses
13:06where two cells come together. So, here
13:07you can see exactly that happening. Now,
13:10this cell here, multipolar
13:13cell, multipolar neuron, specifically
13:15speaking, it's a mitral cell.
13:18And now, these signals
13:20are going to be basically traveling
13:22in between these two cells, you can see.
13:29So, the olfactory bulb is basically
13:32found at the distal ends.
13:35It's the widened distal ends of that
13:38olfactory nerve, you can see right
13:39there.
13:41And then tract, I've given you the
13:42definition of tract.
13:45And so, that's exactly what you're
13:46seeing here.
13:52Now, we've got supporting cells here.
13:54These supporting cells are columnar
13:56cells. They are columnar cells.
13:59And they make up, you can see, they make
14:01up the majority.
14:02They make up the bulk. They make up the
14:05majority of this
14:07penny thin
14:09It's like as as as thin as a penny.
14:14So, again, they're going to be making up
14:16the bulk of this penny thin
14:19epithelial membrane.
14:21Now, this penny thin epithelial
14:23membrane.
14:27And then we can also see their basal
14:29cells. Basal cells are going to be
14:30dynamic stem cells.
14:38And so, here what happens then
14:40you've got the anatomy laid out here.
14:43What's going to happen is
14:47uh
14:48odorants. Odorants are going to come in.
14:50Excuse me, odorants will come in. And
14:52when odorants come in, odorants will
14:54dissolve in this mucus, and they'll go
14:56and they'll bind to receptors that are
14:58going to be found on the olfactory
15:00cilia. So, that's why I told you the
15:01cilia is a little bit different from the
15:03cilia that we've described before.
15:05So, these odorants come and they bind to
15:08these various receptors. And when they
15:10bind to the various receptors, then
15:11they'll excite these cells. These cells
15:14then will say get excited, they're going
15:16to start sending
15:17signals basically to the next cells,
15:18eventually letting
15:20the brain know what we have there that
15:22we're smelling.
15:24And then physio, you'll see we get into
15:26it in full on detail where you can
15:28actually see the receptors and the
15:31odorants, and you see the connection
15:32between the two help to activate a whole
15:35bunch of different uh uh
15:37you can think of activities inside the
15:40cell which are going to then allow us to
15:43be able to smell what we're smelling.
15:45Not only smell what we're smelling, but
15:47also to help create adaptation.
15:50So, you don't just keep smelling the
15:52same thing with that same intensity over
15:54and over. Right? If somebody comes
15:56with this new cologne, after a few
15:57minutes the initial
16:00you know, that initial smell is a pretty
16:02strong smell, but after that
16:05you know, you stop smelling it.
16:07And that's going to be due to
16:07adaptation. And you'll do different
16:09activities there as well where you'll
16:11try to see how long it takes for you to
16:14adapt.
16:17Next then let's move from
16:20sense of smell, we'll move to the next
16:22sense. This will be This will be taste.
16:24But let me go through the different
16:25processes that are taking place here.
16:27You can see now first the odorants will
16:29come in. The odorants come in and
16:30they'll bind to the receptor. Once they
16:32bind to the receptor, what's going to
16:34happen is they'll activate this G
16:36protein-linked receptor system which
16:39you can see here now this GTP gets
16:42activated. This olfactory protein gets
16:45basically gets activated, and it's going
16:47to activate now you can see adenylyl
16:49cyclase. So, there's an enzyme here.
16:52This enzyme, what it does then it
16:54converts ATP
16:56to cyclic AMP.
16:58Now, cyclic AMP then what it does, it
17:00goes and it binds to
17:03these receptors.
17:05These channel receptors.
17:08When it binds to these channel receptors
17:10now, here you can see what it does, it
17:11helps to open up that gated cation
17:15channel.
17:17And you'll learn and you'll see when
17:18these ions move across the membrane, if
17:20you haven't learned in 107, right? When
17:22you talk action potentials, you'll see
17:24this in physio and you'll get this down
17:25there. This will help to create then an
17:27action potential.
17:30As you can see here
17:32leading to the first part,
17:33depolarization.
17:35So, the cell depolarizes
17:38when that sodium is going to rush into
17:40the cell.
17:46Now, when we go through and we talk
17:47about the sense of smell, I want you
17:49guys to know this uh is one of the
17:51senses where signals are not going to
17:54pass through the thalamus.
17:56They do not pass through the thalamus.
17:59Okay? Before stimulating the primary
18:01olfactory cortex. Everything else we've
18:03seen, we said that the thalamus is going
18:04to serve as our
18:07relay station.
18:09It serves as our relay station. So,
18:11since it serves as a relay station
18:13for we said also incoming signals.
18:16So, here you can see is where one sense
18:19is not going to be sending in signals
18:21through the thalamus.
18:23So, secondary areas are going to include
18:25then you can see insula
18:28the orbital frontal cortex, hippocampus,
18:31amygdala, and the hypothalamus.
18:39And then here you can see all those
18:40passageways.
18:50Let's talk gustation. Let's talk taste.
18:52Now, when we talk gustation, we talk
18:54taste. Taste is going to take place
18:56inside the oral cavity, more
18:58specifically speaking, on the tongue.
19:00And we'll see other areas in that oral
19:02cavity as well. Most we'll say primarily
19:05inside the on the tongue because on the
19:07tongue is where we're going to find
19:09taste buds.
19:11And that's where the sense of taste is
19:13going to occur. So, taste buds, tongue
19:15is going to have most of them. There's
19:17some that are going to be found in the
19:18soft palate, the pharynx, the
19:20epiglottis, and also the cheeks as well.
19:22So, that's why I said primarily tongue.
19:26Now, these papillae we're going to go
19:28through and we're going to check out are
19:29going to be various papillae. Now,
19:32they're referred to as your lingual
19:33papillae.
19:35They're going to be projections on the
19:37surface of the tongue. Now, you can see
19:39there's various types. We have
19:41fungiform, we have foliate, we have
19:45vallate or circumvallate,
19:47and we have filiform.
19:50Filiform have no buds inside of them.
19:53They have no taste buds. They're going
19:54to be involved with basically uh
19:58we're going to talk about them in
19:59digestion. Okay, we're going to see that
20:01they're going to be involved with
20:02helping to basically uh
20:05uh give us a little bit of texture kind
20:07of taste there. And um they'll be
20:09involved with uh kind of helping to
20:11manipulate food basically.
20:13Now, the other three we can see here,
20:15they're going to have taste buds. The
20:17foliate, they're going to be basically
20:20containing buds in children. We can see
20:22them the fungiform will have buds there
20:23and then the valley will have buds there
20:25as well. We're not going to go through
20:26every single one of them. What we'll do
20:28then is we'll look at you can see now
20:30the various types. First here we've got
20:32the fungiform. Fungiform now we're going
20:35to see are going to be found scattered
20:37over the entire tongue surface.
20:39The fungiform are going to be scattered
20:42over the entire tongue surface and they
20:45are mushroom shaped.
20:48They are mushroom shaped papillae.
20:57Next up we have our foliate papillae.
20:59Foliate papillae are going to be found
21:01on the lateral aspects of the tongue.
21:03Found on the side walls.
21:07Found on the side walls.
21:10And then we have our vallate or
21:11circumvallate papillae.
21:14So taste buds
21:16you can see
21:18fungiform and foliate and then we said
21:21here
21:24fungiform, foliate and then the third
21:27the vallate or circumvallate they're
21:28also known as as well. So circumvallate
21:32found forming an inverted V.
21:35Found forming an inverted V at the back
21:38of the tongue.
21:39There's about 7 to 12 of them. About 7
21:42to 12 vallate or circumvallate papillae
21:46found forming an inverted V
21:51at the back of the tongue.
21:58So let's look at one one of their
22:00structures. Here we can see the
22:02circumvallate.
22:03So here you can see right on the sides
22:06you've got these taste buds. So what
22:08we'll do is we'll look at one of those
22:09taste buds
22:13and we'll examine that in greater
22:14detail. So let's move from this picture
22:16over to this picture here as well. So
22:18here now when we look at the structure
22:19of a taste bud, you can see they're
22:22going to be made up of gustatory cells
22:24or your taste cells.
22:27Now these are types of epithelial cells.
22:31These are types of epithelial cells and
22:33you can see they're going to be found
22:34making up the majority of
22:37these taste
22:39receptors. These
22:41taste buds
22:42we can say there.
22:45All right, so talking about these
22:47gustatory cells, you can see these
22:49gustatory cells are going to be found
22:51distributed among some supporting cells.
22:53So some of these cells will be
22:54supporting cells and other cells will be
22:56gustatory taste cells.
22:58Now these gustatory cells or these taste
23:00cells, they're epithelial cells. They're
23:03type of epithelial cell and you can see
23:04they're going to make up the taste bud
23:05along with supporting cells. Now we
23:09talked these uh
23:10gustatory cells. These gustatory cells
23:12now we can find these uh
23:15gustatory cells basically you can see
23:17here and we've got these nerve fibers
23:19coming in. Then they'll be penetrating
23:21basically and innervating uh these
23:25gustatory cells. So whenever those
23:26gustatory cells get excited, those
23:28gustatory cells are going to stimulate
23:29basically those cranial nerve fibers and
23:31then sending signals to you know, then
23:34basically to the cortices to just sum
23:36that up real quick. Now again, I was
23:38going to say to the different nerves. So
23:40depending on which part of the tongue
23:42you're at, so it'll be that specific
23:43nerve and then eventually making its way
23:45to the brain. Now
23:47here when we go through we look at one
23:48of the
23:50one taste bud and we look at its
23:51structure. Now I want you guys to see
23:53here what we can see is we can see first
23:55a taste pore.
23:56Now here we've got a taste pore. The
23:59taste pore is going to be an opening.
24:01It's a neck-like opening. It's a
24:04neck-like opening
24:05to each of the taste buds and it's going
24:08to allow now those tastants that are
24:10going to be coming making their way in
24:12with saliva basically allowing them to
24:15make their way into the sensitive the
24:17receptor portion which we're going to
24:19see is going to be the gustatory hairs.
24:23So the taste pore is going to be
24:24important
24:26because it's going to allow the tastants
24:28to make their way
24:30and come into contact now with those
24:33gustatory hairs.
24:35The receptive portion.
24:38Next in here we also have our gustatory
24:39hairs. So when we talk gustatory hairs,
24:41these gustatory hairs are long
24:44microvilli.
24:46They're going to be long microvilli.
24:50And you see the same thing right inside
24:52of here as well. They are long
24:54microvilli.
24:56They're long microvilli that are going
24:57to be found projecting from the tips
25:00of all gustatory cells. They're found
25:04projecting from the tips. You can see of
25:06all of those gustatory cells.
25:11Again, they are the sensitive portion.
25:14They are the sensitive portion. They
25:16contain basically the receptor membrane.
25:19So that is
25:22what the tastants are going to come and
25:23bind to.
25:27Then again you can appreciate those
25:29taste cells.
25:31And you can see how then they are
25:32innervated.
25:35And then as soon as they get excited
25:37they will then send signals along these
25:40sensory nerve fibers.
25:43Then physio you guys will do a lab and
25:44you'll see the importance of saliva. Now
25:47without saliva there it takes
25:49you'll see tasting is close to
25:51impossible basically because the saliva
25:54is there to help guide take basically be
25:56the medium take this tastant to the
26:00sensitive portion.
26:03Now again you also have basal cells here
26:05as well. Again, dynamic stem cells.
26:10So dynamic stem cells they differentiate
26:13and divide into new gustatory cells.
26:17And then taste fibers cranial nerve
26:18fibers is what you see there and then
26:20depending on which uh part of the tongue
26:22you're on, right? Or which part of the
26:24oral cavity you're at then
26:26uh because if we talk tongue, you got
26:28the anterior 2/3, the posterior 1/3 or
26:30uh the anterior uh
26:32uh 2/3, posterior 1/3 and then you've
26:34got the most dorsal portion and the
26:36pharynx included there as well, the
26:38epiglottis. Again, that's going to
26:40contain uh some of these uh taste buds
26:43there as well.
26:44So we talk taste
26:46in the oral cavity.
26:51Let's move then from taste. Let's move
26:53over to
26:55we'll see hearing. Before we jump down
26:58here you can appreciate the pathway now.
27:00So here you can see this pathway for the
27:03sense of taste is going to make its way
27:06right through the thalamus and then
27:08eventually to the specific areas of the
27:11cerebral cortex.
27:15Now we've talked about those specific
27:17areas
27:18already when we talked uh the cortices.
27:23So let's move then to
27:25hearing. Here you can see all the
27:26different nerves I told you you'll be
27:28responsible for knowing about there as
27:29well.
27:33Let's talk hearing. Let's talk ear.
27:36Now we talk ear. Ear you can see here
27:38this is a picture depicting the external
27:40ear or one part of the external ear. Now
27:43when we go through we talk ear, we'll
27:45look at the ear in a greater
27:48uh idea basically we'll get a greater
27:49greater idea of the ear when we look at
27:51this picture here. So here you can see
27:53and appreciate the ear in its entirety.
27:55Now here we go through we talk about the
27:57ear. You can see the ear is going to be
27:58get divided up into three different
28:00parts. You've got an external ear,
28:01you've got a middle ear and then you've
28:02got the internal ear. Now let's go
28:04through and let's talk each of these
28:06divisions one by one first. So here
28:09first we'll start with external ear. Now
28:11we talk external ear, the external ear
28:12is going to consist of a couple of major
28:14parts. You've got first the auricle
28:17which you can see right outside of here
28:19and then here we've got the external
28:20acoustic meatus. So these two main parts
28:23are going to make up what we call our
28:25external ear. So again, it consists of
28:27the auricle and the external acoustic
28:30meatus.
28:31First let's talk auricle. When we talk
28:33auricle, the auricle is what we call the
28:37ear in layman's terms, right? We say
28:38ear, we refer to this as the ear.
28:41Uh now you can see that that's just one
28:43part of the ear. This auricle is a shell
28:47shaped projection.
28:51It's a shell shaped projection.
28:53It's also known as the pinna. You can
28:56see here the pinna.
29:00This shell shaped projection is found
29:05surrounding the opening. It's found you
29:09can see surrounding
29:12the opening
29:14which is the external acoustic meatus.
29:18So what this auricle or this pinna does
29:21is a shell shaped projection. It's going
29:23to help kind of funnel sound into that
29:26opening into the external acoustic
29:28meatus.
29:30What type of uh
29:32cartilage are we talking about here?
29:35Very good. Elastic. Remember it's easy.
29:38It's elastic. Makes up the ear.
29:41And
29:43good job. The epiglottis. Very good.
29:46So here now when we go through we talk
29:48uh
29:49Oracle. You can appreciate that Oracle
29:51there. Now, in relation to the Oracle
29:52itself, we've got a few parts, but not
29:55just to the Oracle, but you can see to
29:57the external ear there as well. Let's go
29:59through these different parts here. Here
30:01you can first appreciate the helix, the
30:04helix. Now, the helix is the is the is
30:07is thick. It's the thickened rim you
30:10could think of. It's the thickened rim
30:16All right, of that Oracle. It's a
30:17thickened rim of the Oracle.
30:21This helix
30:22is going to
30:24project inferiorly
30:27to give rise to the lobule to the
30:29earlobe, to the lobule.
30:35Lobule is the fleshy
30:38dangling
30:40structure, fleshy dangling structure,
30:44and you can see here
30:46adipose.
30:49And then connective basically connective
30:51tissue
30:52support for the epithelial tissue right
30:55on top.
30:59Next here you have your tragus.
31:03Tragus
31:04you can see
31:06is going to help protect
31:08that external acoustic meatus, that
31:10opening. It's going to help protect that
31:11opening.
31:14Tragus is often pierced.
31:20And then here across from the tragus, we
31:22can appreciate the anti-tragus.
31:26Both again helping to block off that
31:28entrance into the ear.
31:33And then we've got the antihelix.
31:36So, first we talked helix. We can see
31:39across from the helix we've got our
31:40antihelix.
31:44So, anti usually you can see is across
31:46from the structure it's named for.
31:50And then here we've got the triangular
31:52fossa. You can see right above the
31:54antihelix.
31:57Triangular fossa.
32:02And then we've got the concha
32:04on the other side.
32:08So, it's when you
32:10stick your finger into your ear without
32:12sticking it into the external acoustic
32:13meatus. So, all of this is all the
32:16concha.
32:17The concha.
32:20You can see that. I don't know why I'm
32:21showing it to you on me. You can see it
32:22clearly in the picture.
32:24Concha.
32:26And then you got that opening, the
32:27external acoustic meatus.
32:30This external acoustic meatus is also
32:32known as the auditory canal.
32:35AKA
32:37auditory canal.
32:40It's a very short
32:42curved
32:44It's a very short curved tube.
32:49And it's going to extend from the Oracle
32:52to the eardrum.
32:56Believe it or not, there's a wrong way
32:58and a right way to put your stethoscope
33:00into your ear. If you don't know what
33:02you're doing and uh you don't uh check
33:05your uh technique, you can end up
33:08placing your stethoscope into the
33:09concha. If you place it in the concha,
33:12now there's no receptors here for
33:14hearing.
33:15So, you have to make sure you push the
33:17ear buds away from you so that way they
33:20follow the contour of that external
33:23acoustic meatus.
33:26Your teachers can tell just from the way
33:29you put your stethoscope into your ear
33:31whether you know what you're doing with
33:32the stethoscope.
33:34So, here you can see those sound waves
33:36are going to get funneled thanks to that
33:37external acoustic meatus into the
33:40tympanic membrane.
33:41So, they're going to pass through that
33:42external acoustic meatus and they're
33:45going to come in and they're going to
33:45stimulate that tympanic membrane.
33:49So, if you stick that uh stethoscope
33:51into the concha
33:53uh it's difficult to hear what you're
33:55trying to listen to.
33:56Especially those sounds, the sounds of
33:58the heart or the sounds of the abdomen
34:00or the sounds of the lungs already uh
34:02sometimes pretty faint in some
34:03individuals.
34:07So, external acoustic meatus you can
34:09appreciate there. Now, this external
34:10acoustic meatus
34:12is going to lead us to the eardrum as we
34:14described, to the tympanic membrane.
34:16Now, within this external acoustic
34:18meatus you're going to be able to
34:19appreciate ceruminous glands, right?
34:21We've talked about these glands before.
34:23Now, ceruminous glands are going to be
34:24modified apocrine glands. They are
34:27modified apocrine glands.
34:32Modified apocrine sweat glands, you can
34:35say more specifically.
34:38Modified apocrine.
34:44Now, these glands, they're going to
34:46secrete a yellow-brown
34:49waxy material called cerumen.
34:55So, they secrete a yellow-brown waxy
34:57material called cerumen or earwax.
35:00And earwax is important. Earwax is
35:03important because earwax is going to
35:04provide as a sticky trap.
35:09It will act as a sticky trap
35:12and help keep foreign bodies and also
35:14help repel insects.
35:17Doesn't always happen. I've removed uh
35:20cockroaches, toys even from
35:25people's external acoustic meatus, from
35:27children to adults.
35:30And uh wax I can't begin to tell you how
35:33many times.
35:38Now, we've got the tympanic membrane
35:40there next. The tympanic membrane is
35:41also known as the eardrum. The tympanic
35:44membrane you can see is going to serve
35:45as the boundary. It's going to serve as
35:46the boundary between that external ear
35:49and the middle ear. So, it's the border
35:51between the external and the middle ear.
35:58Let's move then to the middle ear. Here
36:00you can appreciate the middle ear, but
36:02what we'll do is we'll zoom in on the
36:04middle ear. And we zoom in on the middle
36:06ear, we're going to be able to
36:07appreciate its structures in greater
36:10detail. So, here you can appreciate its
36:11structures then in greater detail. Now,
36:13here first we've got the middle ear. The
36:16middle ear I'd like you to know is also
36:17going to be known as the tympanic
36:19cavity. AKA tympanic cavity. It's a
36:22small air-filled It's a very small
36:26air-filled
36:29mucosa-lined
36:32cavity.
36:35It's found in the petrous portion of the
36:37temporal bone.
36:39In that petrous portion of the temporal
36:41bone.
36:45Tympanic membrane we've already
36:46discussed there. You can appreciate now
36:48a round window and an oval window. The
36:51round window and the oval window are
36:53going to be openings.
36:55They're openings on the bony wall
36:58that lead us to the internal ear.
37:01Openings on that bony wall of the middle
37:04ear
37:05that will lead us to the internal ear.
37:09Now, the oval window you can appreciate
37:11underneath the stapes. So, here you've
37:13got the stapes, one of the bones, the
37:16ossicles we'll discuss in the middle ear
37:17here in a few minutes.
37:19Round window
37:21or oval window and round window you can
37:23see here inferior to the stapes.
37:28So, right underneath it
37:30you've got that oval window. So, deep to
37:33the stapes the oval window. And then
37:34here you can appreciate just inferior to
37:36it you've got the round window. So, this
37:38oval window is covered by the stapes.
37:39Now, the round window is covered by
37:42membrane. It's going to be covered by
37:44membrane. This membrane is going to be
37:46basically a membrane that's going to act
37:48like a valve. What's going to happen is
37:50when the stapes hits up against that
37:52oval window, that's going to help to
37:53create a a wave of basically a movement
37:57of fluid inside that ear. And that
37:59movement of fluid is going to happen
38:02efficiently if that round window is
38:05flexible and if it acts like a valve and
38:07allows basically that motion within the
38:11fluid to
38:12occur, we're going to be able to then
38:14hear the sound. So, we'll check all that
38:16out as we progress. So, I want you to
38:18know there going to be two openings.
38:20However, they're covered you can see.
38:25Next that we have our pharyngotympanic
38:27tube. The pharyngotympanic tube or the
38:30auditory tube, formerly known as the
38:33Eustachian tube.
38:35If you're old school, we used to refer
38:37to it as the Eustachian tube.
38:41It runs obliquely. It's found running
38:43obliquely. It runs obliquely downward.
38:46And it's going to link the middle ear.
38:49It will link that middle ear cavity you
38:51can see here.
38:53It will link that middle ear cavity to
38:56the pharynx.
38:57To more specifically speaking, you'll
38:58see the nasopharynx.
39:01To the nasopharynx. Now, when we get to
39:03when we get to digest No, we get to
39:05respiratory. We get to respiratory,
39:07we're going to look at the other end.
39:10We're going to see where it opens up at
39:11inside that nasopharynx.
39:16So, you can see here when we go up and
39:17down the hill, we want to equalize the
39:19pressure, right? We'll usually plug our
39:20nose and that's what that uh helps us to
39:23do basically there.
39:26Let's talk then. Next we've got our
39:28auditory ossicles. When we talk auditory
39:30ossicles, they are three of the smallest
39:33bones in the body.
39:34They're found in this tympanic cavity.
39:38And they're going to be named according
39:40to their shape. They will be named
39:43according to their shape.
39:46And uh question we can formulate here is
39:49uh which skeletal division do they
39:51belong to?
39:54Very good.
39:56I know you got that right, axial.
40:01So here we can see first we've got the
40:03malleus. Malleus is hammer-shaped.
40:08Malleus is going to be found you can see
40:11one end of it articulating with the
40:13tympanic membrane and the other end and
40:15you can see articulating with the next
40:17bone in line which is going to be the
40:20incus. Now the incus is anvil-shaped.
40:25It's anvil-shaped.
40:28We talk anvil-shaped, you can appreciate
40:30that they're very well. It's uh
40:32basically the structure that blacksmiths
40:35bend metal on and uh do work on.
40:38Or a wrestler from WWF if you remember.
40:43Next then we have our stapes. The stapes
40:46stapes stirrup-shaped
40:50stirrup-shaped.
40:52And you can see here it's going to be
40:53articulating with the incus on one end
40:56and then it's covering that oval window
40:58on the other end.
41:01So three of the smallest bones
41:05you'll find in the body.
41:08Next then let's move to the internal
41:11ear. Let's move to the internal ear. Now
41:14when we talk internal ear
41:19All right, so here we can see that
41:21internal ear. Now we talked this
41:23internal ear
41:26we can see
41:28it's also going to be known now as the
41:30labyrinth. Internal ear will also be
41:33known as the labyrinth. If you look up
41:35the definition labyrinth it's tortuous
41:36maze right and so forth. So here when we
41:40talk now this labyrinth this internal
41:41ear this internal ear is going to be
41:43found lying deep. It's found lying deep
41:45in the temporal bone behind the eye
41:47socket. Found deep in that temporal bone
41:52behind the eye socket. Now
41:55this internal ear is going to get
41:56divided up into two different parts into
41:57two different parts. Now to be able to
41:59appreciate these two different parts
42:00what we'll do is we'll move over to this
42:02picture here.
42:03Now in this picture here you can
42:05appreciate the bony labyrinth and then
42:07you can see within the bony labyrinth is
42:09the membranous labyrinth. So first off
42:12let's talk bony labyrinth. Now when we
42:14talk bony labyrinth the bony labyrinth
42:16is going to be this tortuous maze type
42:19pathway.
42:21It's a system you can think of of
42:23tortuous channels
42:25that's worming
42:28through the bone.
42:32So it's a
42:33you can think of carved out part inside
42:35the bone.
42:37It's going to be filled with a fluid.
42:39The fluid it's going to be filled with
42:40is called perilymph.
42:43Now this perilymph
42:45is a fluid that's going to fill this
42:48bony labyrinth. It fills this bony
42:50labyrinth and this perilymph is a fluid
42:53that's similar to and continuous with
42:57CSF.
43:03Next we have the vestibule. So here
43:05we'll move back. Now we move back here
43:08you can actually appreciate the
43:09vestibule
43:10and coming back here you can see the
43:13vestibule then in greater detail.
43:16So moving back when we talk vestibule
43:18the vestibule is a central egg-shaped
43:21cavity of the bony labyrinth.
43:26Within the sac within this uh vestibule
43:30we're able to appreciate the saccule
43:34and the utricle. So here's the utricle
43:37and here's the saccule within
43:42the vestibule. All within the vestibule.
43:44Now
43:46why is the saccule and the utricle
43:47important? Because we'll see within them
43:49are going to be the maculae
43:51our maculae and we'll talk about our
43:54maculae in a few minutes. So saccule
43:57first. Saccule is the membranous
44:01labyrinth sack.
44:04It's a membranous labyrinth sack.
44:10As is the utricle so utricle also a
44:15membranous labyrinth sack
44:19and they're both suspended
44:21in the perilymph.
44:24Right? They have perilymph around them.
44:26They're suspended within perilymph. And
44:28the reason why the saccule and the
44:30utricle are important because they
44:31contain the maculae. The maculae are
44:33going to be equilibrium receptors.
44:36They are our equilibrium receptors.
44:42Let's move then to the semicircular
44:44canals. So here you can appreciate the
44:46semicircular canals. And now within
44:48those canals you can see are the
44:49semicircular ducts.
44:52Within the canals are the semicircular
44:53ducts.
44:54Now when we talk semicircular canals
44:57semicircular canals are going to be
44:59found lying posterior and lateral to the
45:02vestibule.
45:04Lying posterior and lateral to the
45:07vestibule.
45:10And they're important because they
45:12contain the semicircular ducts.
45:17These ducts now
45:19you can see have these ampullae to them.
45:22The ampulla.
45:24The ampulla is going to be the enlarged
45:27swelling.
45:30It is the enlarged swelling at the end
45:34of the semicircular ducts.
45:37So you can see one here for this
45:40anterior duct
45:42you can see the same thing here for this
45:44lateral
45:45duct and we're going to have the same
45:46thing right back here for this posterior
45:48semicircular duct.
45:52The ampullae
45:53are important because the ampullae are
45:54going to be receptors as well. Also
45:57equilibrium receptors.
46:01So let's discuss the membranous
46:03labyrinth now. So we already took care
46:05of the bony labyrinth. Now when we talk
46:08membranous labyrinth the membranous
46:09labyrinth is a continuous
46:13series.
46:15It's a continuous
46:17series
46:19of membranous sacks and ducts.
46:27Continued within
46:30the bony labyrinth.
46:32So a continuous series of membranous
46:35sacks and ducts
46:37continued within the bony labyrinth
46:41and following its contours.
46:49Now when we talk about this um
46:51membranous labyrinth you'll see this
46:53membranous membranous labyrinth is going
46:55to be filled with a fluid as well. This
46:56fluid here is going to be called
46:58endolymph.
47:05Endolymph.
47:07Now endolymph is going to be chemically
47:09similar to
47:11potassium-rich
47:13intracellular fluid.
47:17Similar to
47:19potassium-rich intracellular fluid. And
47:21now this endolymph this endolymph is
47:23going to be found in the interior of the
47:25membranous labyrinth.
47:28It's found in the interior of the
47:31membranous labyrinth.
47:33So here what we're going to do is we're
47:34going to look at
47:38this
47:40cochlea we'll go into first.
47:44And we'll look at the cochlea first and
47:46then we'll jump into equilibrium. So
47:47let's look at the cochlea here first.
47:49Let's grab this part first and here
47:54we can appreciate that cochlea.
47:57So here you can see what they're doing
48:00in this picture in this image is they're
48:01going to do a nice L cut basically to
48:04this cochlea. Now here with this cut
48:07what this going to allow us to do is
48:08it's going to allow us to appreciate
48:10basically the coils all the way through.
48:12So here what you really have is you have
48:15one
48:16cochlea
48:18you can see here
48:20that's continuous
48:22all the way through
48:26all the way
48:30to the end.
48:33So here now you can see each of these
48:37regions of that cochlea
48:40themselves are divided up you can see
48:42into three different parts.
48:44So inside here you have three parts. You
48:46can have one part on the top you can see
48:48up here
48:49one part in the middle which we see
48:51right here and then the third part on
48:52the bottom which you would got right
48:54there.
48:55So let's unwind this cochlea. Let's grab
48:59it let's unwind it and then we'll do one
49:00cut right through. We're going to do one
49:02cut right through this is what you're
49:03going to have.
49:06Coming back so let's unwind this snail
49:10looking structure. You completely unwind
49:12it pull it all the way open.
49:14Okay? So if you were to pull it all the
49:16way open this is what we're going to
49:17have.
49:18You're going to have something that's
49:19going to look now like this.
49:26Does that make sense?
49:27Right? That's what you have here. Unwind
49:30it this is what we're going to have. And
49:31now within it within it
49:34Okay? So let's continue here.
49:37Pen color, let me switch to blue.
49:41Just to depict the membranous labyrinth.
49:48You'll have something looking like this.
49:53Okay?
49:56So, this is going to be segment one.
49:59Here is
50:01region two.
50:03And then down here we have three, right?
50:06So, unwinding this
50:08in here would be like one, number two,
50:10and then number three. So, let's do
50:12this. Let's move over here.
50:14Here you've got one. Here you got two.
50:16Here you have three. So, number one is
50:18known as the scala vestibuli.
50:20Scala vestibuli, in the middle you got
50:22scala media.
50:25And then here on the bottom, scala
50:26tympani.
50:29Scala tympani.
50:31Now, scala media is important because we
50:32can see here is where we're going to
50:34find the receptor organ for hearing.
50:36This is the spiral organ.
50:38The receptor organ for hearing.
50:40So, moving back
50:42this is our image.
50:44That spiral organ receptor hearing is
50:46all
50:48right in here.
50:51You basically like you can think of
50:53right in here.
50:58All right in here.
51:03Okay?
51:05So,
51:07you can see there, scala vestibuli,
51:09scala tympani, in the middle, scala
51:11media. And then right here we've got the
51:13spiral organ,
51:14organ of Corti,
51:16the sensitive uh
51:18receptor region.
51:20So, here on the outside we're going to
51:22have fluid, right? The bony labyrinth is
51:24what we described here. That's going to
51:25have perilymph,
51:27and then we said endolymph,
51:29and then perilymph. So, you see that
51:30same thing being described here.
51:32Perilymph,
51:33perilymph.
51:35In the middle you got endolymph.
51:38Now, look at here.
51:41These parts are continuous with each
51:42other.
51:44This is the apex.
51:50Right here.
51:51Apex.
51:53At the apex is found at the helicotrema.
51:57Right? This area here is the
51:59helicotrema, and this is where you find
52:01the apex.
52:07So, now here
52:08let's continue to add in here. Here we
52:10have the round window,
52:15covered by membrane. Now, you understand
52:16why I said this is a valve.
52:18Does that make sense now?
52:20The fluid inside is what's going to be
52:22jiggling.
52:23And what do we say is going to be up
52:25here?
52:26So, here we're going to have I'm going
52:27to draw a little bit weird, but here's
52:29the stapes.
52:33Right? And then here we have the
52:36anvil,
52:38incus.
52:40Here we have the malleus,
52:45tympanic membrane,
52:48and then the rest of the ear.
52:53Right? And then the lobe and
52:56all of that is right out here.
52:59So, when we talk sound, sound is
53:01vibrations of the air. These vibrations
53:04of the air are going to make their way
53:05into we said
53:08that ear.
53:11Eventually helping to get that tympanic
53:12membrane moving. When the tympanic
53:14membrane vibrates, the tympanic membrane
53:16is going to get the malleus to move.
53:18Malleus will hit up against the incus,
53:20which will hit up against the stapes,
53:21which is going to hit up against that
53:22oval window,
53:23which will then get the fluid inside of
53:25here to eventually start moving.
53:27You see it's like a domino effect is
53:29what we're trying to get.
53:31So, now here if we're going to see if
53:33sounds are of low intensity, those
53:36sounds are going to make their way
53:37through. They're going to come all the
53:38way through to the apex, and then all
53:40the way around.
53:42They don't ever stimulate
53:44the spiral organ, that's why you don't
53:45hear them.
53:47But now if we talk sounds of higher
53:49intensity, those sounds they're not
53:51going to be making their way all the way
53:52to the back. They're just going to come
53:54right through in here, and when they
53:55come in here they're just going to get
53:57all of this in here to start vibrating.
54:00Now, why do we need all this here to
54:01vibrate? Because we're going to see that
54:03in a few seconds. Let's move over then
54:05to this picture here. So, here you can
54:07appreciate the spiral organ. Look at the
54:09spiral organ, you got the nerve. You've
54:10got these important cells in here, and
54:12then some supporting cells there. And
54:14look at here, you've got a membrane on
54:17top and a membrane on bottom. You've got
54:18a tectorial membrane right here on top,
54:20and we've got a basilar membrane right
54:22down here. So, you can see here that
54:24spiral organ is sandwiched in between
54:26those two membranes.
54:28So, let's zoom in on that then.
54:31This is what you see.
54:33You got your tectorial membrane,
54:35and then down here you got the basilar
54:36membrane.
54:38So, here you can see sandwiched in
54:40between them is two rows of cells.
54:42You've got
54:43one
54:45row of inner hair cells and three rows
54:47of outer hair cells.
54:49So, here what happens now is when sound
54:53comes in, now you can see here to each
54:55of these hair cells you've got hair
54:56bundles. Those hair bundles are embedded
54:58within the tectorial membrane.
55:01So, here what happens is now when sound
55:04comes in
55:05So, when sound comes in, sound is going
55:07to come in we said it's going to go
55:08right through here. It's going to get
55:09that basilar membrane vibrating. Now,
55:12when that basilar membrane starts to
55:13move, here you'll see it's going to get
55:16these cells' hairs to bend. And when
55:19those hairs bend, this will start to
55:23generate signals in the nerves, and
55:25letting then the ear know this is what's
55:27going on.
55:30So, that's how
55:33hearing is done.
55:36Next then let's talk equilibrium. So, we
55:39make sure I've got everything with that
55:40cochlea.
55:41Coachella. One way you guys like to
55:43remember that. Hear sound, Coachella,
55:46cochlea.
55:48So, yeah. We've got everything there.
55:51Let's talk then equilibrium.
55:55So, we talk equilibria then
55:57let's talk
56:00So, this is basically everything we just
56:02went through. You can kind of go through
56:03that.
56:05Okay. Talking about the bending of the
56:07stereocilia, how it's going to open up
56:10ion channels, helping to trigger
56:13electrical signals.
56:23And then again the pathway you can
56:24appreciate there as well.
56:27Let's talk then equilibrium. So,
56:30equilibrium then we'll see is going to
56:31be a sense
56:33that not only depends on input from the
56:35internal ear. So, it's a sense that's
56:37not only going to depend on input from
56:38the internal ear, but also it's going to
56:40depend on information from vision,
56:44and it's going to depend on information
56:45coming from stretch receptors
56:50in relation to our muscles and our
56:51tendons.
56:54And also from our stretch receptors in
56:56relation to our muscles and tendons.
56:59Now, here we have first
57:02our maculae. Our maculae are described
57:05as sensory receptors for static
57:08equilibrium.
57:09Sensory receptors for static
57:11equilibrium. When you talk about their
57:13function, their function is that they
57:15monitor the position of the head in
57:17space.
57:19They will monitor the position of the
57:20head in space.
57:22They also play a key role in posture.
57:29Where are they found? They're going to
57:30be found as we described, one
57:33in each saccule
57:36and utricle wall.
57:41One in each saccule and utricle wall.
57:48Utricle.
57:54Now here when you look at the position,
57:55you can see how each of them are going
57:57to be found. One is
57:59vertically placed, one is a little bit
58:01more horizontally placed.
58:03So, here now what happens is like we
58:04described, they're going to monitor the
58:07position of the head in space.
58:09But not only the monitor not only
58:10monitoring position of the head in
58:11space,
58:13also linear acceleration
58:15we'll see there as well.
58:18Linear acceleration, let's say you're
58:19standing here and all of a sudden you
58:20start to move forward fast.
58:22Right? This is linear acceleration. Even
58:24elevators, right? Moving up and down in
58:26elevator. Okay, vertical acceleration
58:29you've got happening there, but that's
58:30not that common. More is this
58:32uh
58:33you can see this linear acceleration.
58:37Next then here when we go through and we
58:38talk uh
58:39maculae, now what happens here when we
58:41look at their structure, you can see
58:42here in greater detail the maculae are
58:45made up of also supporting cells and
58:47hair cells. Now, these hair cells have
58:49these hair bundles. Those hair bundles
58:52have you'll see now a whole bunch of
58:55stereocilia
58:57and
58:58a kinocilium.
59:01Stereocilia and a kinocilium. So, that
59:04makes up a hair bundle. Those hair
59:05bundles themselves now are embedded
59:08within this otolithic membrane, this
59:11rocky membrane you see there. Otolithic,
59:15rocky membrane. So, you can see that
59:16membrane is going to cover all of those
59:19hair bundles. So, here now what happens
59:22is as soon as you have the position of
59:24the head start to change, what this does
59:27it's going to get those stereocilia
59:30and the kinocilium to start to bend. It
59:32gets those hair bundles to bend. So,
59:34when those hair bundles start to bend,
59:36now depending on whether they're bending
59:38towards or away from the kinocilium,
59:41this will trigger then
59:43action potentials or signals along these
59:45nerves, letting then the brain know
59:47what's going on.
59:52So, you can see exactly that happening.
59:53Here, this individual goes from the
59:55seated position to where they put their
59:57head down a bit, and this gets this
59:59otolithic membrane membrane to start
1:00:01moving.
1:00:04Next then, we have our cristae
1:00:06ampullaris.
1:00:08Now, the cristae ampullaris are going to
1:00:10be receptors for dynamic equilibrium.
1:00:13Receptors for dynamic equilibrium.
1:00:16Their function is that they get
1:00:18stimulated by head movements. Now, they
1:00:21get stimulated by head movements, but in
1:00:23this case, you'll see the majority the
1:00:26major stimulus are going to be rotary or
1:00:29angular head movements. Rotary or
1:00:32angular head movements.
1:00:36Where are these receptors found? These
1:00:38receptors are going to be found
1:00:40in the ampulla of each semicircular
1:00:42canal as we described.
1:00:44In the ampulla of each semicircular
1:00:45canal.
1:00:47Now, here what we have is we'll move
1:00:49over to this picture. Here what we have
1:00:50is you can appreciate now
1:00:53hair cells again, hair bundles. Okay?
1:00:56Again, supporting cells there as well.
1:00:58Now, here you have a cupula on top. Here
1:01:00you have a cupula
1:01:03enclosing all those hair bundles. So,
1:01:05now here what happens is you can see
1:01:08when we have these rotary movements.
1:01:11Okay? These rotary movements are going
1:01:13to cause this endolymph
1:01:17to start to turn in the opposite
1:01:19direction.
1:01:20So, here what happens is you can see
1:01:22now, if we're going to be moving in one
1:01:24direction, this fluid is going to be
1:01:26moving in the opposite direction. And
1:01:28what that does, it gets basically this
1:01:29cupula to start to bend, and that's
1:01:31going to get those, again, same concept,
1:01:34hair cells,
1:01:36their bundles, the hair bundles, to
1:01:37bend, and that's going to start then
1:01:39sending signals to the brain, letting
1:01:41the brain know, "Hey, we've got these
1:01:43rotary movements occurring."
1:01:47So, that there then is equilibrium as
1:01:49well.

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