Understanding the External and Middle Ear Anatomy

Hi Ninge Nerds, in this video we're going to talk about the external ear and the middle ear. The reason why we want to talk about this is before we start going into all the inner ear stuff, talking about the cochlea and the vestibule and the semicircular canals and how airwaves or I'm sorry sound waves can actually get converted into certain electrical potentials and then be perceived in certain ways. I want to make sure that we really have a good understanding of the external ear and the middle ear because they're going to play a crucial role into understanding how these auditory pathways and these vestibular pathways occur. Alright, so let's go ahead and dive into the anatomy of the external and middle ear. So first things first, how are we going to look at a lot of these structures? So if you real quickly, I'm going to draw here a quick little crude diagram here. Imagine here's the skull, okay? Imagine here I put like the cellotursica of the sphenoid bone, and I can separate this into an anterior cranial fossa, I'll separate it into a middle cranial fossa, and then I'll have a posterior cranial fossa with the foramen magnum there, right? And then if you want, you have your crista galli right here with the cribriform plate of the ethmoid bone, all that stuff right there, right? Then, if you come over here, you'll have the external acoustic meatus with the ear, right? And over here, you'll have a external acoustic meatus with the ear. What I'm going to take a look at is we're going to look at some of the structures here off the external ear, and we're going to take a look at this external acoustic meatus, and then what we're going to do is there's going to be this separating structure here that we're going to take a look at a lot. Pretty much most of the video is going to be about this. And it's going to be on this middle ear. And we're going to take a look at it in a box diagram because it's the easiest way to see the middle ear. So what we're going to start off with is we're going to start first off talking about what? The external ear. Not too much to talk about, but we'll discuss some things. But then we're going to spend most of our time looking at the middle ear. And again, we're going to look at it in what's called a box diagram form because it's going to make it the easiest to see. Okay? And easiest for me to draw here. Alright, so let's go ahead and start that. So first off, let's come over here. I know we have a lot of diagrams here pre-john but don't worry we'll go over everything. If you guys just click on the video don't worry you didn't miss anything. Okay so starting off here we're going to talk about the external ear. Okay so external ear biggest thing here you see how you see this big old flap here coming out this sucker right here that I'm flicking on right now I'm holding and moving around. You notice how I'm able to move it around a lot right it's able to be stretched and go back to its normal shape right I'm able to move it around bend it. What's the reason for that? Well first off, what do we call this part here? Not only do we call it two things, you can call it the auricle or you can call it the pinna. Now what's really interesting about the auricle or the pinna is obviously the outer part of it is the skin is supplied with what's called, it's actually covered with stratified squamous epithelial tissue to resist against friction and abrasion. But underneath that, it's primarily made up of a special cartilage called elastic cartilage. And the reason why I'm mentioning this is because there isn't too many places in the body that are actually consisting of elastic cartilage. One is going to be the ear, the external part of the ear, the auricle or the pinna. And the other one is the epiglottis. And again, the purpose of it is for it to be able to be very, very able to stretch but recoil back to its normal position. Okay, so that's one of the really, really cool things about that. Alright, sweet. Nothing much other than that about the external ear, this outer part here. Now, the next thing is, as we go in, to the actual external. So we come from the auricle or the pina and we move into this hole right outside of it. Right so there's going to be a hole right outside of the skull, right outside of the skull and this is going to be called the external acoustic meatus. So this is called the external acoustic meatus. This little canal right here that I'm kind of putting the outlines here in green. The external acoustic meatus is a little bony canal. And inside of this canal you're going to have some, first off the inner part of it is covered with like some stratified squamous epithelial tissue, right? But another thing that's really important about this is that we have these things called ceruminous glands, okay? We have these things here called ceruminous glands. And ceruminous glands are basically like modified apocrine glands, basically. They're like modified apocrine glands. And they can produce a substance called cerumen. all of you probably commonly know as earwax. Okay, so these guys are producing earwax, cerumen, which is kind of coating the inner part of the ear. Now, what is important about this? The importance of this cerumen is to be able to deter insects, believe it or not. So again, what are these glands here called? They're called ceruminous glands, okay? And these ceruminous glands are producing cerumen, or we know it as earwax. And the purpose of this earwax is to deter Certain insects. Now some of you might know that you stick a q-tip in there and you pull out some of that earwax, right? But you have to be careful. Why? Because you've probably been told by your mother or some other person, don't ever stick that q-tip really far down because at the end of the external acoustic meatus, there's a really, really important structure. It's called the tympanic membrane. The tympanic membrane is a very, very important membrane. It's a connective tissue membrane. We'll talk about a little bit more here in just a second. We have the diagram up there to show it. But this pink structure that I'm here separating the external ear from the middle ear. This is the tympanic membrane. So that's kind of a nice separating structure. So what is this pink thing they're called? It's called the tympanic membrane. And like I said it's actually made up of two components. One component is called the pars tensa. Which is a very, very, very heavily dense, fibrous, irregular connective tissue. We'll talk about that one. Okay, so this is the dense connective tissue. And particularly, it's irregular because it's in different bundles or arrangements. Okay? The other one is called the pars flaccida. Don't be thinking about flaccid other things, okay? Just think about pars flaccida. What it means is it's loose. Okay, it's loose. And in this case, it's actually made up of a loose connective tissue, particularly areolar connective tissue. The reason why I'm telling you this, that it's actually made up of two different types, is that if you go and stick the ear Q-tip into the ear and you actually hit the pars flaccida too hard, you can puncture the tympanic membrane. And that would affect the actual middle ear pressure, as well as a lot of other structures open up for certain types of microbes to come in. Okay? Alright, so cool. So what do we have so far for the external ear? We have the auricle or the penile, which is made up of elastic cartilage. Okay? Allows for it to be able to kind of be stretchable and to be able to be stretched, but it always wants to recoil and go back to its normal position. Right? External ear is also going to consist of ceruminous glands, which are producing cerumen, earwax, that are basically lining and coating the external acoustic meatus to provide it with a substance that can deter the insects. And remember, the ceruminous glands are modified African glands. Then... This bony canal, the external acoustic meatus, it gets to this end point here which separates the external ear from the middle ear. And that pink membrane is called the tympanic membrane. And the tympanic membrane is a connective tissue membrane. Two parts of it, one's called the pars tensa, which is made up of a dense irregular connective tissue. That's the inferior part of it. Usually, if I were to kind of make a little cut off here, usually the actual part right here that I separate anything below from this point here to this point is the pars tensa. Usually up here in the top from this point to this point is the pars flaccida and it's a looser type of tissue and what kind? Areola connective tissue. So now let's imagine that I'm gonna look down the ear. Okay I'm gonna take them I'm gonna take it I'm gonna look down this extra acoustic meatus so I'm gonna I'm gonna take and shine a light down this area. So let's pretend that I try to draw a light don't you dare laugh at me. I'm gonna take here I'm gonna have a light here and I'm going to shine some light. into this person's eye. I'm sorry, not into their eye, their ear. Okay? And I'm going to look down the external acoustic meatus at the tympanic membrane. When I look at that, this is what I see. It might not be beautifully as you would normally see it, but this is what you're going to kind of see here with the tympanic membrane. Now, what we see here is we see a couple different things. You can actually kind of see an outline here. You see this kind of structure here in blue? I'm going to outline it here. It's actually an ossicle. It's one of the little bones. And you can kind of see a little outlining of it there. What is this bone here called? That bone is called malleus. It's actually called malleus. It's one of the ossicles, okay? It's one of the three ossicles within the actual middle ear cavity. So you can kind of see like a little bit of an outlining of the malleus. Then you can kind of see these little folds. These little folds here coming inwards like this. And then another fold coming inwards like this. Okay, so this is actually called, since this fold is close to the malleus, it's an anterior mallear fold, and this is the posterior mallear fold. We're not going to actually write these down. They're not significantly important. But again, just kind of giving you an idea here. This is the anterior mallear fold, which is kind of on this side. So this would be the anterior side here. This would be the posterior side of the tympanic cavity. Okay, and again, this is the anterior mallear fold, posterior mallear fold, and kind of an outlining of the malleus. Then, at the bottom part, this is important. Here, connecting to the bottom part of the malleus. is a muscle and this muscle is called the tensor tympani. The tensor tympani, right? The tensor tympani, we talked about this muscle. If you guys watched the video on the trigeminal nerve, remember the trigeminal nerve actually gives off a branch that supplies the tensor tympani which tenses up to... tympanic membrane. We didn't really talk about the mechanism. We will in this video, but we'll say that what happens is this tensor tympani is innervated by the trigeminal nerve, specifically the mandibular division, okay, of the trigeminal nerve, V3. Okay, and that's connecting to that part. Then, remember we said we had the pars flaccida and the pars tensa? This right here, that's all in this really, really dark shade of green. It's pretty much very, very dark. It looks heavily connective tissue-wise, right? This right here is going to be the pars tensa. Okay, that's the pars tensa, which is this really, really dark connective tissue. And this is the only reason we mentioned the mallear folds. The anterior mallear folds and the posterior mallear folds are kind of separating the pars tensa and the pars flaccida. So all this loose connective tissue that I'm kind of just drawing like scattered, this is the pars flaccida. Okay. All right. So what have we covered so far then? We've covered External ear with the auricle and the pina. We covered the external acoustic meatus, the ceruminous glands. We covered the tympanic membrane which is consisting of the pars flaccida and the pars tensa. Pars tensa is dense connective tissue irregular. Pars flaccida is areolar. We also said that you can kind of see it whenever you're looking down the ear canal. You can actually see that it's nice a separation here by the posterior and anterior mallear folds which are separating the pars tensa from the pars flaccida. And then we also said that you kind of see like an outline here of the malleus. And you'll see a muscle here connecting called the tensor tympana, which is innervated by what cranial nerve? The fifth cranial nerve, particularly the mandibular division. So V3 of cranial nerve, five. Okay? Sweet stinking deal. So we covered the external ear. Now, let's go ahead and take a look even deeper now. Okay, so now we're going to take a look even deeper and we're going to start getting into this cavity here. We're going to start looking into the actual tympanic cavity. or the middle ear. Alright guys, so I just want to take a little pause here because I wanted to write down what we're going to talk about because we're going to talk about a lot of stuff. So I want to make sure that we cover every single piece of it. So I just kind of wrote down a list of what I want to talk about. Alright, so first thing we're going to talk about is ossicles. Okay, so ossicles. There's three little ossicles located within the actual middle ear or the tympanic cavity. Okay, what are those ossicles? And what is an ossicle? Ossicles are just tiny little bones. So what we're doing here is we're taking a look at the middle ear And this is actually going to be kind of looking at it. I'm removed. I removed out the anterior wall of the middle ear. Okay, so you can't see the anterior wall of the middle ear. I removed it out. And what we're looking at here is we're looking at a couple different bones. Alright, this first one here that I'm kind of like highlighting. We already said that remember if I'm looking here, I'm shining a light. Remember here was the light. I'm shining the light here. Okay. I'm looking, I see the tympanic membrane. What bone did I kind of see the outline of? The malleus. So what would this bone here be? This would be malleus. And then for the sake of it, what is that muscle that is connecting right here to the malleus right here? And it's actually kind of moving upwards like this. It actually is really long kind of muscle here. It actually moves all the way up over here. Okay. This is that muscle right there. This is what muscle is this called? This is called the tensor tympani, right? Because whenever the cranial nerve five, the mandibular division innervates this nerve, This muscle contracts and it pulls the malleus medially, okay, away from the tympanic membrane, okay? And basically what that does is it tenses up the tympanic membrane to prevent that excessive compression and decompression, okay? To dampen some of the sound waves. All right, sweet. So now malleus is connected to this next little ossicle through a nice little joint here. What is this muscle, I'm sorry, what is this bone here called, this ossicle that I'm highlighting right here? So malleus kind of means like a mallet. So imagine here I'm taking like a mallet and I'm smacking into like a nice little like anvil. Okay. They actually, they thought it looked like an anvil. So they just called this incus. Okay. So you have malleus, then you have incus. Then incus is connected through a nice little joint down here to this next bone. And this bone looks like the stirrups. Like if you ever get onto a horse, it kind of looks like this. Imagine here is this. the actual stapes. This is the stapes and they said it kind of looked like a stirrup, okay, that you can kind of stick your feet in this, right? Like a nice little stirrup. They call this bone here stapes, okay? This is called stapes. So what is this bone right here called? This one is called stapes. Why am I mentioning all of these bones? The reason why is because it's going to lead right into when we talk about how sound waves can actually produce action potentials within the inner ear. And then we can actually consciously perceive those sounds. So it's amazing. We can take sound waves, turn them into action potentials, electrical stimuli, and send them that information up to the brain to perceive. So what happens is, I'm not going to go into the whole detail here because we'll talk about it again later, but what happens is, let's say that these are the sound waves and sound waves are basically sine waves. Okay, so they're sine waves. They have ups and downs and ups and downs, clefts and troughs, right? And what happens is these sine waves or sound waves are hitting the tympanic membrane. And when that hits the tympanic membrane, it vibrates these little ossicles. And which ones? It'll vibrate in order. It'll vibrate malleus then that will actually hit on the incus and vibrate incus and then incus will actually push on stapes and stapes is actually anchored on one end that actually it's actually anchored on a posterior end and the only thing that's hitting it is the anterior end but just imagine it tapping on this window right there it's tapping on the window saying hey I got some sound waves for you and again past this point here would be the inner ear okay like the cochlea all right so what is This structure right here called. This structure here is called the oval window. Okay? So from medial side here, this is the medial side and this is the lateral side. I'm sorry, I lied. This is the lateral side because it's toward the external ear and this is the medial side. Okay? Because this is toward the inner ear. Alright, now what happens is sound waves are coming from the external acoustic venatus, they hit on the tympanic membrane, vibrate the ossicles, and order malleus incus stapes, and stapes taps on the oval window. When stapes taps on the oval window, he'll take this mechanical stimuli, and it'll create fluid-filled vibrations within the actual structure called the cochlea, which will eventually get converted into action potentials, and sent by the cochlear nerve of the cochlear branch. of the vestibulocochlear nerve to the brainstem. We'll talk about that when we get to the inner ear. Okay? So that covers that. Again, ossicles, we got malleus, incus, stapes. The purpose of them is when they vibrate from the sound waves, they tap on the oval window to create fluid-filled vibrations within the inner ear structure. Okay? Done with that part. Let's move on to the next part. Next part here is going to be called the facial canal. It's a tiny little bony canal within the middle ear. If you guys already watched our video, which we put up for the actual facial... nerve you guys will know what we're talking about here. Okay a lot of these are going to connect with some of the cranial nerves that we talked about. So if you remember where was the facial nerve actually coming from? Do you guys remember here? Let's actually kind of show it like this. Remember it was actually kind of located here in this area this was the facial nerve but had a special nucleus. You guys remember that nucleus? It was called the superior salivatory nucleus and if you remember the superior salivatory nucleus comes out through a hole and the skull over here. And this hole in the skull is actually called the internal acoustic meatus. Okay, it's actually called the internal acoustic meatus. What happens is it actually runs through the internal acoustic meatus and from here it actually moves down from the sub-the upper part of the actual, what? The upper and medial part of the middle ear and then it works its way backwards to the posterior wall and then it goes downwards and comes out through the stylo-mastoid foramen. We talked about that in the facial nerve video. Same thing is happening here. We're just looking at it like this. So what nerve would be coming down through this area? This is cranial nerve what? Seven, facial nerve, right? So some of the fibers here are going to come through this bony canal. And they're going to move through this bony canal. And as they're moving through this bony canal, something really, really important happens, right? So these are actually going to be the parasympathetic fibers. But you know the facial nerve also has motor fibers. So it also has motor fibers. Let's actually draw these motor fibers in this nice little blue color here. So here, this is our motor fibers. These motor fibers also move with the facial nerve and they move down through this canal also. So imagine this guy here is moving through this canal. As it's moving through this canal, it gives off a branch here. And this branch comes in through this tiny little hole within the posterior part of the actual middle ear and it supplies This muscle right here. Why is this important? And first off, what is this muscle? This muscle here is called the stapedius. So if you guys remember, this was our stapes. This bone right here was one of the ossicles that was called stapes. And what was stapes doing? It was tapping on the oval window. We have a little control of that. What happens is the facial nerve will innervate the stapedius, which will tense up on that actual stapes. What's the purpose of that? If it contracts on the stapes, the stapes isn't going to tap the oval window as much. Okay? So it's dampening these actual, the mechanical events that the stapes is trying to exert on the inner ear. Because again, the stapes is tapping on the oval window to create fluid-veiled vibrations. within the cochlea. If the actual stapedius contracts it prevents the stapes from doing that excessively. Okay, so it dampens that activity. That's the function of this part here. So again, what nerve is actually running in here? This whole thing right here that we've talked about so far, there's actually one more that we'll talk about. This whole thing that we've talked about so far. is the facial nerve, cranial nerve 7. These green fibers are the parasympathetic fibers and these baby blue fibers here are going to be the motor fibers. And the motor fibers are giving supply to the stapedius. And if you remember it'll continue down through the bony canal and it'll come out through this hole here called the stylomastoid foramen. And then if you really wanted to know, out of the stylomastoid foramen it gives two branches. One goes to the stylohyoid and the digastric posterior belly. And the other one branches out into the temporal, it branches out into the zygomatic, the marginal mandibular, and the cervical branches, right? If you guys remember that, it was the temporal, zygomatic, buccal, marginal mandibular, and cervical branch. And then back here it gives the digastric posterior belly, and it gives it to the stylohyoid. Okay, but we don't need to know about that, just going to give you what's moving through that area. Okay, now. What else is happening here? Remember from the facial nerve we had some other fibers here? Let's do these ones in this due to brown color here. These were actually sensory fibers. These were sensory fibers and these sensory fibers are important because they move in the actual facial canal here too. And what happens is they move down with these green fibers, these parasympathetic fibers. But what happens is they jump out, these sensory fibers. They jump out with these actual green fibers here. Look at this. These guys jump out of that facial canal and they move through a hole within the back of the actual middle ear. So again, what's going to happen here? These parasympathetic fibers, these green fibers are going to jump out and these brown fibers, these sensory fibers are also going to jump out. And then what happens is they're going to move, this is so freaking cool, they move from the posterior all the way out from the anterior, okay? So they move from the posterior part of the middle ear all the way to the anterior part of the middle ear. So again, what will happen here? These fibers here will come from the posterior part of the middle ear and they'll come out through the anterior part of the middle ear. These tiny little suckers here, this is just called the posterior canaliculus. Okay, this is just a little posterior canaliculus. And this is where these fibers come out here and they move over in like a cord in the tympanic cavity, which is called the chord of tympani. We'll write that down in just a second. But then they come out through this tiny little hole in the anterior side of the middle ear. This is called the anterior canaliculus. Okay? And again, what did we say this whole thing is called here? This whole thing, imagine this whole thing here that I'm about to wrap around like this. Moving from the posterior wall of the middle ear to the anterior wall. This whole structure here is called the corda. tympani. And if you guys remember from that video we said that it eventually would go out and it will combine with the lingual nerve and what happens? These fibers actually, these doodoo brown fibers, they move with what nerve? They're gonna move with cranial nerve, five, specifically the lingual nerve, right? And they'll go to the tongue, okay? The lingual nerve will actually supply what? The lingual nerve, the trigeminal component here, will supply touch pain temperature to the anterior two-thirds of the tongue. And these brown fibers here provide taste to the anterior two-thirds of the tongue. And if you remember, this comes out to a ganglion. What was that ganglion called? Submandibular ganglion. And this goes to glands. Sublingual salivary gland and the submandibular salivary gland. Okay, we already talked about this within that video right of the facial nerve Okay, sweet. So so far what do we talked about? We talked about the bony canal the facial canal and then what fibers are moving through it We're not going to cover every single fiber because we already did that in the facial nerve But I just want you to understand that through this Facial canal the facial nerve is moving through and then out of that certain fibers are coming out into the middle ear Which ones? This blue fiber is the motor fiber going to the stapedius, which controls the movement of the stapes. We talked about that. Then we said these green fibers are parasympathetic fibers. These do-do brown fibers are the sensory fibers, our taste fibers, right? And GVA fibers, if you remember. And the green ones are GVE fibers, if you remember. They move down through the facial canal, and then they come out through the posterior canaliculus and move anterior in a cord called the corditum panon. And they come out through the anterior canaliculus, and then again... The green fibers go to the submandibular ganglion, which allows for salivation. And then the brown ones move with the trigeminal nerve, specifically the lingual nerve. Okay? And they go to the anterior two-thirds of the tongue. Sweet stinking deal. All right. So what have we covered so far? We did the facial canal. What else did we cover? We also covered in the process, we covered stapedius. All right. Now let's talk about the next thing, which is actually going to be called the promontory. Okay. So the promontory. What is this promontory? So if you look here, we're looking at the middle ear. So looking at the middle ear here, you're going to see here, this is the medial wall. This is the medial wall of the inner ear, okay? This is the posterior wall of the middle ear. I took a slice here. You can't see the whole thing. So imagine I come, this is the whole anterior wall, I cut it, okay? So this is the anterior wall. But you're only seeing a small portion of it. If I were to bring this thing all the way up and all the way up here to the top, that would be the whole anterior wall. Okay? And then again, down here is just going to be the floor of the middle ear. And I removed the lateral wall. So over here, if I were to imagine coming from this to here, this would be the lateral wall. And that would have the tympanic membrane on it. I removed that so that we could see the cord of the tympani and some of these other structures. Okay? So posterior wall, medial wall, anterior wall. And then again, I remove the lateral wall and you can see the floor of the tympanic cavity. Sweet. On the medial wall, there's a structure that we're going to talk about eventually. It's called the cochlea, right? And what happens is, imagine I'm going to kind of like do it like this here. The cochlea kind of looks like a snail shell, right? And what happens is it actually kind of presses, okay? So the cochlea would actually be behind this. It would actually be behind this over here. So imagine here for a second. I'll show you what I'm talking about. Let's say here I have External ear, right? External acoustic meatus. Let's say here's the tympanic membrane. Let's say this is that wall. I'm shading it in here. This is actually going to be the medial wall. What would be right here next to it? Right here would be the cochlea. Okay? And then again, we'll talk about eventually, get you get to the vestibule and then the semicircular canals. Okay? So right here is actually gonna be the cochlea and the cochlea is pressing in to this actual medial wall and causing this little A bump. And that bump is called the promontory. Why is that bump important? Because there's nerves that run across that. You guys are probably going to hate me, but if you guys remember, let's do this one in pink. We had a nerve, and that was called the glossopharyngeal nerve, right? And it came out from over here, right? Remember, I'm going to kind of write it like this, glossopharyngeal nerve. It actually moves out through a hole. We're not going to show it here, but the jugular foramen. And then if you remember, I'm going to bring it down here, I'm going to come from the bottom, okay? It's going to come from the bottom here, and it's going to move up through this hole on the floor. You see that tiny little cavity right there, that tiny little hole? That's what it's going to move up through. It's going to move up through that. Okay, so this nerve here, glossopharyngeal nerve, is going to come down, down, down, down, down, come from the floor and come up through this tiny little hole within the floor of the tympanic cavity. What is that hole there called? That hole is called the tympanic canaliculus. Okay, so what is it called? It's called the tympanic canaliculus. And what happens is the glossopharyngeal nerve comes up through that. Then as it moves up, it gives off kind of like these little branches over here. Okay? It gives off these little branches. Okay? So again, if you remember, this was coming down. These are actually GVE fibers, so they're coming from a specific area. If you guys remember, it's coming from the inferior, if you want here, I'll write it. It's coming from the inferior salivatory nucleus. These fibers are coming up here through the tympanic canal oculis, and they're giving off these branches here to the promontory. What else is happening? Okay, you're really going to hate me now. Because, if you guys remember, we had another structure moving there too. Remember we had over here, we had the sympathetic nervous system, right? And we had this structure over here. This was called the intermediate lateral gray horn or the lateral gray horns. They come out here and they go to what's called a superior cervical ganglion. And they give off these postganglionic fibers that wrap around the internal carotid artery. Remember this was the internal carotid artery and it forms like a carotid plexus here, like a sympathetic plexus. These fibers come upwards and they give off branches that move through these two little holes. Like this is a superior hole and that's an inferior hole, right? Tiny little superior foramen and an inferior foramen. And what happens is these actual sympathetic nerves move through here, move through these tiny little holes. And they come out. Okay, so let's imagine this one's coming from the superior hole and this one over here is coming from the inferior hole. They come over here and they give off branches here also. Why am I mentioning this? What are these fibers here called? These are actually called the carotid tympanic. Nerves, they're sympathetic nerves. Okay, so they're sympathetic nerves that are coming from the lateral great horn of the spinal cord, coming to the superior cervical ganglion, wrapping around the internal carotid artery, and giving off a branch that moves to the anterior wall to the superior and inferior foramina. Right? They come off and they give off a branch that interacts with the parasympathetic fibers from the glossopharyngeal nerve. What is this form now? It forms a nice little plexus. They call this structure that's on the promontory, they call it the tympanic plexus. And basically all it is is just a connection from the glossopharyngeal nerve, the parasympathetic fibers, and the carotid tympanic nerves which are coming from the sympathetic nervous system and giving off branches that move into the middle ear. Okay? And if you guys remember, we talked about this one already that it gives off these parasympathetic fibers. They give off these branches that moves upwards as a specific nerve. It actually will come off as the lesser petrosal nerve. And then we said from here that the lesser petrosal nerve will move through a hole called the hiatus for the lesser petrosal nerve. And then it will run through a nice little hole in the skull called the foramen ovale. And then it will come out to a specific ganglion here called the otic ganglion. And this, remember, goes to a gland. Specifically, what gland? It goes to the parotid gland. Right? So it goes to a gland here called the parotid gland, which basically produces... the saliva that goes into the oral cavity. All right, and there's so many destinations from the sympathetic fibers. We're not going to go into all that, okay? So again, that's the lesser petrosal nerve, and that moves that way. And then if you guys do remember, just to be, you know, it's always good to have consistency. There's another one that comes off here off the seventh cranial nerve. If you guys remember, this was actually called the greater petrosal nerve, and the greater petrosal nerve actually runs through this area here. So this is called the greater petrosal nerve. It actually runs up through the hiatus of the greater petrosal nerve and it moves through another hole here called the foramen lacerum. And then it goes into what's called the pterygoid canal and into the pterygopalatine ganglion and then eventually it goes to the lacrimal glands and then it goes to the actual palatine glands. Okay? So again, that was the greater petrosal nerve. Okay? And again, it moves up through the hiatus and then it goes through the foramen lacerum. And then it goes down through the pterygoid canal and into the pterygopalatine ganglion and into the lacrimal and then the palatine and nasal glands. All right, holy crap, we did that. Okay, so what have we covered so far? We covered the promontory. We talked about the tympanic plexus. So we talked a lot about the nerve supply. So we did that. So we did the nerve supply with the glossopharyngeal nerve. Oh, you know what we did not do with the external ear? We got to cover one more thing here. Let's do this in, let's do it in purple. Let's do it in purple here. There's actually nerves that supply. If you guys remember, we talked about this in those videos. Remember we had the fifth cranial nerve, cranial nerve five? It gave off what's called an auriculotemporal branch. So it gives sensory supply to the skin of the external ear and a little bit here to the external acoustic meatus. That was the cranial nerve 5. What else did this too? Remember cranial nerve 10 and cranial nerve 9? Glossopharyngeal nerve. So here I'll put here cranial nerve 9 and cranial nerve 10. These also supply this. Remember cranial nerve 10, so it gives a supply to the actual tympanic membrane. Cranial nerve 9 specifically actually gives supply to like the inner part of the tympanic membrane. And then there was another one too which is cranial nerve 7. And cranial nerve 7 also gives fibers out here too. So we can even put here one more cranial nerve 7. And cranial nerve 7 also gives supply to the external acoustic meatus and a little bit of the tympanic membrane. So just reminding you guys that there is a lot of sensory fibers. that are located within the external acoustic meatus and on the tympanic membrane, external part of it, and internal part of it. So just in general, I want you guys to remember what nerves are going to be supplying the external ear and a little bit of tympanic membrane. It will be the ninth cranial nerve, glossopharyngeal, tenth cranial nerve, vagus, seventh cranial nerve, facial, and fifth cranial nerve, trigeminal. Okay, now we cover all the nerve supply. So sweet goodness, we did the nerve supply. We did the stapedias, we did the promontory, we talked about the facial canal, and we talked about the ossicles. Let's now do the tensor tympani and what is its purpose and what is basically serving it. Okay, well we talked a little bit about the tensor tympani. Over here, right? What did we say that the tensor tympani was doing? It was connecting to the malleus and it was pulling the malleus medially, okay? So towards the medial wall, which tensed up the tympanic membrane because you know that the malleus is actually connected to the tympanic membrane here. Alright, so now let's see how this is actually affecting. So let's come over here. If you guys remember, we had another nerve and we talked about him plenty of time. We have a huge video on him, cranial nerve. right? The trigeminal nerve. We have the mandibular division of it. So let's say it gives off, remember it has the three branches. One is the V1 ophthalmic, V2 maxillary, and V3 is going to be mandibular. Well, from the V3 division, it gives off a branch that supplies this muscle right here. Okay, what is this muscle again here called? This muscle is called the tensor tympani. And what does the tensor tympani do? When the tensor tympani contracts, It pulls. So imagine here it's connected to that bone. Obviously the bone will be all the way over here, but I'm just doing it for the sake of it. Okay? What is this bone here called? This is called malleus. It pulls malleus medially. So it pulls the malleus medially. When it pulls on the malleus, it tenses that tympanic membrane. When you tense the tympanic membrane, whenever the compression and decompression of the tympanic membrane is trying to create those vibrations of the ossicles, that'll be dampened a little bit. Okay? And the purpose of this is, you guys know when you're chewing food, okay, muscles of mastication, you know when you're chewing food, right, so you have the temporalis, you have the masseter, you even have other muscles like the medial and lateral pterygoid, a whole bunch of different muscles that are involved in mastication, right? But when you're chewing, you can produce a lot of sounds, a lot of sounds. What happens is the trigeminal nerve is so kind to us and it gives off a branch of the tensor tympani, which tenses the tympanic membrane. If it does that, whenever we're chewing food during the mastication process, It dampens that so that we don't produce so much loud sounds during the eating process or the mastication process when you're chewing your food. Okay, so you better thank your trigeminal nerve next time you're eating and it's not super, super loud. Okay? And also thank your facial nerve who gives supply to the stapedius too because that's also another one who's really important. Because if he gets damaged from Bell's palsy, you could actually cause hyperacusis where remember it can actually continue to keep tapping on the oval window continuously. and you become very, very sensitive to sounds. Remember I told you you have to hold the phone out here for some people because it hurts so much if people are talking to their ear. All right, cool, covered that. Now, one other thing I wanted to talk about, I didn't write it up there, I'm sorry about that. Well, I want to talk about this tube right here. This is a very, very important tube. So it's called the pharyngeal tympanic tube. They have so many names for it. They can call it the auditory tube, the eustachian tube, or we can call it the pharyngeal tympanic tube. I'm just going to call it the phryngiotympanic tube. You can pick from whatever three. Again, phryngiotympanic tube, eustachian tube, or auditory tube. Whichever one. What is the purpose of this sucker here? Okay? This guy is connecting with a specific part within our throat. Let me actually show you over here because it's way better because it's perfect. It's perfectly connected over here. Let's say again, what wall would this one be? This would be the medial wall. You can tell that because it's right next to the promontory. This would be the posterior wall. This would be the anterior wall. Okay? Now what happens is on the anterior wall, there's actually going to be a nice little tube here. A nice little tube. And this tube connects into the pharynx. It connects into the pharynx here. And what happens is what this can do is it can equalize the pressure between the atmosphere and the middle ear. Because what's normally the pressure outside in the atmosphere? Atmospheric pressure is normally 760 millimeters of mercury. Well this one you want to equalize these pressures so that doesn't cause any problems here developing within the middle ear because obviously that could lead to a lot of different situations if there's pressure accumulation in here. Right? It might cause abnormal certain sensations like tinnitus if it's if it's occurring. We don't want that. So what happens here any air and I'll explain where that air can come from can be moved from the middle ear out into the external environment or from the external environment we can bring some of these air in here. It's the whole purpose of the pharyngeal tympanic tube is to equalize pressures with atmosphere and middle ear. That's the whole purpose of it. Okay, so at the end of the day just remember that. Purpose of the pharyngeal tympanic tube is to equalize the pressure within the atmosphere and the pharyngeal tympanic tube. If for some reason you need to get the air that is actually maybe you want to actually have some more air come into the actual Middle ear cavity you have this beautiful structure in the posterior wall a nice beautiful A little structure here. This is called the mastoid sinus. So in the posterior wall, you have a little hole here that connects to the mastoid sinus. So you're going to have a nice little hole back here that connects to the mastoid sinus. And in certain people, not everyone, these people might have mastoid air cells. Not every single person is having mastoid air cells. Okay, but you do have this mastoid sinus here. And the mastoid sinus is going to have a lot of mucus, right? What can happen is some of the air from this mastoid sinus can actually be pushed over here into the middle ear cavity depending upon the needs. Okay, why am I mentioning this mastoid sinus? Because in certain situations when someone might have what's called mastoiditis or certain types of infection or inflammation of the mastoid sinus, it doesn't drain into the nasal cavity. So what happens is in certain people, if they have really bad infection, a nasty infection of the mastoid sinus, they have to put in little shunts. Okay, so they have to put in like tiny little shunts here. that can drain the actual middle ear cavity. Okay, so you actually have to put shunts in that drains the middle ear, I'm sorry, not the middle ear cavity, the mastoid sinus, so that you actually don't have, you want to know why this is important? Because you don't want an infection to develop within the mastoid sinus, because then it can extend. Where can it actually extend? Come here, I'll show you. The mastoid sinus can be right over here, right? So pretend I actually draw it right here. I'm going to erase this out of the way here. Imagine it's back here, and here's your mastoid sinus. What can happen is it can extend upwards into this area. And it can actually affect the glossopharyngeal nerve, it can affect the tenth cranial nerve, the vagus, and it can even affect the accessory nerve. So because of that, if a mastoid sinus infection extends upwards, it can affect a lot of the cranial nerves moving out through that area. Okay? So that's one of the damaging things about mastoid sinus infections, is that you want to take care of that and make sure that you put a shunt in there to drain out any types of substances that might be in there if it's actually accumulating a lot of fluid. Okay? I'm just going to remember another topic here. Oh, here it was. In the, I didn't talk about the roof. We talked about the floor of the medullary cavity, but we didn't talk about the roof. And this is probably one of the most important things about the actual tympanic cavity. So imagine here again, if you remember, this was actually, I'm going to shade it in order. This is actually going to be the what wall? This is the medial wall. This is going to be the lateral wall. This over here, if you imagine, I'll show it like this in green. This wall here is the anterior wall. And in the back here would be the posterior wall and back here would be the masterly sinus right with the air cells. On the roof it's actually made up of a little bone okay and this bony part here is called the tegmen tympani. The reason why I'm telling you this because it's a very very thin bone and if someone develops what's called otitis media middle ear infection it can actually spread upwards very easily through the tegmen tympani. What is separating the middle ear cavity from the actual cranial cavity. Not very much. Not very much at all. If you imagine here, let's say that here's the actual roof right here. Okay, that's the tegmentin panni. The only thing that's really separating it from this point here is just some dura mater. That's all it is. The only thing that's really separating the actual middle ear cavity from the actual cranial cavity is the tegmentin panni and some dura mater. That's it. So if you have an infection, it can actually easily spread up through the tegmentin panni into the actual meninges and cause severe meningitis. Okay, so very very dangerous it can actually cause infections within the brain too that maybe might cause some type of like abscess or something okay okay so we did that part there sweet so what have we covered so far we covered the mastoid sinus okay and we covered a little piece in there the roof of the middle ear cavity called the tegmentum panna and its significance that's another thing you know certain things is actually we'll talk about later is whenever you have infections and you give Certain types of antibiotics you have to be careful about what type of antibiotic you get because aminoglycosides can actually cause ototoxicity, can actually cause more damage to the ear. We'll talk about that when we get to that video though. Okay, next thing that we're going to talk about is the tensor veli palatinae. Okay, so if you guys remember we said that we had what's called the... what's up again? We have the trigeminal nerve, okay? The trigeminal nerve or cranial nerve 5, you have some muscles here. They're actually a part of the soft palate. Let's say that one muscle is going to be like this. So I have one muscle like this. You have a couple different. You have what's called a levator veli palatini. You might even have another one here, which is called the salpingo pharyngeus. And you might even have another one over here, which is called the tensor veli palatini. Okay, so I'll just write these here for a second. Let's say that this is the levator veli palatini. Let's say that this is the tensor veli palatini. And let's say that this is what's called the salpingo pharyngeus. What happens is, is if you remember the trigeminal nerve, the fifth cranial nerve, the fifth Cranial nerve, cranial nerve 5 has the mandibular division that gives fibers to the tensor veli palatini. And the tensor veli palatini, what is it going to do? It's actually going to tense the actual soft palate. Another thing is it's not going to be supplied by the 5th cranial nerve, but if you guys remember, we have the 10th cranial nerve. So cranial nerve 10. It came through the pharyngeal plexus and it supplied the salpingo pharyngeus and it supplied the levator veli palatini. Whenever the cranial nerve 10 supplies the salpingo pharyngeus, that actually elevates the soft palate and the levator veli palatina elevates the soft palate. But the salpingo pharyngeus does something else. It's actually connected to the pharyngeal tympanic tube, a little cartilaginous lamina. And it can pull on that cartilaginous lamina of the pharyngeal tympanic tube to help to equalize the pressures. Between what? Between the middle ear cavity and the atmospheric pressure. Alright, so what have we covered then? We've covered also the tensor velipalatini and the other connection, which was the salpingo pharyngeus. Alright, so that covered that part. Alright guys, so we talked a lot about the external ear. We talked a lot about the middle ear cavity, the tympanic cavity. We went over a lot of different things. In future videos, we'll talk about something else a little bit later called a cholesteatoma, which can accumulate within the middle ear. And it can become very, very, very dangerous. Okay? That will be a discussion that we will talk about later when we get to the inner ear structure and how that can affect the actual auditory impulses. Okay, so we will talk about cholesteasomas. But we talked a lot about a lot of different things about the middle ear and the external ear. I really hope it made sense. I really hope that you guys enjoyed it and you learned a lot. If you guys did please hit the like button, comment down in the comment section and please subscribe. As always Ninja Nerds, until next time.

So if you real quickly, I'm going to draw here a quick little crude diagram here. Imagine here's the skull, okay? Imagine here I put like the cellotursica of the sphenoid bone, and I can separate this into an anterior cranial fossa, I'll separate it into a middle cranial fossa, and then I'll have a posterior cranial fossa with the foramen magnum there, right? And then if you want, you have your crista galli right here with the cribriform plate of the ethmoid bone, all that stuff right there, right? Then, if you come over here, you'll have the external acoustic meatus with the ear, right?

And over here, you'll have a external acoustic meatus with the ear. What I'm going to take a look at is we're going to look at some of the structures here off the external ear, and we're going to take a look at this external acoustic meatus, and then what we're going to do is there's going to be this separating structure here that we're going to take a look at a lot. Pretty much most of the video is going to be about this.

And it's going to be on this middle ear. And we're going to take a look at it in a box diagram because it's the easiest way to see the middle ear. So what we're going to start off with is we're going to start first off talking about what? The external ear.

Not too much to talk about, but we'll discuss some things. But then we're going to spend most of our time looking at the middle ear. And again, we're going to look at it in what's called a box diagram form because it's going to make it the easiest to see. Okay?

And easiest for me to draw here. Alright, so let's go ahead and start that. So first off, let's come over here. I know we have a lot of diagrams here pre-john but don't worry we'll go over everything. If you guys just click on the video don't worry you didn't miss anything.

Okay so starting off here we're going to talk about the external ear. Okay so external ear biggest thing here you see how you see this big old flap here coming out this sucker right here that I'm flicking on right now I'm holding and moving around. You notice how I'm able to move it around a lot right it's able to be stretched and go back to its normal shape right I'm able to move it around bend it. What's the reason for that?

Well first off, what do we call this part here? Not only do we call it two things, you can call it the auricle or you can call it the pinna. Now what's really interesting about the auricle or the pinna is obviously the outer part of it is the skin is supplied with what's called, it's actually covered with stratified squamous epithelial tissue to resist against friction and abrasion.

But underneath that, it's primarily made up of a special cartilage called elastic cartilage. And the reason why I'm mentioning this is because there isn't too many places in the body that are actually consisting of elastic cartilage. One is going to be the ear, the external part of the ear, the auricle or the pinna. And the other one is the epiglottis.

And again, the purpose of it is for it to be able to be very, very able to stretch but recoil back to its normal position. Okay, so that's one of the really, really cool things about that. Alright, sweet.

Nothing much other than that about the external ear, this outer part here. Now, the next thing is, as we go in, to the actual external. So we come from the auricle or the pina and we move into this hole right outside of it. Right so there's going to be a hole right outside of the skull, right outside of the skull and this is going to be called the external acoustic meatus.

So this is called the external acoustic meatus. This little canal right here that I'm kind of putting the outlines here in green. The external acoustic meatus is a little bony canal.

And inside of this canal you're going to have some, first off the inner part of it is covered with like some stratified squamous epithelial tissue, right? But another thing that's really important about this is that we have these things called ceruminous glands, okay? We have these things here called ceruminous glands. And ceruminous glands are basically like modified apocrine glands, basically.

They're like modified apocrine glands. And they can produce a substance called cerumen. all of you probably commonly know as earwax.

Okay, so these guys are producing earwax, cerumen, which is kind of coating the inner part of the ear. Now, what is important about this? The importance of this cerumen is to be able to deter insects, believe it or not. So again, what are these glands here called?

They're called ceruminous glands, okay? And these ceruminous glands are producing cerumen, or we know it as earwax. And the purpose of this earwax is to deter Certain insects.

Now some of you might know that you stick a q-tip in there and you pull out some of that earwax, right? But you have to be careful. Why? Because you've probably been told by your mother or some other person, don't ever stick that q-tip really far down because at the end of the external acoustic meatus, there's a really, really important structure.

It's called the tympanic membrane. The tympanic membrane is a very, very important membrane. It's a connective tissue membrane. We'll talk about a little bit more here in just a second. We have the diagram up there to show it.

But this pink structure that I'm here separating the external ear from the middle ear. This is the tympanic membrane. So that's kind of a nice separating structure.

So what is this pink thing they're called? It's called the tympanic membrane. And like I said it's actually made up of two components. One component is called the pars tensa. Which is a very, very, very heavily dense, fibrous, irregular connective tissue.

We'll talk about that one. Okay, so this is the dense connective tissue. And particularly, it's irregular because it's in different bundles or arrangements.

Okay? The other one is called the pars flaccida. Don't be thinking about flaccid other things, okay?

Just think about pars flaccida. What it means is it's loose. Okay, it's loose.

And in this case, it's actually made up of a loose connective tissue, particularly areolar connective tissue. The reason why I'm telling you this, that it's actually made up of two different types, is that if you go and stick the ear Q-tip into the ear and you actually hit the pars flaccida too hard, you can puncture the tympanic membrane. And that would affect the actual middle ear pressure, as well as a lot of other structures open up for certain types of microbes to come in. Okay?

Alright, so cool. So what do we have so far for the external ear? We have the auricle or the penile, which is made up of elastic cartilage. Okay? Allows for it to be able to kind of be stretchable and to be able to be stretched, but it always wants to recoil and go back to its normal position.

Right? External ear is also going to consist of ceruminous glands, which are producing cerumen, earwax, that are basically lining and coating the external acoustic meatus to provide it with a substance that can deter the insects. And remember, the ceruminous glands are modified African glands.

Then... This bony canal, the external acoustic meatus, it gets to this end point here which separates the external ear from the middle ear. And that pink membrane is called the tympanic membrane.

And the tympanic membrane is a connective tissue membrane. Two parts of it, one's called the pars tensa, which is made up of a dense irregular connective tissue. That's the inferior part of it.

Usually, if I were to kind of make a little cut off here, usually the actual part right here that I separate anything below from this point here to this point is the pars tensa. Usually up here in the top from this point to this point is the pars flaccida and it's a looser type of tissue and what kind? Areola connective tissue. So now let's imagine that I'm gonna look down the ear. Okay I'm gonna take them I'm gonna take it I'm gonna look down this extra acoustic meatus so I'm gonna I'm gonna take and shine a light down this area.

So let's pretend that I try to draw a light don't you dare laugh at me. I'm gonna take here I'm gonna have a light here and I'm going to shine some light. into this person's eye.

I'm sorry, not into their eye, their ear. Okay? And I'm going to look down the external acoustic meatus at the tympanic membrane. When I look at that, this is what I see. It might not be beautifully as you would normally see it, but this is what you're going to kind of see here with the tympanic membrane.

Now, what we see here is we see a couple different things. You can actually kind of see an outline here. You see this kind of structure here in blue? I'm going to outline it here. It's actually an ossicle.

It's one of the little bones. And you can kind of see a little outlining of it there. What is this bone here called? That bone is called malleus. It's actually called malleus.

It's one of the ossicles, okay? It's one of the three ossicles within the actual middle ear cavity. So you can kind of see like a little bit of an outlining of the malleus. Then you can kind of see these little folds. These little folds here coming inwards like this.

And then another fold coming inwards like this. Okay, so this is actually called, since this fold is close to the malleus, it's an anterior mallear fold, and this is the posterior mallear fold. We're not going to actually write these down. They're not significantly important. But again, just kind of giving you an idea here.

This is the anterior mallear fold, which is kind of on this side. So this would be the anterior side here. This would be the posterior side of the tympanic cavity. Okay, and again, this is the anterior mallear fold, posterior mallear fold, and kind of an outlining of the malleus. Then, at the bottom part, this is important.

Here, connecting to the bottom part of the malleus. is a muscle and this muscle is called the tensor tympani. The tensor tympani, right? The tensor tympani, we talked about this muscle.

If you guys watched the video on the trigeminal nerve, remember the trigeminal nerve actually gives off a branch that supplies the tensor tympani which tenses up to... tympanic membrane. We didn't really talk about the mechanism.

We will in this video, but we'll say that what happens is this tensor tympani is innervated by the trigeminal nerve, specifically the mandibular division, okay, of the trigeminal nerve, V3. Okay, and that's connecting to that part. Then, remember we said we had the pars flaccida and the pars tensa? This right here, that's all in this really, really dark shade of green.

It's pretty much very, very dark. It looks heavily connective tissue-wise, right? This right here is going to be the pars tensa. Okay, that's the pars tensa, which is this really, really dark connective tissue. And this is the only reason we mentioned the mallear folds.

The anterior mallear folds and the posterior mallear folds are kind of separating the pars tensa and the pars flaccida. So all this loose connective tissue that I'm kind of just drawing like scattered, this is the pars flaccida. Okay.

All right. So what have we covered so far then? We've covered External ear with the auricle and the pina.

We covered the external acoustic meatus, the ceruminous glands. We covered the tympanic membrane which is consisting of the pars flaccida and the pars tensa. Pars tensa is dense connective tissue irregular.

Pars flaccida is areolar. We also said that you can kind of see it whenever you're looking down the ear canal. You can actually see that it's nice a separation here by the posterior and anterior mallear folds which are separating the pars tensa from the pars flaccida. And then we also said that you kind of see like an outline here of the malleus.

And you'll see a muscle here connecting called the tensor tympana, which is innervated by what cranial nerve? The fifth cranial nerve, particularly the mandibular division. So V3 of cranial nerve, five. Okay? Sweet stinking deal.

So we covered the external ear. Now, let's go ahead and take a look even deeper now. Okay, so now we're going to take a look even deeper and we're going to start getting into this cavity here.

We're going to start looking into the actual tympanic cavity. or the middle ear. Alright guys, so I just want to take a little pause here because I wanted to write down what we're going to talk about because we're going to talk about a lot of stuff. So I want to make sure that we cover every single piece of it.

So I just kind of wrote down a list of what I want to talk about. Alright, so first thing we're going to talk about is ossicles. Okay, so ossicles. There's three little ossicles located within the actual middle ear or the tympanic cavity. Okay, what are those ossicles?

And what is an ossicle? Ossicles are just tiny little bones. So what we're doing here is we're taking a look at the middle ear And this is actually going to be kind of looking at it.

I'm removed. I removed out the anterior wall of the middle ear. Okay, so you can't see the anterior wall of the middle ear. I removed it out. And what we're looking at here is we're looking at a couple different bones.

Alright, this first one here that I'm kind of like highlighting. We already said that remember if I'm looking here, I'm shining a light. Remember here was the light.

I'm shining the light here. Okay. I'm looking, I see the tympanic membrane. What bone did I kind of see the outline of?

The malleus. So what would this bone here be? This would be malleus.

And then for the sake of it, what is that muscle that is connecting right here to the malleus right here? And it's actually kind of moving upwards like this. It actually is really long kind of muscle here.

It actually moves all the way up over here. Okay. This is that muscle right there. This is what muscle is this called? This is called the tensor tympani, right?

Because whenever the cranial nerve five, the mandibular division innervates this nerve, This muscle contracts and it pulls the malleus medially, okay, away from the tympanic membrane, okay? And basically what that does is it tenses up the tympanic membrane to prevent that excessive compression and decompression, okay? To dampen some of the sound waves. All right, sweet.

So now malleus is connected to this next little ossicle through a nice little joint here. What is this muscle, I'm sorry, what is this bone here called, this ossicle that I'm highlighting right here? So malleus kind of means like a mallet.

So imagine here I'm taking like a mallet and I'm smacking into like a nice little like anvil. Okay. They actually, they thought it looked like an anvil.

So they just called this incus. Okay. So you have malleus, then you have incus. Then incus is connected through a nice little joint down here to this next bone. And this bone looks like the stirrups.

Like if you ever get onto a horse, it kind of looks like this. Imagine here is this. the actual stapes.

This is the stapes and they said it kind of looked like a stirrup, okay, that you can kind of stick your feet in this, right? Like a nice little stirrup. They call this bone here stapes, okay? This is called stapes.

So what is this bone right here called? This one is called stapes. Why am I mentioning all of these bones? The reason why is because it's going to lead right into when we talk about how sound waves can actually produce action potentials within the inner ear. And then we can actually consciously perceive those sounds.

So it's amazing. We can take sound waves, turn them into action potentials, electrical stimuli, and send them that information up to the brain to perceive. So what happens is, I'm not going to go into the whole detail here because we'll talk about it again later, but what happens is, let's say that these are the sound waves and sound waves are basically sine waves.

Okay, so they're sine waves. They have ups and downs and ups and downs, clefts and troughs, right? And what happens is these sine waves or sound waves are hitting the tympanic membrane.

And when that hits the tympanic membrane, it vibrates these little ossicles. And which ones? It'll vibrate in order.

It'll vibrate malleus then that will actually hit on the incus and vibrate incus and then incus will actually push on stapes and stapes is actually anchored on one end that actually it's actually anchored on a posterior end and the only thing that's hitting it is the anterior end but just imagine it tapping on this window right there it's tapping on the window saying hey I got some sound waves for you and again past this point here would be the inner ear okay like the cochlea all right so what is This structure right here called. This structure here is called the oval window. Okay? So from medial side here, this is the medial side and this is the lateral side.

I'm sorry, I lied. This is the lateral side because it's toward the external ear and this is the medial side. Okay? Because this is toward the inner ear. Alright, now what happens is sound waves are coming from the external acoustic venatus, they hit on the tympanic membrane, vibrate the ossicles, and order malleus incus stapes, and stapes taps on the oval window.

When stapes taps on the oval window, he'll take this mechanical stimuli, and it'll create fluid-filled vibrations within the actual structure called the cochlea, which will eventually get converted into action potentials, and sent by the cochlear nerve of the cochlear branch. of the vestibulocochlear nerve to the brainstem. We'll talk about that when we get to the inner ear.

Okay? So that covers that. Again, ossicles, we got malleus, incus, stapes. The purpose of them is when they vibrate from the sound waves, they tap on the oval window to create fluid-filled vibrations within the inner ear structure.

Okay? Done with that part. Let's move on to the next part.

Next part here is going to be called the facial canal. It's a tiny little bony canal within the middle ear. If you guys already watched our video, which we put up for the actual facial...

nerve you guys will know what we're talking about here. Okay a lot of these are going to connect with some of the cranial nerves that we talked about. So if you remember where was the facial nerve actually coming from? Do you guys remember here?

Let's actually kind of show it like this. Remember it was actually kind of located here in this area this was the facial nerve but had a special nucleus. You guys remember that nucleus?

It was called the superior salivatory nucleus and if you remember the superior salivatory nucleus comes out through a hole and the skull over here. And this hole in the skull is actually called the internal acoustic meatus. Okay, it's actually called the internal acoustic meatus. What happens is it actually runs through the internal acoustic meatus and from here it actually moves down from the sub-the upper part of the actual, what?

The upper and medial part of the middle ear and then it works its way backwards to the posterior wall and then it goes downwards and comes out through the stylo-mastoid foramen. We talked about that in the facial nerve video. Same thing is happening here. We're just looking at it like this. So what nerve would be coming down through this area?

This is cranial nerve what? Seven, facial nerve, right? So some of the fibers here are going to come through this bony canal.

And they're going to move through this bony canal. And as they're moving through this bony canal, something really, really important happens, right? So these are actually going to be the parasympathetic fibers.

But you know the facial nerve also has motor fibers. So it also has motor fibers. Let's actually draw these motor fibers in this nice little blue color here. So here, this is our motor fibers. These motor fibers also move with the facial nerve and they move down through this canal also.

So imagine this guy here is moving through this canal. As it's moving through this canal, it gives off a branch here. And this branch comes in through this tiny little hole within the posterior part of the actual middle ear and it supplies This muscle right here. Why is this important? And first off, what is this muscle?

This muscle here is called the stapedius. So if you guys remember, this was our stapes. This bone right here was one of the ossicles that was called stapes.

And what was stapes doing? It was tapping on the oval window. We have a little control of that.

What happens is the facial nerve will innervate the stapedius, which will tense up on that actual stapes. What's the purpose of that? If it contracts on the stapes, the stapes isn't going to tap the oval window as much. Okay?

So it's dampening these actual, the mechanical events that the stapes is trying to exert on the inner ear. Because again, the stapes is tapping on the oval window to create fluid-veiled vibrations. within the cochlea.

If the actual stapedius contracts it prevents the stapes from doing that excessively. Okay, so it dampens that activity. That's the function of this part here. So again, what nerve is actually running in here?

This whole thing right here that we've talked about so far, there's actually one more that we'll talk about. This whole thing that we've talked about so far. is the facial nerve, cranial nerve 7. These green fibers are the parasympathetic fibers and these baby blue fibers here are going to be the motor fibers. And the motor fibers are giving supply to the stapedius. And if you remember it'll continue down through the bony canal and it'll come out through this hole here called the stylomastoid foramen.

And then if you really wanted to know, out of the stylomastoid foramen it gives two branches. One goes to the stylohyoid and the digastric posterior belly. And the other one branches out into the temporal, it branches out into the zygomatic, the marginal mandibular, and the cervical branches, right? If you guys remember that, it was the temporal, zygomatic, buccal, marginal mandibular, and cervical branch.

And then back here it gives the digastric posterior belly, and it gives it to the stylohyoid. Okay, but we don't need to know about that, just going to give you what's moving through that area. Okay, now.

What else is happening here? Remember from the facial nerve we had some other fibers here? Let's do these ones in this due to brown color here.

These were actually sensory fibers. These were sensory fibers and these sensory fibers are important because they move in the actual facial canal here too. And what happens is they move down with these green fibers, these parasympathetic fibers. But what happens is they jump out, these sensory fibers.

They jump out with these actual green fibers here. Look at this. These guys jump out of that facial canal and they move through a hole within the back of the actual middle ear.

So again, what's going to happen here? These parasympathetic fibers, these green fibers are going to jump out and these brown fibers, these sensory fibers are also going to jump out. And then what happens is they're going to move, this is so freaking cool, they move from the posterior all the way out from the anterior, okay? So they move from the posterior part of the middle ear all the way to the anterior part of the middle ear.

So again, what will happen here? These fibers here will come from the posterior part of the middle ear and they'll come out through the anterior part of the middle ear. These tiny little suckers here, this is just called the posterior canaliculus.

Okay, this is just a little posterior canaliculus. And this is where these fibers come out here and they move over in like a cord in the tympanic cavity, which is called the chord of tympani. We'll write that down in just a second.

But then they come out through this tiny little hole in the anterior side of the middle ear. This is called the anterior canaliculus. Okay?

And again, what did we say this whole thing is called here? This whole thing, imagine this whole thing here that I'm about to wrap around like this. Moving from the posterior wall of the middle ear to the anterior wall.

This whole structure here is called the corda. tympani. And if you guys remember from that video we said that it eventually would go out and it will combine with the lingual nerve and what happens? These fibers actually, these doodoo brown fibers, they move with what nerve? They're gonna move with cranial nerve, five, specifically the lingual nerve, right?

And they'll go to the tongue, okay? The lingual nerve will actually supply what? The lingual nerve, the trigeminal component here, will supply touch pain temperature to the anterior two-thirds of the tongue. And these brown fibers here provide taste to the anterior two-thirds of the tongue. And if you remember, this comes out to a ganglion.

What was that ganglion called? Submandibular ganglion. And this goes to glands. Sublingual salivary gland and the submandibular salivary gland.

Okay, we already talked about this within that video right of the facial nerve Okay, sweet. So so far what do we talked about? We talked about the bony canal the facial canal and then what fibers are moving through it We're not going to cover every single fiber because we already did that in the facial nerve But I just want you to understand that through this Facial canal the facial nerve is moving through and then out of that certain fibers are coming out into the middle ear Which ones? This blue fiber is the motor fiber going to the stapedius, which controls the movement of the stapes.

We talked about that. Then we said these green fibers are parasympathetic fibers. These do-do brown fibers are the sensory fibers, our taste fibers, right?

And GVA fibers, if you remember. And the green ones are GVE fibers, if you remember. They move down through the facial canal, and then they come out through the posterior canaliculus and move anterior in a cord called the corditum panon. And they come out through the anterior canaliculus, and then again... The green fibers go to the submandibular ganglion, which allows for salivation.

And then the brown ones move with the trigeminal nerve, specifically the lingual nerve. Okay? And they go to the anterior two-thirds of the tongue. Sweet stinking deal.

All right. So what have we covered so far? We did the facial canal. What else did we cover?

We also covered in the process, we covered stapedius. All right. Now let's talk about the next thing, which is actually going to be called the promontory.

Okay. So the promontory. What is this promontory? So if you look here, we're looking at the middle ear. So looking at the middle ear here, you're going to see here, this is the medial wall.

This is the medial wall of the inner ear, okay? This is the posterior wall of the middle ear. I took a slice here.

You can't see the whole thing. So imagine I come, this is the whole anterior wall, I cut it, okay? So this is the anterior wall.

But you're only seeing a small portion of it. If I were to bring this thing all the way up and all the way up here to the top, that would be the whole anterior wall. Okay?

And then again, down here is just going to be the floor of the middle ear. And I removed the lateral wall. So over here, if I were to imagine coming from this to here, this would be the lateral wall.

And that would have the tympanic membrane on it. I removed that so that we could see the cord of the tympani and some of these other structures. Okay?

So posterior wall, medial wall, anterior wall. And then again, I remove the lateral wall and you can see the floor of the tympanic cavity. Sweet.

On the medial wall, there's a structure that we're going to talk about eventually. It's called the cochlea, right? And what happens is, imagine I'm going to kind of like do it like this here. The cochlea kind of looks like a snail shell, right? And what happens is it actually kind of presses, okay?

So the cochlea would actually be behind this. It would actually be behind this over here. So imagine here for a second.

I'll show you what I'm talking about. Let's say here I have External ear, right? External acoustic meatus. Let's say here's the tympanic membrane. Let's say this is that wall.

I'm shading it in here. This is actually going to be the medial wall. What would be right here next to it? Right here would be the cochlea. Okay?

And then again, we'll talk about eventually, get you get to the vestibule and then the semicircular canals. Okay? So right here is actually gonna be the cochlea and the cochlea is pressing in to this actual medial wall and causing this little A bump. And that bump is called the promontory.

Why is that bump important? Because there's nerves that run across that. You guys are probably going to hate me, but if you guys remember, let's do this one in pink.

We had a nerve, and that was called the glossopharyngeal nerve, right? And it came out from over here, right? Remember, I'm going to kind of write it like this, glossopharyngeal nerve. It actually moves out through a hole. We're not going to show it here, but the jugular foramen.

And then if you remember, I'm going to bring it down here, I'm going to come from the bottom, okay? It's going to come from the bottom here, and it's going to move up through this hole on the floor. You see that tiny little cavity right there, that tiny little hole?

That's what it's going to move up through. It's going to move up through that. Okay, so this nerve here, glossopharyngeal nerve, is going to come down, down, down, down, down, come from the floor and come up through this tiny little hole within the floor of the tympanic cavity. What is that hole there called?

That hole is called the tympanic canaliculus. Okay, so what is it called? It's called the tympanic canaliculus. And what happens is the glossopharyngeal nerve comes up through that.

Then as it moves up, it gives off kind of like these little branches over here. Okay? It gives off these little branches. Okay?

So again, if you remember, this was coming down. These are actually GVE fibers, so they're coming from a specific area. If you guys remember, it's coming from the inferior, if you want here, I'll write it.

It's coming from the inferior salivatory nucleus. These fibers are coming up here through the tympanic canal oculis, and they're giving off these branches here to the promontory. What else is happening?

Okay, you're really going to hate me now. Because, if you guys remember, we had another structure moving there too. Remember we had over here, we had the sympathetic nervous system, right? And we had this structure over here. This was called the intermediate lateral gray horn or the lateral gray horns.

They come out here and they go to what's called a superior cervical ganglion. And they give off these postganglionic fibers that wrap around the internal carotid artery. Remember this was the internal carotid artery and it forms like a carotid plexus here, like a sympathetic plexus.

These fibers come upwards and they give off branches that move through these two little holes. Like this is a superior hole and that's an inferior hole, right? Tiny little superior foramen and an inferior foramen. And what happens is these actual sympathetic nerves move through here, move through these tiny little holes.

And they come out. Okay, so let's imagine this one's coming from the superior hole and this one over here is coming from the inferior hole. They come over here and they give off branches here also.

Why am I mentioning this? What are these fibers here called? These are actually called the carotid tympanic.

Nerves, they're sympathetic nerves. Okay, so they're sympathetic nerves that are coming from the lateral great horn of the spinal cord, coming to the superior cervical ganglion, wrapping around the internal carotid artery, and giving off a branch that moves to the anterior wall to the superior and inferior foramina. Right?

They come off and they give off a branch that interacts with the parasympathetic fibers from the glossopharyngeal nerve. What is this form now? It forms a nice little plexus. They call this structure that's on the promontory, they call it the tympanic plexus. And basically all it is is just a connection from the glossopharyngeal nerve, the parasympathetic fibers, and the carotid tympanic nerves which are coming from the sympathetic nervous system and giving off branches that move into the middle ear.

Okay? And if you guys remember, we talked about this one already that it gives off these parasympathetic fibers. They give off these branches that moves upwards as a specific nerve. It actually will come off as the lesser petrosal nerve.

And then we said from here that the lesser petrosal nerve will move through a hole called the hiatus for the lesser petrosal nerve. And then it will run through a nice little hole in the skull called the foramen ovale. And then it will come out to a specific ganglion here called the otic ganglion.

And this, remember, goes to a gland. Specifically, what gland? It goes to the parotid gland.

Right? So it goes to a gland here called the parotid gland, which basically produces... the saliva that goes into the oral cavity. All right, and there's so many destinations from the sympathetic fibers.

We're not going to go into all that, okay? So again, that's the lesser petrosal nerve, and that moves that way. And then if you guys do remember, just to be, you know, it's always good to have consistency.

There's another one that comes off here off the seventh cranial nerve. If you guys remember, this was actually called the greater petrosal nerve, and the greater petrosal nerve actually runs through this area here. So this is called the greater petrosal nerve. It actually runs up through the hiatus of the greater petrosal nerve and it moves through another hole here called the foramen lacerum.

And then it goes into what's called the pterygoid canal and into the pterygopalatine ganglion and then eventually it goes to the lacrimal glands and then it goes to the actual palatine glands. Okay? So again, that was the greater petrosal nerve. Okay? And again, it moves up through the hiatus and then it goes through the foramen lacerum.

And then it goes down through the pterygoid canal and into the pterygopalatine ganglion and into the lacrimal and then the palatine and nasal glands. All right, holy crap, we did that. Okay, so what have we covered so far?

We covered the promontory. We talked about the tympanic plexus. So we talked a lot about the nerve supply. So we did that.

So we did the nerve supply with the glossopharyngeal nerve. Oh, you know what we did not do with the external ear? We got to cover one more thing here.

Let's do this in, let's do it in purple. Let's do it in purple here. There's actually nerves that supply. If you guys remember, we talked about this in those videos. Remember we had the fifth cranial nerve, cranial nerve five?

It gave off what's called an auriculotemporal branch. So it gives sensory supply to the skin of the external ear and a little bit here to the external acoustic meatus. That was the cranial nerve 5. What else did this too? Remember cranial nerve 10 and cranial nerve 9?

Glossopharyngeal nerve. So here I'll put here cranial nerve 9 and cranial nerve 10. These also supply this. Remember cranial nerve 10, so it gives a supply to the actual tympanic membrane.

Cranial nerve 9 specifically actually gives supply to like the inner part of the tympanic membrane. And then there was another one too which is cranial nerve 7. And cranial nerve 7 also gives fibers out here too. So we can even put here one more cranial nerve 7. And cranial nerve 7 also gives supply to the external acoustic meatus and a little bit of the tympanic membrane.

So just reminding you guys that there is a lot of sensory fibers. that are located within the external acoustic meatus and on the tympanic membrane, external part of it, and internal part of it. So just in general, I want you guys to remember what nerves are going to be supplying the external ear and a little bit of tympanic membrane. It will be the ninth cranial nerve, glossopharyngeal, tenth cranial nerve, vagus, seventh cranial nerve, facial, and fifth cranial nerve, trigeminal. Okay, now we cover all the nerve supply.

So sweet goodness, we did the nerve supply. We did the stapedias, we did the promontory, we talked about the facial canal, and we talked about the ossicles. Let's now do the tensor tympani and what is its purpose and what is basically serving it. Okay, well we talked a little bit about the tensor tympani.

Over here, right? What did we say that the tensor tympani was doing? It was connecting to the malleus and it was pulling the malleus medially, okay? So towards the medial wall, which tensed up the tympanic membrane because you know that the malleus is actually connected to the tympanic membrane here.

Alright, so now let's see how this is actually affecting. So let's come over here. If you guys remember, we had another nerve and we talked about him plenty of time. We have a huge video on him, cranial nerve. right?

The trigeminal nerve. We have the mandibular division of it. So let's say it gives off, remember it has the three branches.

One is the V1 ophthalmic, V2 maxillary, and V3 is going to be mandibular. Well, from the V3 division, it gives off a branch that supplies this muscle right here. Okay, what is this muscle again here called?

This muscle is called the tensor tympani. And what does the tensor tympani do? When the tensor tympani contracts, It pulls.

So imagine here it's connected to that bone. Obviously the bone will be all the way over here, but I'm just doing it for the sake of it. Okay?

What is this bone here called? This is called malleus. It pulls malleus medially. So it pulls the malleus medially.

When it pulls on the malleus, it tenses that tympanic membrane. When you tense the tympanic membrane, whenever the compression and decompression of the tympanic membrane is trying to create those vibrations of the ossicles, that'll be dampened a little bit. Okay?

And the purpose of this is, you guys know when you're chewing food, okay, muscles of mastication, you know when you're chewing food, right, so you have the temporalis, you have the masseter, you even have other muscles like the medial and lateral pterygoid, a whole bunch of different muscles that are involved in mastication, right? But when you're chewing, you can produce a lot of sounds, a lot of sounds. What happens is the trigeminal nerve is so kind to us and it gives off a branch of the tensor tympani, which tenses the tympanic membrane.

If it does that, whenever we're chewing food during the mastication process, It dampens that so that we don't produce so much loud sounds during the eating process or the mastication process when you're chewing your food. Okay, so you better thank your trigeminal nerve next time you're eating and it's not super, super loud. Okay? And also thank your facial nerve who gives supply to the stapedius too because that's also another one who's really important. Because if he gets damaged from Bell's palsy, you could actually cause hyperacusis where remember it can actually continue to keep tapping on the oval window continuously.

and you become very, very sensitive to sounds. Remember I told you you have to hold the phone out here for some people because it hurts so much if people are talking to their ear. All right, cool, covered that.

Now, one other thing I wanted to talk about, I didn't write it up there, I'm sorry about that. Well, I want to talk about this tube right here. This is a very, very important tube. So it's called the pharyngeal tympanic tube. They have so many names for it.

They can call it the auditory tube, the eustachian tube, or we can call it the pharyngeal tympanic tube. I'm just going to call it the phryngiotympanic tube. You can pick from whatever three.

Again, phryngiotympanic tube, eustachian tube, or auditory tube. Whichever one. What is the purpose of this sucker here? Okay? This guy is connecting with a specific part within our throat.

Let me actually show you over here because it's way better because it's perfect. It's perfectly connected over here. Let's say again, what wall would this one be? This would be the medial wall. You can tell that because it's right next to the promontory.

This would be the posterior wall. This would be the anterior wall. Okay?

Now what happens is on the anterior wall, there's actually going to be a nice little tube here. A nice little tube. And this tube connects into the pharynx.

It connects into the pharynx here. And what happens is what this can do is it can equalize the pressure between the atmosphere and the middle ear. Because what's normally the pressure outside in the atmosphere?

Atmospheric pressure is normally 760 millimeters of mercury. Well this one you want to equalize these pressures so that doesn't cause any problems here developing within the middle ear because obviously that could lead to a lot of different situations if there's pressure accumulation in here. Right?

It might cause abnormal certain sensations like tinnitus if it's if it's occurring. We don't want that. So what happens here any air and I'll explain where that air can come from can be moved from the middle ear out into the external environment or from the external environment we can bring some of these air in here.

It's the whole purpose of the pharyngeal tympanic tube is to equalize pressures with atmosphere and middle ear. That's the whole purpose of it. Okay, so at the end of the day just remember that. Purpose of the pharyngeal tympanic tube is to equalize the pressure within the atmosphere and the pharyngeal tympanic tube. If for some reason you need to get the air that is actually maybe you want to actually have some more air come into the actual Middle ear cavity you have this beautiful structure in the posterior wall a nice beautiful A little structure here.

This is called the mastoid sinus. So in the posterior wall, you have a little hole here that connects to the mastoid sinus. So you're going to have a nice little hole back here that connects to the mastoid sinus. And in certain people, not everyone, these people might have mastoid air cells. Not every single person is having mastoid air cells.

Okay, but you do have this mastoid sinus here. And the mastoid sinus is going to have a lot of mucus, right? What can happen is some of the air from this mastoid sinus can actually be pushed over here into the middle ear cavity depending upon the needs. Okay, why am I mentioning this mastoid sinus?

Because in certain situations when someone might have what's called mastoiditis or certain types of infection or inflammation of the mastoid sinus, it doesn't drain into the nasal cavity. So what happens is in certain people, if they have really bad infection, a nasty infection of the mastoid sinus, they have to put in little shunts. Okay, so they have to put in like tiny little shunts here.

that can drain the actual middle ear cavity. Okay, so you actually have to put shunts in that drains the middle ear, I'm sorry, not the middle ear cavity, the mastoid sinus, so that you actually don't have, you want to know why this is important? Because you don't want an infection to develop within the mastoid sinus, because then it can extend.

Where can it actually extend? Come here, I'll show you. The mastoid sinus can be right over here, right?

So pretend I actually draw it right here. I'm going to erase this out of the way here. Imagine it's back here, and here's your mastoid sinus.

What can happen is it can extend upwards into this area. And it can actually affect the glossopharyngeal nerve, it can affect the tenth cranial nerve, the vagus, and it can even affect the accessory nerve. So because of that, if a mastoid sinus infection extends upwards, it can affect a lot of the cranial nerves moving out through that area. Okay?

So that's one of the damaging things about mastoid sinus infections, is that you want to take care of that and make sure that you put a shunt in there to drain out any types of substances that might be in there if it's actually accumulating a lot of fluid. Okay? I'm just going to remember another topic here. Oh, here it was. In the, I didn't talk about the roof.

We talked about the floor of the medullary cavity, but we didn't talk about the roof. And this is probably one of the most important things about the actual tympanic cavity. So imagine here again, if you remember, this was actually, I'm going to shade it in order. This is actually going to be the what wall?

This is the medial wall. This is going to be the lateral wall. This over here, if you imagine, I'll show it like this in green. This wall here is the anterior wall.

And in the back here would be the posterior wall and back here would be the masterly sinus right with the air cells. On the roof it's actually made up of a little bone okay and this bony part here is called the tegmen tympani. The reason why I'm telling you this because it's a very very thin bone and if someone develops what's called otitis media middle ear infection it can actually spread upwards very easily through the tegmen tympani. What is separating the middle ear cavity from the actual cranial cavity. Not very much.

Not very much at all. If you imagine here, let's say that here's the actual roof right here. Okay, that's the tegmentin panni.

The only thing that's really separating it from this point here is just some dura mater. That's all it is. The only thing that's really separating the actual middle ear cavity from the actual cranial cavity is the tegmentin panni and some dura mater. That's it. So if you have an infection, it can actually easily spread up through the tegmentin panni into the actual meninges and cause severe meningitis.

Okay, so very very dangerous it can actually cause infections within the brain too that maybe might cause some type of like abscess or something okay okay so we did that part there sweet so what have we covered so far we covered the mastoid sinus okay and we covered a little piece in there the roof of the middle ear cavity called the tegmentum panna and its significance that's another thing you know certain things is actually we'll talk about later is whenever you have infections and you give Certain types of antibiotics you have to be careful about what type of antibiotic you get because aminoglycosides can actually cause ototoxicity, can actually cause more damage to the ear. We'll talk about that when we get to that video though. Okay, next thing that we're going to talk about is the tensor veli palatinae. Okay, so if you guys remember we said that we had what's called the... what's up again?

We have the trigeminal nerve, okay? The trigeminal nerve or cranial nerve 5, you have some muscles here. They're actually a part of the soft palate. Let's say that one muscle is going to be like this. So I have one muscle like this.

You have a couple different. You have what's called a levator veli palatini. You might even have another one here, which is called the salpingo pharyngeus. And you might even have another one over here, which is called the tensor veli palatini. Okay, so I'll just write these here for a second.

Let's say that this is the levator veli palatini. Let's say that this is the tensor veli palatini. And let's say that this is what's called the salpingo pharyngeus. What happens is, is if you remember the trigeminal nerve, the fifth cranial nerve, the fifth Cranial nerve, cranial nerve 5 has the mandibular division that gives fibers to the tensor veli palatini. And the tensor veli palatini, what is it going to do?

It's actually going to tense the actual soft palate. Another thing is it's not going to be supplied by the 5th cranial nerve, but if you guys remember, we have the 10th cranial nerve. So cranial nerve 10. It came through the pharyngeal plexus and it supplied the salpingo pharyngeus and it supplied the levator veli palatini. Whenever the cranial nerve 10 supplies the salpingo pharyngeus, that actually elevates the soft palate and the levator veli palatina elevates the soft palate. But the salpingo pharyngeus does something else.

It's actually connected to the pharyngeal tympanic tube, a little cartilaginous lamina. And it can pull on that cartilaginous lamina of the pharyngeal tympanic tube to help to equalize the pressures. Between what? Between the middle ear cavity and the atmospheric pressure. Alright, so what have we covered then?

We've covered also the tensor velipalatini and the other connection, which was the salpingo pharyngeus. Alright, so that covered that part. Alright guys, so we talked a lot about the external ear.

We talked a lot about the middle ear cavity, the tympanic cavity. We went over a lot of different things. In future videos, we'll talk about something else a little bit later called a cholesteatoma, which can accumulate within the middle ear. And it can become very, very, very dangerous.

Okay? That will be a discussion that we will talk about later when we get to the inner ear structure and how that can affect the actual auditory impulses. Okay, so we will talk about cholesteasomas. But we talked a lot about a lot of different things about the middle ear and the external ear. I really hope it made sense.

I really hope that you guys enjoyed it and you learned a lot. If you guys did please hit the like button, comment down in the comment section and please subscribe. As always Ninja Nerds, until next time.

Transcript for:Understanding the External and Middle Ear Anatomy

Transcript for:
Understanding the External and Middle Ear Anatomy