Hey what’s up. Meditay here. Let’s talk about the anatomy of the respiratory system. In this segment, we will be talking about the anatomy of the Larynx. Alright, so the respiratory system consist of all the organs involved in breathing. These are the Nose, Pharynx, Larynx, Trachea, Bronchi and the Lungs. In our last video, we covered the anatomy of the nasal cavity. Now let’s do the anatomy of the Larynx. So in this video, we'll start with orientation by looking at the anterior and posterior view of the Larynx. Then we'll talk briefly about what cartilages make up the larynx. As well as the ligaments and joints that hold the whole thing together. Then we'll do the walls of the Larynx and talk a little bit about what’s special with the Laryngeal cavity. Alright, so the Larynx is located right about here. It lies between the Hyoid Bone, and the Trachea. And right in front of the Esophagus. Topographically, it starts in the region of 4th 5th Cervical Vertebrae, and ends at the region of 6th-7th cervical vertebrae. Let’s list a few of Larynx’s functions. The first is Air passage. It serves as a passage, so that air can go down into your lungs. Another thing is that your Larynx is also called the Voice Box, because it produces sound. And it does that through a process called Phonation, where these vocal cords rub into each other producing different pitch. I’ll go through this at the end of this video. Now let’s continue with the orientation by looking at the Larynx from different angles. So, if you look at it anteriorly This is how it's gonna look like. And posteriorly This is how it's gonna look like. Notice the hyoid bone above the larynx, and the trachea under it. Now let’s start by understanding how the Larynx is built. So the Larynx is made up of 6 types cartilages in total. 3 paired and 3 unpaired Cartilages. Cartilages that are unpaired means that you only have one of each, and these are the Epiglottis in Purple, Thyroid cartilage, in blue. And the cricoid cartilage, here in light green. The paired, are the cartilages you have two of. These include the Arytenoid cartilage here in yellow, Corniculate cartilage in red, and the Cuneiform cartilage, here in green. These are the cartilages that make up the Larynx. Now let’s switch up to a model from my anatomy program, just to make it look a little more realistic. We have the Epiglottis, The thyroid cartilage and the Cricoid cartilage. We have the Arytenoid, the Corniculate and the Cuneiform cartilages. Let’s now cover each of these cartilages and look at their characteristics, we’ll start with he thyroid cartilage. So again here’s an anterior view and a posterior view of the Larynx. The thyroid cartilage is highlighted here in blue. And just to have an overview, I think it’s better to have a list of the cartilages we’re about to cover. Now the thyroid cartilage is mainly made up of two plates, or two Laminas. There’s the Right lamina, and the Left lamina. These two meets in the middle, and form the laryngeal Prominence, which is also known as Adam’s apple. You’ll notice there are two processes on the thyroid cartilage as well. There’s one going straight up towards the Hyoid bone, called the superior horn, and a process going down towards the cricoid cartilage, called the inferior horn. So that’s the most important structures of the thyroid cartilage for now, let’s check that one from our list. Next is the cricoid cartilage, here in light green located below the thyroid cartilage The cricoid cartilage looks different, depending on which side you’re looking from. Anteriorly, it has an arch protruding forward, and posteriorly, it has a plate with two important surfaces. There’s the arytenoid articular surface, which is where the arytenoid cartilage binds to the cricoid cartilage forming a joint. And it has a Thyroid articular surface, which form a joint with the inferior horn of the thyroid cartilage. So that’s all for the cricoid cartilage, let’s put a checkmark here. Next is the Epiglottis, which is here in purple. It doesn’t really have any specific structure of importance for now. But it lies behind the thyroid cartilage and the hyoid bone, and if you look at a posterior view. It mainly attaches to the thyroid cartilage through ligaments. Its function is mainly closing off for the respiratory system when you swallow and open up when you’re breathing. So that’s the epiglottis. Next is the Arytenoid cartilages, which are paired. They’re located here in yellow, right above the cricoid cartilage. And if you look at them from a sideview, you’ll notice that it has a triangular shape, which an Apex on top, and a base. The base has two parts, or two processes. The anterior process is called the vocal process, since it attaches to the vocal ligament, I’ll show you this later. The posterior process is called Muscular process, which serves as an attachment point for certain muscles. And the base of the arytenoid cartilage, is called Cricoid Articular Surface, since it sits on the cricoid process. So that’s this one. Next we have the corniculate cartilage, which is here in red, and lie on top of the arytenoid cartilage. It doesn’t really have any specific function on its own, other that serving as an attachment point for certain muscles as well. So, let’s tick that one. The last cartilages are the Cuneiform cartilages, here highlighted in green. They’re two small, elongated pieces of yellow elastic cartilage, which lie in something called the aryepiglottic fold. The aryepiglottic fold is essentially a fold that lines the entrance of the Larynx. And the Cuneiform Cartilage form a tubercle on it, which is visible if you’d examine the larynx of a patient. This tubercle is called Cuneiform tubercle. So, let’s go ahead and tick that one as well. So those are the cartilages that make up the Larynx. Now we need to cover the connections in the Larynx, or the Juncturae Laryngis. But to really understand these connections, we need to have a basic understanding of the different connection forms we have in our body. So the articular system in the Larynx si divided into two types of connection. There are Continuous articulation, and discontinuous articulation. Now what are the differences between those? Continuous connections are uninterrupted articular connection, hence the name continuous. Discontinuous connections are interrupted in that, it contains a cavity within the articulation, which form a joint. Now, I like to use the ribs as an example of the continuous connections in the Larynx. Because one of the connection types is called cartilaginous, or Synchondroses. Which is where you’ll find at the point where the rib meets the costal cartilage, called the costochondral synchondroses. The other type of continuous connection you’ll find in the Larynx is a fibrous type of connection, which form membranes, or Ligaments. Very much like the intercostal membrane you see here. Discontinuous connections are joints. In the Larynx you’ll find two synovial joints, just like this one, which are ligaments forming a sac full of synovial fluid. Now let’s do the continuous connections of the Larynx first, then do the discontinuous connections. The Larynx has only one cartilaginous connection point, and that’s between the corniculate cartilage and the arytenoid cartilage. So here is the Larynx. Here is the Corniculate Cartilage, and here is the Arytenoid Cartilage. Here is the cartilaginous connection. It’s a very dense connection, nearly bony joint. For the fibrous connections. We have the Thyrohyoid membrane, which is a membrane between the thyroid cartilage and the hyoid bone, as you see here, so this in green is the thyrohyoid membrane. Theoretically, it has two parts. A median Thyrohyoid membrane and a lateral thyrohyoid membrane, as you see here. Next we have the Cricothyroid membrane, which lies between the Thyroid cartilage and the Cricoid Cartilage. So it’s this one. The cricothyroid membrane is a membrane that are made up by two ligaments. One of them is the median cricothyroid ligament, and the other one is the lateral cricothyroid ligament, or conus elasticus. The conus elasticus is really important, I’ll talk briefly about it later in this video. Then there’s the cricotracheal ligament, between the cricoid cartilage, and the trachea, as you see here. Then we have the thyroepiglottic ligament, which is this one, connecting the Epiglottis to the Thyroid cartilage. And then we have the Hyoepiglottic ligament, which connects the Epiglottis to the Hyoid bone, as you see here. So all of those are the Continuous connections we have in the Larynx. Now let’s do the Discontinuous connections. We have two synovial joints in the Larynx, and if you really paid attention earlier in this video, you’d know these already from when I talked about the cricoid cartilage. Because the first one is the cricothyroid articulation, which is a synovial joint between the inferior horn of the thyroid cartilage, and the cricoid cartilage. The other one is the Cricoarytenoid articulation, between the base of the arytenoid cartilage and the cricoid cartilage. They look like this, filled with synovial fluid for a nice movement of the larynx. Now. Here you see a lateral view of the larynx. If we make a vertical cut of the larynx, as you see here. And look at it from this view, you’ll see this. So, let’s go over some important landmarks. There’s the Epiglottis, The thyroid cartilage, the cricoid cartilage, and the hyoid bone. And between the cartilages, you’ll find the Thyrohyoid membrane. So, let’s now cover the walls of the Larynx. The larynx has 4 layers. We have the Tunica Mucosa, here in blue. Then underneath that, there’s the Tela submucosa, as you see here. Then you have a layer of cartilages and muscles, as you see here. And lastly, there’s the Tunica adventitia, which are connective tissue covering the surfaces of the larynx. Now, let’s go through each of these layers and look at their characteristics. We’ll start with Tunica Mucosa. So again, the tunica mucosa is here, it’s the innermost lining of the Larynx. At the vestibular folds, which is the upper fold, it’s lined by Respiratory epithelium, which are epithelium specialized in filtrating the air, as they contain cilia that catches small particles before they go further down into your lungs. The Vocal folds, are lined by stratified squamous epithelium, which are essentially logical because the vocal folds are under a lot fo strain, allowing you to speak loudly and for a longer period of time without harming your vocal folds. In chronic smokers and people who use their voices a lot like in singers, the respiratory epithelium lining the vestibular folds are often damaged and replaced by stratified squamous epithelium, which makes them more susceptible for lower respiratory infections, since the cilia of the respiratory epithelium are gone. So that’s the lining, but the tunica mucosa also contains glands, or laryngeal glands, lubricating the surface, and small lymph nodules for immunity. So that’s the tunica mucosa. Next we have the tela submucosa, which are here. Remember earlier when we went through the connections of the Larynx, where we talking about the continuous connections, specifically the fibrous membranes of the Larynx? Well, at some places the Fibrous membranes form a so called Fibroelastic membrane, which are elastic membranes playing a key role in you being able to speak. There are two fibroelastic membranes in the Larynx. The first one is the Quadrangular Membrane, which are here. If we look at a posterior view of the Larynx. It’s much easier to see this membrane. It’s a membrane that goes between the Vestibular Folds and the Epiglottis, as you see here. There’re two margins left that aren’t connected to anything, The upper margin, form the aryepiglottic fold, if you remember from earlier, the aryepiglottic fold is a fold lining the entrance of the larynx. The lower margin forms the vestibular ligament, which is a ligament you see down here, going between the arytenoid cartilage and the thyroid cartilage. The other fibroelastic membrane we have is the Conus Elasticus, or the Lateral Cricothyroid Ligament. It’s this one, if you remember it from earlier. IF we turn it around, you’ll see that it’s connected to the Cricoid cartilage, the Arytenoid cartilage and the thyroid cartilage. But it has one free margin, and that’s the upper margin, which form the Vocal ligament. This ligament is a part of the vocal fold which is the fold that makes it possible to speak once they vibrate, I’ll show you this later. So that is the tela submucosa. Next, we have the Cartilage and Muscle Layer, as you see here. We’ve already covered the cartilages, but the muscles of the Larynx are grouped according to their function. So we have three groups of muscles in the Larynx. The first ones are the muscles that open and narrow the laryngeal inlet, or the entrance, so this one. It opens and narrows this entrance into the Larynx. The next ones are the muscles that open and narrow the Rima Glottidis. And the Rima glottidis is here, situated between the Vocal folds, or the Vocal Cords. The fold superior to the Rima glottidis is called Rima Vestibuli, between the vestibular folds. And again, don’t forget that the Vocal Ligaments are here, as you remember earlier, formed by the superior margin of Conus Elasticus. So, the vocal ligament is a part of the vocal cords. And the Rima glottidis is between the vocal cords. And if we look at the larynx looking from this direction, you’ll see this. With the epiglottis here and the aryepiglottic fold here. So the vocal ligament is located right about here. Always remember that this pointy end is the anterior side, and the rounded one is the posterior side. Now. Rime glottidis is here, between the vocal cords, rima vestibuli, is here, between the vestibular folds. So, the muscles that open and narrow the rime glottidis, work like this. They open, or narrow. The rima glottidis. The last muscle group are the muscles that act on the vocal cord itself. Earlier I told you that the vocal ligament is situated here, but that’s not entirely correct. Look closely at the structures here. The vocal ligament is located within the mucus membranes. So the mucus membrane together who the vocal ligament, is what’s referred to as the vocal cord, so that’s essentially what I mean by the last group of muscles. They act directly on the vocal cord, which essentially is the vocal ligament. There are muscles that tenses the vocal cord, such as the cricothyroid muscle. This muscle is situated here, as you see. And when they contract, they pull the thyroid cartilage to the front, tensing the vocal ligament. If we look posteriorly, and zoom in. When the thyroid cartilage move forward, the vocal cord is tensed. The other muscles decrease the tension of the vocal cord, such as vocalis muscle, situated right next to the vocal cords, as you see here. And when they contract, they pull the arytenoid cartilage forward to decrease the tension of the vocal cord. Lastly, we have the Tunica Adventitia. So here’s the Larynx. Tunica adventitia is a covering around the larynx, which is a tough connective tissue consisting mainly of dense collagen fibers. So that was the Layers of the Laryngeal Wall, the last thing I wanna talk about in this video is the Laryngeal Cavity. So the Laryngeal Cavity, or Cavitas Laryngis, is this whole cavity here. It starts at the Laryngeal Inlet, or entrance, and ends at the lower border of the cricoid cartilage. But we generally divide it into three landmarks. The first one is the Laryngeal Vestibule, going from the laryngeal entrance to the Vestibular Folds. Then there’s Glottis, between the Vestibular Folds and the Vocal Cords, or the Vocal folds it’s a synonym. There’s an important thing we need to discuss here. Remember, the Rima glottis is here. We generally divide this cavity into two parts based on the structures around it. The anterior 3/5 is called intermembranous part, since it’s between membranes. The posterior 2/5 is intercartilaginous part, situated between cartilages. And if we change up to a more realistic one. Here you see that the anterior 3/5 of it is between membranes, and the posterior part lying between cartilages, between the arytenoids here. Now why is this important? Because they give you the possibility to speak! When you’re speaking, the vocal cords rub into each other, in a process called phonation. But when you breath, the folds are open for air to pass through. Now when you look closely at the glottis, notice there is a pouch at either side, called Laryngeal ventricles, which acts as a resonator. It resonates the sound as you speak. From the Vocal Cords, we have the Infraglottic cavity, which is until the lower border of the cricoid cartilage. From this point. That’s where your Trachea is going to be. And that’s a topic for our next video.