Dear friends, this is Juan José Sánchez, welcome once again to another anatomy video. Today we will talk about the anatomy of the pharynx, which, due to its content, I decided to divide it into two videos. At the end of this video I will leave you the link so you can watch the second video. In this first shot we will talk about the generalities of the pharynx, as well as its layers; First of all, the pharynx is nothing more than a muscular tube of striated muscle, that is, a muscle that we can find mostly at will that will form a hollow space in everything that is posterior to the oral cavity and posterior to the nasal cavity, anatomically it will go from the base of the skull, see that it begins at the base of the skull exactly where these bones are, this would be the sphenoid bone, specifically the body of the sphenoid and see here the joint with the occipital bone , specifically with the bacillary portion of the occipital bone, that would be its upper limit, what is called the base of the skull; while its lower limit will be at the level of this vertebra, which is C6, it will precisely correspond to the lower edge of this cartilage, it is the cricoid cartilage and that is why it is said that it goes from the base of the skull to the C6 vertebra, it It is going to continue below with what is the esophagus, okay? but upwards it will have communication with what is the nasal cavity, with what is the oral cavity and with what is the larynx, that is why the pharynx is a quite complex structure because there is a union of two large systems of the body, there is a union of the respiratory system with what is the digestive system, it is seen in the following image, well we see a posterior view of the pharynx, in the previous image it is a lateral cut so in this image we are going to see the pharynx in In the posterior part we also see the communication with the nasal cavity, the communication with the oral cavity forward and the communication with what is the larynx just below the communication with the oral cavity, this elevation that you see here that corresponds to the cricoid cartilage , then as I told you, the lower edge of the cricoid cartilage tells me that the pharynx reaches there, so from there downwards is where the esophagus begins, which I just said is the lower continuation of what the pharynx is, this is a posterior view With all its muscular apparatus we see that laterally it is related to the styloid process and the muscles that are inserted in it, I am referring to this one, which is the stylopharyngeus and this one, which is the stylohyoid muscle, as well as with masticatory muscles such as the This is the medial pterygoid muscle, in addition to that, see this is a view of a cross section that was made at the level of C2, we are seeing it from the top down here we can see the tongue, this would be the pharynx, this hole that you see Here is the entrance to what is the larynx, okay? then this would be the lowest part of the pharynx, almost reaching the esophagus, see then that later it is related to what are the first six cervical vertebrae from C1 to C6 with these two muscles that are the prevertebral muscles, specifically this would be the length of the neck, remember also that these pre-vertebral muscles were wrapped by the pre-vertebral aponeurosis which would also be a posterior relationship of what is the pharynx, laterally it will be related to the neurovascular package of the neck, see the following image how it is related with what is the internal carotid as is this case here and it is related to the common carotid, as well as with the internal jugular vein in the vagus nerve that would be a posterolateral relationship, it also has a very intimate relationship with the thyroid gland because see that the thyroid gland, this is a later view I remind you, embraces both the esophagus and the lower part of what is the pharynx, so structurally the pharynx has three large divisions, a more superior division that would be the rhinopharynx or nasopharynx. because? because it is located behind the nasal cavity, for the Greeks that was the nasolana but for the Latins that was the rhino, nose is rhino, so it is indistinct what I want to call it, I can call it or rhinopharynx or nasopharynx. Then we have the part of the pharynx that is posterior to the oral cavity, which is what the Greeks called it, but for the Latins it is an oral cavity, which is why we can call it oropharynx or oropharynx and finally the part of the pharynx that is behind What is the larynx, okay? We are going to call that part the laryngopharynx, which will be the most inferior and final portion of the pharynx. After the laryngopharynx, when it reaches the lower edge of the cricoid cartilage, it becomes the esophagus. See this later view, this would then be the nasopharynx. , this would be the oropharynx and this would be the laryngopharynx. So the pharynx is going to be made up histologically of four layers: first, the innermost layer, which is the one we see here, which is the one with many structures that we will specify in the next video, this layer is made of epithelium, that is what What we call the mucosal layer, in medicine the mucosal layer is not a layer that has mucus, it is called that because those mucous layers generally have mucus but mucous refers to epithelial tissue, so this epithelium that covers the pharynx on the inside is what We call the mucosal layer, then if we section that mucosal layer we find a bilayer. Why a bilayer? Because it is the muscular layer along with the fibrous layer, I am going to start talking to you first about the fibrous layer: the fibrous layer is what gives it the structure, which serves as the skeleton of the pharynx so that it adopts that shape, this fibrous layer They are going to be that series of tendons and ligaments of insertion of precisely the muscular layer, that is why I am giving them together, for example up here you see that the muscular layer is inserted into the base of the skull thanks to this aponeurosis that is the fascia p pharyngobacillary aponeurosis, here below see how the longitudinal muscles of the pharynx are inserted into what would be the layer or pharyngeal aponeurosis, then all these fibrous structures see it here ahead the pharyngobacillary aponeurosis, see the tendinous rapha, the tendinous arch sorry, Look at this structure that is behind the stylohyoid ligament, which is fibrous, which is what makes up the fibrous layer, which is the skeleton of the pharynx, then the muscular layer, well, these are precisely those muscles that we will see in more detail right now, which is muscle. striated to remember that we can find at will that they conform to the pharynx and then outside that muscular layer there we have the fourth and last layer of the pharynx which is the adventitial layer, that adventitial layer is this one that you see here that It erases from the outside what the pharynx is. That adventitial layer is formed by this aponeurosis, which is the oropharyngeal aponeurosis. This one you see here is the oropharyngeal aponeurosis. It is called that because it covers both a muscle of the mouth and the buccinator muscle. like the constrictor muscles of the pharynx but on the outside, so much so that after the adventitial layer in the posterior part we find a space, see this gap that is there, that is the retropharyngeal space and after the space our pharyngeal, well What is coming is the prevertebral aponeurosis of the deep cervical aponeurosis, okay? Now see in this image again what the epithelial layer that is lining it on the inside looks like, then the muscular layer along with the fibrous ones that here you can see insertions with the pharyngobacillary fascia and finally, on the outside of what is the muscular fibrous layer we go to find the adventitial layer which is what forms the oropharyngeal aponeurosis, in this image we see much more schematized in this green line, that green line corresponds to what the oropharyngeal aponeurosis is. You see that after it is posterior to what the oropharyngeal aponeurosis is. pharynx continues its journey being posterior to what is the esophagus, that would be the adventitial layer. Now we are going to talk about the mucosal layer, well the mucosal layer, as I told you, are epithelia of the pharynx epithelium, it is different in its portions and that depends on the type of system it corresponds to, it is very easy I will explain to you, the respiratory epithelium in anatomy is a ciliated pseudostratified cylindrical epithelium, they have to have cilia because those cilia are little hairs that have a very important respiratory that is not relevant, then the nasal cavity together with the nasopharynx share the same epithelium, which is the ciliated pseudostratified columnar epithelium, ok? because that is clearly the air system of the respiratory system because the only thing that passes through there is air, but the oropharynx and laryngopharynx are mixed structures because as much air that comes from the nasal cavity and the oral cavity as food will pass through there. that come from the oral cavity, that is why the epithelium of the oropharynx and laryngopharynx must also be prepared for the passage of food because they are also part of the digestive system, they must have digestive epithelium and that digestive epithelium is the stratified epithelium non-keratinized plane, in many books instead of finding it with the name of plane they find it with the name of squamous, scaly and flat is the same because the scale of fish or a scale is flat, so in anatomy the scaly planes is what same. So see here how the respiratory system shares both the bucopharynx and the laryngopharynx along with the digestive system because it is a common pathway, so that is why the bucopharynx and the laryngopharynx have the same epithelium because they are digestive tracts. and air, but the nasopharynx only passes air through there, food does not pass through there and that is why its epithelium is different, it is purely respiratory. After the mucosal layer, I will explain the muscular layer, which are the muscles that make up the pharynx. This muscular layer will be made up of two groups: an external group of muscles, which are three, which are circular. See that the muscle follows a content or a let's say a circular path, but when we section in the internal part we will see that there are muscles that run longitudinally from top to bottom. Let's start with the circular layer, we start then with the superior constrictor muscle of the pharynx, that superior constrictor of the pharynx has three places of origin, it originates first in the pterygoid hook of what is the sphenoid bone, it originates from the which is the lower jaw, as well as the lateral edge of the tongue, some authors name this raphe that you see here called the maxillary pterygoid raphe because they see that it goes from the pterygoid process to what is the lower jaw, so there some Authors say that there is also the origin of the superior constrictor muscle of the pharynx as can be seen in this image, then towards the back one more insertion that I forgot to tell you about the lateral edge of the tongue, in this image it is not seen but in another image I will explain them to you later, see that this superior constrictor muscle of the pharynx is directed backwards in a circular manner and is inserted into the oropharyngeal aponeurosis, which would be sorry, pharyngobacillary, which would be this, and into what is the pharyngeal tubercle , which is a bony extension that It has the bacillary portion of the occipital bone, in addition to that, a tendinous raphe reaches the midline, which is called the middle pharyngeal tendinous raphe. All the constrictors of the circular layer have an insertion in that middle tendinous raphe. After the superior constrictor, we will then talk about the middle constrictor, that middle constrictor has two places of origin: one is the hyoid bone specifically at the junction of the greater horn with what is the lesser horn, which is this angle that you see here, and the other is the stylohyoid ligament, which is this ligament. What you see here, what happens is that the origin of this muscle is covered here by the hyoglossus because precisely the origin is covered by that muscle, but see in the following image I have a medial view of the pharynx, see what we are seeing the pharynx but inside the oral cavity, this would be the upper constructor, okay? and here it would be the inferior constrictor, see the lesser horn of the hyoid bone, see the greater horn and how the union of that angle is what originates what is the inferior constrictor muscle of the pharynx, as well as this ligament, which is the ligament stylohyoid, I take advantage of this image to show you the superior constrictor, this would be the maxillary pterygoid raphe, there is the pterygoid process, here in the middle you can see the tip and here the lower jaw, this little bit that you see here, this extension is the one that goes towards the lateral edge of the tongue, the one that I told you just now is one of the origins of the superior constrictor, okay the image to explain this. Then finally see in the posterior part how the middle constrictor comes then the greater horn which is this what you see here, up to what the middle tendinous raphe which would be the insertion of the superior constrictor muscle of the pharynx, then the inferior constrictor is important because he is the last one, the circular layer he has two places of origin: a place that comes from the oblique line of the thyroid cartilage, okay? which would be the thyropharyngeal portion, which are fibers that go obliquely upwards, but it has a portion that runs from the back of the cricoid cartilage towards what is the pharynx, which are straight fibers, that would be the cricopharyngeal portion, that cricopharyngeal portion is very important. because it also has insertions in the esophagus, that is why it is said that it helps form the upper esophageal sphincter, which is like the valve that has the esophagus on top, which is what keeps the esophagus closed, okay, see in the part posteriorly as then the inferior constrictor also reaches the middle tendinous raphe, its oblique fibers that would be the pharyngeal fibers while its transverse fibers that would be the cricopharyngeal fibers reach both the pharynx and what is the most superior portion of the esophagus. Now we talk about the longitudinal layer, which is very easy, it also has three muscles. We start first with the palatopharyngeal muscle. It is called that because it comes from the soft palate, but its origin itself is on the dorsum of the bony palate and its insertion fibers on the side walls. of the pharynx, as well as having insertions in what is the thyroid cartilage; Then we have the salpingopharyngeal muscle, salpingo in anatomy salpin means tube, then salpingopharyngeal because it originates in the pharyngotympanic tube, which in this structure that you see here, is also called eustachian tube, auditory tube and is inserted into the side walls of the pharynx is why it is called salpingopharynx and lastly we have the stylopharyngeal muscle that originates in what is the styloid process of the temporal bone, it is inserted between the superior and middle constrictor of the pharynx and see it here how it comes out, if it is this What happens is that here they cut the pharynx in half and opened it like a sheet, so this one here is this same stylopharyngeus that goes between the superior and middle constrictor, see here how it is coming out between the superior and the middle then This stylopharyngeal originates in the styloid process and is inserted into what is the thyroid cartilage as well as into the lateral walls of the pharynx, okay? So the function of these muscles will be mainly swallowing, the main elevators of the pharynx, which are the ones that are least kept elevated, are the stylopharyngeus and a muscle that is not part of the pharynx but that helps to elevate what is the tensor pharynx. soft palate that we will see in the palate videos. To finish, the innervation of the pharynx is of two types: a sensory innervation, which is what innervates the mucosa, we can have a gag reflex, we can feel tactile sensations of cold or heat in the pharynx, that sensitive pharyngeal plexus comes given by the glossopharyngeal nerve, the afferent fiber that goes to the central nervous system goes through the glossopharyngeal, it is so sensitive that the glossopharyngeal also sensitively innervates the palate and the posterior third of the tongue, but motorally all those muscles of the pharynx move them the vagus nerve, okay? It is the one that mainly gives the motor innervation, which forms the pharyngeal plexus, but listen carefully, this nerve that you see here would be the vagus and this one down here is the eleventh cranial nerve, which is the accessory nerve, that accessory nerve of a cranial branch that joins the vagus and the authors all agree that in that cranial branch of the eleventh cranial nerve which forms the majority of the fibers of the pharyngeal plexus, then the pharyngeal plexus is formed by the vagus but the information, The innervation, as they say, is given by the eleventh cranial nerve, so be very careful with this detail, specifically with the cranial branch that joined the vagus. So the vagus, through the pharyngeal plexus, is going to innervate me. Listen, it is very important to all the muscles of the pharynx except one. That exception is precisely the stylopharyngeal muscle, which is the only muscle of the pharynx that is not generated by the vagus. because? Because this stylopharyngeal muscle is motorally innervated by the glossopharyngeal nerve, okay? which, by the way, is the only muscle that is innervated by the glossopharyngeus because it does not innervate a muscle, in addition to this this pharyngeal plexus innervates all the muscles of the palate that you do not see in these classes but take advantage and I will tell you all those of the soft palate except one which is the external peristaphaline muscle, that external peristaphaline muscle is not in this image but it is also called the tensor veli palatini and the one innervated by the trigeminal nerve but not by the vagus nerve, ok? In addition to this, I tell you that the inferior constrictor has double innervation, that is in very few books but they say that it is innervated by both the pharyngeal plexus of the vagus and the superior laryngeal nerve, okay? which is a branch of the vagus, see that the superior laryngeal nerve gives an external branch and this external branch innervates the cricothyroid, which is from the larynx, which we will see in another video, like the inferior constrictor since this inferior constrictor has double innervation, The irrigation is given mainly by branches of the facial artery, we are going to see the ascending palatine artery, which we see here, as well as the tonsillar branch of the facial artery, in addition to that we are going to see the ascending pharyngeal artery, which is a branch of the external carotid that helps irrigate what is the pharynx, as well as branches of the subclavian, very important the inferior thyroid artery, which is a branch of the subclavian that gives an inferior laryngeal artery and that inferior laryngeal artery although it is not In this image it also helps to irrigate what is the pharynx. So friends, this has been the entire video, I'll wait for you in the next video, right now I will leave the link here so you can see it in which we will break down the structures, the ultra structure that the parts of the pharynx have, the parts that the nasopharynx has , the oropharynx, laryngoarynx which was too long to do in a single video. Don't forget to give it a thumbs up below, share it and subscribe to the little circle that appears here, also follow me on Instagram at @juan_sanchez1315. Thank you very much for your collaboration!