 Good day everybody, Dr. Sanjosh Sanyal, Professor of Department Chair. This is going to be a demonstration of the laryngeal pharynx from the pustry aspect. We can see this structure in front of us, this is the laryngeal pharynx. It extends from C3 to C6, and this also is the same limit of the larynx itself. We can see these muscle fibers here. These are the muscles of the inferior pharyngeal constrictor, which I shall mention just now. But before that, this was covered by two layers of fascia. One was the buccal pharyngeal fascia, which is the upward continuation of the pre tracheal fascia. The reason why it's called buccal pharyngeal fascia is because the fascia covers the buccinator muscle anteriorly. It forms the pterigomandibular raffae and also covers the superior pharyngeal constrictor of the pharynx. That's why it is called buccal pharyngeal fascia. So we removed the buccal pharyngeal fascia. The space between the buccal pharyngeal fascia and the vertebral column, which is of course not here, is the retro pharyngeal space, which is the potential site of abscess formation, which can communicate with the posterior varia strana. It was a thin layer of fascia called the ALR fascia. We have removed all that and now we can see the muscles. In this particular dissection, we can see only the inferior pharyngeal constrictor. And these muscle fibers that we see, these are the thyropharyngeal parts of the inferior pharyngeal constrictor. In the midline, they fuse to form a pharyngeal raffae, which is actually a thickened part of another fascia, which is present on the inner surface and that is known as the pharyngobase raffae. Pharyngeal raffae gets attached to the pharyngeal tubercle on the base of the skull. And it continues down and both the sides, pharyngeal constrictors fuse and meet at the pharyngeal raffae, which is the thickened part of the pharyngobase raffae. To continue with the thyropharyngeal muscle, we can see that the upper fibers are more oblique. And if you look lower down, we find that the lower fibers are more transverse. These transverse fibers are the cricopharyngeal part of the muscle, which is taking origin from the cracoid cartilage and going circular across. They are the ones which constitute the cricopharyngeal sphincter or the upper esophageal sphincter. And by looking at this dissection itself, we can see that this portion is very narrow. As indeed, this is the narrowest part of the elementary tract, which is the upper esophageal sphincter, which is located 15 centimeters from the incisor teeth when we are doing an esophagoscopy. And this is the potential site of impaction of foreign body. So this thyropharyngeal muscles, which are oblique and the cricopharyngeal muscle, which is horizontal, there is a small triangular space in between the two. And that triangular space is a potential area of weakness. And that is referred to as chelons dehycens. What is the significance of this chelons dehycens? The chelons dehycens is a potential site of what is known as the zenker's diverticulum, which is the type of pulsion diverticulum of the pharynx. And how does it work? Because this cricopharyngeal muscle acts as a upper esophageal sphincter, if it is under spasm and or if there is improper peristalsis of the esophagus during the esophageal phase of swallowing, the food bolus will try to come down, but it will be obstructed by the cricopharyngeas. And therefore it tends to bulge the mucous membrane at the point of chelons dehycens here. And it will produce a dilatation here. And that is referred to as zenker's diverticulum. It's a pulsion type of diverticulum. When we do radiological image, we will be able to see it as a form of a dilatation between the pharynx and the vertebral column. This is the barium swallow to show a zenker's diverticulum through the chelons dehycens. We have sliced this and I'm going to reflect this to show very important landmarks on the inner surface. Now we are looking at the interior of the laryngopharynx. So what are the landmarks that we can see here? First of all, we can see this depression on either side. This depression is referred to as the pyriform fossa or the pyriform sinus. What are the boundaries of this pyriform fossa? Pyriform fossa is bounded medially by this fold of mucus membrane on either side. We can see this is the ariepiglottic fold. This ariepiglottic fold actually contains a ligament called the ariepiglottic ligament, which is the upper free margin of the quadrangular membrane, which is the one of the fibroelastic membranes of the larynx. And that when it is covered by mucus membrane, it is called ariepiglottic fold. So this is the medial margin of the pyriform fossa. This same ariepiglottic fold also happens to be one of the margins of the laryngeal inlet, which we can see here. The next margin that we can see here is this fold of mucus membrane. This is extending from the epiglottis to the pharynx. This is called the pharyngo epiglottic fold. And we can see the pharyngo epiglottic fold on this side also. So ariepiglottic fold medially, pharyngo epiglottic fold superiorly. Further medially, we have this prominence, which is formed mostly by the lamina of the cricard cartilage. And the lateral boundary of this pyriform fossa is where my finger is located. And if I turn it, we will see that it is formed by the thyroid hybrid membrane and by the lamina of the thyroid cartilage. So this is the pyriform fossa. The clinical significance of this pyriform fossa, there are two important clinical significance. Number one, this is a very common site of fish bone infection when we swallow food without removing the fish bone properly and it gets impacted here. That is one important point. The second point is when we are trying to remove this foreign body, where means of endoscopy, we are liable to injure two nerves, which are running just under the mucus membrane of the pyriform fossa. One of them is coming from above, and that is the internal laryngeal nerve. And we can see the internal laryngeal nerve. When I turn it again, we can see this nerve here. This is the internal laryngeal nerve on this side and when I turn it this side, we can see the internal laryngeal nerve on this side. Internal laryngeal nerve is the upper larger division of the superior laryngeal nerve. And we can see that it is located right under the mucus membrane of the pyriform fossa. So therefore, if you puncture through, we can injure the internal laryngeal nerve and then there will be loss of sensation in the upper half of the larynx and the patient will lose his cough reflex. Lower down in the piriform fossa again under the mucous membrane we have yet another nerve and that is the inferior laryngeal nerve. So when I turn this we can see that the inferior laryngeal nerve is the continuation of the recurrent laryngeal nerve and we can see it here. Similarly on this side we can see that the inferior laryngeal nerve is the continuation of the recurrent laryngeal nerve. The inferior laryngeal nerve is the one which supplies all the muscles of the larynx and it also supplies sensation below the vocal cord. That also is likely to be injured lower down when we are trying to remove a foreign body and that will lead to vocal cord paralysis. So that is the significance of the piriform fossa. That is the most important landmark that we can see in the larynx of the larynx. The other landmark that we can see in the larynx of the larynx is this bulge which I already mentioned this is the bulge of the cricoid lamina. The cricoid cartilage is the only part of the larynx which forms a complete ring and it is like a reverse signet ring. The posterior part of the cricoid is wider the anterior part is narrow and so therefore this white part is visible in the posterior aspect and sitting on top of the cricoid lamina we have these structures which are covered by mucous membrane. There is an adenoid cartilage here with the inter adenoid fold and we have two smaller cartilage known as the corniculate and the cuneiform cartilages which are all covered by mucous membrane. Now let's trace further down. As I mentioned that this is the location of the cricoferringial sphincter or the upper esophageal sphincter and this is the narrowest part of the elementary tract and we can see that indeed it is the narrowest part and after that we can see the mucosa of the esophagus here. The upper one third of the esophagus is skeletal muscle and the middle one third is mixed and the lower one third is smooth muscle. Now I'm going to turn this and we are going to see the interior of the larynx as much as we can see in this particular view. This is the laryngeal inlet and we can see the laryngeal inlet is bounded by the following structures one this is the epiglottis the epiglottic cartilage it is a triangular-shaped cartilage apex is below base is above apex is that as to the inner surface of the thyroid cartilage by means of the thyroepiglottic ligament and then as it goes up it is attached to the hyoid bone by means of the hyoepiglottic ligament which is here and further up it is attached to the tongue by means of the glossoepiglottic fold. Then extending from the epiglottis we have this adi-epiglottic fold which I mentioned just a little while back and then we have the inter-itinoid fold so this is the laryngeal inlet then the portion below that is called the laryngeal vestibule and if you look further inside we can see this elevation where my instrument is pointing this is the false vocal chord or the vestibular ligament which is the lower free margin of the quadrangular membrane and further below we can see the true vocal chord which is the vocal ligament which is the upper free margin of the conus elasticus or the preco vocal membrane and if I were to put my instrument further down and it is going into the trachea now this is the entry to the trachea this is rhima glottitis that is the space between the two vocal chords and that is the one which is responsible for phonation respiration and various other functions this is what we can see of the larynx and the laryngeal larynx in this particular view thank you very much for watching Dr. Sanjay Sanyal signing out David who is a camera person if you have any questions or comments please put them in the comment section below have a nice day