 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 terecomandibular 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 a 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 part 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 pharyngeal basal 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 pharyngeal basal raffae. To continue with the hyropharyngeal 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 crico pharyngeal part of the muscle Which is taking origin from the cricoid cartilage and going circular across We are the ones which constitute the crico pharyngeal 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 alimentary 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 crico pharyngeal 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 a Zenker's diverticulum, which is the type of Pulsion diverticulum of the pharynx and how does it work because this crico pharyngeal 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 crico pharyngeus 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 and 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 laryngeal pharynx 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 mucous 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 mucous 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 mucous 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 had this prominence which is formed mostly by the lamina of the cricard cartilage and The lateral boundary of the spireiform fossa is where my finger is located and if I turn it We will see that it is formed by the thyroid 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 Impaction 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 by means of endoscopy We are liable to injure two nerves Which are running just under the mucous 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 mucous 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 pyriform 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 pyriform fossa That is the most important landmark that we can see in the laryngeal pharynx The other landmark that we can see the laryngeal pharynx 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 crico pharyngeal 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 these are figures 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 thyroid epiglottic 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 glossopeglottic 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-itonoid 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 cord or the vestibular ligament Which is the lower free margin of the quadrangular membrane and Further below we can see the true vocal cord, 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 Rhyma glottitis that is the space between the two vocal cords And that is the one which is responsible for phonation, respiration and various other functions That's all for now. Thank you very much for watching. Please like and subscribe Dr. Sanjay Sanyar, Sunny out. If you have any questions or comments, please put them in the comment section below Have a nice day