 Good day everybody. Dr. Sanger Sanyal, professor department chair. This is going to be demonstration of the laryngeal pharynx and this is the first part. We have completely eviscerated the laryngeal pharynx with accompanying blood vessels and the nerves. So let's start off with the anterior view. First, the skeleton of the larynx. This structure is the body of the hyoid bone and posteriorly we have the greater corner of the hyoid bone. Below that we have the thyroid cartilage. This is the thyroid hyoid membrane. We notice that the middle part of the thyroid membrane, the median thyroid membrane is very thick while laterally it becomes a little thin. So the thyroid membrane is the whole thing, median and lateral parts. This is the superior thyroid notch and this is the laryngeal prominence which is felt as Adam's apple in maize. These two flat portions are the lamina of the thyroid cartilage and the thyroid cartilage also has got a superior horn and inferior horn which is not visible clearly here. This cartilage in the structure that we see here, this is the cricoid cartilage. The cricoid cartilage is the only cartilage of the larynx which forms a complete ring. And in between the thyroid cartilage and the cricoid we have this membrane structure. This is the cricothyroid ligament. This also has got two parts, a median cricothyroid ligament and lateral cricothyroid ligament. The lateral cricothyroid ligament as we shall see later is the lower part of the fibroelastic membrane of the larynx which is referred to as a conus elasticus or the crico vocal membrane. And then we have the tracheal rings. So therefore there is a membrane between the two also which is referred to as the crico tracheal ligament. So we have seen the various cartilaginous and the bony parts of the larynx. This is the skeleton of the larynx. The point to be remembered is the hyoid bone is the only bone of the skeleton of the larynx. These are the infrared hyoid strap muscles. The most superior one that we see here, this is the sternohyoid. And under that we have this cut portion. This is the hyrohyoid which came from the oblique line of the thyroid and went in attached to the hyoid bone. We have reflected them up here. Now let's take a look at the neurovascular structures that we can see in this view. We can see this nerve here. This is the internal laryngeal nerve which is the larger terminal division of the superior laryngeal nerve on the right side. On the left side we can see the internal laryngeal nerve here. The internal laryngeal nerve pierces through the thyroid membrane and it supplies sensation to the larynx up to the vocal cord. This is the one which is responsible for cough reflex. This serves as the afferent limb of the cough reflex. Anesthetists use this nerve to anesthetize the superior part of the larynx by piercing through the thyroid membrane before any endo-laryngeal procedure so that the cough reflex will be eliminated. Accompanying this internal laryngeal nerve, we have this artery. This is the superior laryngeal artery which is the branch from the superior thyroid artery. This is the superior thyroid artery. We can see it is going down entering through the upper pole of the thyroid gland. Accompanying the superior thyroid artery, this is the external laryngeal nerve which is the smaller terminal division of the superior laryngeal nerve which supplies the cricothyroid muscle which I am going to mention just now. External laryngeal nerve is liable to injury when we are doing a thyroidectomy and we are ligating the superior thyroid artery. Therefore, we have to be careful to ligate the superior thyroid artery very close to the upper pole of the thyroid gland. And incidentally, we can see a remnant of the superior thyroid vein also here on this side. To come to the left side, we can see again, this is the internal laryngeal nerve. This is the superior laryngeal artery. We cannot see the rest of the artery but we can see the superior thyroid artery entering here separately in the upper pole of the left lobe. Now, let's come a little lower down. We can see these neurovascular structures. This is the right vagus and the right vagus as we know goes posteriorly and it has already started going posteriorly. And the right vagus is giving this recurrent branch. This is the right recurrent laryngeal nerve. In real life, this hooks under the right subclavian artery. This recurrent laryngeal nerve is giving multiple branches. The recurrent laryngeal nerve supplies all the muscles of the larynx except the cricothyroid. And here, as it's going up, it is accompanied by the inferior thyroid artery. In this particular cadaver, we see that the inferior thyroid artery is arising in a little variant location. Ideally, the inferior thyroid artery is supposed to arise from the thyroceribular trunk, which is from the first part of the subclavian artery. Recurrent laryngeal nerve is also liable to injury during thyroectomy when we are ligating the inferior thyroid artery. So therefore, we usually ligate the inferior thyroid artery very far from the gland to protect the recurrent laryngeal nerve. This recurrent laryngeal nerve, as it travels up, it travels in the tracheoesophageal groove. And when it crosses the inferior cricothyroid joint, it becomes known as inferior laryngeal nerve. And after that, it divides into an anterior and a posterior division. The posterior division supplies the posterior cricoidenoid, the oblique and the transverse erytenoids. And the anterior division supplies the remaining muscles of the larynx. And it also supplies sensation below the vocal cord. Now let's come to the left side. This is the vagus on the left side we can see. And it is going in front of the arch of the aorta. And if I lift this up, we can see it is giving a recurrent branch which is going under the arch of the aorta. And it is accompanied by these branches also. And if I reflect it, we can see the recurrent laryngeal nerve on the left side which I have picked up. And this recurrent laryngeal nerve also travels in the tracheoesophageal groove on the left side. And it is accompanied by this branch here. This is the inferior thyroid artery on the left side. And it also travels in the same way as on the right side. So we have seen all the neurovascular structures on both the sides of the larynx. Now I shall show you the muscles. I'm going to turn this slightly and we can see these muscle fibers. They are arising from the thyroid cartilage. This is the thyropharyngeal part of the inferior pharyngeal constrictor. And lower down, we can see the muscle fibers are becoming more horizontal. This is the creco-pharyngeal part of the inferior pharyngeal constrictor. So therefore the inferior pharyngeal constrictor has got two parts. The upper part is the thyropharyngeal and the lower part is called the creco-pharyngeal. And the creco-pharyngeal muscle is the one which constitutes the creco-pharyngeal sphincter or the upper esophageal sphincter. Now I'm going to turn this and we'll see the same thing on the right side. We can see these oblique muscle fibers. These are the right thyropharyngeal muscles. And as we go lower down, we find that the fibers are becoming more horizontal. That's the creco-pharyngeal. Now let's come again to the front. We can see these muscle fibers extending from the cracoid cartilage to the thyroid. This is the creco-thyroid muscle. And this side also the creco-thyroid muscle. This creco-thyroid muscle is the one which I said is supplied by the external laryngeal nerve, branch of the superior laryngeal nerve. The function of the creco-thyroid muscle is tensor of the vocal cord. So therefore it modulates the pitch of the voice. External laryngeal nerve supplies not only the creco-thyroid muscle, it also supplies the inferior pharyngeal constrictor. The inferior laryngeal nerve, which is upward continuation of the recurring laryngeal nerve, supplies all the remaining muscles of the larynx. It also supplies the middle and the inferior pharyngeal constrictor. And it also supplies the upper one-third of the esophagus, which is skeletal muscle. Let's come to another clinical correlation. If we see an emergency situation where the person is having acute respiratory distress, a stridor, because of some injury or found body inhalation, and the person cannot breathe at all. In order to gain time to transport the patient to the hospital, we can do an emergency procedure called preco-thyrostomy. We can take a large bone needle and we can puncture it between the thyroid cartilage and the cracoid cartilage, exactly shown by my instrument here. And we puncture it and we can establish a temporary airway for the person to breathe. And that procedure is referred to as the preco-thyrostomy, because we are going through the median preco-thyroid ligament. So that's an emergency life-saving procedure, preco-thyrostomy. So that's all that we can see in the anterior view. Thank you very much for watching Dr. Sanjay Sanyal Sanyo, 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.