 Good day everybody. This is Dr. Sanjay Sanyal from the department chair. So this is going to be a demonstration of the submandibular region that is a dicastric triangle, submandibular salaric land, and the related structures. This is a supine cadaver. We are showing the right side. So just to bring up the speed, this is the mesetra muscle, and we have removed this mesetra muscle. So that will give us a better view of the submandibular triangle. So let's take a look at the boundaries of the submandibular triangle first. It is bounded posteriorly by this muscle here. This is the posterior belly of dicastric. There's supposed to be the stalohydrate muscle also, but in this particular cadaver it is not present. Then we can see an intermediate tendon, which is attached by means of a facial sling to the hyoid bone, and then we can see another belly. This is the anterior belly of dicastric. So the anterior belly takes origin from the mandible, posterior belly takes origin from the mastoid process, and the intermediate tendon gets attached by means of a facial sling to the hyoid bone. So these are the two boundaries. The third boundary is this. This is the margin of the body of the mandible, till the angle. And from the angle we take an imaginary line till the mastoid process. So this is the third boundary of the dicastric or the submandibular triangle. Now what we shall do is we shall remove this just to show more clearly. Now we can see the interior of the infrared lymphosa, and that is going to give us a clear picture of the contents. This submandibular triangle was roofed over by the platysma, and the floor of the submandibular triangle is composed of three different muscles. What are the three different muscles? To understand the muscles I will remove this dicastric up. I have cut it from the attachment to the hyoid bone. First we can see this muscle here. This is the mylohyoid muscle, which we have cut, but I will show it later. The next muscle which forms the floor is this muscle here. This is the hyoglossus muscle, and the third muscle which forms the floor is this muscle here. This is the middle pharyngeal constrictor. So these are the three muscles which form the floor of the submandibular or the dicastric triangle. Now let's take a look at the contents of the submandibular or the dicastric triangle. The most important and the largest content is this gland here. This is the submandibular celibate gland. And it also contains many other structures which I shall show as we go along. So henceforth our distinction and description is going to focus on the structures related to the submandibular celibate gland. So this is the submandibular celibate gland. We have removed it here. We can see first of all that this is grooved by this artery here. This is the facial artery. And you can see the facial artery is coming from the extracellular artery. This is the facial artery. And the facial artery first makes a loop up like this. And it goes under the mandible. And then it curves down and it makes a deep groove on the posterior aspect of the submandibular celibate gland. And after going through, it comes out here. And then it runs on the surface of the mandible like this in a very tortuous fashion. It is located just anterior to the basita muscle which we removed just a little while back. So this is one important content in relation of the submandibular celibate gland. When we are doing surgery, we have to be cognizant of this facial artery here. The next structure which is present is this. This is the hypoglossal nerve. And we can see the hypoglossal nerve by its characteristic course. It runs superficial to the hyoglossus muscle. This is the sternocranial nerve. And then it goes and supplies the muscles of the tongue. The next structure that we can see is this one here. This is also a little bit of the content of the submandibular region. This is the lingual artery. The lingual artery is crossed over by the hypoglossal nerve. The lingual artery also makes an upward loop like this and the hypoglossal nerve crosses it. But the lingual artery goes deep to the hyoglossus and we can clearly see that here. So again, take a look please. The hypoglossal nerve goes superficial to the hyoglossus. The lingual artery goes deep to the hyoglossus. And we shall see the further course of the lingual artery just a little later when I remove the myelohyate muscle. The next structure which comes to our view is this structure. For that we'll have to start from the infractable fossa. We have retracted the lateral teregoid and the medial teregoid and we can see this nerve. This is the lingual nerve. And below that we can see this nerve here with its small branch. This is the inferior alveolar nerve which is running inside the mandible. And this is the nerve to the myelohyate. So we can see the nerve to the myelohyate on the surface of the myelohyate muscle here. This is the nerve to the myelohyate. This is the one which supplies the myelohyate muscle and the antebellium digastric. Let's come to the lingual nerve itself. The lingual nerve is a very important nerve and it supplies the flow of the mouth and the tongue. Anterior two thirds of the tongue with sensory fibers. This lingual nerve, it enters into the submandibular salivary gland. And we can see the course of the lingual nerve here. Now let's take a look at what happens to the submandibular salivary gland. The salivary gland is split into superficial and deep parts by this lateral border of the myelohyate. So let me retract this and show the myelohyate here. And we can see deep to the myelohyate is this small portion of the gland. This is the deep portion of the submandibular gland. The vast majority of the gland is superficial to the myelohyate. To show the further course of the gland, I'm going to now retract the myelohyate muscle which I've already cut. So I have retracted the myelohyate muscle here and I'm retracting the myelohyate muscle here also. So therefore now we have shown the structures deep to the myelohyate. And we can see the continuation of the deep part of the gland here. This is the deep part of the gland. And we can also see the continuation of the lingual nerve here. The point I would like to draw your attention to is this is the vartan's duct or the submandibular salivary duct. It is closely related to the lingual nerve. The lingual nerve loops around under the vartan's duct. The vartan's duct further first moves between the myelohyate and the hyoglossus. And we can clearly see that here. This is the myelohyate, this is the hyoglossus. It runs anterior superiorly. And as it goes further anteriorly it runs between the sublingual salivary gland and the genioglossus muscle. And then it opens it to the sublingual papilla. Now that we have shown the structures in the floor of the mouth, now is the right time to identify some of the other structures deep to the myelohyate. So we have mentioned this is the deep myelohyate. The muscle that we see deep to that this is the geniohyate. The geniohyate is supplied by a branch from the, a branch which comes from the hypoglossal nerve. This is the hypoglossal nerve. But it does not belong to the hypoglossal. It is a branch of the superior limb of cancer cervical is C1, C2. Then the rest of the hypoglossal nerve it ramifies inside the muscles of the tongue. And we can see that happening here. Also deep to the myelohyate that we have retracted, I want to bring your attention to this structure which I have lifted up now. This is the continuation of the lingual artery. The lingual artery as we know it went under the hyoglossus. And inside the tongue it divides into these three branches, the dorsal lingual artery, the deep lingual artery and the sublingual artery. So this is the dorsal lingual artery. And if you notice, if I give traction here, it moves here. So this is one principle branch of the lingual artery. This is also located deep to the myelohyate. The next structure which I will draw your attention to is this nerve here. This is the glossopharyngeal nerve. And we can see the glossopharyngeal nerve is accompanied by this muscle here. This is the stylopharyngeal muscle. The stylopharyngeal muscle and the glossopharyngeal nerve, they enter into the pharynx between the superior pharyngeal constrictor and the middle pharyngeal constrictor. So we can see that happening here. The next structure that I will draw your attention to is this muscle here. This is the styloglossus. It also takes origin from the stylo process. So taking origin from the stylo process, we have the stylopharyngeus, the stylo glossus. As I told you in the beginning, we do not see the stylohyoid muscle here. When we are doing a surgery of the cementibular salivary region, so therefore the structures that we need to safeguard are the facial artery, the lingual artery, the lingual nerve, hypoglossal nerve and there is a nerve coming from the facial nerve which runs parallel to the inferior border of the mandible that is called the marginal mandibular branch. We have to safeguard these structures. Before I conclude, I want to quickly show you the muscles of the pharynx. This muscle that we see here, this is the superior pharyngeal constrictor and this fibro structure that we see in front, this is the pterigomandibular raffae which is formed by the buccal pharyngeal fascia. So therefore anterior to the pterigomandibular raffae, this is the buccinator muscle that we can see it is being pierced by the parotid duct and posterior to the pterigomandibular raffae is the superior pharyngeal constrictor. The next muscle is this one here. I have lifted up the higher bone. This is the middle pharyngeal constrictor and further inferiorly these muscles that we see here, this is the inferior pharyngeal constrictors. So between middle pharyngeal constrictor and inferior pharyngeal constrictor, this is the thyroid membrane and we can see it is being pierced by the internal laryngeal nerve which is the branch of the superior laryngeal nerve which is the branch of the phagus. This is the facial vein. We can see it is opening into the internal jugular vein. How do we identify the submandibular salivary duct, the water duct? The submandibular water duct, it opens in the sublingual papilla, in the lingual frenulum. We cannulate it and we inject it to die and we can see the course of the duct and we look for strictures stones. The saliva in the submandibular salivary gland is more thick so therefore stones and strictures are more common than the parotid. It may be necessary to remove this. That is called submandibular silent anectomy and in that situation we have to be careful of all the structures which I mentioned earlier. The nerve supply of the submandibular salivary gland is by means of the corded tympani nerve which carries secretor motor fibres to the submandibular salivary gland as well as to the sublingual salivary gland and this corded tympani nerve runs with the lingual nerve and therefore we can see the course of the lingual nerve. It is going into the submandibular gland and then it is continuing further into the submandibular salivary gland and that is where I mentioned it forms a close relationship with the water duct. It loops under the water duct. So these are the points which I wanted to mention to you in the submandibular salivary gland and the region. Thank you very much for watching. Dr. Sanjya Sanyan signing out. Mr. Kendal Kamburbhai is the camera person. If you have any questions or comments please put them in the comment section below. Have a nice day. Please like and subscribe.