 demonstrate the triangles, most of which are located in the anterior cervical region. So let's start off with the one median triangle here. This triangle that is being traced by my instrument, this is the submetre triangle. This is bounded by the body of the hyoid bone. On one side, we have this muscle here, anterior balear digastric. And the other side is the other side anterior balear digastric. And both of them, they meet at the apex of the triangle, which is near the symphysis mentai. In this patient, we have an accessory fiber of the anterior digastric. So this is the submetre triangle. The floor of the submetre triangle is formed by this muscle that we can see here. This, and on this side also, we can see the same muscle. This is the mylohyoid muscle. And if you look very closely, you'll see the fibers of the mylohyoid are running like this. They run slightly obliquely and they meet in the midline, in the fibrous structure called the mylohyoid raffae. So that is the floor of the triangle. The roof of the triangle is formed by the platysma, part of which we have retained here. These are the fibers of the platysma, which form the roof. The contents of the triangle are the submetre lymph nodes, which drain the dip. And the beginning of the anterior jugular vein, we can see it here. The anterior jugular vein is formed by the submetre veins. So they are also located in the submetre region. And we can also see a few branches of the submetre artery. So this is the submetre triangle. All of the triangles are bilateral. So let's take the next triangle here. This triangle that I'm tracing out, this is the submandibular or the digastric triangle. Submandibular because it contains a submandibular gland. Digastric because it contains the digastric muscle. So let's take a look at the boundaries of this triangle. This is the posterior digastric from the mastoid process all the way to the hyoid bone. Then we have an intermediate tendon here. And then we have the antebelli of digastric. So these are the two boundaries. The third boundary is the inferior boundary of the body of the mandible till the angle. And then an imaginary line from the angle to the mastoid process. So therefore this triangle is the submandibular triangle or the digastric triangle. The floor of the triangle please look very closely are formed by three muscles. One muscle is this one here. This I mentioned just now is the mylohyoid. The next muscle just behind that you can see this muscle here going up from the hyoid bone. This is the hyoglossus. And the third muscle is when I reflect the submandibular gland. We can see a muscle deep inside. That is the middle pharyngeal constrictor. So these are the three muscles which form the floor. The roof is formed by again the platysma which is the superficial fascia. At this juncture I need to mention that the anterior cervical region does not have any deep fascia. Therefore the superficial fascia namely the platysma forms the roof in all these triangles. So this is the next triangle that we see here. Let's go a little below that. The next triangle is this one which is being traced by my instrument here. We have put back the sternocleomastoid in its original position. So therefore the superior boundary is the posterior belly of digastric. The posterior boundary is the upper part of the sternocleomastoid anterior border. And the inferior boundary is the this muscle here. This is the superior belly of the omohyoid. This triangle is called the carotid triangle. Again this is roofed over by the platysma and the floor of the triangle is formed by the muscular component of the pre tracheal fascia. Contents of this triangle. The most important content as the term implies is the carotid artery. Bifurcation of the common carotid artery into internal carotid, external carotid, bulb of the carotid that is the carotid sinus and the carotid body and the nerve supplying them. So these are the most important content and that is the reason why this is called the carotid triangle. Not forgetting just lateral to that we have this vein here. This is the internal jugular vein with all the tributaries. And finally not visible clearly here will be the parts of the ancer cervicalis. So these are all the contents of the carotid triangle. Muscular or the omotracheal triangle. This is the triangle which is being traced out by my instrument imaginary midline. Then we have this muscle again which we have picked up. This is the superebellia of the omohide. Incidentally we can see the superebellia of omohide this side also. And inferiorly we have the again the anterior part of the sternocleic mastoid the lower half. So therefore this triangle. This is the omotracheal or the muscular triangle. Why is it called omotracheal because of the omohide and the trachea? Why is it called the muscular triangle? Because one of the main contents of this triangle are these muscles that we can see here. These are the intrahyoid strap muscles. Namely the sternohyoid under that we have the sternothyroid and we have the thyrohyoid. Proof of the triangle is again the platysma and the floor of the triangle is the visceral component of the tracheal fascia. Because another important content of this triangle is the thyroid gland which we can see here. And the thyroid gland is covered by the visceral component of the pre tracheal fascia. There is yet one more content. Part of that we can see on this side here. The right side has been removed. This is the anterior jugular vein. The anterior jugular vein is formed by the union of the submetal veins. They unite they descend down on each side as the anterior jugular veins. So this is the left anterior jugular vein that we can see here. Both these anterior jugular veins as they descending down they give communication to the facial vein which is not visible here. And then the two anterior jugular veins they unite just above the suprasternal notch. And this union is referred to as the jugular venous arch. And we can see the jugular venous arch here. And emerging from the jugular venous arch on the right side we can see the anterior jugular vein which will open into the external jugular vein. This jugular venous arch is located not in the pre tracheal fascia but between the two layers of the investing layer of deep cervical fascia. And this is a remnant of that. The investing layer of deep cervical fascia one layer is attached to the deep margin of the manubrium. The other layer is attached to the superficial margin of the manubrium. And the small triangular space in between is referred to as the suprasternal space of burns which contain the jugular venous arch and a lymph node. So that is the clinical significance of this suprasternal space of burns in the jugular notch of the manubrium. That's also a content of the muscular or the omotracheal triangle. That's all for now. Thank you very much for watching. Dr. Sanjay Sanyal signing out. Please like and subscribe. If you have any questions or comments please put them in the comment section below. Have a nice day.