 Good day everybody. Dr. Sajja Sanyal, Professor of the Department Chair. This is going to be a demonstration mostly of the lateral cervical region. We have got my assistants on my either side of me. This is a supine cadaver. This is the right side. I'm standing on the right side. The camera person is also on the right side. So first to give you a quick overview. We have decided out the right side of the neck mostly and also a little bit of the left side. We have already removed the thoracic cavity, the wall, so you can see the thoracic contents here. We have removed the clavicle here. So let's give you a quick overview of what are the structures which are visible in this dissection. Imagine the clavicle was here, where my instrument is located. So we can see a triangular structure here. This is the lateral cervical region. So what are the boundaries of the lateral cervical region? The anti-boundary is the sternocleidomastoid, which is being held by one of my assistants here. The posterior boundary is this muscle here. This is the anterior descending fibers of this trapezius muscle. And this bone that you see here, this is the remnant of the clavicle. We have cut out the rest of the clavicle, which would have come all the way from here to here. So this is the inferior boundary. And as we all know, the sternocleidomastoid takes origin from the manoeuvring of sterni, which has been removed. And it also takes origin from the clavicle. That's why it's called sternocleidomastoid. So therefore, this is the lateral cervical region. In surgical parlance, it's also called the posterior triangle of the neck. This was covered by the investing layer of deep cervical fascia, which we have removed. And that was forming the roof of the lateral cervical region. And after removing that, these are the structures which are visible here. So let's take them. These white things that we see here, these are all the branches of the cervical plexus. Now, we cannot accurately say which are the which branches, but we can generally say that the upper branches will be the great auricular and the lesser occipital nerve. Next branch will be the transverse cervical. And the largest going down, this, this will be the supraclavicular. Supraclavicular, as it descends down, it breaks up into a medial, intermediate and lateral. So these are the branches of the cervical plexus. The next thing that we see here are the structures which form the floor of the lateral cervical region. And that is what we are going to focus on right now. To understand the floor, now what we will do is, we will retract the sternocleomastoid. So I am retracting the sternocleomastoid so that we can have a better view. So what do we see? Here we can see one muscle here. These muscles were all covered by the pre-vertebral layer of deep cervical fascia. So this muscle that we see here, this is the sclerous capitis. The first muscle which forms the floor. Then we have the next muscle here. This is the libator scapulae. And running on the libator scapulae will be the spinal accessory nerve, which we cannot see here. Since we are talking of the spinal accessory nerve, let me show you the remnant of the spinal accessory under the sternocleomastoid. This is the sternocleomastoid which we have retracted. And we can see this is the spinal accessory which is supplying the sternocleomastoid from its under surface. This is one branch of the spinal accessory. Then the rest of the spinal accessory will run on the libator scapulae and it will enter into the deep surface of the trapezius. The next muscle that we see here is this big muscle here. This piece, this whole muscle. In order to see it better, I am going to remove these branches of the cervical plexus. And we can see this whole muscle. And I am going to put my instrument underneath here. This is the sclerous posterior muscle. And we know it goes into the second rib. And I will prove it to you just now. Let's continue further down. We can see this muscle here, which I have lifted up now. This is the sclerous medius muscle. And finally, I am going to show you the next muscle. This pink muscle that we see here, this is the sclerous anterior. So, sclerous medius and sclerous anterior are inserted on the first rib. This, where my finger is touching, this is the remnant of the first rib. And you can see when I am pressing on the remnant of the first rib, the sclerous anterior is moving and the sclerous medius is moving. So, therefore, we know that this is the scalyne triangle. So, what are the boundaries of the scalyne triangle? Scalyneus anterior, scalyneus medius, first rib. What is the importance of the scalyne triangle? So, let's take a look at the important structures coming through the scalyne triangle. This is the composite structure which is coming through the scalyne triangle. Down below, this is the artery, the subclavian artery. The third part of the subclavian artery, it emerges through the scalyne triangle and it crosses the first rib. And after that, it becomes the axillary artery. So, this is likely to be entrapped in the scalyne syndrome which all of us know very well. The rest of the structures are these which I have lifted up here. This are the upper and the middle trunk of the brachial plexus. This is the brachial plexus. The trunks of the brachial plexus pass through the scalyne triangle. So, these can also get entrapped in the scalyne syndrome. So, therefore, to summarize, this is the scalyneus medius. This is the scalyneus anterior. This is the first rib. So, therefore, this is the scalyne triangle. And we can see these are the structures which are likely to be entrapped. So, the question that you are supposed to ask me is what about the subclavian vein? The subclavian vein does not pass through the scalyne triangle. This is the remnant of the subclavian vein in this cadaver. It was highly macerated but we have managed to salvage something. And this instrument is going into the jugular vein which also has been damaged by the embalming process. So, therefore, you can see clearly that the subclavian vein goes in front of the scalyne triangle. It goes in front of the scalyneus anterior muscle and it joins with the internal jugular vein to form the right brachioscephalic vein. Now, this cadaver also had another problem. Her right brachioscephalic vein was continuous with the superior vena cava which itself was continuous with the right atrium which is shown here. And this I have shown in a previous video of the thorax and the superior vena cava is continuous with the inferior vena cava which you can see here. So, she has quite a bit of venous and ugly on the right side. To come back to where we were, now I am going to retract this and I will show you the next structure. This is the scalyneus anterior as I mentioned earlier. So, we can see a nerve running in front of the scalyneus anterior. What do you think this nerve is? This is the phrenic nerve. This is also a branch of the cervical plexus. C345 and it is a mixed nerve. So, therefore, it goes all the way down in front of the scalyneus anterior. It goes behind the subclavian vein and it continues into the thorax. And we can see it is going right up to the diaphragm. So, this and on the other side also we can see if you look carefully, but this is the phrenic nerve on the right side. But we have to sit down on the left side. This phrenic nerve, as it goes in front of the scalyneus anterior, it goes behind the subclavian vein. Rarely there can be a situation where the nerve to the subclavius. This is the subclavius muscle, the remnant of the subclavius muscle. The nerve to the subclavius, which comes from the brachial plexus, can give an accessory phrenic nerve, which can run in front of the subclavian vein and can unite with the main phrenic nerve. In such situation, they can entrap the subclavian vein and can potentially injure the subclavian vein, but that is not a very common condition. The next point which I want to draw your attention to is what we have seen in the thorax. We can see this is the arch of aorta, ascending aorta, arch of aorta, and descending aorta, thoracic. Let's retract this and see what we can do. We can see this is the brachioscephalic trunk. And the brachioscephalic trunk divides into the right common carotid. In this cadaver again, you can see this perforation where they had done the embalming process. That's why the whole thing is macerated. This is the right common carotid. And further up, when we dissect more, we will be able to show you where it divides into an internal and external carotid. But we have not completed that dissection yet. The next branch of the brachioscephalic trunk is this one here. What is this? This is the right subclavian artery. And we can see some branches of the right subclavian artery. For example, we can see this branch going down into the thorax. This is the internal thoracic artery. Then we can see this branch. This is the vertebral artery. This is the ascending cervical artery. And this is the thyroservical trunk. So these are the branches that we can see from the right subclavian artery. To continue with the story, this is the left common carotid, which we have shown only in the thorax. And this is the left subclavian. And I just want to draw your attention to some of the muscles that we are... We can see the strapped muscles, the thin muscles. So this instrument, which is being held by my assistant here, this is the omohioid. Can we see it is making a bend here? So this is the inferior belly of the omohioid. This is the facial sling, which is being held by this instrument. And this was attached to the clavicle. And therefore, this is the superior belly of omohioid. This extends from the superior border of the scapula, near the supraster scapular notch. It bisects the lateral cervical region. So if the lateral cervical region had been like this, it bisects it. If you put back the sternum of the mastoid, this facial sling would have been behind it. So this is the triangle. Then they put up on this triangle here, which is called the subclavian triangle. Also called the omoclamicular triangle. And now you know why it is called the subclavian triangle, because the subclavian artery is located in that triangle. So this is the inferior belly of omohioid. This is the superior belly of omohioid, and it gets inserted onto the hyoid bone, which is right up here. The next muscle that we can see here is this one here. This extended from the manobrium sternum to the thyroid cartilage, so therefore this is the sternum thyroid. And above that, there will be a sternum hyoid, which will go right up to the hyoid bone. So these are the strap muscles that we can see here. In our subsequent section, we are going to show the branches of the answer cervicalis, which supply these strap muscles. And finally, since we have already shown you the common carotid and the internal jugular vein, it will not be out of place to show you the vagus nerve. This is the vagus. The vagus nerve runs on the posterior aspect of the carotid sheath. We have separated it out completely. And then it crosses in front of the subclavian artery, and we can see that. And it descends down, and we can see behind the trachea, it divides into a plexus. But as it crosses the subclavian, we can see it is giving off this branch here. And I want everybody to see it very clearly. This looping branch. What is this branch? This is the recurrent laryngeal nerve. Recurrent laryngeal nerve is part of the vagus accessory complex. It is coming from the vagus, and it is going under the subclavian artery on the right side. And we can see on the other side, this is the recurrent laryngeal nerve. Again, let's see it. We can see it from this side. And we can see it on that side. This recurrent laryngeal nerve will climb up in the trachea. It's a vagal groove. It will give branches to the upper one third of these of vagus in fear of laryngeal constrictor. And it will enter into the larynx where it will form the inferior laryngeal nerve. So you're curious to see the left side recurrent laryngeal nerve. So I have retracted the arch of the aorta. And we can see the left side recurrent laryngeal nerve. This is the left recurrent laryngeal nerve on the left side. But we have not decided about the rest of the course. This recurrent laryngeal nerve can be injured when there is a... And when there is a tumor, pancreas tumor on the right side. And then it can produce hoarseness of the voice. So these are the structures which I wanted to show you in this particular dissection. Thank you very much for watching Dr. Sanjay Sanyal signing out. MD1 students are my assistants. If you have any questions or comments, please put them in the comment section below. Have a nice day. Please like and subscribe.