 Good day everybody, this is Dr. Sanjay Sanyal, Professor Department Chair. So this is going to be a demonstration of various structures in the neck, mostly in the anterior cervical region, the neurovascular structures. So just to give you a quick overview, this is a supine cadaver. This is the right side. I'm standing on the right side, camera person is on the right side and my assistants are on both sides. So what are the structures which are initially visible in front of us? We have completely opened up the thorax and the right side of the neck. This muscle that you see here, that we have retracted up and pinned up here, this is the right side sternocleidomastoid. We have removed the clavicle on the right side. So the clavicle, the other portion is here. This is the internal jugular vein on the right side. And we can see the internal jugular vein is receiving the common facial vein as well as the retromandibular vein. There is no retromandibular vein forming the external jugular vein in this particular cadaver. We can see this is the retromandibular vein which divides into an anterior and posterior division. Anterior division means with the facial vein, the posterior division is opening into the internal jugular vein. This is the internal jugular vein which we have lifted up with our instrument here. This is highly macerated because in the embalming process, they had perforated it and therefore there is extravisation of blood here. This is the remnant of the subclavian vein on the right side. We have mentioned all these things in a previous video. The next structure that we see here is this one here. This is the common carotid. This also, as you can see, it has been perforated during the embalming process and therefore there's a lot of extravisation of blood. Both these were encircled in the carotid sheath and behind that we can see this is the vagus nerve on the right side. I'm going to show more of it as I go along. All these were enclosed in the carotid sheath. The next structure that we see here is this muscle here. This is the omohiod. This is the inferior failure of omohiod. This is the facial sling which we have lifted up with our instrument here. This was created by the pre-tracheal layer of deep cervical fissure and this was attached to the clavicle and therefore this is the superior belly of omohiod and which is attached to the hyoid bone. The next structure that we can see here, I'm going to retract this is this muscle here. This is the sternohyoid and we can see it is going from the sternum which has been removed to the hyoid bone up here and I'm going to lift it up here and we are going to, my assistant is retracting it. Under that we can see this muscle here. This is the sternohyroid. It is going to the thyroid cartilage and above that this piece that we see here this is the thyroid hyoid. This is the thyroid gland. This is the thyroid gland. And this muscle that we see here this is the cricothyroid muscle. So therefore this is the thyroid cartilage. This is the laryngeal prominence. This is the superior thyroid notch. Below that this is the cricoid cartilage. So therefore this muscle is the cricothyroid and up here we can feel it but we cannot see it as the hyoid bone. This is the other side. We have retracted the muscles without separating them and we can see the great vessels coming out from the arch of aorta. This is the arch of aorta. This is the bricocephalic trunk. This is the common carotid as I mentioned earlier. This is the right subclavian on the right side. This is the left common carotid and this is the left subclavian. And we can see there's a gap between approximately one centimeter between the bricocephalic trunk and the left common carotid. Down below this is the trachea and we can see it is bifurcating at the level of the sternal angle of Louis and further posteriorly we can see this is the isophagus. With this background, let's go a little deeper and we shall bring back the structures in the normal position. We shall retract this sternothyroid also and we shall pin it up stairs and I'm going to pin it now. So having retracted that out of the way, let's start with the common carotid here. As I told you, the common carotid is highly macerated because of the embalming process but we have salvaged quite a bit of it. The right common carotid as it goes up approximately at the level of the upper border of the thyroid cartilage, we can see it is dividing into two branches. This branch, the smaller one, this is the external carotid and this one is the internal carotid. Internal carotid has got a bulb here. This is the carotid sinus and in between the two, in this connective tissue, there is a fibro structure which is called the carotid body which acts as a chemoreceptor, a peripheral chemoreceptor. The carotid sinus acts as a paroreceptor. I will draw your attention to this nerve which is running in front of the bifurcation which I have lifted up with my instrument. What is this nerve? This is the hypoglossal nerve. Hypoglossal nerve causes in front of the bifurcation and it enters and I've shared more about this as I go along. This pink structure that we see here, this is the submandibular salivary gland and this is a little bit of the carotid gland that we can see here and this muscle that we see here, a little bit is visible, this is the mesetermosal. We have not descended out any further than that. Having shown the common carotid and its bifurcation into internal and external carotid, now let's take a look at the subclavian artery on the right side. So this is the subclavian artery on the right side and we can see this is the first part of the subclavian artery. How do we determine the subclavian artery, the parts? We can determine it by this muscle here. I will draw your attention to this muscle which starts from here and goes down and further down it becomes pinkish in color, this brown and pink muscle. It is attached to the first rib. So you have guessed it already, this is the scariness anterior muscle. So therefore the portion of the subclavian artery from the origin to the medial border of the subclavian, scariness anterior, this is the first part of the subclavian artery. The second part is behind the sub-scaliness anterior and the third part is from the lateral border of the scariness anterior to the outer border of the first rib. So this much is the third part and after that it becomes known as the axillary artery. So therefore this piece that we see here this triangular space between this brown muscle and this brown muscle and the pink muscle. This is the scalyne triangle bounded by the scalyness anterior, the scalyness medius, both of which are inserted on the first rib and emerging through the scalyne triangle are this neurovascular bundle. What are they? The upper trunk of the brachial plexus, the middle trunk of the brachial plexus and the lower trunk of the brachial plexus. And apart from that, definitely not the least is this third part of the subclavian artery. So therefore all these structures together are the contents of the scalyne triangle. And therefore any one or more of these can be entrapped in what is known as the scalyne syndrome. Having mentioned that, now let's come back to the branches of the first part of the subclavian artery and the second part that we can see in this dissection. As I told you earlier, the first part of the subclavian artery is from its origin to the lateral medial border of the scalyne's anterior. What are the branches that we can see here? This is the first branch. This is the internal thoracic artery and you can see this is a cut portion here. It was entering into the thorax, it's going down. It was running on the inner surface of the chest wall. And I will draw your attention to where my finger is tracing right now. This is the internal thoracic artery on the left side and similarly on the right side that you see. I'm going to shine the light here. You can see this is the internal thoracic artery on the right side. So therefore this internal thoracic artery is this internal thoracic artery. This is the first one. The next branch that we can see in the first part is this big artery here which I have lifted up. This big artery. What is this? This is the vertebral artery and take a very good look. We will see the vertebral artery is starting from here and it is disappearing in this place here. So therefore there is a pyramidal-shaped space here which I'm going to trace just now with my instrument. This is one boundary of the pyramidal space. This is another boundary of the pyramidal space. This is the scalenus anterior, as I mentioned earlier, and this is the longus coeli muscle. It goes through this pyramidal space. So this is the first part of the vertebral artery or the V1, the so-called cervical part. After that it will go into the transverse pyramid of C6 up and that will be known as the vertebral part. Then it will go become the suboccipital part and then it will become the intra-cranial part. So this is the first part of the vertebral artery. So that's the next branch of the first part of the subclavian artery. Then we have the next branch. The next branch of the subclavian artery is this one here, which I have lifted up. This is the thyroservical trunk which I have lifted up here. Please take a good look at this. This is the thyroservical trunk. Now, thyroservical trunk is supposed to give four branches, but in this case, again, we have a small anatomical variation. The first branch is the inferior thyroid artery, but in this case, it is not coming from the thyroservical trunk. It is coming separately and I have lifted it up here. This is the inferior thyroid artery. We can see it is coming separately and the inferior thyroid artery, if you note carefully, it goes up like this and it makes a loop like this. This is the classical course of the inferior thyroid artery. And this inferior thyroid artery is going towards the thyroid gland and you can see this is the thyroid gland. So it is going towards the thyroid gland. And this inferior thyroid artery is accompanied by this nerve. Can you see here? This is the recurrent laryngeal nerve. I will show more of the recurrent laryngeal nerve just a little while later. So therefore, when we are ligating the inferior thyroid artery during thyroidectomy, we have to be very careful not to injure the recurrent laryngeal nerve. This is a point to be remembered and noted. Let's continue with the branches. This, as I told you, was a thyroservical trunk. We can see the other branches. This is the ascending cervical artery. This is the transverse cervical artery and this is the suprascapular artery. So ideally, the thyroservical trunk is supposed to give four branches. The inferior thyroid, transverse cervical, suprascapular ascending cervical. The ascending cervical and inferior thyroid are supposed to be the terminal branches. But in this case, we had a slight anatomical variation. That brings me to a few quick words about the transverse cervical itself. The transverse cervical is also called the cervical dorsal in some books. And the cervical dorsal or the transverse cervical, as it goes, it becomes divided into two branches, a superficial and a deep. Now in this case, we can see it is dividing. It is dividing into a superficial and a deep. The superficial one runs with the spinal accessory nerve on the levator scapulae. This is the spinal accessory which I have lifted up. And it runs on the levator scapulae where my instrument is tracing right now. But this deep branch, as you can see, the deep branch is going inside. The deep branch is known as the dorsal scapular artery. And this is the one which runs deep, medial to the scapula and it participates in the scapula and nostromosis. And it's the one which is responsible for the dancing scapula which is seen in coactation of aorta. So that's about the cervical dorsal or the transverse cervical artery. The suprascapular artery, which I mentioned just now, is accompanied by this nerve here. This is coming from the upper trunk of the brachial plexus. This is the suprascapular nerve which goes and supplies the supraspinitis and infraspinitis muscle. So we have seen the four, three branches of the first part to recap vertebral artery, internal thoracic artery, thyro-survival trunk. Thyro-survival trunk giving four subbranches, in this case, a little variation. Now let's come to the second part of the subclavian artery. The second part is behind the scallionis anterior. And we can see it is rather difficult, but we shall pull it out and we can see that this is the second branch from the second part. This is the costoservical trunk. Why is it called costoservical? Because it gives two branches. One is the supreme intercostal, to the first and second intercostal spaces. And the other is the deep cervical, which supplies the muscles of the neck. That's why this trunk is called the costoservical trunk. The third part of the subclavian artery does not usually have any branches, but sometimes the suprascapular artery, which I showed you here, or the torsoscapular artery may arise from the third part of the subclavian artery. So we have seen the full course of the subclavian artery and we have also seen how it can be entrapped in the scallionis anterior syndrome, and we have seen the branches of the subclavian artery. Now let me show you another structure. This was the internal jugular vein, as I told you earlier. This is the common carotid artery, which divided up. This nerve that we see running, it was running in the carotid sheath. This is the vagus nerve. And if you trace the vagus nerve, we can see it is coming, arising from way high up, and I'm retracting these structures here. You can see the vagus is arising from here. You can see my instrument has gone way, way, way up. It comes out through the jugular foramen, and it runs straight down. Where does it run? It runs in the carotid sheath. Behind the internal jugular, and the common carotid and internal carotid. So this is the vagus nerve. So let's see what happens to this vagus nerve. The vagus nerve on the right side, we can see it's coming down. It runs in front of the subclavian artery, and we can see it is running in front of the subclavian artery. And then it goes behind the trachea and it divides into aplexus. And after that it will do many further things. But I will draw your attention to this branch of the vagus. We can see this branch. This is the vagus accessory complex. In this particular case, it is known as the right recurrent laryngeal nerve. Let me show you the same thing from the other side. This is the right recurrent laryngeal nerve. Again, let me show you. This is the vagus. This is the right recurrent laryngeal, and this is the right recurrent laryngeal. This right recurrent laryngeal nerve, it runs in the tracheoesophageal groove. This is the trachea, and behind that is the esophagus. And it runs up like this, and it is in accompaniment with the inferior thyroid artery, which I mentioned earlier. And we can see both of them. I'm going to hold both of them together. This is the one I said has to be safeguarded while we are doing the thyroidectomy. This is a very important relationship which I wanted to draw your attention to. The next important relationship that I will draw your attention to is this branch of the external carotid artery. This branch, this is the superior thyroid artery. How do we know? Because this was a thyroid gland. So therefore this is the superior thyroid artery. And we can see the superior thyroid artery is accompanied by this small nerve here, which I have lifted up. And we can see the two of them are running together and I've held both of them close together. So you have guessed it. What is this nerve here? This is the externalaryngeal nerve which supplies the cricothyroid muscle. So again, when we're doing a thyroidectomy, we have to be very careful while ligating the superior thyroid artery so as to not to injure and to safeguard the externalaryngeal nerve. If you injure the externalaryngeal nerve then we will produce a parallel of the cricothyroid muscle and that will lead to a weakness, the voice. In contrast, if you injure the recurrent laryngeal nerve while ligating the inferior thyroid artery, we will produce hoarseness of the voice. Now let's take a quick look at the opposite side. This is the left common carotid. On this side, we can see this is the remnant of the internal jugular vein. This is the left subclavian. The running behind is this the left phrenic nerve. This is the vagus on the left side and it is giving a separate branch to the trachea here. What about the recurrent laryngeal nerve on the left side? The recurrent laryngeal nerve on the left side, it comes under the arch of aorta here. And we have cut it here but we can see the rest of the recurrent laryngeal nerve here and I've lifted it up here. This also follows the same course as the right side and it runs in accompaniment with the inferior thyroid artery but we have not dissected the nerve and so therefore we have to follow the same precaution on the left side as we did on the right side. So these are the structures which I wanted to show you and before we conclude, just to draw your attention, this is the media stynum that we have removed. This is the arch of aorta. We can see the three main branches. This is the descending aorta. This is the bifurcation of the trachea and this is the isophagus and we can see the trachea, the thyroid and the descending aorta is giving rise to the posterior intercostal arteries. So these are the structures which I wanted to show you in the dissection of the neck and the media stynum. Thank you very much for watching. Dr. Sanjay Sanyal signing out. My MD1 students are my assistants as well as the camera persons. Please like and subscribe. Have a nice day.