 Good day everybody. Dr. Sanjay Sanyal, Professor, Department Chair. This is Supankadevar, right side of the neck. I'm standing on the right side. Camera person is also on the right side. This is going to be a demonstration of the thyroid gland and its neuro vascular relationships. So this side we have dissected out the right thyroid gland. So this is the supia pole of the thyroid. This is the inferior pole. This is the right lobe. This is the medial surface. The medial surface we can see is in relation to the larynx and below here is the trachea. The thyroid gland is covered by two layers of fascia. The outer layer is actually false capsule and that is pre tracheal fascia, the visceral component of the pre tracheal fascia. And under that there's a condensation of the fibrous tissue around the thyroid which you can see here. This is the true capsule. So we have removed the false capsule. That is the pre tracheal layer of deep cervical fascia. Now let's take a look at the important neuro vascular relationships of the thyroid. We can see this artery coming out from here. This is a branch from the external carotid artery. And we can see it is giving a branch to the larynx. This is the superior laryngeal artery. And the rest of the artery is then continuing down and it is entering the thyroid gland from its superior pole. This is the superior thyroid artery which supplies superior anterior and lateral aspect of the upper half of the thyroid. And we can see it is accompanied by the superior thyroid vein which is opening into the internal jugular vein. Also accompanying the superior thyroid vessels we can see this nerve here. This is the external laryngeal nerve which goes in like this and it supplies the cricothyroid muscle. This external laryngeal nerve is a branch of the superior laryngeal nerve which I picked up. And the superior laryngeal nerve as we know divides into an internal laryngeal nerve which is sensory for the larynx and external laryngeal nerve which I picked up which accompanies the superior thyroid artery. The significance of this relationship is when we are doing a thyroidctomy and when we have to ligate the superior thyroid vessels we are liable to catch the external laryngeal nerve. In which case the person will have paralysis of the cricothyroid muscle and the person will have a weakness of the voice. So therefore to prevent injury to the external laryngeal nerve we have to ligate the thyroid lead as close to the upper pole as possible preferably where I am holding with my instrument. And that way we can safeguard the external laryngeal nerve and safeguard the cricothyroid muscle. The next relationship is this vessel which I want to show you. I picked up inferior thyroid artery. The inferior thyroid artery is a branch from the subclavian artery. This is the subclavian artery that we have picked up here and we can see this cut portion here. The thyracervical trunk came out from this cut portion. One of the branches of the thyracervical trunk is the inferior thyroid artery. And we can see the inferior thyroid artery is entering the lower pole of the thyroid gland. The inferior thyroid artery enters from the inferior surface and it revifies on the inferior, medial and posterior surface of the gland. The inferior thyroid artery is the main supplier of the parathyroid which also receives supply from the communication between the superior and the inferior thyroid. Accompanying this inferior thyroid artery we can see this nerve here. This again we can see is ramifying and it's going along the peculiarity of the visual group. This is the recurrent laryngeal nerve. Where did this recurrent laryngeal nerve come from? This is the branch of the vagus which I picked up here. The vagus nerve as it goes in front of the subclavian artery it gives off this branch. And we can see this branch here which I have lifted up. This is the recurrent laryngeal nerve which then hooks under the subclavian artery and it comes on this side. This recurrent laryngeal nerve as it climbs up on the tracheoesophageal groove once it crosses the cricothyroid joint it becomes known as the inferior laryngeal nerve. And it supplies all the muscles of the larynx except the cricothyroid. And we can see how closely associated the recurrent laryngeal nerve is with the inferior thyroid artery. So here again when we are doing a thyroidectomy and when we are ligating the inferior thyroid artery we are liable to injure the recurrent laryngeal nerve as shown by my instrument here. So therefore the rule of thumb here is when ligating the inferior thyroid artery we should do it as far from the gland as possible. Some surgeons prefer to individually diathermize the branches of the inferior thyroid artery so as to prevent injury to the recurrent laryngeal nerve. Well that is an individual preference of surgeons. Having shown these structures in Psi 2 I will show the same structures on a dissected out specimen of a cadaver. This is an evis-related specimen of the contents of the neck and partly of the media stand-up. So this is the archipelodor and we can see this is the recusiballic trunk. This is the left common carotid, left subclavian. And on the recusiballic trunk we can see on the right side is dividing into the common carotid and subclavian artery. These are the intrahyoid muscles. This is a remnant of the sternohyoid which we have cut and reflected up and this is the other cut portion and under that we can see this is the thyroid on this right side and this is the thyroid on the left side. And this is the remnant of the sternohyroid. So we have reflected all these. These are all the muscles that we have to cut during thyrodectomy. So we can see the thyroid gland in front of us. The extent of the thyroid is from C5 to T1. The isthmus of the thyroid is located here between the right lobe and the left lobe. And we can see both the lobes here. This is the isthmus. This is in front of the second, third, fourth, tracheal rings. Here also we can see the neurovascular structures. So we can see this is the superior thyroid artery. And the superior thyroid artery is giving this branch here. This is the superior laryngeal artery which is accompanying the internal laryngeal nerve which is a branch from the superior laryngeal nerve. This pierces through the thyroid membrane and supplies sensation to the upper part of the larynx. And accompanying the rest of the superior thyroid artery, we can see this nerve here. This is the external laryngeal nerve which is the other branch from the superior laryngeal nerve which supplies the cricothyroid. This is the one which I mentioned we have liable to endure when we are doing a ligation of the superior thyroid artery. This is a remnant of the superior thyroid vein. Now let's take a look at the inferior part of the gland. We can see again this bundle of nerves here on the right side. These are the branches from the right laryngeal nerve. And they are accompanied by the branch from the inferior thyroid artery. If we were to take a look on the left side, we can see again, this is the left superior thyroid artery and left inferior thyroid artery. And here we can see the recurrent laryngeal nerve on the left side which is very closely associated with the inferior thyroid artery. The recurrent laryngeal nerve on the left side is different from the recurrent laryngeal nerve on the right side. The right side I showed you in the other section. On the left side, this is the vagus nerve on the left side. And as it descends down in front of the arch of the aorta, we can see it is giving a branch which is hooking under the arch of the aorta. And when we were to trace this, we find that it comes on the left side of the neck. And this is the other portion of it. This is the recurrent laryngeal nerve on the left side which then climbs up and it goes to the larynx and becomes the inferior laryngeal nerve. So these are the two structures which are liable to be injured when we are doing a thyroidectomy, namely the recurrent laryngeal nerve and the external laryngeal nerve on the upper part, which is in relation to the superior thyroid artery. When we are doing a tracheostomy, we have to cut the east muscle of the thyroid. That is where we do a tracheostomy in relation to second, third and fourth tracheal rinks. The various surgeries that we do with a thyroid are we can do an esthetic to me for lignus thyroiditis when the thyroid is hard and frozen. We can do a lobectomy. We can do a hemothyroidectomy. We can do a sub-total thyroidectomy for multinodular goiter. Or we can do a near-total thyroidectomy for thyroid cancer. So these are the various forms of thyroid surgery that we do. And in each of those cases, we have to safeguard these nerves, which I mentioned, namely the recurrent laryngeal nerve and the external laryngeal nerve. So that is all for now. Thank you very much for watching. Dr. Sanjeev Sanyal signing out. David, who is the camera person. If you have any questions or comments, please put them in the comment section below. Have a nice day.