 Good day everybody. Dr. Sanjeev Sanyal, Professor of Department Chair. This is going to be a demonstration of certain structures in the post-tree media channel. This is a subhand canaver, I'm standing on the left side of the canaver and the camera person, which is myself, is also on the left side. Just to bring you up to speed, we have completely removed all the thoracic contents after removing the anterior wall of the thorax. And we can see the open-out thorax here. And the structures that we can see in front of us, these are all the contents of the post-tree media channel. We shall be focusing mostly on the arch of aorta and the descending aorta. But before that, just to orient you with the other structures, let me show you these structures here. This is the right brachiocephalic vein, the left brachiocephalic vein. You're adding to form the superior vinakiava. This is the arch of aorta. This is the trachea, which is bifurcating behind the arch of aorta. This structure that we can see here, this is the bifurcation of the pulmonary trunk. This is the left pulmonary artery, and these are the two right pulmonary arteries. Going further down, we can see the left principal bronchus here, and the right principal bronchus is further behind. This is the isophagus, the thoracic part of the isophagus. This is the part of the diaphragm that we can see here. And we can see the isophagus is coming out through the diaphragm. And we can see this is the abdomen, and we can see the continuation of the aorta into the abdominal aorta. So this is the orientation. And finally, just to complete the picture, this is the left side posterior thoracic wall with the neurovascular structures. And this is the right side, posterior thoracic wall with the neurovascular structures. Having mentioned that, now let's come to the arch of aorta and the descending aorta. The part of the arch of the aorta was inside the fibrosperic artery, and we had to remove it. And the fibrosperic artery emerges with the tunic advencia of the arch of aorta. So therefore, this portion of the aorta was inside the pericardial cavity. The ascending portion of the arch, then we have the arch itself, and then we have the descending thoracic aorta. The ascending aorta ends at the level of the sternal angle of Louie, which is the T5. The arch begins and ends at the level of T5. So therefore, the entire arch in the supine person is in the superior merestanum. The descending thoracic aorta begins at the sternal angle of Louie, T5 level. This arch, it does not go straight to the left. We can see it is going posteriorly and to the left. And therefore, when it curves like this, it compresses the ease of figures. And I shall show you how it compresses the ease of figures by turning it. And you can see it is compressing the ease of figures behind. So therefore, this is one of the ease of figure constrictions, which we see in a barium swallow, which is approximately at the level of 25 centimetres from the insides of teeth. And that is best seen because it is compressing from the side. It is best seen in an anterior posterior view. This is a barium swallow to show constriction of this thoracic part of the ease of figures by the arch of aorta. Under the arch of aorta, we can see this structure here. This is the recurrent line gel now on the left side. This is the vagus. The vagus is descending down. It goes behind the heilum of the lung and it gives this structure, which is hooking under the arch of aorta. This is the left recurrent line gel now. This goes just to the left of the ligamentum arteriosum, which connects the arch of aorta to the pulmonary trunk and then it goes up. If a person has an aneurysm of the inferior surface of the arch of aorta, it can compress the left recurrent line gel nerve and can lead to hoarseness of voice. Aneurysm of the arch of aorta is well known. In earlier days, when tertiary syphilis was very common, syphilitic erotitis generally tended to involve the arch and it produced aneurysmal dilatation and it can rupture. And at least one well-known celebrity has died from rupture of tertiary syphilitic aneurysm of the arch of aorta. Now let's continue the descending thoracic aorta. In the initial part of its course, it is situated to the left of the isophagus and we can see that here. But as it descends down, the aorta moves slightly to the right and concomitantly, the isophagus moves slightly to the left in front of the aorta. Finally, the isophagus goes out from the diaphragm at the isophageal hiatus at the level of T10, while the aorta itself continues and exits the diaphragm through the erotic hiatus at the level of T12. Arch of aorta and the descending aorta, it makes a deep impression on the medial surface of the left lung and in the lower part of the left lung, this isophagus lower part makes an impression just in front of the aorta. That brings me to the branches. The arch of aorta has got these three principal branches and we can see them here. The first branch that we can see here is this one. This is ptocephalic trunk, which divides into right common carotid and a right subclavian. The next branch that we can see here is this one. This is the left common carotid and the third branch that we can see here is this one. This is the left subclavian. So, these three branches are in the root of the neck. Now, let's take a look at the branches of the descending thoracic aorta. Here we shall follow what is known as the vascular plane concept. The vascular plane concept says, branches of the aorta are in three planes. The first plane arbitrarily referred to as plane A is the unpaired visceral plane, where a whole series of unpaired branches come out from the front of the aorta. And these are called unpaired visceral branches and most of them supply the esophagus. They are the esophageal branches. They also supply the pericardium, which has been removed, and they also supply the mediastina. Then we have the paired visceral branch, which comes on one side to the left and to the right. They are the bronchial arteries. Two left bronchial arteries and one right bronchial artery, which of course can also arise from the posterior intercostal artery. That is called plane B for the paired visceral branch. And then we have the paired parietal branch, which goes posterior laterally and we can see them here. These are the posterior-costal arteries on the left side and these are the posterior-costal arteries on the right side. All the posterior-costal arteries except the first or the superior, the supreme intercostal artery, which comes from the costosurviger trunk, the rest are all branches of the descending thoracic aorta. So this is what is called the vascular plane concept. Now let's mention a few important clinical correlations pertaining to the aorta. I have already mentioned aneurysm of the arch of aorta and the subsequent image that I will show you shows an aneurysm of arch of aorta. I have also mentioned about syphilitic aneurysm, but that is not very common nowadays. This is an orangeogram to show a large aneurysm of the descending aorta. This is definitely not syphilitic. The thoracic aorta is prone to what is known as dissecting aneurysm, especially in hypertensive patients. If there is a small interval tear, blood contract between the intima and the tunica media or into the tunica media itself, if there is cystic medial necrosis and it can track down and this can lead to a tearing, crushing pain which is radiating to the back which can mimic myocardial infarction and it can lead to occlusion of the branches of the aorta. That is called dissecting aneurysm. The aorta is a very important and a useful root for angiograms of all sorts, whether it is the aorta gram itself or the branches. Or we can even use the aorta as a root for coronary angiogram and the access to the aorta is through the femoral artery which is way down here. This is a digital suppression angiogram of arch of aorta to show the three main branches of arch. To continue, we have a digital anomaly involving the arch of aorta and that is referred to as coactation of aorta. We can have two types of coactation of aorta, one is called a pre-ductal coactation which occurs in infants and that is before the ductus arteriosus. That is usually associated with the patient ductus arteriosus, we shall not talk about that. There is a much more common one which occurs in adults and that is called the post-ductal coactation that is after the ductus arteriosus. When there is a post-ductal coactation of aorta then the lower part of the body is not receiving enough blood supply and therefore in order to compensate what happens is the posterior intercostal arteries wax eloquent. They become very big and they become tortuous and the blood flow in the posterior intercostal arteries get reversed. Normally the blood flow goes from the aorta all the way across like this to the chest and then they go to the front of the chest where they are most with the anterior intercostal arteries which are branches of the internal thoracic but in coactation of aorta because the lower part of the body is not receiving enough blood supply the blood flows from internal thoracic artery one of which we can see here that flows from the internal thoracic artery and it goes from the anterior intercostal arteries through the posterior intercostal arteries and back to the aorta to supply the body. In such situations the posterior intercostal arteries on both the sides they become dilated and tortuous and they can produce notching of the ribs. That's a very important sign. Additionally in an x-ray because of the coactation we can see what is known as the number 3 sign of the aortic knuckle. The arch of aorta radiologically appears as a knuckle which is a radiological sign but in this case because of the coactation it looks like a 3 that is called the number 3 sign. This is a chest x-ray to show the number 3 sign of the aortic knuckle and the notching of the ribs in coactation of aorta and this is another plain x-ray to show a normal aortic knuckle produced by the arch of aorta. And because of the dilatation of the posterior intercostal arteries and their communication with the tortuous scapular arteries there will be pulsation between the scapula on the back and that is referred to as dancing scapula. So these are some of the findings that we can see in coactation of aorta because in coactation of aorta the blood supply to the distal part of the aorta and the rest of the body is seriously jeopardized and this is the compensation. The point to be remembered is this reversal of flow in the posterior intercostal arteries occurs only up to the ninth intercostal space because the 10th, 11th and the 12th, 12th is a sub-costal they do not have any anterior intercostal arteries so therefore there is no reversal of flow. Reversal flow occurs only up to the ninth intercostal space so that is about the coactation of aorta. We can have a few other congenital anomalies pertaining to the subclavian artery we can have the right subclavian artery arising from the left side and going behind the isofagus that is referred to as a retro isofagal subclavian artery. Sometimes really we can have a double aortic arch both these conditions can trap the isofagus and lead to dysphagia. So these are some of the congenital anomalies and other clinical correlations pertaining to the thoracic aorta and their branches. Thank you very much for watching. Dr. Sanjay Sanyal signing out. If you have any questions or comments please put them in the comment section below. Have a nice day.