 Good day everybody, this is Dr. Sanjay Sanyal, Professor of the Department Chair. So this is going to be a section of the media standard. So we have completely exposed the thoracic cavity, we have removed the two lungs from here, we have removed the heart from here, which I shall bring into the focus. Just to bring you up to speak, I am standing on the right side of the cadaver. Camera person is also on the right side. My assistants are on the either side. This is the head end. This is the foot end. You can see the two bones of the diaphragm here. This is the right side. That is the left side. So we have completely cleaned up the medistinal structures. First let's take a look at the obvious structures which are easily identifiable. So we can see this is the ascending aorta. The ascending aorta then becomes the arch of aorta. And the arch of aorta then goes to the left and posteriorly. And it continues down as the descending thoracic aorta. And after that it will escape through the aortic hiatus in the diaphragm. So ascending aorta is in the middle medistinum. The arch of aorta is in the superior medistinum. And the descending thoracic aorta is in the posterior medistinum. While you are looking at the arch of aorta, I will draw your attention to these three important vessels. We can see this one here. This is the brachioscephalic trunk, which will go up in the neck and it will divide into right subclavian and right common carotid artery. Next, this one here. This is the left common carotid. And the third one that you see here, these are the great vessels. This is the left subclavian artery. These great vessels, great branches of the arch of aorta are located in the root of the neck. While we are also looking at the arch of aorta, I will draw your attention to this ligamentous structure here. And if you feel it, you can feel that it is tendinous and chord-like. This ligamentous structure is the remnant of the ligamentum arteriosum, which was connected to the bifurcation of the pulmonary trunk, which I am going to show you in a different view. It is not visible here. And while we are looking at the ligamentum arteriosum, I will draw your attention to this structure here. This is the curving recurrent laryngeal nerve, which curves just lateral to the ligamentum arteriosum. And if I turn the arch, you can see this nerve. This is the recurrent laryngeal nerve. And I have picked it up with my forcep here. The recurrent laryngeal nerve comes from that side, lateral to the ligamentum arteriosum, and it curves under the arch of aorta and it climbs up on the neck. So this is the recurrent laryngeal nerve. So when there is an aneurysm of the arch of aorta, it can compress on the recurrent laryngeal nerve and it can produce hoarseness of voice. This is an important clinical correlation to be remembered. The next structure, which is visible to us, is the bifurcation of the trachea. So this is the trachea. We can see the tracheal rings. The trachea rings are C-shaped, elastic cartilage, and posteriorly the trachea rings are absent. They are covered by a muscle called the trachealis muscle. And at the level of approximately the sternal angle of Louis, they bifurcate into a right-principle bronchus and a left-principle bronchus. Now if you look very carefully, you will find that the right-principle bronchus is almost a direct continuation of the trachea. So therefore foreign body, inhaled accidentally, inhaled foreign body, will go directly into the right lung most often, more than 90% of the cases. That's why when we are doing a suspected foreign body removal, we will check in the right lung first through fiber-optic bronchoscopy. The left bronchus, principal bronchus, is slightly at an angle. We have removed the lung, which I am going to show you just after I have dissected this out. So this is the next structure. Remember the trachea is in the superior mediastinum. It does not extend beyond the superior mediastinum because it bifurcates at the level of sternal angle of Louis, which is the level of the fifth thoracic vertebra. And we can see the soft trachealis muscle at the back here. That's the next structure that we see here. Finally what we can see here is this structure which I have lifted up here. Guess what this is? This is the isophagus, the thoracic isophagus. It is in the posterior mediastinum. It starts from the superior mediastinum here. You can see it here. And then it goes from the superior to the posterior mediastinum. This does not have any cirrhosa. This was only covered by endothoracic fascia, which has been removed here. And that endothoracic fascia had the perisophageal vessels, perisophageal veins, and the parisophageal lymph nodes, which have all been removed. That is the problem. If the thoracic isophagus ruptures, it can produce very serious condition known as mediastinitis. The rupture of the thoracic isophagus because there is no cirrhosa to protect the thoracic isophagus. These are some of the remnants of the fascia which I am cutting just now. The next structure which I will draw your attention to is this vein that you see here. I am tracing with my instrument. This blueish colored structure that you see here. Guess what this is? This is the azygous vein. The azygous vein enters from the abdomen through the hiatus of the azygous vein. It is the same hiatus as the aorta, and then it becomes abdominal. And as it goes up, you can see it is receiving these veins. These are the posterior intercostal veins, and they are all draining into the azygous vein. And they are clearly visible here, and they are thrombosed. And if you feel it here, I can feel the thrombosed. In this particular cadaver, the veins, all the veins have got lots of abnormalities including thrombosis, which I shall allude to just a little later. To continue, the azygous vein, as it goes up, it goes behind the principal bronchus, which has been removed here, and you can see it is making an arch forward. We can clearly see that. This is called the arch of the azygous vein. It hooks forward, and it opens into the superior vena keva. So you are going to ask me, where is the superior vena keva? I will show it to you just in a little while. So this is the next structure that we see in the medias terrum. So what all we have seen till now? We have seen the ascending aorta, arch of the aorta, descending aorta. We have seen the trachea. We have seen the trachea and its bifurcation. We have seen the esophagus. We have seen the azygous vein. What we could not find in this particular cadaver was the thoracic duct. Quite often the thoracic duct is not visible, and in this particular cadaver, it was very small atrophied, and it was not clearly discernible. Having shown you that, I will show you a few other structures, which were the normalities in this particular cadaver. First, take a look at this venous structure here. We notice that this is a venous structure, because I can put my instrument here. This is the endothelium of the vein, and you can see my instrument has gone in. You can see this other end. My instrument has gone in here. If I trace it distally, you will find that my instrument goes in through another structure here. This lower portion here, if you focus the camera, you will see this lower portion here. This is the inferior vena cava. We just entered the abdomen through the cable hiatus. After that, the inferior vena cava is technically supposed to open into the right atria. I will show you the right atria, or what is left of it in the heart just now. We can see that this is continuous, and here it expands. This is actually the remnant of the right atria. Further up, this structure that we see here, this is the superior vena cava. Therefore, the superior vena cava and the inferior vena cava are almost in a straight continuous line with the remnant of the right atria intervening in between. This is the line which is the representative of the crystal terminalis in the right atria. The right atria was highly atrophied, and it was almost a part of the superior and inferior vena cava. Therefore, now we can understand that this particular vein that we see here, this is the right subclavian vein which is communicating with the internal superior vena cava which is aphelic which becomes continuous as the superior vena cava. So that is what we see in this particular cadaver. So this is one high abnormality. To bring you up to context, let me now take the heart itself and show you. So this is the heart. This was the orientation of the heart inside, and we can see that there's a big gap here. This was the location of the atria. And we can see this is the location of the atria ventricular orifice. So this was the location of the atrium. So from below was opening the inferior vena cava. From above is supposed to be the superior vena cava. It was located like this. This was how it was located. And again to show you the context, the heart was located here. And we can see this is the aorta. This is the aortic vestibule, and then it continues as the ascending aorta. And this is the pulmonary outflow, the infundibilum or the conus arteriosus. So you'll ask me where are the pulmonary vets, pulmonary arteries? I had to remove the pulmonary arteries because the pulmonary trunk was thrombose and quite disorganized so I had to remove it. But I retained the branches of the pulmonary artery in the lungs. So I shall bring the lungs into field of view right now. So this is one lung here. This is the right lung. And we can see this is the right pulmonary artery. It was here, like this. It was just below the arch of the aorta. So this is the right pulmonary artery. And we can see it is dividing into a superior and inferior just before it enters the high lung of the lung. Since we are already at the high lung of the lung, I will draw your attention to this structure here. This is the right principal bronchus. And further below, we can see these structures here. These are the pulmonary veins. There was no clear cut left atrium in this particular cadaver. That's why we could not see the clear left atrium. All the pulmonary veins drained into a very rudimentary kind of left atrium. So now I'm going to remove the right lung. Now I'll show you the same thing on the left lung. So this left lung was located like this. You can see only one fissure here. And we can see this is the left principal bronchus. You can feel the cartilage on the margins. And I can feel the tracheolus muscle behind. Then this is the left pulmonary artery. A single one entering into the left lung. And the lower most we can see this structure here. These were the pulmonary veins. And you can see two of them, one here and one here. So these pulmonary veins, two from the left and two from the right, are supposed to open into the left atrium. But we could not identify the left atrium. Therefore, this is the, come back to this structure here. This is the ligamentum arteriosum, which was connecting the arch of the outer to the bifurcation of the pulmonary trunk, which has been removed. But I showed you the pulmonary arteries in the two lungs. And just lateral to that we can see this is the recurrent aniginous nerve curbing around. Okay, let's come back. The next structure I will draw your attention to is this here. The left and right end has lift up the other side. What are these two structures? These are the phrenic nerves. The phrenic nerves that come from the neck C345 and they run on the surface of the pericardium. I have completely separated them and they disappeared into the diaphragm. As you can see, the left phrenic nerve is disappearing into the left dome of the diaphragm. Now the right phrenic nerve is disappearing into the right dome of the diaphragm. They also supply the pericardium with sensory branches. So these phrenic nerves run in front of the pulmonary hyalum. So if there's any lesion of the pulmonary hyalum, like for example enlarged lymph nodes and they expand anteriorly, they can compromise the phrenic nerves and can produce hemi paralysis of the diaphragm. So these are the structures that we can see in this section of the medial sternum. Just to recap quickly, these are the phrenic nerves. This is the ascending arch of the aorta with the three branches from the arch and the descending thoracic aorta in the posterior medial sternum, the isophagus extending from the superior to the posterior medial sternum, the trachea with its bifurcation right in the left principal bronchus, the pulmonary trunk which has been, which was thrombosed and destroyed so therefore we had to remove it. But I showed you the pulmonary trunk arteries in the lung specimen. Then we have this vein here. This is the azagus vein on the right side which is closely adhering to the vertebral bodies and this is the arch of the azagus vein which was opening into the superior vena keva and we can see the posterior intercostal veins draining into the azagus vein. So these are the structures which I wanted to show you in this particular section of the cadaver. Thank you very much for watching ladies and gentlemen. Have a nice day. Dr. Sanyas Sanyas signing out please like and subscribe.