 So, this is going to be a demonstration of the medial stannum and the intrathoracic contents. Basically, we shall give an overview. So, this is the thoracic cage which has been stripped of all its muscles. Let's take a few landmarks. This is the juggler notch of the manabrium sterni. This is at the level of the upper border of T3 vertebra. This is the manabrium sternal joint which corresponds to the sternal angle of Louis. Second rib is attached here. This is at the level of upper border of T5 vertebra. And this is the zeefe sternal joint where the seventh rib is attached here. And this corresponds to the upper border of the ninth thoracic vertebra. So, T3 vertebra, T5 vertebra, T9 vertebra. So, that brings me to classification of the medial stannum. From T3 to T5, that portion of the medial stannum is referred to as superior medial stannum. From T5 to T9 is the so-called inferior medial stannum. But we don't call it inferior medial stannum. We subdivided further into an anterior medial stannum, a middle medial stannum and a posterior medial stannum. Before I tell you the contents, just to complete the story, above T3, above the juggler notch, is the root of the neck or the thoracic inlet. And that is bounded by the juggler notch here, the first rib here and the first thoracic vertebra. The first rib here is sloping at an angle of 60 degrees with the horizontal. And therefore anteriorly it is articulating with the medial stannum here, which is at the level of T3. But posteriorly it is articulating with the first thoracic vertebra which is at the fold. The sloping first rib constitutes the root of the neck and the thoracic inlet. Let's come to the contents of each of those, which I shall show you once I remove the chest wall. The superior medial stannum contains basically the arch of aorta, bifurcation of the pulmonary trunk and the superior venequeva. The anterior medial stannum is the portion just behind the sternum. And that contains mostly fibro fatty tissue, and it contains a little bit of the thymus in children. The middle medial stannum is the one which is occupied by the heart and the pericardium. And the posterior medial stannum are the structures between the heart and the vertebral column, thoracic vertebrae. More specifically, the aesophagus, the azygous vein, thoracic duct. So these are the contents. And now I shall show you the contents by removing this chest wall. We have already cut it on the lateral margin. We have cut it on the lateral side here. And now we are going to remove the chest wall. Now we are seeing the entire intratheuristic contents inside. So before I go to the other parts of the contents, let me repeat what I had mentioned earlier. Basically, what is the medial stannum? The medial stannum are the contents between the two plural cavities. The superior medial stannum we said is the arch of aorta. And this is the arch of aorta here. And just next to that is the pulmonary trunk. And on this side is the superior vena cava. So these are located in the superior medial stannum. This structure that we see here, this is the fibrospericardium enclosing the heart. This occupies the middle medial stannum. And I had already mentioned that between the heart and the sternum, there is a very small space which was filled with fibrophatic tissue which we have removed. That was the anterior medial stannum. And not visible here, but it will be visible once we remove the heart and the pedicardium will be the posterior stannum. Which is between the heart and the thoracic vertebra. And just to complete the whole story, these are the branches from the great lessons. Namely, the brachiosephalic artery, the right brachiosephalic vein, the left brachiosephalic vein from in the superior vena cava. These are the ones which are located in the root of the neck or the thoracic inlet. The thoracic inlet basically are the structures which go from the neck to the thorax and vice versa. And they also contain the branches of the great vessels. So these are the classifications of the medial stannum and the broad distribution of the contents. The lower limit of the chest is the diaphragm here. This is the remnant of the left dome of the diaphragm and this is the remnant of the right dome of the diaphragm. So this is the full extent of the intrathoracic cavity. Now let's take a quick overview of the intrathoracic contents inside. This is the right pleural cavity. This is the left pleural cavity which is occupied by the respective lungs. So these are located in the pleural spaces. And here we can see, I put my finger between the lung and the chest wall, remnant of the chest wall here. This is the pleural space. The inner margin of the chest wall is covered by the parietal pleura and outside that is the endothoracic fascia. This surface is covered by the visceral pleura. The potential space in between the two where my finger is facing that is the pleural space. The same thing can be shown here. This is the chest wall. This is the pleura. So this is the potential space. This is the pleural space which we have highly exaggerated in this dissection. So between the two pleural cavities and the lungs, the segment of the structures which are located in the chest cavity they are called the medial stannum. And here we can see that the middle medial stannum is the one which is most prominently visible here which is the heart occupied by the pericardium. And the great vessels emerging from the heart or entering the heart and their branches and the root of the neck. So this is the overview that I wanted to give you. Thank you very much for watching. If you have any questions or comments, please put them in the comment section below. Dr. Sanjay Sanyal signing out. Mr. Kendal Kambor Batch is the camera person. Have a nice day.