 Dr. Sanjay Sanyal, Professor, Department Chair. Today, we are going to demonstrate the structures which are inside the heart. So, let's start off with the semilunar valves. So, here in front of us, we can see the semilunar valves of the aortic outflow, the posteriorly, and these are the semilunar valves of the pulmonary outflow. So, let's start with the semilunar valves of the aortic outflow. The aortic outflow of the semilunar valves, we have got two anterior and one posterior. And these are the cusps of the valves. Just above the cusps of the valves, there are small dilatations of the aortic valve, which are referred to as the aortic sinuses. The valve margins are called lunules, and the central portion of the valve is known as a nodule, which is a slightly thickened portion, and this allows a watertight junction. The aortic outflow has got, as I mentioned, an out-right anterior and a left anterior. And at this sinuses, we have the ostium for the right coronary artery and for the left coronary artery. The posterior aortic sinus does not have any coronary vessel, therefore it is referred to as the non-coronary sinus. The same principle applies to the pulmonary semilunar valves. The only thing is that the sinuses do not have any structures coming out of them, but otherwise the structure of the valves are the same, namely a margin called the lunule and the central portion called the nodule. The other difference on the pulmonary side is that there are two posterior, right and left, and one anterior, gusp. So these are the outflow. This is the outflow of the pulmonary, which is called the pulmonary infundibulum or the conus arteriosus, and this is the outflow of the aorta, which is referred to as the aortic vestibule. Having mentioned that, now let's come to the interior of each of the chambers of the heart. So this is the external view of the right atrium. And how do we know this is the right atrium? We can see the opening of the supirevena caver here, and we can see the opening of the infirevena caver here. And there's a shallow sulcus on the outside, which is referred to as the sulcus terminalis. We will reflect the walls of the atrium. These are the structures that we can see inside. First of all, we can see the smooth portion, posteriorly. This is the inflow portion of the right atrium, and this is referred to as the sinus venerian. This is the portion which has been denied from the sinus venousis. And the rough anterior portion, which is being held here by my assistants, this portion and this portion, this is called the pectinate part. And these ridges are referred to as the muscular pectinatei or the pectinate muscles. What separates the smooth portion from the pectinate portion? We can see a ridge here. This is called the crista terminalis. Crista terminalis is the counterpart of the sulcus, which is on the outside, the crista is on the inside. This is one part of the crista terminalis, and if we were to turn this, we will see the other part of the crista terminalis here. The portion anterior to that is the pectinate part, the posterior to that is the sinus venerian. From here, we can see the opening of the supirevina keva and we can see the opening of the inferior vina keva. We can see the opening of the coronary sinus here. This is the opening of the coronary sinus. My probe has gone into the opening of the coronary sinus. Now if you were to look at it from inside, we will see that there is an indistinct valve at the opening of the inferior vina keva and there is a valve at the opening of the coronary sinus. The one at the opening of the coronary sinus is referred to as the Thebesian valve. We can see a depression here in the interatrial septum. This depression is the remnant of the foramanoval and that is referred to as the fossa ovalis. An vitriol node is located at the upper end of the crista terminalis near the opening of the supirevina keva. So it is in this region. The atrioventricular node is located near the opening of the coronary sinus. It is in this region. Finally, if you were to look deep inside, we can see the right atrioventricular valve or the tricuspid valve. Now let me turn the specimen and show the left atrium. These are the pulmonary veins. The two right pulmonary veins and the two left pulmonary veins. So we have split it open here and we can see the interior. The interior of the left atrium is completely smooth. This is the region of the interatrial septum. Here there is no fossa ovalis. Instead, this is the remnant of the septum primum and that is referred to as the valve of the fossa ovalis. And finally, on the left atrium, if you were to look deep inside, we will see the leaflets of the mitral valve and my finger has gone into it. So we have seen the right atrium and we see the left atrium. Now I am going to turn the model. I have made an incision on the anterior surface of the right ventricle. And for that, now we will lift it up here. Straight away we can see the structures related to the right atrioventricular valve. That is the tricuspid valve. Tricuspid valve has got three cusps. This is the anterior cusp. This is the posterior cusp behind and this is the septal cusp which is arising from the septum. The anterior cusp, these fibres that we see, these are the caudate intinane and they are all getting inserted onto the anterior papillary muscle. This is the posterior papillary muscle which also is attached to the caudate intinane of the posterior cusp of the valve. And this is the septal cusp which also is attached to the caudate intinane of the septal cusp of the valve. And I will show you the entry of the valve from the atrial side by putting my finger in. And once I put my finger in, you can see it is coming into the right ventricle. So therefore, the one this is anterior, the one which is towards the septal side is the septum and the one behind my finger is the posterior. We can see one ridge of muscle coming from the septum to the base of the anterior papillary muscle. This is referred to as the moderator band or the septomarginal trapeculae. A special set of conduction fibers travel through the septomarginal trapeculae or the moderator band and they initiate impulses in the anterior papillary muscle. And it is postulated that the function of the septomarginal trapeculae is to modulate and synchronize the contraction of the papillary muscles during contraction of the ventricle. And the function of the papillary muscles is that when the ventricle contracts the papillary muscles also contract so as to prevent prolapse of the leaflets of the valve back into the atrium. This ridge portion of the ventricular wall that we see here, this is referred to as the trapeculae carnea. These are thick muscular portions and which gives the ridge appearance. This is the outflow of the right ventricle which is referred to as the pulmonary infundabilum or the conus artigiasis. And we can see when I put my finger inside it is coming out through the pulmonary outflow. And these are the three cusps of the pulmonary valve, semilunar valves which I had mentioned earlier. We can see that the outflow portion is smooth while the trapeculae carnea is the ridge portion and there is a ridge. And that ridge is referred to as the supraventricular crest which separates the trapeculae carnea from the smooth outflow portion. And finally, where my finger is touching this is the muscular part of the intraventricular septum. So these are the structures that we can see in the right ventricle. Now let me turn the heart a little bit and show you the structures inside the left ventricle. And for that, again, we have made a special incision and this is the interior of it. The left ventricle is approximately three times as thick as the right ventricle because the left ventricle has to supply blood to the entire systemic circulation. It has to supply blood at a pressure of 120 mmHg. What are the structures do we see? We can see again, see the trapeculae carnea which is the thick ridge muscular part of the ventricle. Let's take a look at the valves. For that, I'll put my finger in the left atrium. Again, I put my finger in the left atrium it comes into the left ventricle. So keeping my finger in place we can see in front of my finger these are the anterior papillary muscles. And again, we can see that the tips of the anterior papillary muscles are attached to the corded tendinate which in turn are attached to the cusps of the mitral valve. And behind my finger we can see the posterior papillary muscle. This posterior papillary muscle is very clearly visible but we can see that these are the corded tendinate which are attached to the apex of the papillary muscles which in turn will be attached to the posterior cusp of the mitral valve. So this is the mitral atrium ventricular orifice. I'm going to put my finger in the aortic outflow and my finger is coming out through the aortic outflow. And we can see that when I put my finger in this portion is referred to as the aortic outflow, the aortic vestibule. And it is coming out and these are the three cusps of the semilunar valves of the aorta. Before I conclude, I need to show something significant. The blood flows from the right atrium into the right ventricle and my finger is pointing in that direction. After it comes then the blood has to flow out through the pulmonary trunk like this. So if you were to look at the direction of my both fingers you see that it makes a 90 degrees bend. The blood enters the ventricle and then it flows out of the ventricle and there's a 90 degree angle between my two fingers. In contrast, when I do the same exercise on the left side I put my finger in the left atrium and then I put my other finger in the aortic vestibule we can see that my finger is making a 180 degrees bend. So in a nutshell, in the left ventricle the blood makes a 180 degrees bend when it comes out of the ventricle. In the right ventricle the blood makes a 90 degrees bend when it comes out of the ventricle. So these are the structures which I wanted to show you inside the chambers of the heart. 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. Have a nice day.