 Let me give you a quick overview of the pulmonary outflow and the aortic outflow. The anterior one is the pulmonary outflow, the posterior one is the aortic outflow. Pulmonary outflow is also referred to as the infundibular. If you take a look, these are the three semi-lunar valves. They are called semi-lunar because they are shaped like half a moon. The pulmonary outflow, the three semi-lunar valves are named one anterior left and right. In the case of the aortic outflow, we can see that the valves are closed already. Here, the relationship is opposite. Here we have two anterior left and right and one posterior. Let's mention a few quick words about the semi-lunar valves themselves. The margin of the valve is called the lunule. And the central portion of the valve is a little thick and that is called the nodule. And we can see the nodule in this closed aortic valve. This nodule is responsible for allowing tight closure of the valve. And that is what we see. Above the testament of the semi-lunar valves to the respective valve, either to the pulmonary or to the aorta, we see there is a small dilatation. That is referred to as the sinus. So in the case of aorta, this is referred to as the aortic sinus. In the case of the aortic sinus, they are more important functionally and clinically. This is the right aortic sinus. And this is the left aortic sinus. These are the places which are responsible for diastolic filling. That means during diastole, when the valves are closed, these sinuses fill up with blood. The right aortic sinus gives passage to the right coronary artery. And we can see the opening of the right coronary artery if we look very closely here. And my instrument has gone in. This is referred to as the right coronary osteum. Similarly, on the left side, we have this left aortic sinus and that gives passage opening to the left coronary artery. So during diastolic filling, it gets filled with blood and the coronary arteries get filled up with blood. And in the case of the aorta, the posterior aortic sinus does not have any coronary. In the case of the pulmonary artery, the sinuses are not so functionally important. This is the mitral valve on the left side, anterior cusp, posterior cusp. And we can see the cordy tendinitis to the papillary muscles. The most common pathology involving the mitral valve is the what is known as mitral stenosis where there is narrowing of the mitral valve. The opposite condition is called mitral regurgitation where the valves do not close during systole and therefore blood moves from the left ventricle to the left atrium. So stenosis means narrowing. Regurgitation means non-closure, leading blood to flow in the opposite direction. We can have a similar pathology on the right side also. So this is the tricuspid valve. We can see the anterior, posterior and septal. We can have tricuspid stenosis, tricuspid regurgitation. However, mitral stenosis is more common. Again, we can get erotic stenosis and erotic regurgitation. In erotic stenosis, the blood does not flow out symmetrically and in regurgitation, blood flows back down into the left ventricle. Similarly, we can get pulmonary regurgitation and pulmonary stenosis. However, erotic stenosis is more common than pulmonary. The most common condition where you can get valvular pathology is atherosclerosis, ischemia or congenital defects. Though, of course, they can also be due to rheumatic heart disease. So these are some common defects which involve the erotic valve, pulmonary valve, tricuspid valve and mitral valve. The next point which I want to mention to you was about the location of hearing the sounds. Mitral valve sound is heard at the apex of the heart, which is in the fifth left intercostal space, one palm width from the midline. Tricuspid valve closure is heard in the left fourth intercostal space. Pulmonary valve closure is heard in the second left intercostal space and erotic valve closure is heard in the second right intercostal space. So these are some clinical correlations pertaining to the four valves of the heart.