 I am holding the ebisterated heart in my hand. Let's take a look at the aortic vestibule that's the aortic outflow here. So we can see that the aortic outflow has got three cellular valves and three aortic sinuses. This is the right aortic sinus. This is the left aortic sinus. And this is the posterior aortic sinus. Sinuses are small dilatations of the aortic wall just about the cellular valves. And this is where blood fills up during distal and it leads into the coronary osteum. So let's take a look at the right coronary osteum. My instrument has gone into this coronary osteum here. This is the right coronary osteum from the right aortic sinus. And if I were to turn this, we can see the left coronary osteum in the left aortic sinus. So this is where the coronary arteries originate from. Now let's trace the right coronary artery. This is the right coronary artery. Initially it runs in the right part of the atrial ventricular groove and it is partly under cover of the right oracle. As it runs to the right, it goes to the posterior aspect of the heart. Now it's in the right posterior coronary groove. And here it is known as the right posterior coronary artery. When it reaches the crux of the heart. The crux of the heart is a communication between the posterior interventricular groove and the posterior coronary groove. So this is the region of the crux of the heart. When it reaches the crux of the heart, the right posterior coronary artery makes a 90 degrees bend and it travels in the posterior interventricular groove. And here it is known as posterior descending artery. You notice that this artery is very tortuous here. This is the feature wherever arteries are located in organs which are mobile they tend to be tortures. So, this is the posterior descending artery and this runs in the posterior ventricular groove and here it terminates in the lower part of the posterior ventricular groove. The point to be remembered is that this does not enastomose with the anterior intram ventricular artery which I am going to show it just a little later. This is the coronary angiogram of the right coronary artery to show the course of the RCA. Now, let's take a look at the branches which are coming out from the right coronary artery. We can see these branches this one here and this one here. These are the branches unnamed branches to the right ventricle. The coronary artery supplies the majority of the right ventricle and the right atrium. You cannot see the branch to the right atrium but there is a branch which goes and that's known as the anterior branch to the right atrium and that's the one which supplies the SA node in 60% of the population. Then we see this branch here. This is the right marginal branch. This runs along the inferior part of the heart which is formed by the right ventricle. Now, let's take a look at the right posterior coronary artery. We can see this branch. This branch goes into the substance of the heart and this is the one which supplies the atrium ventricular bundle of his and it also supplies the AV node in 80% of the population and finally we have this portion of the right coronary artery which I mentioned was the posterior descending artery and this supplies the inferior or the diaphragmatic surface of the heart which is formed mostly by the left ventricle. Therefore ischemia of this portion will produce inferior wall myocardium infarction. That is the point to be remembered. While it is traveling in the posterior ventricular groove it gives multiple septal branches and if you lift this up we can see the some septal branches going into the interventricular septum and these septal branches supply the posterior one third of the interventricular septum. So this is the full course of the right coronary artery. Again I'm turning the heart back to show the left coronary artery. This is again the left osteum, the aortic sinus and my probe has gone into the left coronary artery. So this is the left main coronary artery. This also runs in the left part of the interventricular groove. In the initial part of the course it is partly under cover of the left oracle and there it divides into two main branches. This is the anterior interventricular artery also known as the left anterior descending artery and this is the circumflex artery. This is the left coronary angiogram to show the division into LAD and circumflex. Let's take the anterior interventricular artery first. This is the one which descends down in the anterior part of the interventricular groove. It is also referred to as the LAD, left anterior descending artery in clinical parlance. As it descends down in the anterior part of the interventricular groove then it goes beyond the apex of the heart and it goes a little bit into the posterior interventricular groove. The point to be remembered here is that it does not anastomose with the posterior interventricular artery. So this is the full course of the LAD. Now let's take a look at the branches of the LAD. We can see these branches here. These are known as diagonal branches. In short they are referred to as D. There can be more than one. So here we can see D1, D2, D2 itself is dividing into 1 and 2. Then we have D3, D4. These are the ones which supply majority of the left ventricle. LAD also supplies a little bit of the right ventricle. Then we have branches which go into the septum, interventricular septum and if I retract this we can see the septal branches here. These are the septal arteries and these septal arteries they supply the anterior two-thirds of the interventricular septum and they also supply the right and the left bundles of the atrioventricular bundle. The LAD also supplies the atrioventricular bundle of his. Now let's take a look at the circumflex artery. The circumflex is called circumflex because it winds around in the posterior part of the atrioventricular groove and as it winds around here it is accompanied by the great cardiac vein. So here we have an anatomical curiosity. Normally when an artery accompanies a vein blood in the two of them flow in opposite directions that is the normal anatomical situation. Here we have a groove where the artery and the vein are running together and the blood in both of them are flowing in the same direction. The circumflex winds around the atrioventricular groove and goes to the posterior aspect and as it goes it gives off this branch here. This is known as the left marginal branch. In clinical power lines it is also referred to as the obtuse marginal. In this category we see only one but there can be more than one in which case it is referred to as OM1, OM2 etc. So here we have OM1 and then the circumflex continues and it goes into the substance of the left ventricle and it supplies the majority of the left ventricle. The circumflex artery also supplies the atrioventricular bundle of his. So therefore the atrioventricular bundle of his is supplied by anterior interventricular artery, posterior interventricular artery and the circumflex artery. So this is the full course of the three major arteries. This is the digital subtraction angiogram to show the LAD and the circumflex. Now let me mention some important clinical correlations. As we all know the coronary circulation is important from the perspective of angina pectoris and myocardial infarction and this is a very common site of occlusion by atherosclerosis. So let's take a look at the frequency of occlusion of these arteries according to worldwide statistics. Most frequent site of occlusion is the LAD. The second most frequent site of occlusion is the initial part of the RCA, right coronary artery. The third most common site of occlusion is the circumflex. The fourth most common site of occlusion is the left main coronary artery. The fifth most common site of occlusion is posterior descending artery. This is the one I mentioned when it gets occluded it produces diaphragmatic or inferior wall ischemia. In such a situation the pain is not the typical anginal pain instead the pain will be felt in the epigastrium and it can mimic gastritis and can lead to a diagnostic confusion. And the sixth most common site of occlusion is the right posterior coronary artery. So these are the sites of coronary occlusion in order of frequency. So that brings me to yet another important clinical correlation and that is coronary artery bypass grafting. Whenever there's any occlusion we need to bypass the occlusion. The usual method of doing it is either to take the long syphilis vein or to use the left internal mammary artery. That is one method that is CAVG. The other method which is preferred by cardiologists is to first do an angiogram and after the block has been located it is opened up by means of a special technique called angioplasty and then a stent is inserted and that is referred to as percutaneous transcornery angioplasty. Root can be either through the femoral artery or through the radial artery or through the brachial artery. So these are the two techniques which are used worldwide for overcoming an occluded portion of the coronary artery. That's all for now. Thank you very much for watching. Don't forget to send your send your sunny out. Please like and subscribe. If you have any questions or comments please put them in the comment section below. Have a nice day.