Arteries and Veins – Anatomy of the Heart

00:00 So, again, let’s talk a little bit about one of the other structures in the heart that’s important- the coronary arteries. The coronary arteries are like the fuel line in your car.

00:10 If you don’t have a good open fuel line and gasoline doesn’t get in or diesel fuel doesn’t get in your motor, you know what happens- the motor doesn’t function. The same is true about the heart. It needs oxygenated blood to nourish it and to enable it to continue to do its mechanical activity. And the heart is a remarkable organ. Remember it beats constantly, has to continue beating of course, if you want to stay alive. Sometimes for many, many years, 80, 90 years, sometimes even a 100 years. It’s a remarkable, strong muscle that is very resistant to injury except when certain diseases occur, but in fact, often tries to do its best job even when injured. So, there are, of course, two main coronary arteries - there is the left coronary artery and the right coronary artery. You say to me, “Wait… wait… wait a minute, my uncle had a triple coronary bypass. Where is the third coronary artery?” The third coronary artery occurs because the left coronary artery branches early on after its origin. It branches into the left anterior descending coronary artery and the left circumflex coronary artery. So, what are we talking about here? We are talking then about two main arteries that start, but one very quickly divides into two main branches so that’s how we have the three coronary arteries that are talked about.

01:32 We are going to come back and talk more about the coronary arteries and I am going to show you some pictures from a CAT scan, but let’s take a look inside the heart for a moment.

01:41 I wanted to just reiterate the return of venous blood to the heart. What you are seeing here is a little diagram of the inside of the right atrium and you will notice that there are three circles, and these three circles represent the venous drainage coming into the heart.

02:00 The highest one, the one that’s up top, is the entrance of the blood from the superior vena cava, that blood enters the right atrium and drains the venous blood from the upper part of the body. Now, if you look at the second one just below that, that’s the one from the inferior vena cava that’s draining blood from the bottom of the body. So, what’s the opening there on the right hand side? That’s the coronary sinus, that’s the heart’s venous system coming back in, because of course the heart’s getting oxygenated blood, it has to have venous return to the heart so it returns also to the right atrium.

02:37 So, upper part of the body, the lower part of the body and the heart all drain into the right atrium and then of course, they pass through the tricuspid valve into the right ventricle, they are pumped to the lung where the blue blood becomes red as it takes on oxygen and gives off carbon dioxide.

02:55 So, here we are back to the coronary arteries- and this is actually a CAT scan that shows you… it’s colorized by the way. These are artifical colors put in to make it look realistic. But in fact, you can see very clearly the coronary arteries here. You can see the right coronary artery, the left anterior descending, and the left circumflex. The right coronary artery supplies the right ventricle, part of the septum- the wall between the left and right ventricles and part of the back of the heart. The left anterior descending coronary artery supplies the front of the heart and part of the septum. And the left circumflex coronary artery supplies the lateral wall of the heart and also part of the back of the heart. And of course, blockage in any one of these can cause a myocardial infarction or a heart attack. Here you see, the CT in its natural state- not colorized artificially, but you can see very clearly the coronary arteries coming off the left, the right, the anterior descending and the circumflex.

03:58 So, we have reviewed the heart anatomy. The one thing we haven’t talked about is the pericardium. The pericardium, of course, is the constraint. It’s the plastic bag, if you will, that keeps the heart nicely shaped within the chest, doesn’t allow it to over expand and protects the heart as well. It’s filled with a little bit of fluid so that the heart is able to move smoothly within the pericardium. When disease happens to the pericardium and it becomes thickened or weeps fluid into that space, then of course we can have restriction of heart function and we are going to talk about pericardial diseases as we go along.

04:37 Well, that was a quick run through cardiac anatomy. You see a few references here that can help you to read a little more about it. I would like to reiterate what I have done here is given you a very quick view, if you will, like in an airplane from 35,000 feet. If you want to have a little more detailed look at the ground, you need to do some more reading to… more fully understand the cardiac anatomy. We are looking forward now to the next lecture, where we are going to talk about the function of the heart, that is it's physiology.