Since this is a lecture about heart anatomy, perhaps we should talk about the heart's anatomy. So just to remind you where we are, here is my thoracic cavity and my pleural cavities inside, and this is all mediastinum, and inside of that, a pericardial cavity. And inside pericardial cavity, here's my heart. Within life, the heart sits kind of on its side, and it also sits with its right atrium and right ventricle facing you, which means the left ventricle and the left atrium are sort of on the backside of how the heart actually sits in the body. I want you to have this perspective because the next picture that I'm actually going to draw on is how the heart has the heart in this position, and I don't want you to forget the orientation. In lab, when we dissect sheep hearts or pig hearts or whatever kind of hearts we can get our hands on, we will, you will have to orient yourself for what is anterior and posterior on the heart, and that will certainly help you identify various heart structures. So let's take a look at, let's start labeling heart parts. First of all, we have the diaphragmatic surface because if you imagine this heart could set down, that's a diaphragm. It could set, like it does, it rests upon the diaphragm. And so therefore, this end down here is the diaphragmatic surface. Diaphragmatic surface. Diaphragm. That's interesting. Okay, and I told you already that the right ventricle and the right atrium are facing us. There's the right atrium. This is the right ventricle. Fantastically, there is an interventricular structure that separates the left and right ventricles and it actually is slicing down the inside of the balloon-like heart. Did you just follow what I just said? And there's a structure on the outside. It's a sulcus. It's a gully. It's a dip. And it's the anterior interventricular sulcus. And I'm not going to be able to draw it, but there's vessels in it. I don't know who those guys are, but this is the anterior interventricular, that says ventricular sulcus, dip. Just like we saw sulcuses in the nervous system, in the brain. So it's just a dip. And look, who's living inside of that dip? We actually have some blood vessels that are feeding and draining the heart. And we're going to talk about those guys down here when we talk about coronary circulation. The anterior interventricular sulcus separates the right ventricle and the left ventricle. So over here, this is left ventricle. The apex of the heart is the point. And the other surface anatomy structure of the heart that isn't really in the surface, in the inside of you, is the base of the heart. And the base, I can't show you, because the base, look at what I'm going to do. The base is back there. So did you see how I like showed you? That's like super cool perspective. That's the bases back there. And also back there is a posterior interventricular sulcus that is a little groove that blood vessels live in. And it separates the right and left ventricles on the other side. So you can imagine that if I'm heading around, this is left ventricle, left ventricle, left ventricle, left ventricle, but eventually back there somewhere, we're going to start being right ventricle again. And it's separated by another really nice sulcus filled with blood vessels. There's another sulcus here. This one is called the coronary sulcus.  It almost goes between the right ventricle and the right atrium, and it's the coronary sulcus. Think about it, and we'll talk about this in coronary circulation, but since we're here, the heart is pumping blood to everybody.  The heart feeds itself first. The heart puts on its oxygen mask first by draining blood immediately out of the fresh, delicious oxygenated blood. It gets drained immediately into the heart muscle because if the heart muscle doesn't have enough food and energy, it's not going to get food and energy to anybody else. So it's pretty much worthless to try and feed everyone else if you don't feed yourself first. Got that? All right, good lesson from the heart. Thanks, heart. I think that's everything that I need to show you from the outside of the heart. And once we start adding in our vessels, this is what we're going to do next, then we're going to have... then things are going to get more... I don't know what I'm even trying to say. I'm just going to leave now because I don't know how they're going to get. Goodbye.