 Valves are the critical anatomical structures that prevent blood from going backwards. For whatever reason, our blood flows from atria to ventricles to somewhere, to atria to ventricles to somewhere, to atria to ventricles to somewhere, and it goes in that order, and it has to go in that order. It flows in a direction, and if the blood flowed back and forth, we really couldn't ever clean it, and we, like, wholly inefficient, bad idea. Let's not do it. Let's employ some valves. There are three types of valves I want to talk about, and only two of them are found in the heart. So, who are they? The first valves you're going to look at are, oh, geez, did I really, what was that? Nobody knows. The first valves I want to look at are called AV valves. AV valves are also known as atrioventricular valves, and atrioventricular valves are between the atrium and the ventricle done, and yes, you can call them AV valves if you would like. I wonder if that's standard, or if you have to spell it out in most classes. If my AV valves are between, I'm going to color my AV valve in yellow. Here's my atrium, here's my ventricle. That means that this is my right AV valve, and the right AV valve is also called the tricuspid valve. So, if you hear tricuspid, it's the right AV valve that they're talking about. Guess who this guy is over here? Between the left atrium and the left ventricle, that is the left AV valve. Let's just do that right and left. The left AV valve doesn't just have one additional name, bicuspid. It has two additional names. It's also called the mitral valve. So, the mitral valve and the mitral bicuspid or tricuspid or right and left AV valves, whatever you prefer. Isn't that fun? Choose your own adventure. Okay, here's the other interesting thing about my AV valves. I'm going to draw them in here because they aren't actually drawn in. You have these amazing connective tissue, like crazy strong cords that connect your floppy little valves to the walls of the ventricles. And this is only, they're only found in our AV valves. And they're called cordae tendinae. Cordae tendinae. The cordae tendinae are attached to, like little bumpy muscle projections of these R-cardiac muscle and they're called papillary muscles. And they help hold, you could imagine, I mean the valves are floppy. Like they're almost like folds of endothelium and they've definitely been reinforced by some kind of super strong connective tissue because they're unbelievable structures. But if you didn't have them, if you didn't have the cordae tendinae attached to these things, they would flap backwards because they're just kind of a little too floppy. And so the papillary muscles in the cordae tendinae hold onto and anchor the AV valves. Do semi-lunar valves have cordae tendinae and papillary muscles attached to them? No, no, no, except I haven't even told you what semi-lunar valves are yet. Oh, I'm getting super ahead of myself which is always fun, especially when there's nobody here to say, hey, blow your roll, doggie. Semi-lunar valves, semi-lunar valves, okay, I'll put them right here. Semi-lunar valves are my valves that are preventing backflow from the ventricles out to wherever we're going. So, and they're not called right and left. But they're just as easy because if this is a semi-lunar valve, I'm gonna point my little arrow here and go semi-lunar valve and know you cannot abbreviate the semi-lunar valve, sorry. What vessel is this giant tall tree-like vessel coming out of the right ventricle? That's the pulmonary trunk. So guess what kind of semi-lunar valve that is? It's the pulmonary semi-lunar. That says pulmonary. Pulmonary semi-lunar valve? Here's another semi-lunar valve, except this one is attached or preventing backflow from the ascending aorta, which means it is the aortic semi-lunar valve. Those are my semi-lunars. I have to tell you this part because I think it's so cool. Did I already tell you this? Why aren't you answering me? I'm just kidding. I know that you're not really there. It is late in the evening though. Okay, this is the coolest thing about valves. Go ahead and listen to your heart. You can totally hear your heart beating, right? Love dub, love dub, love dub. Guess what? Love comes from your AV valves. Oh, jeez, love. Your AV valves snap, shut, and you hear love. And the dub, or dub, comes from the snapping shut of the semi-lunar valves. What? That's crazy talk. Can you look at them? You'll be like, uh-uh, not possible, sorry. There's no snapping of those little floppy pieces of floppiness, but it's true. They make your heart sounds. So a heart murmur is when the valves don't snap all the way shut and a little bit of blood creeps through and you can hear it. Instead of hearing dub, you hear shh, love shh, shh, dub. I can't hear it for anything to save my life, but you guys someday will be listening to heart sounds and you will be able to hear it. I said there were three types of valves and I'm going to give you a hint and I'm going to put my third type in this color, hint, hint. We actually have valves in our veins and the valves in your veins are very similar to the semi-lunar valves in that they don't have cordy tendin A, they don't have papillary muscles attaching them, but they're just these little flaps that however they structure, they prevent back flow of blood in your veins. If your venous valves start to get floppy or break down, you can get varicose veins. Varicose veins are just kind of blown out and expanded vessels, veins, because the valves in your veins aren't working. Okay, now you have all the valves that you've ever wanted to have. You know everything you want to know about the heart. We're going to like play with fresh and preserved hearts in lab and it's been a great day and we'll talk to y'all later.