 Drastic! Hey everybody, Dr. O, in this video I'm going to cover the key internal structures of the heart, and then in the next video I'll actually cover the path that blood takes through the heart. So again, we won't go through everything. We've already covered the external features. I just want to cover the main things that we can only see by cutting the heart open. So just so you know, the atrial ventricular septum between the two atria and ventricles has been removed or else you couldn't see the valves. And the interatrial septum, the chunk of flesh between the left and right atrium, you can't see that because it's hiding behind the pulmonary trunk and the aorta there. Let's see. So first we see our two atria are now open. Remember those are the receiving vessels. The right atrium is going to receive blood from the superior and inferior vena cava. The left atrium will receive blood from the pulmonary veins. So what you can't really see here, they didn't do a great job with on this picture, but there is kind of a, some of the structures inside the atria are going to be a little bit rough and that's going to be called pectinate muscle. So it's not going to be some parts of the atria are smooth, but if you ever dissect a heart or look inside a heart and you see a rough structure on the inside of the atria, that is called pectinate muscle. What else? The oracles have also been removed. So if you ever dissect a heart, you remember the expandable pouches that kind of look like an ear on top of the two atria, those are called the oracles. You do see a structure here called the fossa ovalis and I'll be highlighting these as I go. The fossa ovalis is just an indentation in the wall of the right atrium, but when you, when you were in your mother's womb, that was the foramen ovale, a foramen is a hole. So that connected the two atria. So if that doesn't close properly, that would be a heart defect. So the fossa ovalis is the remnant of a hole that used to be there when you were receiving oxygen from the placenta rather than your own lungs. Okay. Another thing you really can't see, but we always talk about the heart pumping in the muscle, but there is a cardiac skeleton here. Your heart is built on a connected tissue frame. You can't see that, but I just want to bring that up because this term cardiac skeleton is important because it insulates the heart and make sure that the heart, the heart beats in order. You don't want the atria and ventricles contracting at the same time. This cardiac skeleton, make sure that the two atria contract first and then the two ventricles. So you squeeze blood into the ventricles and then squeeze them out to the rest of your body. Okay. The valves themselves, let's look at the atrial ventricular valves first so that like the names imply they, they connect the atria from the ventricles. Now you don't see those terms on here because these are usually going to be called the mitral and tricuspid valves. So on the right side, you see the tricuspid valve, the reason it's called that is because it has three of these flaps. Now you can't see all three. They've been dissected away, but the tricuspid valves connects the right atrium to the right ventricles. The bicuspid valve, because it only usually has two flaps, is going to connect the left atrium and left ventricle. It's also called the mitral valve. That actually comes from the fact that a mitre, I guess it looks like a bishop's hat. The term mitral valve comes from. All right. So those are going to be your AV or atrioventricular valves. Then you have the semilunar valves. You see here, they're called the aortic and pulmonary valves. I usually call them the aortic semilunar valves and the pulmonary semilunar valves. They're called, I'll show you the valves a little bit more close detail, but they're called that because they have a half moon shape and these are different. They're not actually connected to anything. They rest on each other and that's how they open and then close when they bang into each other. So those are going to be your semilunar valves. Other structures here, you see the cusps of those valves, the bicuspid and tricuspid valves are actually connected to these tendinous tissue flaps. These cords of tissue called the cordae tendinae. So their job is going to be when they tense up, their job is to make sure that these valves only close, but then don't swing the opposite direction. So basically they form doors, but they only open in one direction. So the cusps of the valves are connected to these cords called the cordae tendinae. And those cords are then connected to what are called papillary muscles. Papilla means nipple. So these are nipple-like structures. These muscles actually will tense up, which pulls on these cords and that's what stiffens the flaps of your tricuspid and bicuspid valves. So they work. If this system were to break down, they wouldn't work anymore and you would have blood would be swooshing and moving the wrong direction and you would have a heart murmur. All right, the last important structure here is just the internal structure of the ventricles is called the trabeculae carnae. That's that roughened appearance that you see there. All right, so those are all the key internal structures here on this picture. I do want to show you the valves a little more close up. So here we see in this view the bicuspid and tricuspid valves are open while the semi-lunar valves are closed. This gives you a really good look at those semi-lunar valves. So usually there's three of them and they actually just lean on each other and that's how they close. And then on this image now the valves of the bicuspid and tricuspid valves are closed and here you see the semi-lunar valves are open. I'll show you these two images again when we talk about heart sounds. So the last thing to see here then is just an image from an actual dissected heart. Here you see those cordae tendinae connected to the papillary muscles and remember their job is to tense up right before the rest of the heart contracts to make sure that your valves stiffen up and they don't let blood flow the wrong direction. All right, so those are the key internal structures of the heart. Next we'll talk about the path that blood takes through the heart. I hope these help. Have a wonderful day. Be blessed.