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Studying for a test? Prepare with these 15 lessons on Circulatory system diseases.
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Voiceover: So, I want to talk about non cyanotic heart disease, but before I do that, let's do a quick review of blood flow through the heart. So blood is coming back from the rest of the body. As it's coming back, it is going to be deoxygenated because the body was using up all the oxygen and now it's sending the blood back to the heart and it hardly has any oxygen in it, it's actually deoxygenated. So, this is coming back to the right side of the heart, and from that right side, as the heart is beating, it is going to send the blood, the deoxygenated blood via these vessels and they're going to go to the lungs. And it's a good thing that they're going to the lungs, because here's what's happening in the lungs: As it's passing through these little vessels that we call pulmonary capillaries, as it's passing through those capillaries, it's going to pick up something that's very important, and the thing it's going to pick up is oxygen. And as it picks up that oxygen, you'll see that it kind of becomes a brighter red color, a brightish red color; before it was very dark, but as it's picking up that oxygen it is changing color to where it's kind of bright red. And that blood is going to come back to the left side of the heart and it's going to go through the left side of the heart and as the heart beats, it's going to send that oxygenated blood now throughout the rest of the body, so this is that blood, it's going through all of these vessels and it's going throughout the body, which makes sense, it's delivering the oxygen to the body. Now, here's the thing: You want to have this separation, you want the right side to have your deoxygenated blood so that it can go through the lungs and then come back via this left side, so that can then go in its oxygenated form to the body. Now, in individuals that are born with non cyanotic heart disease, there is some kind of a defect and I'm showing a defect here, where there's a hole in the heart and that defect allows for, of course, blood is going to pass through that hole. Even though that's not where you want the blood to pass, if the hole is there and the heart is beating, the muscle is contracting, it's going to send blood through that opening, but the question is, which direction is the blood going to flow? And to answer that question, let's just think logically about what's happening here: On the right side, this side of the heart is beating and when the heart is beating, this side is sending blood, it's not going a far distance, it's going right next door to the lungs, to come back to the left side, but when the left side contracts, when that beats, it's sending blood all throughout the body, it's going to the head, it's going to the neck, it's going to the arms and the legs and all throughout the body and this has to do significantly more work. You can see here that the muscle, here, is significantly thicker on the left side than we have on the right side. And as a result of that, we're going to have significantly more pressure over here. And if you have more pressure over here, that is going to squeeze the blood through that opening and it's going to go from the left side to the right side. And that's exactly what we have with non cyanotic heart defect. It's a congenital disease; and congenital just means that that individual is born with it, that causes blood to shunt from left to right. Okay, so what's the problem here? Okay, so we have blood that's shunting from left to right because we have a hole in the heart. And you often hear about a hole in the heart and you wonder maybe "That must be bad, right?" Well, let's think about what's happening, let's get back to that color that we were using before. What kind of blood do we have over here on the left? Well, it's oxygenated blood. And if some of that squeezes through that little opening and gets into the left side, okay, that oxygenated blood is going to go back to the lungs and as it goes back to the lungs with the rest of the blood, they're going to be picking up oxygen and then that's going to go back to the right side of the heart, as we expect it to go, and then it's going to go to the body and some of it might go back through. Is that a real problem? Well, usually when we have individuals with a small hole in the heart, it's asymptomatic because what we're doing is we're just sending oxygenated blood back to the lungs. That is not efficient, this is not an efficient system. But, it's still functional, the oxygen levels are going to be adequate for normal function and, of course, the body needs oxygen in order to do all of the things that need to be done, so that it can have the energy that it needs. And with this oxygenated blood that's going back, we still end up with normal levels of oxygenation on this right side, so it's going to be asymptomatic. And it doesn't matter if the hole is down here, or up here, the fact is you have higher pressure on the left side and that is going to always overpower the lower pressure on the right side. So you will always have that left to right shunting; and that is in non cyanotic heart disease.