What role do the chordae tendineae and papillary muscles play in ...

Question

What role do the chordae tendineae and papillary muscles play in the normal function of the AV valves?

Accepted Answer

Welcome back, everyone. Let's look at our next question. It says, how do the papillary muscles contribute to the prevention of backflow of blood into the atria during ventricular systole A, they contract to close the semi linear valves. B they brace the A V valves, limiting their movement. C, they pump blood back into the atria during Sicily or D none of these. Well, we can eliminate one answer right away without even going any further because choice C says they pump blood back into the atria during Sicily, but this would be backflow into the atria. And our question asks, how do these muscles contribute to the prevention of this flow of blood into the atria? So choice C is wrong just because it's the exact opposite of what we say the papillary muscles do. So let's just get that out of the way, right, right out front. So let's think about, well, where are the papillary muscles? What's their connection to preventing blood from flowing into the atria? So just putting up a really rough diagram and just for simplicity's sake, I've only drawn one side here. It happens to be the left side of the heart but obviously a similar thing is happening on the right side. So this is a diagram of when the A V valve is open blood is flowing from the in this case, left atrium, put L A indicated by the red arrow through the open A V valve in this diagram right now. So highlight that A V valve in yellow, it's open blood is flowing through it into the left ventricle. Down below label that lb our papillary muscles are these things like stalagmites, sort of soft stalagmites coming out of the walls of the ventricle towards the bottom. And these are the papillary muscles. And as you can see from my drawing of these black lines connecting the papillary muscles to that a V valve, they are connected by those tendons called the Cordy tenon. So this diagram is ha obviously happening during ventricular diastole. The ventricle is relaxed. We're asked how the papillary muscles contribute to preventing backflow of blood back into the atrium during ventricular cysto. So let's draw that situation. The ventricle has begun to contract and the V valve has closed that a valve has closed due to pressure building up in the ventricle as it contracts it's full of blood. And that blood is now exerting pressure upward as indicated by the little red arrows pointing up, I've just drawn. However, you then risk as this pressure mounts that the A V valve will sort of blow open back into the atrium and under pressure, that blood will flow back into the atrium. So what prevents that? Well, we've got these tendons right here. Our cordi tendon attach to the papillary muscles. These muscles are going to contract during Sicily, just like all the other heart muscles. Now imagine as these muscles contract, they've got tendons attached to them, the muscles contract, they put pressure on those tendons and those tendons are pulling on the A V valve, counteracting the blood pressure building up in the ventricle. So that leads us to our answer choice, which is choice. CB, excuse me, they brace the A V valves limiting their movement. So they're sort of pulling back against the pressure from the blood to be thorough. Let's look at our other answer. Choices. Choice D we can eliminate obviously because we have a correct answer. And when we look at choice A, it says they contract to close the semi lunar valves. Well, the semi lunar valve is this valve over on the other side, which is the left side of our diagram that leads out to the aorta. In this case. Since it's the left side of the heart, it's the exit to the ventricle. And that is not controlled by the papillary muscles or their tendons. The semi lunar valves close due to pressure from arterial blood. So in ventricular systole, when that pressure builds up high enough, the semi lunar valve opens blood flows out of the heart. But then as the pressure drops within the ventricle as we come to the end of ventricular cysto blood begins to flow back from the arteries into the heart. And the pressure of that backflow closes that semi lunar valve. So that's why that's not our correct answer. But again, when we talk about how papillary muscles contribute to the prevention of backflow into the atria during ventricular systole. That will be choice B they brace the A V valves limiting their movement. See you in the next video.

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What role do the chordae tendineae and papillary muscles play in the normal function of the AV valves?

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