If the papillary muscles fail to contract, (a) the ventricles wil...

Question

If the papillary muscles fail to contract, (a) the ventricles will not pump blood, (b) the atria will not pump blood, (c) the semilunar valves will not open, (d) the AV valves will not close properly, (e) none of these happen.

Accepted Answer

Welcome back everyone. Our next question says, what may cause heart valve cusps to close improperly and lead to a V valve regurgitation. A left bundle branch blockage B, right bundle branch enlargement, C malformation of the moderator band or D problems with the papillary muscles or cordi tendon. E Well, to answer this question, we have to think about what controls the closing of those heart valve cusps. And is it muscular in nature or electrical in nature? Because we've got both things going on muscle contractions and electrical signals in the heart. So I'm just going to put up a rough little diagram of one side of the heart with the valve in it. So we can think about this just for simplicity's sake. I've only shown half the heart. Obviously, the uh structure is similar on the other side. So this happens to be the left side of the heart with the left atrium on the top and the left ventricle on the bottom. Since it's the left side, the aorta is that opening where blood exits the heart with the semi lunar valve being the valve leading out to the aorta. But we're talking about the heart valve cusps. We have a bicuspid valve and a tricuspid valve. This one on the left happens to be the bicuspid or mitral valve. So two cusps, while the one between the right atria and ventricle is the tricuspid valve with three cusps. But the principles here are the same for both. So highlighted in yellow again is RAV valve. So the A P valve is now closed and it's saying what might cause them to close improperly leading to a V valve regurgitation. So, in regurgitation, we recall that when the ventricle is in Sicily, the blood inside is being squeezed as the muscles contract. And therefore, that pressure is going to put pressure on the A V valve, blood pushing back against the A V valve. And if the that A V valve is improperly closed, some of the blood will be forced back into the atrium. So what usually prevents that from happening? And that would be the contraction of the papillary muscles, which are these sort of stalagmite looking structures sticking out of the ventricle papillary muscles that are attached to the black lines I've drawn here, those tendons, the Cordy tendon, which in turn are attached to the A V valve. So let's imagine what happens as the muscles in the ventricle contract that includes the papillary muscles, they contract, thereby exerting pressure, pulling on those tendons of the cordi tendon. They in turn are exerting pressure on the A V valve, preventing it from blowing backwards and causing that regurgitation. So, a problem that might cause them to close improperly would be choice d problems with the papillary muscles or the cord tendon since they essentially brace the A V valve preventing that regurgitation. So let's just to be thorough and look at our other answer choices. A and B. Similar reason they're wrong. Left bundle branch, blockage, right, bundle branch enlargement, the bundle branches carry the electrical signal from the A V node to the ventricles, right and left as indicated by their names. So if you had a left bundle branch blockage, you might expect problems with the signal being conducted to the left ventricle or with the right bundle branch en enlargement. You'd expect problems with the signal being conducted to the right ventricle but not causing this regurgitation. So that's why they're not our correct answer. And finally, choice. C malformation of the moderator band is a muscular band around the right ventricle from the septum to the papillary muscles. And it actually conducts the electrical signal to those papillary muscles on the right side. And this so essentially serves as a shortcut to the right side there, making sure that the electrical signals are co-ordinated to coordinate the contractions of the ventricle on the left and right side. So this one's just a little bit tricky or since it does have a connection with the papillary muscles, but since its primary purpose is conducting that electrical signal and helping with the contractions. It would probably cause a problem in the conduction of that signal, telling the ventricles when to contract on the right side. But it isn't going to be causing those heart valve cup cuss to close improperly as you would if you had some sort of physical problem with those muscles of the cord tendon knee. So that's why it's not our correct answer. So again, what might cause the heart valve cusp to close improperly leading to a V valve regurgitation is choice B problems with the papillary muscles or Cordy tendon knee. See you in the next video.

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If the papillary muscles fail to contract, (a) the ventricles will not pump blood, (b) the atria will not pump blood, (c) the semilunar valves will not open, (d) the AV valves will not close properly, (e) none of these happen.

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