An abnormal sound (murmur) due to narrowing or stenosis of the mitral valve might be heard during:
a. diastole
b. systole

The correct answer to the question: An abnormal sound (murmur) due to narrowing or stenosis of the mitral valve might be heard during:, would be, A: Diastole.

Explanation:

It is first important to know that a murmur comes from the sound the blood makes as it passes either through a hardened tissue, like is the case of stenosis of a valve, or because it leaks back from where it came, due to regurgitation, because the valve is defective and cannot close properly. During the cardiac cycle, there is a process of systole, and of diastole, that ensure the filling and expulsion of the blood inside the heart towards the body, and from the body into the heart, so that a constant flow is ensured. In the process of filling and emptying, two sets of valves, the mitral and tricuspid, and the aortic and pulmonary, open and close to allow blood flow towards the different chambers of the heart, and out into the blood vessels of the body, and prevent the blood from returning towards where it came. In the case of mitral stenosis, which is the toughening of the mitral valve of the heart, the blood flowing through it makes a murmuring sound that can be caught up through a stethoscope. This sound is prominent during diastole, and that is why medically this murmur is known as a diastolic murmur.

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