The first heart sound (S1) is produced by the closure of which valves?

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Multiple Choice

The first heart sound (S1) is produced by the closure of which valves?

Explanation:
The first heart sound comes from the closure of the atrioventricular valves—the mitral valve on the left and the tricuspid valve on the right—as the ventricles begin to contract. This closure prevents backflow into the atria and creates the characteristic “lub” of S1. By contrast, S2 is produced by the closure of the semilunar valves (aortic and pulmonary) at the end of systole. S3 and S4 are additional heart sounds related to ventricular filling and atrial contraction, not valve closures.

The first heart sound comes from the closure of the atrioventricular valves—the mitral valve on the left and the tricuspid valve on the right—as the ventricles begin to contract. This closure prevents backflow into the atria and creates the characteristic “lub” of S1. By contrast, S2 is produced by the closure of the semilunar valves (aortic and pulmonary) at the end of systole. S3 and S4 are additional heart sounds related to ventricular filling and atrial contraction, not valve closures.

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