If the beating heart makes a "lub-dup" sound, the "dup" sound is caused by
A) the apex of the heart hitting the anterior chest wall.
B) a stenotic atrioventricular valve.
C) the large force of the contracting ventricles.
D) vibrations that result from the semilunar valves slamming shut.

Question

Quizplus · Accepted Answer

The "dup" sound of the heartbeat is caused by the semilunar valves, specifically the aortic and pulmonary valves, closing at the end of systole (contraction of ventricles). This creates a vibration that is heard as the "dup" sound.

If the Beating Heart Makes a "Lub-Dup" Sound, the "Dup