If "lub-dup" describes a heartbeat, the "dup" part of the 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" part of the sound is caused by vibrations that result from the semilunar valves slamming shut. The closure of these valves prevents blood from flowing back into the ventricles and causes the characteristic sound of a heartbeat.

If "Lub-Dup" Describes a Heartbeat, the "Dup" Part of the Sound