The first heart sound, "lub," is caused by the closure of the ________ valves.
A) semilunar
B) pulmonary
C) atrioventricular (AV)
D) aortic

Question

Quizplus · Accepted Answer

The first heart sound, "lub," is caused by the closure of the atrioventricular (AV) valves. These valves are located between the atria and ventricles and include the tricuspid valve on the right side and the mitral valve on the left side. When the ventricles contract, the AV valves close, causing the first heart sound.

The First Heart Sound, "Lub," Is Caused by the Closure