The First Heart Sound _______

Question

The first heart sound _______.
A) marks the beginning of ventricular diastole
B) is caused by the closure of the AV valves
C) is caused by the closure of the semilunar valves
D) answers a and b are correct

Accepted Answer

The first heart sound, also known as S1, is caused by the closure of the AV valves (tricuspid and mitral valves) at the beginning of ventricular systole.