The first heart sound
A) occurs when the AV valves close.
B) occurs when the semilunar valves close.
C) signals the onset of ventricular systole.
D) occurs when the AV valves close and signals the onset of ventricular systole.
E) occurs when the semilunar valves close and signals the onset of ventricular systole.

Question

Quizplus · Accepted Answer

The first heart sound, also known as S1, occurs when the AV valves close and signals the onset of ventricular systole. Therefore, choice D is the correct answer. Choices A, B, and E are incorrect because they do not describe the correct timing or location of the first heart sound.

The First Heart Sound