The Two Heart Sounds are Caused by the Closing of the Semilunar

Question

The two heart sounds are caused by the closing of the semilunar and atrioventricular valves.

Accepted Answer

This is true. The first heart sound (lub) is caused by the closing of the atrioventricular valves (mitral and tricuspid) at the beginning of systole, while the second heart sound (dub) is caused by the closing of the semilunar valves (aortic and pulmonary) at the end of systole.