At the instant following the second heart sound, which heart valves are open?
Atrioventricular valves only
Both atrioventricular valves and semilunar valves
The correct option is D All valves are closed
The second heart sound indicates the beginning of diastole.The second heart sound, “Dup,” is due to the closure of the semilunar valves.The heart is in systole between the first and second heart sounds.During systole, the heart pumps blood from the ventricles, and the atrioventricular valves are closed to prevent regurgitation into the atria.The closure of the semilunar valves is the start of a brief period of “isovolumetric relaxation. All valves are closed during the second heart sound.