The 2nd heart sound is associated with the closing of which valves?

The second heart sound, commonly referred to as "S2," is produced primarily by the closure of the pulmonary and aortic valves at the end of ventricular systole. This closure marks the transition from the contraction phase (systole) to the relaxation phase (diastole) of the heart cycle.

When the ventricles empty their blood into the aorta and pulmonary artery, the pressure in these arteries becomes greater than that in the ventricles, causing the aortic and pulmonary valves to close. This closure generates a distinct sound that is crucial in assessing heart function. The separation of these two sounds can also be observed in various physiological and pathological conditions, offering insight into the heart's behavior during different states of the cardiac cycle.

In contrast, the mitral and tricuspid valves are associated with the first heart sound (S1), which is produced by their closure at the beginning of ventricular contraction. Other combinations mentioned do not include the correct valves that correlate with the S2 sound created during the normal cardiac cycle.