ANATOMY

Detailed explanation-1: -S2. The second heart sound, called S2, makes a “dub” sound caused by the closure of the semilunar (aortic and pulmonary) valves following ventricular systole. S2 is split because aortic valve closure occurs before pulmonary valve closure.

Detailed explanation-2: -The second heart sound (S2), described as a dupp, results from the sudden closing of the aortic and pulmonic valves, which bulge backwards towards the ventricles until their elastic stretch recoils the blood back into the arteries.

Detailed explanation-3: -Listen to the Lub-Dub The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart.

Detailed explanation-4: -During each cardiac cycle two prominent sounds are produced which can be easily heard through a stethoscope. The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid valves whereas the second heart sound (dub) is associated with the closure of the semilunar valves.