EVERYDAY SCIENCE

Detailed explanation-1: -All valves are closed during the second heart sound.

Detailed explanation-2: -Heart Sounds The second heart sound (S2) represents closure of the semilunar (aortic and pulmonary) valves (point d). S2 is normally split because the aortic valve (A2) closes before the pulmonary valve (P2).

Detailed explanation-3: -Heart sounds are created from blood flowing through the heart chambers as the cardiac valves open and close during the cardiac cycle. Vibrations of these structures from the blood flow create audible sounds-the more turbulent the blood flow, the more vibrations that get created.

Detailed explanation-4: -The vibrations of the second heart sound occur at the end of ventricular contraction and identify the onset of ventricular diastole and the end of mechanical systole.

Detailed explanation-5: -In healthy adults, there are two normal heart sounds, often described as a lub and a dub that occur in sequence with each heartbeat. These are the first heart sound (S1) and second heart sound (S2), produced by the closing of the atrioventricular valves and semilunar valves, respectively.