ANATOMY

Detailed explanation-1: -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-2: -The first sound, a low-pitched, slightly prolonged “lub, ” occurs when the atrioventricular valves close as the ventricles of the heart begin to contract. After a brief pause, this sound is followed by a sharper, higher-pitched “dup, ” produced by closure of the aortic and pulmonary valves.

Detailed explanation-3: -The first heart sound (S1) represents closure of the atrioventricular (mitral and tricuspid) valves as the ventricular pressures exceed atrial pressures at the beginning of systole (point a). S1 is normally a single sound because mitral and tricuspid valve closure occurs almost simultaneously.