MICROANATOMY

Detailed explanation-1: -"Lub” is the sound of the atrioventricular (AV) or tricuspid and bicuspid valves closing. This occurs at the start of ventricular systole. “Dub” is the sound of closing of the semilunar valves at the root of the aorta and the pulmonary artery. This happens at the beginning of ventricular diastole.

Detailed explanation-2: -These two sets of audible vibrations are temporally related to closure of the mitral and tricuspid valves. The first heart sound coincides with contraction of the ventricles, thus identifying the onset of ventricular systole and the end of mechanical diastole.

Detailed explanation-3: -Heart Sounds 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.

Detailed explanation-4: -The first heart sound, the “lub” sound, is produced during the closing of the two atrioventricular valves. There are two atrioventricular valves in the heart, namely: bicuspid and tricuspid valves.

Detailed explanation-5: -The first sound LUB is produced when the atrioventricular valves i.e. tricuspid and bicuspid valves close at the start of ventricular systole. The second sound DUB is produced at the beginning of ventricular diastole when the pulmonary and aortic semilunar valves close.