MICROANATOMY

Detailed explanation-1: -The first sound LUB is produced when the atrioventricular valves i.e. tricuspid and bicuspid valves close at the start of ventricular systole.

Detailed explanation-2: -Normal heart sounds come in pairs. The sounds are often described as a constant “lub-dub, lub-dub.” The first “lub-dub” is the sound of the mitral and tricuspid valves closing. The second “lub-dub” is the sound of the aortic and pulmonary valves closing soon after.

Detailed explanation-3: -The first heart sound, S1, is associated with the closing of the atrioventricular valves during ventricular contraction. The second heart sound, S2, is associated with closing of the semilunar valves during ventricular relaxation.

Detailed explanation-4: -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.