ANATOMY

Detailed explanation-1: -The heart tone “lub, ” or S1, is caused by the closure of the mitral and tricuspid atrioventricular (AV) valves at the beginning 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: -Heart Sounds are associated with Valve Closure We hear these vibrations as two distinct sounds; lub-dub. The first sound, “lub", is associated with the closing of the AV valves. The second sound, “dub", is associated with the closing of the semilunar valves.

Detailed explanation-4: -The right atrioventricular valve is the tricuspid valve. The left atrioventricular valve is the bicuspid, or mitral, valve.

Detailed explanation-5: -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.