ANATOMY

Detailed explanation-1: -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-2: -This sound comes from the valves shutting on the blood inside the heart. The first sound (the lub) happens when the mitral and tricuspid valves close. The next sound (the dub) happens when the aortic and pulmonary valves close after the blood has been squeezed out of the heart.

Detailed explanation-3: -At this time, semilunar valves are open, and both the AV valves (bicuspid-tricuspid valves) are closed. The closing of the AV valves during the ventricular systole produces the first heart sound called “LUB".

Detailed explanation-4: -Due to the closure of the atrio-ventricular valves, dup sound is produced.

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.