ANATOMY

Detailed explanation-1: -The first heart sound (lub) is associated with the closure of the tricuspid and bicuspid (mitral) valves whereas the second heart sound (dub) is associated with the closure of the semilunar valves. These sounds are of clinical diagnostic significance.

Detailed explanation-2: -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-3: -The first heart sound (S1) is composed of several high-frequency components; only the first two are normally audible. These two sets of audible vibrations are temporally related to closure of the mitral and tricuspid valves.

Detailed explanation-4: -Bicuspid and tricuspid valves are open during both joint diastole and atrial systole. The opening of atrioventricular valves allows the blood to flow from the atria to the ventricles.

Detailed explanation-5: -The increased ventricular pressure during ventricular systole causes closure of the bicuspid & tricuspid valves to avoid the backflow of blood into the atria.