AP BIOLOGY

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. The second sound DUB is produced at the beginning of ventricular diastole when the pulmonary and aortic semilunar valves close.

Detailed explanation-2: -The two distinct sounds are heard, a low, slightly prolonged “lub” (first sound) occurring at the beginning of ventricular contraction or systole and a sharper, higher-pitched “dup” (second sound), caused by the closure of aortic and pulmonary valves at the end of systole.

Detailed explanation-3: -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. The heart tone “dub, ” or S2 ( a combination of A2 and P2), is caused by the closure of the aortic valve and pulmonary valve at the end of ventricular systole.

Detailed explanation-4: -These are called Lub-Dub noises by doctors. When the valves between the upper chambers (atria) and lower chambers (ventricles) close, a “lub” sound is heard. When the valves in the pulmonary and aortic arteries leaving the heart close, a “dub” sound is heard followed by a longer pauseLub-DubLub-Dub.

Detailed explanation-5: -Due to the closure of the atrio-ventricular valves, dup sound is produced.