Question

‘Lub’ sound of Heart is caused by the___________.

• A. closure of the semilunar values
• B. opening of tricuspid and bicuspid values
• C. opening of the semilunar valves
• D. closure of the tricuspid and bicuspid valves

Answer 1

The Correct Option is D

The “lub” sound (S1) of the heart is caused by the closure of the atrioventricular valves (tricuspid and bicuspid/mitral valves) at the beginning of ventricular systole (contraction). This prevents blood from flowing back into the atria.
The “dub” sound (S2) is caused by the closure of the semilunar valves (pulmonary and aortic valves).