Question

First heart sound occurs by

• A. Opening of semi lunar valve
• B. Closing of semi lunar valve
• C. Onset of artibular systole
• D. Sudden closure of A.V valves.

Answer 1

The correct option is D Sudden closure of A.V valves.

The “ lub” is the first heart sound, commonly termed S1, and is caused by turbulence caused by the closure of mitral and tricuspid valves at the start of systole. The second sound,” dub” or S2, is caused by the closure of aortic and pulmonic valves, marking the end of systole.