Question

Which one of the following is mainly responsible for the second heart sound?

• A. Closure of atrioventricular valves
• B. Opening of atrioventricular valves
• C. Closure of semilunar valves
• D. Thrust of blood on ventricular wall during atrial contraction

Answer 1

The correct option is C Closure of semilunar valves

Contraction of heart chambers and closure of valves produce “LUB-DUP” sounds during the heartbeat. Contraction of ventricles and closure of atrioventricular valves produces the first heart sound, “lub,” which lasts longest and has a lower pitch.

Relaxation of ventricles and closure of semilunar valves produces the second heart sound, “dup”.

The opening of heart valves and pressure of blood on walls of heart chambers do not produce any heart sound.

The thrust of blood on the ventricular wall during atrial contraction is known as pulse.

So, the correct answer is option C.