Question

Which heart sound is produced by the closure of heart valves?

• A. Lubb--closure of AV valves
• B. Dub--closure of semilunar valves
• C. Dub--opening of AV valve
• D. Both 'A' and 'B'

Hint:

Remember the heart sounds: \[ \boxed{ \begin{aligned} \text{LUBB} &\rightarrow \text{Closure of Mitral and Tricuspid valves}\\ \text{DUB} &\rightarrow \text{Closure of Aortic and Pulmonary valves} \end{aligned} } \] LUBB begins ventricular systole, whereas DUB begins ventricular diastole.

Answer 1

The Correct Option is D

The first heart sound (S1, "lub") is caused by the closure of the mitral and tricuspid (atrioventricular) valves at the onset of ventricular systole. The second heart sound (S2, "dub") results from the closure of the aortic and pulmonary (semilunar) valves at the end of ventricular systole.