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

Concept: During each cardiac cycle, the heart produces two characteristic sounds: \[ \boxed{ \begin{aligned} \text{First heart sound (LUBB)} &\rightarrow \text{Closure of atrioventricular (AV) valves}\\ \text{Second heart sound (DUB)} &\rightarrow \text{Closure of semilunar valves} \end{aligned} } \] These sounds are produced due to the closing of heart valves, not by the flow of blood itself.

Step 1: Understand the first heart sound (LUBB).
The first heart sound is produced when the atrioventricular valves close. These valves are \[ \boxed{ \begin{aligned} &\text{Tricuspid valve}\\ &\text{Bicuspid (Mitral) valve} \end{aligned} } \] This sound marks the beginning of ventricular systole.

Step 2: Understand the second heart sound (DUB).
The second heart sound is produced by the closure of \[ \boxed{ \begin{aligned} &\text{Aortic valve}\\ &\text{Pulmonary valve} \end{aligned} } \] These are collectively called semilunar valves. This sound marks the beginning of ventricular diastole.

Step 3: Analyse the options.

• Option (A): Correct.

• Option (B): Correct.

• Option (C): Incorrect because heart sounds are produced by valve closure, not opening.
Hence, \[ \boxed{\textbf{Option (D)}} \] is the correct answer.