Question

The heart sound 'dup' is produced when

• A. mitral valve is closed
• B. semi-lunarval ves at the base of aorta get closed
• C. tricuspid valve is opened
• D. mitral valve-is opened.

Answer 1

The Correct Option is B

The question asks about the cause of the second heart sound, often denoted as 'dup.' The options provided relate to different valves of the heart and their states during the cardiac cycle. Here is the explanation for each option:

1. Mitral valve is closed: The mitral valve closure contributes to the first heart sound, known as 'lub,' during the start of ventricular systole. Therefore, this is incorrect for the 'dup' sound.
2. Semi-lunar valves at the base of aorta get closed: The closure of the semi-lunar valves, specifically the aortic and pulmonary valves, occurs at the end of ventricular systole, marking the onset of ventricular diastole. This closure produces the second heart sound, 'dup.' Therefore, this is the correct answer.
3. Tricuspid valve is opened: The tricuspid valve opens during ventricular diastole, but it does not produce a distinct heart sound. Thus, this is incorrect.
4. Mitral valve is opened: The opening of the mitral valve occurs during ventricular diastole and similarly does not produce a distinct sound. Thus, this is not the correct answer.

Conclusion: The heart sound 'dup' is produced by the closure of the semi-lunar valves at the base of the aorta, marking the end of systole and the start of diastole. This physiological process helps in preventing the backflow of blood into the ventricles.