The 'Lubb' and "Dupp" heart sound are due to `:-`

Options

A. Opening of heart valves
B. Action of papillary muscles
C. Closing of heart valves
D. Activity of pace maker

Answer

**Step-by-Step Solution:**

1. **Understanding Heart Sounds**: The heart produces two main sounds known as 'Lubb' and 'Dupp' (or 'Dub'). These sounds are associated with specific actions in the heart during the cardiac cycle.

2. **Identifying the Source of Sounds**:
- The 'Lubb' sound (first heart sound, S1) is produced when the atrioventricular (AV) valves close. These valves include the tricuspid valve (between the right atrium and right ventricle) and the mitral valve (or bicuspid valve, between the left atrium and left ventricle).
- The 'Dupp' sound (second heart sound, S2) occurs when the semilunar valves close. These valves include the pulmonary valve (between the right ventricle and pulmonary artery) and the aortic valve (between the left ventricle and aorta).

3. **Function of the Valves**: The primary function of these valves is to prevent the backflow of blood. When the heart contracts, the pressure causes these valves to close, resulting in the characteristic sounds.

4. **Conclusion**: Therefore, the 'Lubb' sound is due to the closing of the tricuspid and mitral valves, while the 'Dupp' sound is due to the closing of the semilunar valves.

5. **Final Answer**: The 'Lubb' and 'Dupp' heart sounds are due to the closing of heart valves.

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