First Heart sound is due to

Options

A. Closure of semilunar valve
B. closure of pulmonary s Aorti valve
C. sound produced after closure of mitral and Tricuspid valve
D. Vibration after clousre of pulmonary s Aortic valuve

Answer

To answer the question "First Heart sound is due to," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Heart Sounds**: The heart produces sounds due to the closing of its valves. There are two main heart sounds: the first heart sound (S1) and the second heart sound (S2).

2. **Identifying the First Heart Sound (S1)**: The first heart sound, commonly referred to as "lub," occurs at the beginning of ventricular contraction (systole).

3. **Valves Involved in S1**: The first heart sound is specifically produced by the closure of the atrioventricular (AV) valves, which include the mitral valve (bicuspid valve) and the tricuspid valve.

4. **Evaluating Options**:
- **Option 1**: Closure of the semilunar valves - This is incorrect as it produces the second heart sound (S2).
- **Option 2**: Closure of the pulmonary and aortic valves - This is also incorrect as it relates to the second heart sound (S2).
- **Option 3**: Sound produced after the closure of the mitral and tricuspid valves - This is correct as it describes the first heart sound (S1).
- **Option 4**: Vibration after closure of the pulmonary and aortic valves - This is incorrect as it pertains to the second heart sound (S2).

5. **Conclusion**: The first heart sound (S1) is due to the closure of the mitral and tricuspid valves.

### Final Answer:
The first heart sound is due to the closure of the mitral and tricuspid valves.

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