The first heart sound is associated with :

Options

A. Clasure of the semilunar valves
B. Clasure of the tricuspid and bicuspid valves
C. Opening of the semilunar valves
D. Opening of the Eustachian valve

Answer

To answer the question "The first heart sound is associated with:", we will analyze the options provided and identify the correct association with the first heart sound.

### Step-by-Step Solution:

1. **Understanding Heart Sounds**:
- The heart produces two primary sounds during each heartbeat, commonly referred to as "LUB" and "DUB".

2. **Identifying the First Heart Sound**:
- The first heart sound, known as "LUB", occurs at the beginning of ventricular systole.

3. **Mechanism of the First Heart Sound**:
- The "LUB" sound is produced by the closure of the atrioventricular (AV) valves, which include the tricuspid valve (right side) and the bicuspid (mitral) valve (left side).

4. **Analyzing the Options**:
- **A. Closure of semilunar valves**: This is associated with the second heart sound ("DUB").
- **B. Closure of the tricuspid and bicuspid valves**: This is the correct answer, as it corresponds to the first heart sound.
- **C. Opening of semilunar valves**: This does not produce a heart sound.
- **D. Opening of Eustachian valve**: This is not related to heart sounds.

5. **Conclusion**:
- Therefore, the first heart sound is associated with the closure of the tricuspid and bicuspid valves, making option B the correct answer.

### Final Answer:
**B. Closure of the tricuspid and bicuspid valves**