Closure of which of the following makes louder sound of heartbeat ?

Options

A. Thebesian
B. Eustachian
C. Semilunar valves
D. Atrio ventricular valves

Answer

To determine which closure makes the loudest sound of the heartbeat, we need to analyze the heart's structure and the sounds produced during its function.

### Step-by-Step Solution:

1. **Understand Heart Sounds**: The heart produces two main sounds during its cycle, commonly referred to as "LUB" and "DUB". These sounds correspond to the closure of different heart valves.

2. **Identify the Valves**:
- The **LUB** sound is produced by the closure of the **atrioventricular (AV) valves**, which include the mitral valve (between the left atrium and left ventricle) and the tricuspid valve (between the right atrium and right ventricle).
- The **DUB** sound is produced by the closure of the **semilunar valves**, which include the aortic valve (between the left ventricle and the aorta) and the pulmonary valve (between the right ventricle and the pulmonary artery).

3. **Determine Which Sound is Louder**:
- The LUB sound, associated with the closure of the AV valves, is typically louder than the DUB sound. This is because the closure of the AV valves occurs when the ventricles contract and push blood into the arteries, creating a more forceful closure.

4. **Conclusion**: Therefore, the closure of the **atrioventricular valves** (mitral and tricuspid) produces the louder sound of the heartbeat.

### Final Answer:
The closure of the **atrioventricular valves** makes the louder sound of the heartbeat.