During each cardiac cycle , two prominent sound are produced which can be easily heard through a stethoscope . The second heart sound is associated with :

Options

A. Closure of the bicuspid valves
B. Closure of the tricuspid valves
C. Closure of the semilunar valves
D. Opening of the semilunar valves

Answer

To solve the question regarding the second heart sound during the cardiac cycle, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Cardiac Cycle**: The cardiac cycle consists of a sequence of events that occur during one heartbeat. It includes the contraction (systole) and relaxation (diastole) of the heart chambers.

2. **Identify the Heart Sounds**: There are two primary heart sounds:
- The first heart sound (S1) is often referred to as "lub" and is associated with the closure of the atrioventricular (AV) valves (bicuspid and tricuspid valves).
- The second heart sound (S2) is referred to as "dub" and is associated with the closure of the semilunar valves (aortic and pulmonary valves).

3. **Analyze the Options**: The question provides multiple-choice options regarding what the second heart sound is associated with:
- **Option 1**: Closure of the bicuspid valve (produces the first heart sound, "lub").
- **Option 2**: Closure of the tricuspid valve (also produces the first heart sound, "lub").
- **Option 3**: Closure of the semilunar valve (produces the second heart sound, "dub").
- **Option 4**: Opening of the semilunar valve (not associated with any heart sound).

4. **Select the Correct Answer**: Based on the analysis, the correct answer is **Option 3: Closure of the semilunar valve**, as this is what produces the second heart sound ("dub").

### Final Answer:
The second heart sound is associated with the **closure of the semilunar valve**.

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