Which of the following statements about heart sound is correct?

Options

A. Lub is diastolic heart sound.
B. Lub occurs due to opening of semilunar valves
C. Dub can't be easily heard with a stethoscope.
D. Dub occurs due to closure of semilunar valves.

Answer

To solve the question regarding which statement about heart sounds is correct, we can follow these steps:

### Step 1: Understand Heart Sounds
Heart sounds are produced by the beating of the heart and the flow of blood through it. There are two primary heart sounds known as the first heart sound (S1) and the second heart sound (S2).

### Step 2: Identify the Heart Sounds
- **First Heart Sound (S1)**: This is often referred to as the "lub" sound. It occurs when the atrioventricular (AV) valves (mitral and tricuspid valves) close at the beginning of ventricular contraction (systole).
- **Second Heart Sound (S2)**: This is referred to as the "dub" sound. It occurs when the semilunar valves (aortic and pulmonary valves) close at the end of ventricular contraction.

### Step 3: Analyze the Options
Now, let's evaluate the provided options one by one:

1. **"Lub is a diastolic heart sound"**: This statement is incorrect because the "lub" sound occurs during systole, not diastole.

2. **"Lub occurs due to opening of semilunar valves"**: This statement is also incorrect. The "lub" sound is produced by the closing of the AV valves, not the opening of the semilunar valves.

3. **"Dub sound can't be easily heard with a stethoscope"**: This statement is incorrect as well. The "dub" sound is high-pitched and can be easily detected with a stethoscope.

4. **"Dub occurs due to closure of semilunar valves"**: This statement is correct. The "dub" sound is indeed produced by the closure of the semilunar valves.

### Step 4: Conclusion
After analyzing all the options, the correct statement about heart sounds is that the "dub" sound occurs due to the closure of the semilunar valves.

### Final Answer:
The correct statement about heart sounds is: **"Dub occurs due to closure of semilunar valves."**

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