In cardiac cycle, "Dup" sound is heard when

Options

A. Mittral valves close
B. Mittral valves open
C. Semilunar valves close
D. Tricuspid valve close

Answer

**Step-by-Step Solution:**

1. **Understanding the Cardiac Cycle**: The cardiac cycle consists of a series of events that occur during one heartbeat. It includes the contraction and relaxation of the heart muscles, leading to the pumping of blood.

2. **Identifying Heart Sounds**: There are two primary heart sounds that can be heard during the cardiac cycle:
- The first sound (S1), known as "lub," is produced by the closure of the atrioventricular (AV) valves, which include the tricuspid and mitral valves.
- The second sound (S2), known as "dup," is produced by the closure of the semilunar valves, which include the aortic and pulmonary valves.

3. **Focusing on the "Dup" Sound**: The question specifically asks about the "dup" sound. This sound occurs at the end of ventricular systole when the ventricles are contracting and pumping blood into the arteries.

4. **Determining the Cause of the "Dup" Sound**: The "dup" sound is associated with the closure of the semilunar valves (aortic and pulmonary valves). This closure prevents the backflow of blood into the ventricles after the blood has been ejected into the aorta and pulmonary artery.

5. **Evaluating the Options**: The options provided are:
- A) Mitral valve closed
- B) Mitral valve open
- C) Semilunar valve closed
- D) Tricuspid valve closed

Since the "dup" sound is related to the closure of the semilunar valves, the correct answer is option C: "Semilunar valve closed."

6. **Conclusion**: Therefore, the "dup" sound in the cardiac cycle is heard when the semilunar valves close.

**Final Answer**: The "dup" sound is heard when the semilunar valve closes (Option C).

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