Which one of the following is correct for the mitral valve of the human heart ?

Options

A. It guards the opening of right atrium and right ventricle.
B. It is associated with deoxygenated blood in the right side of heart.
C. It's closure is associated with the first heart sound (LUB) .
D. Its closure is associated with the second heart sound (DUB) .

Answer

To solve the question regarding the mitral valve of the human heart, we will analyze each statement provided in the options.

### Step-by-Step Solution:

1. **Understanding the Mitral Valve**:
- The mitral valve is one of the four main valves in the human heart. It is located between the left atrium and the left ventricle.

2. **Evaluating the First Statement**:
- The first statement claims that the mitral valve guards the opening of the right atrium and right ventricle.
- **Analysis**: This statement is incorrect. The mitral valve actually guards the opening between the left atrium and the left ventricle, not the right side of the heart.

3. **Evaluating the Second Statement**:
- The second statement suggests that the mitral valve is associated with deoxygenated blood in the right side of the heart.
- **Analysis**: This statement is also incorrect. The mitral valve is associated with oxygenated blood, as it is located on the left side of the heart where the left atrium receives oxygenated blood from the lungs.

4. **Evaluating the Third Statement**:
- The third statement indicates that the closure of the mitral valve is associated with the first heart sound (S1).
- **Analysis**: This statement is correct. The closure of the mitral valve occurs at the beginning of ventricular contraction, contributing to the first heart sound (S1).

5. **Evaluating the Fourth Statement**:
- The fourth statement claims that the closure of the mitral valve is associated with the second heart sound (S2).
- **Analysis**: This statement is incorrect. The second heart sound (S2) is associated with the closure of the semilunar valves (aortic and pulmonary valves), not the mitral valve.

### Conclusion:
- The correct answer is the third statement: "Its closure is associated with the first heart sound."