Bicuspid and tricuspid valves are closed during

Options

A. ventricular systole
B. ventricular diastole
C. atrial systole
D. late joint diastole

Explanation

To determine when the bicuspid and tricuspid valves are closed, we need to understand the phases of the cardiac cycle and the function of these valves.

### Step-by-Step Solution:

1. **Understand the Cardiac Cycle**: The cardiac cycle consists of three main phases:
- Atrial Systole
- Ventricular Systole
- Joint Diastole

2. **Define Systole and Diastole**:
- Systole refers to the contraction phase of the heart.
- Diastole refers to the relaxation phase of the heart.

3. **Identify the Function of Bicuspid and Tricuspid Valves**:
- The bicuspid valve (mitral valve) is located between the left atrium and left ventricle.
- The tricuspid valve is located between the right atrium and right ventricle.
- These valves are also known as atrioventricular (AV) valves.

4. **Analyze Each Phase**:
- **Atrial Systole**: During this phase, the atria contract, pushing blood into the ventricles. The AV valves are open to allow blood flow from the atria to the ventricles.
- **Ventricular Systole**: In this phase, the ventricles contract to pump blood out of the heart. The AV valves are closed during this phase to prevent backflow of blood into the atria.
- **Joint Diastole**: Both the atria and ventricles are relaxed, and the AV valves are open, allowing blood to flow from the atria into the ventricles.

5. **Conclusion**: The bicuspid and tricuspid valves are closed during the ventricular systole phase of the cardiac cycle to prevent the backflow of blood into the atria.

### Final Answer:
The bicuspid and tricuspid valves are closed during **ventricular systole**.

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