When ventricular systole occurs -

Options

A. Auricular diastole coincides
B. Tricuspid and bicuspid valves close
C. Semilunar valves guarding pulmonary artery and aorta are forced to open
D. All

Answer

### Step-by-Step Solution:

1. **Understanding Ventricular Systole**:
- Ventricular systole refers to the phase of the cardiac cycle when the ventricles of the heart contract. This contraction is crucial for pumping blood out of the heart.

2. **Events During Ventricular Systole**:
- During this phase, the following events occur:
- **Atrial Diastole**: While the ventricles are contracting, the atria (upper chambers) are in diastole, meaning they are relaxed and filling with blood from the veins.
- **Closure of Atrioventricular (AV) Valves**: The tricuspid and bicuspid (mitral) valves close to prevent backflow of blood into the atria. This closure is essential to ensure that blood flows in the correct direction, from the ventricles into the arteries.
- **Opening of Semilunar Valves**: The semilunar valves (pulmonary and aortic valves) open during ventricular systole. This allows blood to be ejected from the right ventricle into the pulmonary artery and from the left ventricle into the aorta.

3. **Summary of Events**:
- During ventricular systole:
- Atria are in diastole (filling with blood).
- AV valves (tricuspid and bicuspid) are closed.
- Semilunar valves (pulmonary and aortic) are open.

4. **Conclusion**:
- Therefore, during ventricular systole, the atria are relaxed, the AV valves are closed to prevent backflow, and the semilunar valves are open to allow blood to exit the heart.