In human oxygenated blood flows from :-

Options

A. Left atrium to left ventricle during atrial systole
B. Right atrium to right ventricle during ventricular systole
C. Right ventricle to aorta during ventricular systole
D. Pulmonary vein to left atrium during atrial systole

Answer

To answer the question "In human, oxygenated blood flows from:", we will analyze the options provided and determine the correct pathway of oxygenated blood in the human circulatory system.

### Step-by-Step Solution:

1. **Understanding Oxygenated Blood**:
- Oxygenated blood is the blood that has absorbed oxygen in the lungs and is ready to be distributed to the body.

2. **Identifying the Source of Oxygenated Blood**:
- In humans, oxygenated blood returns from the lungs to the heart via the pulmonary veins.

3. **Pathway of Blood Flow**:
- The oxygenated blood enters the left atrium from the pulmonary veins.
- When the left atrium contracts (during atrial systole), it pushes the oxygenated blood into the left ventricle.

4. **Examining the Options**:
- **Option A**: Left atrium to left ventricle during atrial systole – This is correct as it describes the flow of oxygenated blood.
- **Option B**: Right atrium to right ventricle during ventricular systole – This is incorrect as this pathway involves deoxygenated blood.
- **Option C**: Right ventricle to aorta during ventricular systole – This is also incorrect as this pathway involves deoxygenated blood being sent to the lungs.
- **Option D**: Pulmonary vein to left atrium during atrial systole – This is incorrect because the blood flows from the pulmonary vein to the left atrium, but this option does not specify the flow to the left ventricle.

5. **Conclusion**:
- The correct answer is **Option A**: Oxygenated blood flows from the left atrium to the left ventricle during atrial systole.