Three major veins are the superior vena cava, the inferior vena cava, and veins in portal systems.
Here's a more detailed breakdown:
- Superior Vena Cava: This major vein brings blood from the upper body to the heart.
- Inferior Vena Cava: This major vein brings blood from the lower body to the heart.
- Veins in Portal Systems: These are major veins.
