The inferior vena cava is the bigger vein. It's the largest vein in your body, carrying oxygen-depleted blood from the lower part of your body (below your diaphragm) back to your heart. The superior vena cava, your second biggest vein, brings oxygen-poor blood from your upper body to your heart.
The inferior vena cava is responsible for transporting blood from the legs, abdomen, and pelvic region, making it a larger vessel than the superior vena cava, which handles blood flow from the head, neck, and arms.
The size of these veins is important because they handle a significant amount of blood flow.
