What do the veins superior and inferior vena cava specifically do in the body?

The superior and inferior vena cavae are crucial components of the body's circulatory system, specifically responsible for returning deoxygenated blood to the right atrium of the heart.

The superior vena cava collects blood from the upper body, including the head, neck, arms, and upper trunk, while the inferior vena cava gathers blood from the lower body, including the legs, abdomen, and lower trunk. Once this deoxygenated blood reaches the right atrium, it is then directed to the right ventricle and eventually pumped to the lungs for oxygenation. This process is vital for maintaining the efficiency of the circulatory system, ensuring that oxygen-poor blood is brought back to the heart to be reoxygenated.

In contrast, other functions mentioned in the choices do not align with the specific roles of the vena cavae. They do not supply oxygen, as the blood returning via these veins is low in oxygen. They do not connect capillaries, which is the function of smaller blood vessels that facilitate exchange between arteries and veins. Additionally, while veins can have a role in blood pressure regulation, the primary responsibility of the vena cavae is not to regulate blood pressure but to transport blood back to the heart.