대정맥, or the superior vena cava, is a large vein in the human body that carries deoxygenated blood from the upper half of the body back to the heart. It collects blood from the head, neck, arms, and upper torso, ensuring that this blood returns to the right atrium of the heart for reoxygenation. The 대정맥 works in conjunction with the inferior vena cava, which returns blood from the lower half of the body. Together, these two major veins play a crucial role in the circulatory system, maintaining efficient blood flow and supporting overall cardiovascular health.