superior vena cava, the second largest vein of the body, returning deoxygenated blood from the upper half of the body to the right atrium. It is about 2 cm in diameter and 7 cm long. The section of the superior vena cava closest to the heart composes about one half of the vessel’s length and is within the pericardial sac, covered by the serous pericardium. It has no valves. Compare inferior vena cava.
