Either of 2 large veins into which all circulating (deoxygenated) blood drains. The venae cavae (superior and inferior) deliver blood to the right atrium of the heart for pumping to the lungs.
The superior vena cava starts at the top of the chest, close to the sternum, and passes down through the pericardium before connecting to the right atrium. It collects blood from the upper trunk, head, neck, and arms. The inferior vena cava starts in the lower abdomen and travels upwards in front of the spine, behind the liver, and through the diaphragm before joining the right atrium. It collects blood from the legs, pelvic organs, liver, and kidneys.