The inferior vena cava (IVC) is the largest vein in the human body, collecting deoxygenated blood from the lower half. It lacks valves and runs to the right of the abdominal aorta, passing through the caval opening in the diaphragm. The visceral tributaries include hepatic, renal, and genital veins, while the parietal tributaries consist of lumbar and inferior phrenic veins.