 Portal veins are a slight exception to this.In humans the only significant example is the hepatic portal vein which combines from capillaries around the gastrointestinal tract where the blood absorbs the various products of digestion; rather than leading directly back to the heart, the hepatic portal vein branches into a second capillary system in the liver.The heart pumps oxygenated blood to the body and deoxygenated blood to the lungs.