Vein veins), not their oxygen content. In addition, deoxygenated blood that is carried from the tissues back to the heart for reoxygenation in the systemic circulation still carries some oxygen, though it is considerably less than that carried by the systemic arteries or pulmonary veins. Although most veins take blood back to the heart, there is an exception. Portal veins carry blood between capillary beds. For example, the hepatic portal vein takes blood from the capillary beds in the digestive tract and transports it to the capillary beds in the liver. The blood is then drained in the gastrointestinal tract and
Superficial vein tend to bulge out. This can be readily witnessed in the hand: raised above the heart and the blood should drain; lowered below the heart and it will fill. Veins become more visually prominent when lifting heavy weight, especially after a period of proper strength training. Physiologically, the superficial veins are not as important as the deep veins (as they carry less blood) and are sometimes removed in a procedure called vein stripping, which is used to treat varicose veins. Superficial vein Superficial vein is a vein that is close to the surface of the body. This differs from deep