A vein is a blood vessel that returns blood to the heart. Veins transport deoxygenated blood from the body back to the heart, with the exception of the pulmonary veins, which transport oxygenated blood from the lungs to the heart.
A vein is a blood vessel that returns blood to the heart. Veins transport deoxygenated blood from the body back to the heart, with the exception of the pulmonary veins, which transport oxygenated blood from the lungs to the heart.