blood vessel - a vessel in which blood circulatesvas, vessel - a tube in which a body fluid circulates ductus arteriosus - a blood vessel in a fetus that bypasses pulmonary circulation by connecting the pulmonary artery directly to the ascending aorta; normally closes at birth vasa vasorum - any small blood vessel ramifying on the outside of a major artery or vein vein, vena, venous blood vessel - a blood vessel that carries blood from the capillaries toward the heart; all veins except the pulmonary carry unaerated blood |