These are the channels running throughout the body and transports blood from the heart to every part and also brings back all that blood back to the heart which is then sent for purification to the lungs.
Veins:
Veins carry deoxygenated (impure) blood rich in carbon dioxide from all parts of the body to the heart (except the lung vein called the pulmonary vein which carries oxygenated blood).
Blood vessels that carry blood back to the heart from all parts of the body are called veins which lie closer to the surface of the skin and can be seen as greenish-blue lines in the hands and legs.