4b. why would the vena cava be classified as a vein? all veins carry blood back to the heart, except for the pulmonary vein. the vena cava empty into the right side of the heart, so they technically bring blood to the

The blood is being carried from organs and is returning to the heart after it has left the kidney and liver to then be transported to the lungs via the pulmonary artery as the blood is returning to the heart it is classified as a vein, it also has a very vide tunica interna as well as a relatively thin tunica media.