Veins, on the other hand, have thinner walls and less defined layers than arteries. The third layer, the tunica adventitia, is the thickest of the three.

A huge vein is the Vena Cava. It has a thinner wall than the aorta and fewer identifiable layers.

Blood is transported from the heart to the systemic and pulmonary circulations via arteries. The tunica medium is the thickest layer, and it has a lot of elastic tissue in it.