How are veins and arteries adapted to the transport of blood?

Artery walls are made up of smooth muscle tissue and a thick elastic layer which allows them to expand and contract easily, coping with the changes in blood volume that occur with each heartbeat. The muscle tissue and supporting connective tissue makes them strong enough to withstand the high pressure of blood which has just left the heart.Vein walls are thinner in comparison, as they only have to carry blood towards the heart at very low pressure so don't need to be as elastic. Instead, they have pocket valves which prevent the back-flow of blood under the influence of gravity and keep the blood flowing constantly towards the heart.