There are two types of channels that carry blood around our bodies. The arteries are muscular tubes that take blood away from the heart and deliver it to the body s organs. The heart has to drive blood to every part of the body, so the blood pressure in the arteries has to be high to make sure that it will carry along the many metres of blood vessels. The heart pumps the blood in pulses and the arteries are able to expand as the strong pulses move along the vessel. Artery walls are built with a smooth inner layer to reduce friction between the blood and the artery, a thick layer of elastic muscle, which allows them to expand and then relax as the pulse moves along the vessel, and a protective outer layer.
Veins deal with blood that is being returned to the heart.
By now the pressure, in the pulses of blood that the heart pumps through the body, has dropped so much that the blood can not return to the heart on its own. Instead of using a second pump to return the blood to the heart, normal movements of the muscles in our bodies gently massage the veins to push the blood along the vein. Valves in the veins make sure that blood doesn t flow backwards. Breathing also helps move blood through the veins. When we take a deep breath, this causes a drop of pressure in the chest that pulls blood up into the large veins in the chest area, which in turn draws blood into the smaller veins in the periphery of the body.