The system of blood vessels in the human body measure about 60,000 miles (96,560 kilometers). Arteries carry oxygen-rich blood from the heart through the body. Veins carry oxygen-poor blood back ...

Contain valves to prevent back flow of blood: Walls are made of semi-permeable membrane to allow transport of gases and nutrients into and out of the blood: Function; Artery: ...

The semilunar valves stop the back flow of blood into the heart. There is a semilunar valve where the aorta leaves the left ventricle and another where the pulmonary artery leaves the right ventricle.