How is the structure of veins related to their function?

Answer 1

Veins are blood vessels that transport deoxygenated blood to the heart at low pressure. The structure of the vein is adapted in several ways to serve this purpose.

* The vein has thinner walls than arteries do as the blood is transported at low pressure. However the vein still has a wall made up of 3 layers. * The tunica intima is made up of a thin layer of endothelium. The tunica media is made up of elastic fibres and some smooth muscle, however, this layer is much thinner in the vein than in arteries as the blood pressure is lower. Also the thinner walls means that the veins can expand and recoil more easily. * The tunica externa is the outer layer of the vein wall, and is made up, for the most part, of connective tissue (collagen mostly). This has a protective function, and protects the vein from damage due to external pressures and physical damage - this is particularly important given that veins often run close to the skin. * Because blood in the veins is at low pressure, there are valves which prevent backflow of blood. These valves are semilunar folds of the tunica intima. They are present in pairs. * Venous flow of blood, unlike in the arteries, is due to the milking action of the skeletal muscles, and partly due to the action of the slight negative pressure in the thorax on inhalation.

Answer 2

Veins have valves to prevent the back flow of blood. The walls of veins are thin so skeletal muscles can exert pressure on these blood vessels. They also have a thin outer layer of muscle fibers to provide structural support. Their lumens are wide t enable to large volume of blood to flow through.