Question

give the reasons for each of the following 1 arteries have thick wall 2veins have thin walls 3veins have valves

Answer 1

1. Arteries have thick wall to maintain the blood pressure as well as blood flow of the oxygenated blood from heart throughout the body.
See,in arteries the oxygenated blood is carried , heart needs to give this blood to all parts of the body except pulmonary artery which carries deoxygenated blood. So, to supply this oxygenated blood it needs a lot of pressure.The tubes of arteries should be strong enough to be not harmed , so in case it is made up of a thick walls which protects it.

2.In veins it carries deoxygenated blood except pulmonary vein.It doesn't need much pressure because the blood is only carried from the body to heart through which it is carried by pulmonary artery to lungs where it is purified & carbon dioxide is released which is thrown out by nase. So,veins have thin walls.

3. Valves assure blood flow in one direction. Arteries have high pressure through its narrow lumen and need not to develop any kind of valve in it to maintain the flow in uni-direction. Rather there is low blood pressure though the vein. Thus direction of flow should be maintained. Hence there is a need of valves to resist the back flow blood.