PATHOLOGY

Detailed explanation-1: -The blood passing through the veins is deoxygenated (except in pulmonary veins ) and flows at a low pressure. It flows slow and steady against the direction of gravity. Therefore, veins have valves to prevent the backflow of blood.

Detailed explanation-2: -Arteries are blood vessels that carry oxygenated blood to all parts of the body. They have thick muscular walls and have no valves in their inner linings. Veins carry deoxygenated blood and have thin muscular wall. They have valves in their inner lining to prevent the backward flow of blood.

Detailed explanation-3: -Heart valves control the flow of blood so that it moves in the right direction. The valves prevent blood from flowing backward.