CBSE Class 10 Answered

a. Arteries carry oxygenated blood from the heart to the different body parts. Blood emerges from the heart under high pressure. In order to withstand this pressure, arteries have thick walls.

b. Veins carry deoxygenated blood from the body parts back to the heart. Blood flowing through the veins is not under high pressure. Therefore, veins do not have thick walls. They are thin-walled blood vessels.

c. Veins have valves in them to prevent the backflow of blood. This prevents the mixing of oxygenated blood with the deoxygenated blood.