1. The walls of arteries are made up of muscle fibers and are elastic. When the blood enters with a pressure into the arteries then walls will stretch and this enables the arteries to withstand the increase in the pressure without bursting.
2. Veins are closer to the skin and contain valves. They are made of connective tissue called Tunica adventitia or Tunica externa. Middle layer has bands of smooth muscle called Tunica media. Generally veins are thin, lined internally with endothelial cells Tunica intina.
3. Blood capillaries are microscopic vessels made of single layer of cells. They allowdiffusion of various substances. They establish continuity between arterioles and venules. Capillaries is the Latin word which means “hair” because they were as thin as the finest of hairs.
