Question

State the differences between artery, vein and capillary.

Answer 1

	Arteries	Veins	Capillaries
(i)	Arteries are thick-walled, tough, and elastic blood vessels.	Veins are thin-walled and less elastic blood vessels.	Capillaries are one-cell-thick, very thin-walled blood vessels.
(ii)	They have a narrow lumen.	They have a wide lumen.	They have a very narrow lumen, just wide enough for a red blood cell to pass through.
(iii)	They carry blood away from the heart to different parts of the body under high pressure.	They carry blood towards the heart from different parts of the body under low pressure.	They connect arterioles to venules and carry blood from arteries to veins.
(iv)	They do not have valves (except at the base of the heart).	They have valves to prevent the backward flow of blood.	They do not have valves.
(v)	They usually carry oxygenated blood (except the pulmonary artery and umbilical arteries).	They usually carry deoxygenated blood (except for the pulmonary and umbilical veins).	They allow the exchange of oxygen, carbon dioxide, nutrients, water, salts, and wastes between the blood and body tissues.