Blood helps in the transportation of oxygen , Carbondioxide and nutrients.
Arteries are the vessels which carry blood away from the heart to various organs of the body. since the blood emerges from the heart under high pressure, the Arteries have thick , elastic vessels.
Veins collect the blood from different organs and bring it back to the heart . They do not need thick walls because the blood is no longer under pressure, instead they have valves that ensures the blood flows only in one direction.
Arteries divide into very fine vessels called Cappilaries. Which bring the blood in contact with the individual cells . These Cappilaries have one cell thick walls which help in exchanging of material between the blood and surrounding cells . The Cappilaries then join together toformveinsthatconveythebloodaway from oragn to tissue.
