Arteries carry oxygenated blood to all the parts the body where  as veins carry deoxygenated  blood from body parts to the heart for oxygenation
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Arteries and veins are the blood vessels. there functions are: 
1)arteries walls are thick and veins has thin walls
2)vales are present in both arteries and veins
3)pressure in arteries is high when compared to veins
4)veins carry DE-oxygenated  from body parts to the heart exception case pulmonary veins carries oxygenated blood
5)arteries carries oxygenated blood exception case pulmonary arteries carries DE-oxygenated blood
the biggest artery is aorta (please mark it as best)