Why Are Valves Present In Veins But Not Arteries?

Veins have valves because the blood has to flow through the heart without flowing back because blood has to fight the force of gravity by flowing up the leg.

I hope that helps!

Wrong, veins has a much lower pressure compared to arteries. Therefore, veins have valves to prevent the backflow of blood, arteries do not because the pressure received from the left ventricle in the heart ensures it moves in only one direction.

Veins need valves to create pressure to pump the blood to the heart. I got this from yahoo answers