Where would you find valves?
Veins
Veins contain valves which ensure that the blood flows in only one direction. Arteries except for the aorta and pulmonary trunk do not have valves. Arteries don't require valves because pressure from the heart is so strong that blood is only able to flow in one direction. Valves also help the blood to travel back to the heart against the force of gravity. Capillaries and lymph node also don't have valves.