Veins

Veins are large blood vessels which carry blood toward the heart. They carry blood under low pressure. They have thinner and less muscular walls than arteries. This is due to low pressure blood flows. Veins have cup-shaped valves at intervals along their length. This prevents the backflow of blood. Most veins carry deoxygenated blood to the heart except the pulmonary veins which carry oxygenated blood from the lungs to the heart.

The veins have venules. These are minute vessels that link the veins to the capillaries.

The main function of the vein is the transport of blood to the heart.