The veins are the vessels that carries non-oxygenated blood towards the heart. They are large and thicker walls blood vessels. Seeing in the skin surface, the veins appeared to be blue. This is because of the yellow pigment which changes the appearance of the blood.

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As observed, the blood flowing in the veins are much more darker because it already lost its oxygen. The blood in the veins moves slower than the other vessels considering that the blood is under very little pressure. The walls of this blood vessel is delicate and wider.

There are valves inside the veins which keeps the travel of the blood in one direction. The valves are located in intervals along their length of the veins. When the blood flows forward, the valves will open to allow the bloods entrance. When the bloods starts to go backward, the valve closes.

Schematic Representation of Venous valve

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The blood from the capillaries enters the vein with a little pressure. The blood in the veins runs smoothly and evenly since there is light and constant pressure.