Skin Circulation

Skin is a complex organ that covers almost all the body’s surface.

The skin has a blood supply from many small arterioles: small blood vessels that take blood at higher pressure into the capillary networks. The capillary networks are made up of many tiny vessels with very thin walls. From these networks the blood flows back into the venules, which are small veins that take the blood back to the larger veins and ultimately to the heart.

Blood flow in the capillary networks can be controlled by the body using both hormones and nerves. When the body is too hot more blood is allowed into the capillary networks and so more heat is lost to the air around the body. In this case the skin turns pink or red (flushing or blushing).

When the body is too cold blood is not allowed into the capillary networks and so heat is kept in the body as the skin acts as insulation. This makes the skin look very white.

Thread veins of the legs occur when the venules dilate (get bigger) and become large enough to be visible through the skin.

Thread veins of the face are usually more related to increased flow in the feeding arterioles of the network.