Capillaries

http://biology.about.com/library/organs/heart/blcapillary.htm http://www.innerbody.com/anim/blood.html Capillaries are really small blood vessels located in your body tissue. They connect the arteries and veins and transporte. The walls of the capillaries are very thin and, oxygen, carbon dioxide, nutrients, and wastes are exchanged throught the walls. Ex) from the site- The capillaries are so small the red blood cells can only flow single file. 5-10 microns in diameter.When the blood flows throught the arteries and vein the capillaries contain small mucsle fibers that allow them to contract. Sphincters are what what allow the blood from the arteries and veins to travel into the capillary beds. The capillaries are very thin and fragile. Also, the it's actually only one epilthelial cell thick. For example, there really thin that the only blood cells can pass through them in a single line. The receive carbon dioxide and oxygen is in the thin capillaries wall. The red blood cells from the capillaries release the oxygen which the oxygen goes through the wall and into the surrounding tissue. Then the tissue releases the waste, such as an carbon dioxide which pass through the wall and to the red blood cells. Inside the capillaries, arteries and veins run parallel throughout the body with a web like network. Capillaries are involved in the body releasing the heat. For example, during the exercise your body and your blood get's heated so then the cells help the body take out the heat by delivering the blood to the capillaries which quickly releases to the tissue. So that's the reason your body get's red.