Capillary

A capillary is one of several types of blood vessels that transport blood around the body.
Other blood vessels include arteries, arterioles, veins and venules.

The structure of a capillary is:

Capillaries are tiny (extremely narrow) blood vessels, of approximately 5-20 micro-metres (one micro-metre = 0.000001metre) diameter.

There are networks of capillaries in most of the organs and tissues of the body. These capillaries are supplied with blood by arterioles and drained by venules.

Capillary walls are only one cell thick, which permits exchanges of material between the contents of the capillary and the surrounding tissue.

The functions of capillaries include:

• To supply tissues with components of, and carried by, the blood, and also to remove waste from the surrounding cells - as opposed to simply moving the blood around the body, in the case of other blood vessels.
• The exchange of oxygen, carbon dioxide, water, salts, etc., between the blood and the surrounding body tissues.

For more information about blood vessels and the components (sometimes called the 'constituents') of blood see the pages about the the structure and functions of blood vessels and the structure and functions of blood. This might interest students of holistic massage, reflexology, beauty therapies, or health-related courses.