There are four valves located in the heart. Each valve either consists of two or three folds of thin tissue. When closed, the valve prevents blood from flowing backwards to its previous location. When open the valve allows blood to flow freely. Valve problems can occur because of congenital abnormalities, infection, or other causes.
Review Date: 10/11/2005
Reviewed By: A.D.A.M. Medical Illustration Team
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