scar, fibrous connective tissue that forms at the site of injury or disease in any tissue of the body. Scar tissue may replace injured skin and underlying muscle, damaged heart muscle, or diseased areas of internal organs such as the liver. Dense and thick, it is usually paler than the surrounding tissue because it is poorly supplied with blood, and although it structurally replaces destroyed tissue, it cannot perform the functions of the missing tissue. Scar tissue may therefore limit the range of muscle movement or prevent proper circulation of fluids when affecting the lymphatic or circulatory system. Extensively scarred tissue may lose its ability to function normally.
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