A scar is the name applied to fibrous tissue which forms across a healed wound, ulcer, or breach of internal tissue. In the case of scars on the surface of the skin, the scar tissue which forms over the wounded surface is at first soft and has a redder tint than the surrounding tissue because it is delicate in texture and richly provided with blood vessels. Gradually the fibrous tissue contracts, becomes more dense, and loses its blood vessels, so that an old scar is hard and white. Scarring is also a process in the repair of internal organs, nerves and bones.
A wound whose edges are accurately brought together and in which healing is rapid, shows far less contraction afterwards and leaves a fainter scar. Burns which remove the skins produce some of the worst scarring. Infection of a wound also can result in a wide, unsightly scar which causes puckering of the surrounding skin as it contracts. Such scars stretch easily and can form ulcers with irritation. Scars which involve sensory nerves can be extremely painful, as in the case of scarring after amputation of part of a limb.