A permanent mark left in the tissue after wound healing is complete. Scar tissue is thicker than the surrounding tissue, and also paler and denser because it has a reduced blood supply. It is limited in function, including movement, circulation, and sensation. An overgrowth of fibrous tissue following trauma to the skin results in a keloid scar. Keloid scars do not resolve spontaneously and tend to extend beyond the original wound. Hypertrophic scars consist of raised scar tissue and do not extend beyond the boundaries of the original wound and may reduce over time.