The Biology of Scar Formation
Maureen A. Hardy
What are scars? Scars are such a common occurrence in everyone's experience that little attention is paid to them unless a large area is involved or a cosmetic or functional problem results from the location of the scar. Scars are regarded as products of the natural repair of injured tissue. The healing of surgical incisions or lacerations which are closed by approximation with sutures differs from the healing of open wounds such as third-degree burns, stasis ulcers, or decubitus ulcers. Other types of scars may be produced by infections or certain inflammatory diseases. The healing of surgical wounds begins with the body's outpouring of blood and serum into the defect, the formation of fibrin from fibrinogen, and the migration of fibroblasts and blood vessels into this matrix. New collagen is laid down by the fibroblasts, and a new epidermal surface forms from the migration of epidermal cells across the wound gap. At first the newly formed collagen is very cellular and richly supplied with blood vessels, but in time both the cellularity and blood vessels diminish. The bright red color of the new scar gradually fades to a pearly color in a year or so, and at this point the scar remains more or less stable. In superficial wounds, where only a portion of the dermis is destroyed, epithelial cells may migrate from the remnants of sweat glands or hair follicles to form the new surface. The final healing might be a slightly depressed scar such as often is seen in acne or the deeper infections of impetigo or chicken pox. Large boils or papular or cystic acne may produce considerably deeper scars, sometimes of the "ice-pick" variety. Large deep wounds - where the dermis is destroyed, such as in third-degree burns - pose a different problem for the body. In the absence of adnexal structures such as hair follicles, sebaceous and sweat glands, repair of the defect is by way of granulation tissue. Granulations are capillary buds extending upward to the surface and carrying with them fibroblasts and inflammatory cells. Once a good granulating surface is established, epidermal cells may migrate across to cover the healing surface, but if the wound is large, grafts may be required. Beneath the new thin epidermis new collagen is laid down. The resulting scar may be smooth, but often it presents an irregular, sometimes ropy surface. Shrinkage of the tissue may result in contractures and deformity. Keloids and hypertrophic scars result from an abnormal growth of collagen tissue in a scar. They are elevated, swollen, tense, and sometimes painful. Usually keloids and hypertrophic scars develop in recently healed wounds. Keloids may be quite massive and deforming; excision frequently results in an even larger keloid. This type of growth is most commonly seen in the black race, and often they are found on the upper portions of the trunk, neck, or ears. Unlike keloids, hypertrophic scars may regress spontaneously after a few months, but at times the distinction between hypertrophic scars and keloids is impossible to make. Treatment may take up to 18 months for very old keloids at difficult locations, eg. chest. Although time consuming, treatment is important to eliminate the itch and pain that precedes aggressive growth.
See 1. Silicon sheet
2. Mili scar ointment
3. Keloid FAQ
4. Hei Ba Gao
6. Salviae Miltiorrhizae |
