Wound Healing

Categories of Wound Healing

Category 1

Primary wound healing or healing by first intention occurs within hours of repairing a full-thickness surgical incision. This surgical insult results in the mortality of a minimal number of cellular constituents.

Category 2

If the wound edges are not reapproximated immediately, delayed primary wound healing transpires. This type of healing may be desired in the case of contaminated wounds. By the fourth day, phagocytosis of contaminated tissues is well underway, and the processes of epithelization, collagen deposition, and maturation are occurring. Foreign materials are walled off by macrophages that may metamorphose into epithelioid cells, which are encircled by mononuclear leukocytes, forming granulomas. Usually the wound is closed surgically at this juncture, and if the "cleansing" of the wound is incomplete, chronic inflammation can ensue, resulting in prominent scarring.

Category 3

A third type of healing is known as secondary healing or healing by secondary intention. In this type of healing, a full-thickness wound is allowed to close and heal. Secondary healing results in an inflammatory response that is more intense than with primary wound healing. In addition, a larger quantity of granulomatous tissue is fabricated because of the need for wound closure. Secondary healing results in pronounced contraction of wounds. Fibroblastic differentiation into myofibroblasts, which resemble contractile smooth muscle, is believed to contribute to wound contraction. These myofibroblasts are maximally present in the wound from the 10th-21st days.

Category 4

Epithelization is the process by which epithelial cells migrate and replicate via mitosis and traverse the wound. This occurs as part of the phases of wound healing, which are discussed in Sequence of Events in Wound Healing. In wounds that are partial thickness, involving only the epidermis and superficial dermis, epithelization is the predominant method by which healing occurs. Wound contracture is not a common component of this process if only the epidermis or epidermis and superficial dermis are involved.