Wounds are a break in the skin and/or a disruption of the skin's normal barrier function. Wound healing is a step-wise cellular response involving fibroblasts, macrophages, endothelial cells, and keratinocytes that restore the structural and functional integrity of the skin. The four general stages of wound healing are exudative, resorptive, proliferative, and maturation. While the three initial stages take place within the first two weeks, the last stage proceeds over months. Many factors affect wound healing, including the size of the wound, tension on wound edges, the presence of foreign bodies or infection, and the baseline health and nutrition of the patient. In addition, chronic health conditions such as and can slow the wound healing process. may lead to the formation of a chronic wound.
Phases of wound healing
|Phases of wound healing |
|Phase||Timing||Cells involved||Characteristics||Involved tissue mediators|
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|Maturation|| || |
Risk factors for delayed wound healing: DID NOT HEAL
- Drugs (e.g., steroids, cytotoxics, and other immunosuppressive agents)
- Nutritional deficiency (e.g., iron-deficiency anemia)
- Oxygen (hypoxia)
- Toxins (e.g., alcohol consumption, smoking) 
- Excessive tension on the wound edges
- Acidosis/Another wound
- Local anesthetics
Wound healing complications
or chronic wound formation
- Usually occurs in patients with multiple risk factors that cause slowing or failure to progress through one or more stages of wound healing
- The proliferative wound healing phase is delayed in individuals with copper and vitamin C deficiency.
- Zinc deficiency can delay wound healing because the collagenases responsible for collagen remodeling require zinc to function properly.
- Occurs when initial injury cannot be repaired solely by cell regeneration
- Cells that cannot be regenerated (e.g., due to chronic injury or because acute injury is too severe) are replaced by connective tissue.
- After 3 months, 70–80% of tensile strength is regained. 
- Maximum strength of scar tissue is approx. 80% of that of unwounded skin. 
- Dysregulation of the wound healing process during the proliferative stage and maturation stage leads to excess fibroblast replication and collagen deposition.
- Molecular mechanisms 
- Increased production of:
- Decreased production of:
- Cutaneous condition characterized by high fibroblast proliferation and collagen production that leads to a raised scar that does not grow beyond the boundaries of the original lesion.
- See “ .”
- Skin lesions caused by high fibroblast proliferation and collagen production in excessive tissue response to typically small skin injuries
- Lesions grow beyond the original wound margins, leading to a ”claw-like” appearance.
- See “ .”
- Excessive proliferation in myofibroblasts during proliferative and maturation phases leads to contraction of the wound.
- Excessive contraction can reduce the functionality of the injured limbs or organs.
- Wounds that cross a joint (e.g., on the hands and fingers) are at high risk for causing functional deficits from contracture. Periodic exercise of the involved limb can help preserve normal function.