• Clinical science

Wound healing


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 diabetes and peripheral vascular disease can slow the wound healing process. Delayed wound healing may lead to the formation of a chronic wound.

Wound healing categories

Primary wound closure

  • Usually a small, straight, and clean incision
  • Primary approximation of the wound edges without irregularities
  • Minimal inflammation
  • Minimal to no granulation tissue
  • Organ-specific tissue forms at the site of healing
  • Hairline scar or no scar formation

Secondary wound closure

  • Usually larger open wounds with irregular edges (most common type of wound)
  • Irregular wound edges that cannot be perfectly approximated
  • Pronounced inflammation
  • Requires the formation of granulation tissue (increase the length of healing)
  • Wound replaced with increased proliferation of fibroblasts
  • Scar formation

Tertiary wound closure (also called delayed primary closure)

  • Due to an interruption in normal wound healing
  • Combination of primary closure and secondary closure
  • Results in a larger scar than with primary or secondary closure
  • Wounds created by specialists

Phases of wound healing

Phase Timing Characteristics


Day 1


Days 1–3


Days 3–7
Maturation Weeks to 1 year


Wound healing complications

Delayed wound healing 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.

Excessive scar

Dysregulation of the wound healing process during the proliferative stage and maturation stage leads to excess fibroblast replication and collagen deposition.


  • 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.


last updated 09/02/2020
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