Wound Healing Pathophysiology

Phases of Wound healing

  1. Inflammatory Phase
  2. Proliferative Phase
  3. Remodelling Phase
  • duration of phases depends on the extent of injury and healing environment


Inflammatory Phase

  • inflammation occurs at time of injury
  • prepares wound environment for healing
  • blood vessel constriction
  • thrombus formation
  • vasodilation
  • increased capillary permeability
  • phagocyte emigration
  • digest debris
  • neutrophils arrive first, ingest bacteria, gone by day 3-4
  • macrophages appear 24hr after injury, remaining for an extended period
  • macrophages function in phagocytosis
  • macrophages release growth factors stimulating epithelial cells proliferation and angiogenesis
  • wounds may heal in absence of neutrophils, they cannot heal without macrophages

Proliferation Phase

  • begins within 2-3 days of healing
  • lasts up to 3wks
  • function – tissue building to fill wound space
  • fibroblasts produce collagen and other intracellular elements required for wound healing
  • 24-48hrs post injury fibroblasts and vascular endothelial cells begin proliferation of granular tissue (the foundation of scar tissue)
  • tissue is fragile and bleeds easily during to the # of newly formed capillary buds
  • in primary intention healing, epidermal cells seal the wound within 24-48h
  • epithelial cells require a moist surface for proliferation, therefore will wait to migrate under newly formed scab.
  • In cases of excessive granular tissue formation, re-epitheliarization may be impeded. Chemical cauterization may be required to allow healing to proceed
  • collagen synthesis peaks at 5-7days, continuing for several weeks

Remodelling Phase

  • 3 wks post injury, continuing 6 months or longer
  • cycle of collagen synthesis and collagenolysis
  • wound tensile strength increases
  • wounds will not regain original unwounded tensile strength
  • sutures provide 70% of tensile strength of non wounded skin
  • at suture removal 1 week post surgery, wound has only 10%
  • tensile strength increases to 70-80% over the next 4 wks before plateau

Factors Affecting wound healing

  1. Malnutrition
  2. blood flow & O2 delivery
  3. Impaired Inflammatory and Immune Response
  4. Infection, Wound separation and foreign bodies

Martin, Glenn and Porth, Carol, Mattson. 2009. Pathophysiology Concepts of Altered Health States. 8th ed. Lippincott Williams and Wilkins. Philadelphia


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