The four stages of wound healing

September 17, 2012 | By | Reply More

The four stages of wound healing

When specialized tissue is destroyed it cannot be replaced, and a stereotyped response called repair then follows in four stages.
  • Haemostasis: immediate. In response to exposed collagen, platelets aggregate at the wound and degranulate, releasing inflammatory mediators. Clotting and complement cascades activated. Thrombus formation and reactive vasospasm achieve haemostasis
  • Inflammation: 0-3 days. Vasodilatation and increased capillary permeability allow inflammatory cells to enter wound, and cause swelling. Neutrophils amplify inflammatory response by release of cytokines; reduce infection by bacterial killing; and debride damaged tissue. Macrophages follow and secrete cytokines, growth factors, and collagenases. They phagocytose bacteria and dead tissue and orchestrate fibroblast migration, proliferation, and collagen production

  • Proliferation: 3 days-3 weeks. Fibroblasts migrate into the wound and synthesize collagen. Specialized myofibroblasts containing actin cause wound contraction. Angiogenesis is stimulated by hypoxia and cytokines and granulation tissue forms
  • Remodelling: 3 weeks-1 year. Re-orientation and maturation of collagen fibres increases wound strength.

Category: Pathology, Surgery

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