Monday, September 4, 2017

Basics of Tissue Healing

There are 3 phases of tissue healing that are inter-related and overlap with one another:

Phase I: Inflammatory (Acute)
  • Lasts 24-48 hours, completely over by 2 weeks 
  • 5 cardinal signs of : 
    • Redness 
    • Swelling 
    • Pain 
    • Heat 
    • Loss of function
  • Initial vasoconstriction to limit blood loss with release of serotonin 
  • Followed by histamine release which increases permeability of capillaries, so fluid escapes 
  • Also released are bradykinin, other proteins and enzymes which generally increase pain so individual protects part from further injury 
  • White cells move in to remove debris via phagocytosis 
  • Minimizing the release of debris (protein, enzymes) from the damaged cells and minimizing hemorrhage decreases the size and amount of injury, even after the fact 

Phase II: Proliferation or Repair (Subacute)
  • Lasts 4-21 days 
  • Increased tissue tolerance, yet still fragile 
  • Synthesis, orientation, and deposition of new collagen is random 
  • Characterized by: muscle tightness, weakness, local edema, resolving pain (hopefully) 
  • Rapid proliferation of collagen with fibroblastic activity

Phase III: Remodeling (Chronic) 

  • Day 9- onward 
  • Steady increase in scar matrix 
  • Collagen fibers begin to align themselves with the prevailing tissue stresses 
  • Tissue gradually assumes the appearance & function of the “host” tissue 
  • Scar tissue is rarely as strong, mobile or vascular as the host 
  • If new tissues are immobilized for prolonged periods, new collagen becomes highly disorganized and random

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