Repair

• Repair


  Replacement of damaged tissue by a new healthy one
• Types of cells according to power of cell division

  • Labile cells (continuously dividing)
  • Quiescent/Stable cells (divide when needed)
  • Permanent cells (non-dividing)
• Types of repair


  • Regeneration
  • Fibrosis/Gliosis
• Regeneration


  Replacement of damaged cells by new healthy cells of the same type, done by proliferation of adjacent healthy cells
• Fibrosis/Gliosis


  Replacement of damaged tissue by fibrous tissue or glial tissue (in CNS)

  
• Wound healing


  1. Hemostasis

  2. Inflammation

  3. Granulation tissue formation and Re-epithelialization

  4. Fibrous tissue formation and remodeling
• Hemostasis


  • Vasoconstriction, platelets aggregation, fibrin network formation to stop bleeding
• Inflammation


  • Mediated by polymorphs and macrophages, killing organisms and liquefying necrotic debris
• Granulation tissue formation and re-epithelialization

  • Fibroblasts migrate, angiogenesis forms new capillaries, epidermal cells proliferate and migrate inwards
• Fibrous tissue formation and remodeling

  • Fibroblasts lay down collagen, excess collagen degraded by collagenase
• Wound contraction


  Process done by myofibroblasts to give healing wound more strength
• Types of wound healing

  • Healing by primary union (clean, non-gaping wounds)
  • Healing by secondary union (extensive tissue loss)
• Local factors affecting repair

  • Type of damaged cells
  • Severity of damage
  • Foreign body
  • Necrotic tissue
  • Infection
  • Irradiation
  • Blood supply
• General factors affecting repair

  • Age
  • Nutrition status
  • Diseases (diabetes, malignancy, anaemia)
  • Drugs (corticosteroids, chemotherapy)
• Complications of wound healing

  • Ulcers
  • Sinus
  • Fistula
  • Weak atrophic scar
  • Hypertrophied scar
  • Keloid formation
  • Wound contraction
• Keloid


  Large sized scar that grow beyond boundaries of original wound, due to overproduction or defective degradation of collagen, affects genetically predisposed persons, treated with radiotherapy