Inflammation : Cellular response

Cellular response

  • Blood flow through capillaries in area of inflammation slows as fluid is lost and viscosity increases
  • Neutrophils and monocytes move to inner surface of capillaries and then migrate through capillary wall to site of injury
    • Chemotaxis
      • Directional migration of WBCs along concentration gradient of chemotactic factors
      • Mechanism for accumulating neutrophils and monocytes at site of injury
    • Neutrophils
      • First leukocytes to arrive at site of injury (6 – 12 hours)
      • Phagocytize bacteria, other foreign material, and damaged cells
      • Short life span (24 – 48 hours)
      • Pus is composed of
        • Dead neutrophils accumulated at site of injury
        • Digested bacteria
        • Other cell debris
      • Bone marrow releases more neutrophils in response to infection, resulting in elevated WBC
    • Monocytes
      • Second type of phagocytic cells to migrate to site of injury from circulating blood
      • Attracted to the site by chemotactic factors
      • Arrive within 3 to 7 days after onset of inflammation
      • On entering tissue spaces, monocytes transform into macrophages
      • Assist in phagocytosis of inflammatory debris
      • Macrophages have a long life span and can multiply
    • Macrophages
      • Important in cleaning area before healing can occur
      • May stay in damaged tissues for weeks
      • Cells may fuse to form multinucleated giant cell
    • Lymphocytes
      • Arrive later at the site of injury
      • Primary roles of lymphocytes involve
        • Cell-mediated immunity
        • Humoral immunity

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