Phases of The Inflammatory Response

Phases of The Inflammatory Response


Vascular Phase

Cellular Phase: Leukocyte Margination, Adhersion and Transmigration

Leukocyte Activation and Phagocytosis Phase


  1. Vascular Phase


  • Characterized by changes in the small blood vessels @ the site of injury


  • Begins with momentary vasocontriction followed rapidly by vascodilation

  • Increases capillary blood flow

  • Results in: causes heat and erythema


  • Increases vascular permeability

  • Results in: causes protein-rich exudate emigration to tissues


  • Capillary osmotic pressure decreases with decreased intracapillary protein content


  • Interstitial osmotic pressure then increases

  • Results in: swelling, pain and impaired function


  • Decreased intracapillary volume results in decreased blood flow and clotting

  • Results in: localizing infection spread

 2. Cellular Phase: Leukocyte Margination, Adhersion and Transmigration


  • Leukocytes (mostly Neutrophils) delivered to site of injury

  • leukocytes then function in host defense


Leukocyte delivery is categorized by:

  • adhesion to capillary wall

  • margination – flattening cell to capillary wall

  • transmigration – squeezing though capillary wall

  • chemotaxis – following chemical gradient through tissues to injury site


Leukocyte recruitment to precapillary venules of injury facilitated by

  • slowing of blood flow

  • margination of leukocytes along vessel surface


Leukocyte adhesion and transmigration from the vascular space into the extracellular tissues is facilitated by:

  • complementary adhesion molecules (selectins and integrins) on leukocyte and endothelial surfaces

  • Leukocytes then migrate through tissues toward the site of injury by chemotaxis

 3. Leukocyte Activation and Phagocytosis


  • Ab binds foreign particle and receptor on phagocyte cell surface

  • Phagocyte engulfs Ab bound foreign particle

  • Phagocyte digests foreign particle


  1. Opsonization of microbe by complement factor and Ab facilitates recognition by neutrophil and Ab receptor

  2. Receptor activation triggers intracellular signalling and actin assembly in the neutrophil, leading to formation of pweudopods that envelop the microbe

  3. The phagocyte then fuses with an intracellular lysosome to form a phagosome into which lysosomal enzymes and oxygen radicals are released to kill and degrade the microbe


  • increased permeability of capiliaries

  • thrombocytes arrive, form clot

  • leukocytes arrange themselves along the endothelial lining – diaphoresis, move out into cellular tissue

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

p.383 see diagram


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