Microcirculation and inflammation

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Microcirculationandinflammation

• M. Jurajda

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Anatomy of capillary bed
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Starlings principle
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Four signs of inflammation

• Rubor et tumor cum calore et (dolore)
• caused by hyperaemia of inflammed tissue
• Cohenheim 1867 watched and described this events
  in the mesentery of the living frog

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• What happens when arterioles dilate?
• Systemic pressure is not affected because limited
  area is involved
• Flow acceleration and capillary pressure rise.
• Venules become distended, but capillary
  dilatation is minimal

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The triple response of the skin

• Sir Thomas Lewis (1920)
• Histamine mediated three step reaction
• 1. red line
• 2. red flare
• 3. wheal develops local oedema of the skin

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• The initial trauma to the skin releases the
  histamine. Histamine causes the vasodilatation
  and vascular leakage. The flare is caused by axon
  reflex.

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Increased perfusion of inflammed tissue

• Dilution of noxious materials.
• Increased temperature. Thermotaxis?
• Diapedesis
• Exudation antibodies escapes blood vessels

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Inflammatory swelling

• Vascular leakage
• Filtration pressure increase
• Reabsorption decrease due to protein escape into
  extracellular spaces

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The structure of the capillary wall

• Endotelium, BM, pericytes

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Mechanisms of vascular leakage

• Impairment of endothelial layer causes lost of
  permeability barrier and plasma leaks out,
  basement membrane (BM) holds the vessel together
• Destruction of BM causes hemorrhage.

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Methods for demonstrating vascular leakage

• Soluble dyes
• Colloidal suspensions of pigment
• Bacteria in circulation tend to localize in
  inflammed tissue
• Presence of fibrin in extracellular space is the
  histological sign of vascular leak

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Types of vascular leakage

• Direct injury of vessels destroys endothelia in
  arterioles, capillaries and venules
• Histamine mediated leakage leakage is
  restricted only to the venules, endothelia of
  venules are equipped with histamine receptors and
  reacts by contracting itself

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• Late capillary leakage develops after 12 18
• Probably effect of IL-1, TNF a INF-gamma
• Cytoskeletal changes

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• Direct injury
• Histamine
• Cytokines
• Neutrophils
• Prostaglandins - vasodilatation
• Regenerating vessels leaky sprouts