Download Patofyziologie základních hematologických chorob

Microcirculation
and
inflammation
M. Jurajda
Anatomy of capillary bed
Starling‘s principle
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
• 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
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
• The initial trauma to the skin releases the
histamine. Histamine causes the
vasodilatation and vascular leakage. The
flare is caused by axon reflex.
Increased perfusion of inflammed
tissue
•
•
•
•
Dilution of noxious materials.
Increased temperature. Thermotaxis?
Diapedesis
Exudation – antibodies escapes blood
vessels
Inflammatory swelling
• Vascular leakage
• Filtration pressure increase
• Reabsorption decrease due to protein
escape into extracellular spaces
The structure of the capillary wall
• Endotelium, BM, pericytes
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.
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
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
• Late capillary leakage develops after 12 –
18
• Probably effect of IL-1, TNF a INF-gamma
• Cytoskeletal changes
•
•
•
•
•
•
Direct injury
Histamine
Cytokines
Neutrophils
Prostaglandins - vasodilatation
Regenerating vessels – leaky sprouts