Major components and early vascular changes of acute inflammation
THE CONTEXT
Acute inflammation delivers plasma proteins and leukocytes to sites of infection or tissue injury through coordinated vascular and cellular responses.
Three major components
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Acute inflammation consists of dilation of small vessels, increased microvascular permeability, and emigration of leukocytes from the microcirculation.
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Most of these changes occur in postcapillary venules. Their walls respond to stimuli and are sufficiently thin to permit passage of fluid and proteins.
Functions and local control
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Vasodilation slows blood flow and prepares for subsequent reactions.
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Increased vascular permeability allows plasma proteins to enter the affected tissue.
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Transmigration moves leukocytes through the vessel wall into sites of infection or necrosis, where they destroy harmful agents and clear damage.
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These responses are induced by cytokines and other inflammatory mediators produced at the site of infection or necrosis.
Early vasodilation
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Vasodilation is among the earliest reactions of acute inflammation and produces visible redness, or erythema, and warmth.
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Histamine is the most important chemical mediator of vasodilation.