Page 84 - Veterinary Immunology, 10th Edition

VetBooks.ir Inflammatory Mediators

In its classic form, acute inflammation is said to have five major
symptoms (or cardinal signs): heat, redness, swelling, pain, and loss

of function. These symptoms result from changes in small blood
vessels brought about by “vasoactive” molecules (Fig. 3.5).
Immediately after injury, the blood flow through small capillaries at
the injection site decreases. This gives leukocytes an opportunity to
bind to the blood vessel walls. Shortly thereafter, the small blood

vessels in the damaged area dilate, and blood flow to the injured
tissue increases greatly.

FIG. 3.5 The major signs of acute inflammation and how they are
generated.

At the same time as these changes in blood flow occur, cellular
responses are also taking place. Changes in nearby vascular
endothelial cells permit neutrophils and monocytes to adhere. If the

blood vessels are damaged, platelets may bind to injured
endothelium and release vasoactive and clotting molecules.
Inflamed tissues swell as a result of leakage of fluid from blood

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