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How do changes in blood flow and blood-vessel permeability contribute to inflammation?

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In the context of inflammation, vascular changes are critical for the body's defensive response to injury. These changes occur in two primary stages:

Vasodilation and Blood Flow

Following a brief period of constriction, blood vessels undergo vasodilation, which significantly increases blood flow to the site of injury. This process is triggered by chemical mediators, most notably histamine, which is released from mast cells and basophils upon tissue damage.12

Increased Vascular Permeability

As inflammation progresses, the walls of the blood vessels become more permeable, allowing protein-rich fluid known as exudate to leak into the surrounding tissues. This fluid contains essential components such as antibodies and clotting factors that help neutralize pathogens and contain the injury.1

This leakage causes blood flow to become more sluggish, which facilitates the movement of white blood cells toward the vessel walls. These cells then adhere to the endothelium, a necessary step for them to emigrate into the tissue to combat the source of inflammation. Various substances, including kinins and complement proteins, actively regulate this permeability.12