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Why does increased blood flow make an inflamed area look red?
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immune system
Stimulation of immune response by activated helper T cells. Activated by complex interaction with molecules on the surface of a macrophage or some other antigen-presenting cell, a helper T cell proliferates into two general subtypes, TH1 and TH2. These in turn stimulate the complex pathways of the cell-mediated immune response and the humoral immune response, respectively.
The redness observed in an inflamed area is primarily caused by the vasodilation of small blood vessels at the site of injury. Following an initial, brief period of vasoconstriction, these vessels dilate, which significantly increases the volume of blood flowing into the affected area. This surge in blood flow is a key component of the inflammatory response, as it facilitates the delivery of essential immune cells and proteins to the site to combat potential infection and initiate healing.123