During the inflammation phase, which process occurs?

• A. The immune system releases histamines, which cause vasodilation and increased capillary permeability, resulting in local redness and swelling.
• B. White blood cells are forced away from the injury site, thus allowing an increase in the flow of red blood cells, resulting in increased blood flow.
• C. The veins and arteries at the injury site constrict and platelets aggregate, which stops bleeding and causes a temporary increase in the size of the wound.
• D. The blood vessels in and around the injury site constrict, which forces bacteria and other microorganisms away, thus preventing significant infection.

Answer: (A)

During inflammation, chemical mediators release signals that cause blood vessels to dilate and become more permeable. This vasodilation increases blood flow to the area, and the higher capillary permeability allows fluids, proteins, and immune cells to move into the tissue. The result is redness and swelling as the body brings in cells to defend and repair the damage. Histamines from nearby mast cells are key drivers of this process, promoting both the dilation of vessels and the leakage of fluid into the surrounding tissue. The other options describe processes outside of the inflammatory response (such as constriction for stopping bleeding or incorrect directions of immune cell movement), so they don’t fit as accurately with what happens during inflammation.