What mainly causes local capillaries to leak during inflammation?

• A. Reduction of blood flow
• B. Increased presence of pathogens
• C. Vasodilation due to inflammatory mediators
• D. Constriction of surrounding muscles

Answer: (C)

The correct answer is related to the role of inflammatory mediators in causing vasodilation, which increases the permeability of local capillaries. During inflammation, the body releases various chemicals, such as histamines, prostaglandins, and leukotrienes, which are part of the inflammatory response. These substances cause the blood vessels to expand (vasodilate), allowing more blood flow to the affected area, and simultaneously, they increase the permeability of the capillaries.

As a result, fluid and immune cells can pass through the capillary walls more easily, leading to the accumulation of fluids in the surrounding tissues, which is commonly observed as swelling (edema). This process is essential for delivering necessary immune cells to the site of injury or infection, aiding in the body's defense mechanisms.

The other options do not directly affect capillary leakage in the same manner. For instance, a reduction of blood flow would not promote leakage but rather limit it, while increased presence of pathogens, although relevant to the immune response, does not specifically trigger the capillary leakage by itself. Lastly, constriction of surrounding muscles would typically limit blood flow and would not contribute to the leakage of capillaries in the context of inflammation.