Final answer:
The redness of inflamed gingiva is primarily caused by increased vasodilation and secondarily by increased vascular permeability.
Step-by-step explanation:
The redness of inflamed gingiva is due to increased vasodilation. Many inflammatory mediators, such as histamine, are vasodilators that increase the diameters of local capillaries. This causes increased blood flow and is responsible for the heat and redness of inflamed tissue. It allows greater access of the blood to the site of inflammation.
Increased vascular permeability is also a factor in inflammation. Inflammatory mediators increase the permeability of the local vasculature, causing leakage of fluid into the interstitial space, resulting in swelling or edema associated with inflammation.
In summary, the redness of inflamed gingiva is primarily caused by increased vasodilation and secondarily by increased vascular permeability.