The term hyperemia indicates the presence of an excessive quantity of blood inside the vessels that supply a specific body region; for this reason it is often followed by the adjective "local".
Didactically we recognize two different types of hyperemia: active hyperemia and passive hyperaemia. In the first case, the increased blood supply is the result of a relaxation of the precapillary sphincters and the dilation of the arteriolar wall. Passive hyperemia, on the other hand, results from the prevention of normal blood flow, a phenomenon typical of inflammatory processes. In most cases, hyperemia remains an absolutely physiological process, consequent to the increased metabolic activity of a particular organ (for example of muscle when it is contracted during an effort, of digestive organs after meals, or of the male penis during erection, a phenomenon that starts thanks to an active hyperemia and is maintained through a passive hyperaemia)
