Hyperemia is defined as excess blood (especially in the capillaries) in a part. The part is red, swollen, warmer than normal, and there may be a pulse. It is mediated actively by purposeful dilation of arterioles to increase blood flow in response to some stimulus.

Figuratively, hyperemia is represented in this way:


Usually, in any particular part of the body, blood is flowing through some capillaries and not others. However, when hyperemia happens, ALL the capillaries in a particular area dilate so there is markedly increased blood flow.

Hyperemia usually only happens locally. If it happened all over the body, the animal would go into shock because there wouldn't be enough blood in the major vessels.

Hyperemia is an active process and is represented grossly as REDNESS. In addition, the area is usually swollen and warmer than usual and painful. Rubor et tumor cum calor et dolor.

Visual examples of hyperemia »