Exogenous

Exogenous (or exogeneous) (from the Greek words "exo" and "gen", meaning "outside" and "production") refers to an action or object coming from outside a system. It is the opposite of endogenous, something generated from within the system.


 * In biology, "exogenous" refers to an action or object coming from the outside of a system. For example, an exogenous contrast agent in medical imaging refers to a liquid injected into the patient intravenously that enhances visibility of a pathology, such as a tumor.


 * In biology, an exogenous factor is any material that is present and active in an individual organism or living cell but that originated outside of that organism, as opposed to an endogenous factor.
 * Exogenous factors in medicine include both pathogens and therapeutics.
 * DNA introduced to cells via transfection or viral infection (transduction) is an exogenous factor.
 * Carcinogens are exogenous factors.


 * In attentional psychology, exogenous refers to attention being drawn without conscious intention (see Posner, 1980). An example of this would be attention drawn to a flashing light in the periphery of vision.