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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.
Posner, M.I. (1980), Orienting of attention. Quarterly Journal of Experimental Psychology, 32: 3 – 25.