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 an
economic model, an
exogenous change is one that comes from outside the model and is unexplained by the model. For example, in the simple
supply and demand model, a change in consumer tastes or preferences is unexplained by the model and also leads to
endogenous changes in demand that lead to changes in the
equilibrium price. Put another way, an exogenous change involves an alteration of a variable that is autonomous, i.e., unaffected by the workings of the
model.
* 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 IV in the patient 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.
* The word exogenous is also used in
geology. Exogenous processes are all taking place at the outside of the
Earth and all the other
planets.
Weathering,
erosion, transportation and
sedimentation are the main exogenous processes.
*
Endogenous
