Not all substances absorbed from the gastrointestinal tract can be used in their absorbed
form by the cells.
The liver changes the chemical compositions
of many of these substances to more usable forms,
and other tissues of the body—fat cells, gastrointestinal
mucosa, kidneys, and endocrine glands—help modify the
absorbed substances or store them until they are needed.
The liver also eliminates certain waste products produced
in the body and toxic substances that are ingested.