<Tr> <Th> MeSH </Th> <Td> D041981 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <P> The gastrointestinal tract (digestive tract, digestional tract, GI tract, GIT, gut, or alimentary canal) is an organ system within humans and other animals which takes in food, digests it to extract and absorb energy and nutrients, and expels the remaining waste as feces . The mouth, esophagus, stomach, and intestines are part of the gastrointestinal tract . Gastrointestinal is an adjective meaning of or pertaining to the stomach and intestines . A tract is a collection of related anatomic structures or a series of connected body organs . </P> <P> All bilaterians have a gastrointestinal tract, also called a gut or an alimentary canal . This is a tube that transfers food to the organs of digestion . In large bilaterians, the gastrointestinal tract generally also has an exit, the anus, by which the animal disposes of feces (solid wastes). Some small bilaterians have no anus and dispose of solid wastes by other means (for example, through the mouth). </P>

What are the main purposes of the gastrointestinal