Some migratory birds have adapted to use protein from many parts of their bodies, including protein from the intestines, as additional energy during migration.
When the intestines are involved, the condition is known as "enteroptosis"; when the stomach is found below its normal position, the term "gastroptosis" is used.
Such transport also plays a vital role in acid-base movements in the stomach, pancreas, intestine, kidney, reproductive organs and the central nervous system.
