Bile

A bitter yellow fluid, secreted by liver cells of practically all vertebrates and stored in most species in the gall bladder, where it is considerably concentrated by absorption of water, with a change of its reaction from slightly alkaline to weakly acidic, it is eventually excreted into the duodenum, whence its essential constituents, the bile acids, return to the liver. The most important components of this aqueous solution, besides the alkali salts of the bile acids, are alkali carbonate, bile pigments, lipids, including cholesterol, and mucin. Bile is an emuslifying agent for lipids, thus essential for their digestion.