Bile
Bile, bitter, neutral, or slightly alkaline fluid secreted by the liver and passed through a duct into the gallbladder, where it is stored and, as necessary, released into the duodenum. As formed in the liver, bile is a thin, watery fluid to which the gallbladder adds a mucous secretion, forming a complex thickened and stringy substance consisting of salts and bile salts, proteins, cholesterol, hormones, and enzymes. The gallbladder returns water containing salts and other materials to the circulation and concentrates the complex further by a tenfold reduction of the bile salts, which the liver synthesizes from cholesterol. Such foods as fats, egg yolk, and foods rich in cholesterol cause concentrated bile, together with secretions from the pancreas, to be discharged into the duodenum to promote digestion, to stimulate peristalsis and absorption, and to carry off excess cholesterol and the disintegration products of overage red blood cells. The hemoglobin of such disintegrating cells ...