Synthesized in the
liver, bile is an essential fluid for
digestion.
Bile consists primarily of
water,
cholesterol,
lecithin,
inorganic salts,
bile salts and bile pigments. The bile salts are comprised of cholesterol derived acids which are synthesized in the liver. The bile pigments are
hemoglobin metabolites. The two major bile pigments are
biliverdin and
bilirubin.
After being manufactured in the liver, bile is transported through the
hepatic duct to the
gall bladder, where it is stored until needed. While sitting in the the gall bladder, the bile is concentrated as the inorganic salts are actively transported out. This creates an
osmotic imbalance, inducing water to flow out of the bile.
Bile has three major functions.
- First, because of its strong alkalinity, it is important in the final stages of digestion to neutralize the strong gastric acids.
- Second, the bile salts are able to disperse fat and lipid soluble vitamins for easy digestion and transport through the blood. Because bile salts are amphipathic, they can bind the non-water soluble material while staying in solution themselves.
- Third, the bile carries some of the water insoluble waste substances that are removed from the bloodstream by the liver such as hemoglobin pigments, cholesterol, steroids and various drugs. These are then expelled along with the remaining digestive waste.