Bile: Definition, Composition, Biliary Salts, Training and Functions

Also known as gall, it is a greenish-yellow liquid that is made in the liver.

It then passes to the gallbladder for storage, changes its concentration and is transported to the duodenum, which is the first region of the small intestine.

Composition of bile

This secretion is highly complex and aqueous nature, has a solid content of less than 5%.

Bile can be sampled in the bile ducts and consists of a variety of organic and inorganic solutes .

Inorganic solutes consist mainly of secreted passive ions and whose concentrations in the bile are mostly similar to those in the blood plasma.

Anions and organic cations are highly concentrated in the bile due to active transport mechanisms in the bile canalicular membrane.

Bile is formed by salts and bile acids, cholesterol, phospholipids, water, pigments and electrolytic chemicals that keep the solution slightly alkaline, with an approximate pH of 7 to 8.

Bile salts

The most prevalent organic solutes in bile are bile salts.

Bile salts are composed of four different types of free bile acids such as cholic acid, deoxycholic acid, chenodeoxycholic acid and lithocholic acid, each of these acids can be combined with glycine or taurine to form more complex acids and salts .

These bile salts and acids can be extracted into the liver through the bloodstream or synthesized from cholesterol.

The liver extracts from the blood, insoluble wastes in water such as cholesterol, steroids, drugs and hemoglobin pigments , these are transported through the liquid to the excretory system.

In the bile can be found residues of substances such as fatty acids, neutral fats, lecithin, mucus, serum proteins and urea.


The formation of bile is a unique function of the liver that is vital for the survival of the organism.

Bile is continuously secreted from the liver cells into the common bile duct and the gallbladder, once in the gall bladder, usually concentrates approximately 5 times, and sometimes up to 18 times, the strength of the secretion original.

The hormones cholecystokinin, secretin , gastrin and somatostatin and the vagus nerve control the amount of bile secreted in the duodenum.

About 800 to 1,000 ml of bile (before concentration) are produced daily by the liver.

Bile originates in hepatocytes and is modified distally by the transport, absorption and secretion systems in the epithelium of the bile duct.


The main function of bile is to aid in the digestion of lipids in the duodenum .

Bile salts and acids are transported together with water, sodium, chlorine and bicarbonates.

Bile neutralizes the hydrochloric acid that moves from the stomach to the small intestine.

The bile salts when they pass to the small intestine, act by emulsifying the fat and reducing the surface tension in the fat droplets and prepare them for the action of the pancreatic and intestinal enzymes.

The salts are ions with a large negative charge and can not be easily absorbed by the upper region of the small intestine, and consequently, they remain there until most of the lipids are digested.

The salts and acids are absorbed in the lower small intestine, and return to the bloodstream until they are removed again by the liver, this recycling, is called the hepatic whole circulation.

Some of the salts and acids are lost during this process, and are replaced in the liver due to the continuous synthesis of cholesterol.

Bile salts usually do not reach the colon, but when they do, they can inhibit the absorption of water and sodium, causing watery diarrhea.

Bile is also the main excretory pathway for potentially harmful exogenous lipophilic substances, and other endogenous substrates such as bilirubin and bile salts that are not easily filtered or excreted by the kidney.

Bile salts are the main organic solutes in bile and usually work to emulsify dietary fats and facilitate their intestinal absorption.

Bile is the main route for cholesterol elimination.

Bile protects the body from enteric infections by excreting immunoglobulin A, inflammatory cytokines and stimulating the innate immune system in the intestine .

Bile is an essential component of the cohehepatic and enterohepatic circulation, and finally, many hormones and pheromones are excreted in the bile, and contribute to the growth and development of the intestine.

Bile secretion for the health of the organism becomes more important when this secretion is affected by cholestatic developmental diseases, genetic or acquired.

This is demonstrated most dramatically by children born with biliary atresia who develop progressive cholestatic liver injury, biliary cirrhosis and, ultimately, liver failure and death.