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

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

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

Composition of bile

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

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

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

Anions and organic cations are highly concentrated in the bile due to active transport mechanisms in the canalicular bile 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 organism’s survival.

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

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

The liver produces about 800 to 1,000 ml of bile (before concentration).

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


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

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

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

When they pass to the small intestine, the bile salts act by emulsifying the fat and reducing the surface tension in the fat droplets and preparing 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; 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 whole hepatic circulation.

Some 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 primary 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 and inflammatory cytokines and stimulating the innate immune system in the intestine.

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

Bile secretion for the organism’s health becomes more critical 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 a progressive cholestatic liver injury, biliary cirrhosis, and, ultimately, liver failure and death.