in the setting of bile stasis, i.e. cholestasis
. H&E stain
is a dark green to yellowish brown fluid, produced by the liver
of most vertebrate
s, that aids the digestion
s in the small intestine
. In humans, bile is produced continuously by the liver (liver bile), and stored and concentrated in the gallbladder
(gallbladder bile). After eating, this stored bile is discharged into the duodenum
. The composition of gallbladder bile is 97% water, 0.7% bile salts
, 0.2% bilirubin
, 0.51% fats (cholesterol, fatty acids and lecithin
), and 200 meq/l inorganic salts.
Bile was the yellow bile
in the four humor
system of medicine, the standard of medical practice in Europe from 500 B.C. to the early nineteenth century. About 400 to 800 ml of bile is produced per day in adult humans.
Bile acts to some extent as a surfactant
, helping to emulsify
the lipids in food. Bile salt anion
s are hydrophilic
on one side and hydrophobic
on the other side; consequently, they tend to aggregate around droplets of lipids ( triglycerides
s) to form micelle
s, with the hydrophobic sides towards the fat and hydrophilic sides facing outwards. The hydrophilic sides are negatively charged, and this charge prevents fat droplets coated with bile from re-aggregating into larger fat particles. Ordinarily, the micelles in the duodenum have a diameter around 14–33 μm.
The dispersion of food fat into micelles provides a greatly increased surface area for the action of the enzyme pancreatic lipase
, which actually digests the triglycerides, and is able to reach the fatty core through gaps between the bile salts. A triglyceride is broken down into three fatty acids and a monoglyceride
, which are absorbed by the villi
on the intestine walls. After being transferred across the intestinal membrane, the fatty acids reform into triglycerides (re-esterified), before being absorbed into the lymphatic system through lacteal
s. Without bile salts, most of the lipids in food would be excreted in faeces, undigested.
Since bile increases the absorption of fats, it is an important part of the absorption of the fat-soluble substances, such as the vitamin
, and K
Besides its digestive function, bile serves also as the route of excretion for bilirubin, a byproduct of red blood cells
recycled by the liver. Bilirubin derives from hemoglobin
Bile tends to be alkali on average. The pH of common duct bile (7.50 to 8.05) is higher than that of the corresponding gallbladder bile (6.80 to 7.65). Bile in the gallbladder becomes more acidic the longer a person goes without eating, though resting slows this fall in pH. As an alkali, it also has the function of neutralizing excess stomach acid before it enters the duodenum, the first section of the small intestine. Bile salts also act as bactericide
s, destroying many of the microbes that may be present in the food.
In the absence of bile, fats become indigestible and are instead excreted in feces
, a condition called steatorrhea
. Feces lack their characteristic brown color and instead are white or gray, and greasy. Steatorrhea can lead to deficiencies in essential fatty acid
s and fat-soluble vitamins
. In addition, past the small intestine
(which is normally responsible for absorbing fat from food) the gastrointestinal tract
and gut flora
are not adapted to processing fats, leading to problems in the large intestine.
contained in bile will occasionally accrete into lumps in the gallbladder, forming gallstones
. Cholesterol gallstones are generally treated through surgical removal of the gallbladder. However, they can sometimes be dissolved by increasing the concentration of certain naturally occurring bile acids, such as chenodeoxycholic acid
and ursodeoxycholic acid
On an empty stomach – after repeated vomiting
, for example – a person's vomit may be green or dark yellow, and very bitter. The bitter and greenish component may be bile or normal digestive juices originating in the stomach. The color of bile is often likened to "fresh-cut grass", unlike components in the stomach that look greenish yellow or dark yellow. Bile may be forced into the stomach secondary to a weakened valve ( pylorus
), the presence of certain drugs including alcohol, or powerful muscular contractions and duodenal spasms.
Biliary obstruction can be caused by a variety of dietary factors. Most biliary obstructions are caused by the high consumption of sugar, fat and processed foods. These foods can cause gallstones
. Primarily, biliary obstruction is caused by blockage in the bile ducts
. Bile ducts carry bile from the liver and gallbladder
through the pancreas. A huge amount of the bile is then released into the small intestine duodenum
. The remaining bile is stored in the gallbladder. After food consumption the bile in the gallbladder is released to help with digestion and fat absorption.
Society and culture
In medical theories prevalent in the West from Classical Antiquity
to the Middle Ages
, the body's health depended on the equilibrium of four "humors"
, or vital fluids, two of which related to bile: blood, phlegm
, "yellow bile" (choler), and "black bile". These "humors" are believed to have its roots in the appearance of a blood sedimentation test made in open air, which exhibits a dark clot at the bottom ("black bile"), a layer of unclotted erythrocytes ("blood"), a layer of white blood cells ("phlegm") and a layer of clear yellow serum ("yellow bile").
Excesses of black bile and yellow bile were thought to produce depression and aggression, respectively, and the Greek names for them gave rise to the English words cholera
(from Greek kholé
) and melancholia
. Those same theories explain the derivation of the English word bilious from bile
, the meaning of gall in English as "exasperation" or "impudence", and the Latin word cholera
, derived from the Greek kholé
, which was passed upon several Romance languages in words meaning "anger" such as
(French) and cólera
Bile from dead mammals can be mixed with soap. This mixture, called bile soap, can be applied to textiles a few hours before washing and is a traditional and rather effective method for removing various kinds of tough stains.
Bile in food
"Pinapaitan" is a dish in Philippine cuisine
that uses bile as flavoring.
In regions like Asia where bile products are a popular ingredient in traditional medicine
, there are several cases of abuse of bears
from which bile is farmed.
Principal bile acids
Image:Cholic acid.png| Cholic acid
Image:Chenodeoxycholic acid.png| Chenodeoxycholic acid
Image:Glycocholic acid.png| Glycocholic acid
Image:Taurocholic acid.png| Taurocholic acid
Image:Deoxycholic acid.png| Deoxycholic acid
Image:Lithocholic_acid_acsv.svg| Lithocholic acid