Editing Bile

{{Short description|Dark greenish-brown fluid aiding in the digestion of fats}}
{{About|the fluid produced by the liver}}
[[File:Cholestasis 2 high mag.jpg|thumb|Bile (yellow material) in a [[liver]] [[biopsy]] stained with [[H&E stain|hematoxylin-eosin]] in a condition called [[cholestasis]] (setting of bile stasi)]]

'''Bile''' (from Latin ''bilis''), also known as '''gall''', is a yellow-green/misty green fluid produced by the [[liver]] of most [[vertebrate]]s that aids the [[digestion]] of [[lipid]]s in the [[small intestine]]. In humans, bile is primarily composed of [[water]], is produced continuously by the liver, and is stored and concentrated in the [[gallbladder]]. After a human eats, this stored bile is discharged into the first section of the [[small intestine]], known as the [[duodenum]].<ref>{{Cite journal |last=Puestow |first=Charles B. |title=The Discharge of Bile into the Duodenum |date=1931-12-01 |url=https://doi.org/10.1001/archsurg.1931.01160120127008 |journal=Archives of Surgery |volume=23 |issue=6 |pages=1013–1029 |doi=10.1001/archsurg.1931.01160120127008 |issn=0272-5533}}</ref>

==Composition==
In the human [[liver]], bile is composed of 97–98% [[water]], 0.7% [[bile salts]], 0.2% [[bilirubin]], 0.51% fats ([[cholesterol]], [[fatty acid]]s, and [[lecithin]]), and 200 meq/L inorganic salts.<ref>{{cite book |last1=Barrett |first1=Kim E. |url=https://archive.org/details/ganongsreviewofm0000unse/page/512/ |title=Ganong's Review of Medical Physiology |last2=Barman |first2=Susan M. |last3=Boitano |first3=Scott |last4=Brooks |first4=Heddwen L. |publisher=McGraw-Hill Medical |year=2012 |isbn=978-0-07-178003-2 |edition=24th |location=New York |pages=512}}</ref><ref>{{cite book |last=Guyton and Hall |title=Textbook of Medical Physiology |date=2011 |publisher=Saunders Elsevier |isbn=978-1-4160-4574-8 |location=U.S. |page=784}}</ref> The two main pigments of bile are [[bilirubin]], which is orange-yellow, and its oxidised form [[biliverdin]], which is green. When mixed, they are responsible for the brown color of [[Human feces|feces]].<ref>{{Cite web |title=Bile pigments - Oxford Reference |url=https://www.oxfordreference.com/view/10.1093/oi/authority.20110803095505664 |access-date=2020-01-20 |website=www.oxfordreference.com |language=en}}</ref> About {{Convert|400 to 800|ml|U.S.oz|abbr=off}} of bile is produced per day in adult human beings.<ref>{{Cite web |title=Secretion of Bile and the Role of Bile Acids In Digestion |url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html |access-date=2017-03-31 |website=www.vivo.colostate.edu |language=en}}</ref>

==Function==
[[File:Lipid and bile salts.svg|thumb|Action of bile salts in digestion]]
[[File:Bile recycling.png|thumb|Recycling of the bile]]

Bile or gall 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 ([[triglyceride]]s and [[phospholipid]]s) to form [[micelle]]s, with the hydrophobic sides towards the fat and hydrophilic sides facing outwards.<ref>{{cite book |last= A. Potter|first= Patrica|date= 2013|title=Fundamentals of Nursing, 8th edition |publisher= Elsevier, Inc.|page= 1000|isbn=978-0-323-07933-4}}</ref> 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 1–50&nbsp;[[μm]] in humans.<ref>{{Cite book |url=https://books.google.com/books?id=7nAoDwAAQBAJ&pg=PA22 |title=Food Colloids: Self-Assembly and Material Science |last1=Dickinson |first1=Eric |last2=Leser |first2=Martin E.|date=2007-10-31|publisher=Royal Society of Chemistry|isbn=978-1-84755-769-8 |pages=22 |language=en}}</ref>

The dispersion of food fat into micelles provides a greatly increased surface area for the action of the enzyme [[pancreatic lipase]], which digests the triglycerides, and is able to reach the fatty core through gaps between the bile salts.<ref>{{Cite journal|last=Lowe|first=Mark E.|date=2002-12-01|title=The triglyceride lipases of the pancreas|journal=Journal of Lipid Research|language=en|volume=43|issue=12|pages=2007–2016|doi=10.1194/jlr.R200012-JLR200 |doi-access=free |issn=0022-2275|pmid=12454260}}</ref> A triglyceride is broken down into two fatty acids and a [[monoglyceride]], which are absorbed by the [[Intestinal villus|villi]] on the intestine walls. After being transferred across the intestinal membrane, the fatty acids reform into triglycerides ({{nowrap|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 feces, undigested.<ref>{{Cite book|url=https://books.google.com/books?id=IsOcq_1PnlMC&pg=PT650|title=Biology: Concepts and Applications|last=Starr|first=Cecie|date=2007-09-20|publisher=Cengage Learning|isbn=978-0-495-11981-4|pages=650|language=en}}</ref>

Since bile increases the absorption of fats, it is an important part of the absorption of the fat-soluble substances,<ref>{{Cite web|url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html|title=Secretion of Bile and the Role of Bile Acids In Digestion|website=www.vivo.colostate.edu|access-date=2016-06-05}}</ref> such as the [[vitamin]]s [[vitamin A|A]], [[vitamin D|D]], [[vitamin E|E]], and [[vitamin K|K]].<ref>{{Cite web|url=http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html|title=Secretion of Bile and the Role of Bile Acids In Digestion|website=www.vivo.colostate.edu|language=en|access-date=2018-04-09}}</ref>

Besides its digestive function, bile serves also as the route of excretion for bilirubin, a byproduct of [[red blood cell]]s recycled by the liver. Bilirubin derives from [[hemoglobin]] by [[glucuronidation]].

Bile tends to be [[alkaline]] 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 [[acid]]ic the longer a person goes without eating, though resting slows this fall in pH.<ref>{{cite journal | last1 = Sutor | first1 = D. June | year = 1976 | title = Diurnal Variations in the pH of Pathological Gallbladder Bile | journal = Gut | volume = 17 | issue = 12 | pages = 971–974 | doi = 10.1136/gut.17.12.971 | pmc = 1411240 | pmid=14056}}</ref> 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.<ref>{{Cite journal|last1=Merritt|first1=M. E.|last2=Donaldson|first2=J. R.|date=2009-09-17|title=Effect of bile salts on the DNA and membrane integrity of enteric bacteria|journal=Journal of Medical Microbiology|volume=58|issue=12|pages=1533–1541|doi=10.1099/jmm.0.014092-0|pmid=19762477|issn=0022-2615|doi-access=free}}</ref>

==Clinical significance==

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.<ref>{{cite journal |vauthors=Barabote RD, Tamang DG, Abeywardena SN |title=Extra domains in secondary transport carriers and channel proteins |journal=Biochim. Biophys. Acta |volume=1758 |issue=10 |pages=1557–79 |year=2006 |pmid=16905115 |doi=10.1016/j.bbamem.2006.06.018|display-authors=etal|doi-access= }}</ref> Steatorrhea can lead to deficiencies in [[essential fatty acid]]s and [[fat-soluble vitamins]].<ref>{{Citation|last1=Azer|first1=Samy A.|title=Steatorrhea|date=2019|url=http://www.ncbi.nlm.nih.gov/books/NBK541055/|work=StatPearls|publisher=StatPearls Publishing|pmid=31082099|access-date=2020-01-20|last2=Sankararaman|first2=Senthilkumar}}</ref> 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.<ref>{{Cite journal|last=Gorbach|first=Sherwood L.|date=1971-06-01|title=Intestinal Microflora|url=https://www.gastrojournal.org/article/S0016-5085(71)80039-2/pdf|journal=Gastroenterology|language=en|volume=60|issue=6|pages=1110–1129|doi=10.1016/S0016-5085(71)80039-2|pmid=4933894|issn=0016-5085|doi-access=free}}</ref>

The [[cholesterol]] contained in bile will occasionally accrete into lumps in the gallbladder, forming [[gallstone]]s. 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]].<ref>{{Citation |last=Bell |first=G. D. |title=Drugs used in the management of gallstones|date=1980-01-01|url=http://www.sciencedirect.com/science/article/pii/S0378608080800420|series=Side Effects of Drugs Annual |volume=4 |pages=258–263 |editor-last=Dukes |editor-first=M. N. G.|publisher=Elsevier|doi=10.1016/S0378-6080(80)80042-0 |isbn=9780444901309 |access-date=2020-01-20}}</ref><ref>{{Cite journal |last1=Guarino|first1=Michele Pier Luc a |last2=Cocca |first2=Silvia |last3=Altomare |first3=Annamaria |last4=Emerenziani |first4=Sara |last5=Cicala |first5=Michele |date=2013-08-21 |title=Ursodeoxycholic acid therapy in gallbladder disease, a story not yet completed |journal=World Journal of Gastroenterology |volume=19 |issue=31 |pages=5029–5034 |doi=10.3748/wjg.v19.i31.5029 |issn=1007-9327 |pmc=3746374 |pmid=23964136 |doi-access=free }}</ref>

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.<ref>{{Cite web|url=http://www.nhs.uk/conditions/vomiting-adults/Pages/Introduction.aspx|title=Nausea and vomiting in adults - NHS Choices|last=Choices|first=NHS|website=www.nhs.uk|access-date=2016-06-05}}</ref> Bile may be forced into the stomach secondary due to a weakened valve ([[pylorus]]), the presence of certain drugs including [[Alcohol (drug)|alcohol]], or powerful muscular contractions and duodenal spasms. This is known as [[biliary reflux]].<ref>{{Cite book|url=https://books.google.com/books?id=UeYJEAIG3HQC&pg=PA71|title=Gastrointestinal and Liver Pathology E-Book: A Volume in the Series: Foundations in Diagnostic Pathology |last1=Iacobuzio-Donahue |first1=Christine A. |last2=Montgomery |first2=Elizabeth A. |date=2011-06-06 |publisher=Elsevier Health Sciences |isbn=978-1-4557-1193-2 |pages=71 |language=en}}</ref>

===Obstruction===
Biliary obstruction refers to a condition when [[bile duct]]s which deliver bile from the gallbladder or liver to the duodenum become obstructed. The blockage of bile might cause a buildup of [[bilirubin]] in the [[bloodstream]] which can result in [[jaundice]]. There are several potential causes for biliary obstruction including gallstones, cancer,<ref>{{Cite journal |last1=Boulay |first1=Brian R |last2=Birg |first2=Aleksandr |date=2016-06-15 |title=Malignant biliary obstruction: From palliation to treatment |journal=World Journal of Gastrointestinal Oncology |volume=8|issue=6|pages=498–508 |doi=10.4251/wjgo.v8.i6.498 |issn=1948-5204 |pmc=4909451|pmid=27326319 |doi-access=free }}</ref> trauma, [[choledochal cysts]], or other benign causes of bile duct narrowing.<ref>{{Cite journal |last1=Shanbhogue |first1=Alampady Krishna Prasad |last2=Tirumani|first2=Sree Harsha |last3=Prasad |first3=Srinivasa R. |last4=Fasih |first4=Najla|last5=McInnes |first5=Matthew |date=2011-08-01 |title=Benign Biliary Strictures: A Current Comprehensive Clinical and Imaging Review|journal=American Journal of Roentgenology |volume=197 |issue=2 |pages=W295–W306 |doi=10.2214/AJR.10.6002 |pmid=21785056 |issn=0361-803X}}</ref> The most common cause of bile duct obstruction is when gallstone(s) are dislodged from the gallbladder into the cystic duct or common bile duct resulting in a blockage. A blockage of the gallbladder or [[cystic duct]] may cause [[cholecystitis]]. If the blockage is beyond the confluence of the pancreatic duct, this may cause gallstone [[pancreatitis]]. In some instances of biliary obstruction, the bile may become infected by bacteria resulting in [[ascending cholangitis]].

==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 [[humorism|four "humors"]], or vital fluids, two of which related to bile: blood, [[phlegm#Phlegm and humourism|phlegm]], "yellow bile" (choler), and "black bile". These "humors" are believed to have their 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").<ref>{{cite book|url=https://books.google.com/books?id=VfDNu2bWRFQC&q=Medicine+&pg=PP1|title=Medicine & Philosophy: A Twenty-First Century Introduction|last1=Johansson|first1=Ingvar|last2=Lynøe|first2=Niels|date=2008|publisher=Walter de Gruyter|isbn=9783110321364|page=27|quote=If blood is poured into a glass jar, a process of coagulation and sedimentation starts. It ends with four clearly distinct layers: a red region, a yellowish one, a black one, and a white one (Figure 4, left) ... The lowest part of the same column consists of sediment that is too dense to permit light to pass through. Therefore, this part of the column looks black and might be referred to as the 'black bile'. On the top of the column there is a white layer, which we today classify as fibrin; it might correspond to Galen's 'phlegm'. The remaining part is a rather clear but somewhat yellowish fluid that surrounds the coagulated column in the middle. It might be called 'yellow bile', but today we recognize it as blood serum.|access-date=2015-04-23}}</ref>

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 χολή ''kholē'', "bile") and [[melancholia]]. In the former of those senses, the 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 along into some Romance languages as words connoting anger, such as ''[[wikt:colère|colère]]'' (French) and ''cólera'' (Spanish).<ref>{{Cite book|url=https://books.google.com/books?id=GDsqDwAAQBAJ&pg=PA10|title=Pain: A Very Short Introduction|last=Boddice|first=Rob|date=2017|publisher=Oxford University Press|isbn=978-0-19-873856-5|pages=10|language=en}}</ref>

===Soap===
Soap can be mixed with bile from mammals, such as [[ox gall]]. This mixture, called bile soap<ref>{{cite journal|title=The invention of certain improvements in the manufacture of soap, which will be particularly applicable to the felting of woollen cloths.|journal=The London Journal of Arts and Sciences; and Repertory of Patent Inventions|year=1837|first=W. |last=Newton|volume=IX|pages=289 |url=https://books.google.com/books?id=GhMAAAAAMAAJ&dq=bile+soap&pg=RA19-PA291|access-date=2007-02-08}}</ref> or gall soap, can be applied to textiles a few hours before washing as a traditional and effective method for removing various kinds of tough stains.<ref>{{Cite book|url=https://books.google.com/books?id=m85TAAAAMAAJ&q=%22Ox+gall+contains%22|title=The Modern Soap and Detergent Industry: The manufacture of special soaps and detergent compositions|last=Martin|first=Geoffrey|date=1951|publisher=Technical Press|pages=15|language=en}}</ref>

===Food===
[[Pinapaitan]] is a dish in [[Philippine cuisine]] that uses bile as flavoring.<ref>{{Cite web|url=http://www.angsarap.net/2013/08/13/pinapaitan/|title=Pinapaitan - Ang Sarap|date=2013-08-13|website=Ang Sarap (A Tagalog word for "It's Delicious")|access-date=2016-06-05}}</ref> Other areas where bile is commonly used as a cooking ingredient include [[Lao cuisine|Laos]] and northern parts of [[Thai cuisine|Thailand]].

During the [[Boshin War]], [[Satsuma Domain|Satsuma]] soldiers of the early [[Imperial Japanese Army]] reportedly [[Human cannibalism|ate human livers]] boiled in bile.<ref>{{cite book |last1=牧原 Makihara |first1=憲夫 Norio |title=文明国をめざして |date=December 26, 2008 |publisher=小学館 Shōgakukan |location=Japan |isbn=4096221139}}</ref> The practice of eating a slain enemy's liver, known as {{Nihongo|''[[hiemondori]]''|冷え物取り}}, was a tradition of the Satsuma people.

=== Bears ===
In regions where bile products are a popular ingredient in [[Traditional Chinese medicine|traditional medicine]], the [[Bile bear|use of bears]] in bile-farming has been widespread. This practice has been condemned by activists, and some pharmaceutical companies have developed synthetic (non-ursine) alternatives.<ref>{{Cite news|url=https://www.theguardian.com/environment/radical-conservation/2015/apr/09/bear-bile-china-synthetic-alternative|year=2015|title=Is the end of 'house of horror' bear bile factories in sight?|journal=The Guardian|author=Hance, J.}}</ref>

==Principal acids==
<gallery class="center; skin-invert-image">
File:Cholic acid.svg|[[Cholic acid]]
File:Chenodeoxycholic acid.svg|[[Chenodeoxycholic acid]]
File:Glycocholsäure.svg|[[Glycocholic acid]]
File:Taurocholic acid.svg|[[Taurocholic acid]]
File:Deoxycholic acid.svg|[[Deoxycholic acid]]
File:Lithocholic acid acsv.svg|[[Lithocholic acid]]
</gallery>

==See also==
{{Portal|Medicine|Animals}}
* [[Bile acid sequestrant]]
* [[Enterohepatic circulation]]
* [[Intestinal juice]]

== References ==
{{Reflist}}

==Further reading==
* {{cite web | url = http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html | title = Secretion of Bile and the Role of Bile Acids In Digestion | work = Colorado State Hypertextbook article on Bile | last = Bowen | first = R. | date = 2001-11-23 | access-date = 2007-07-17| archive-url= https://web.archive.org/web/20070529085534/http://www.vivo.colostate.edu/hbooks/pathphys/digestion/liver/bile.html| archive-date= 29 May 2007 | url-status= live}}
* {{cite journal | last = Krejčí | first = Z |author2=Hanuš L. |author3=Podstatová H. |author4=Reifová E | title = A contribution to the problems of the pathogenesis and microbial etiology of cholelithiasis | journal = Acta Universitatis Palackianae Olomucensis Facultatis Medicae| pages = 279–286 | volume = 104 | year = 1983 | pmid = 6222611 }}
* {{cite book | last = Maton | first = Anthea | author2 = Jean Hopkins | author3 = Charles William McLaughlin | author4 = Susan Johnson | author5 = Maryanna Quon Warner | author6 = David LaHart | author7 = Jill D. Wright | title = Human Biology and Health | publisher = Prentice Hall | year = 1993 | location = Englewood Cliffs, New Jersey | url = https://archive.org/details/humanbiologyheal00scho | isbn = 0-13-981176-1 | url-access = registration }}
* Seleem HM, Nada AS, Naguib MA, Abdelmaksoud OR, El-Gazzarah AR (2021). [http://www.mmj.eg.net/text.asp?2021/34/4/1275/333263 Serum immunoglobulin G4 in patients with nonmalignant common bile duct stricture]. Menoufia Med J; 34:1275-83.

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{{Gastrointestinal physiology|state=collapsed}}

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[[Category:Body fluids]]
[[Category:Digestive system]]
[[Category:Biomolecules]]
[[Category:Hepatology]]