Bile

Bile(from Latinbilis), orgall,is a yellow-green fluid or it could be a green misty colour produced by theliverof mostvertebratesthat aids thedigestionoflipidsin thesmall intestine.In humans, bile is primarily composed ofwater,produced continuously by the liver, and stored and concentrated in thegallbladder.After a human eats, this stored bile is discharged intothe first section of the small intestine.^[1]

Composition

In the humanliver,bile is composed of 97–98%water,0.7%bile salts,0.2%bilirubin,0.51% fats (cholesterol,fatty acids,andlecithin), and 200 meq/L inorganic salts.^[2]^[3]The two main pigments of bile arebilirubin,which is orange-yellow, and its oxidised formbiliverdin,which is green. When mixed, they are responsible for the brown color offeces.^[4]About 400 to 800 milliliters (14 to 27 U.S. fluid ounces) of bile is produced per day in adult human beings.^[5]

Function

Action of bile salts in digestion

Recycling of the bile

Bile or gall acts to some extent as asurfactant,helping toemulsifythe lipids in food. Bile saltanionsarehydrophilicon one side andhydrophobicon the other side; consequently, they tend to aggregate around droplets of lipids (triglyceridesandphospholipids) to formmicelles,with the hydrophobic sides towards the fat and hydrophilic sides facing outwards.^[6]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 theduodenumhave a diameter around 1–50μmin humans.^[7]

The dispersion of food fat into micelles provides a greatly increased surface area for the action of the enzymepancreatic lipase,which digests the triglycerides, and is able to reach the fatty core through gaps between the bile salts.^[8]A triglyceride is broken down into two fatty acids and amonoglyceride,which are absorbed by thevillion 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 throughlacteals.Without bile salts, most of the lipids in food would be excreted in feces, undigested.^[9]

Since bile increases the absorption of fats, it is an important part of the absorption of the fat-soluble substances,^[10]such as thevitamins A,D,E,andK.^[11]

Besides its digestive function, bile serves also as the route of excretion for bilirubin, a byproduct ofred blood cellsrecycled by the liver. Bilirubin derives fromhemoglobinbyglucuronidation.

Bile tends to bealkalineon average. ThepHof 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 moreacidicthe longer a person goes without eating, though resting slows this fall in pH.^[12]As an alkali, it also has the function of neutralizing excessstomach acidbefore it enters the duodenum, the first section of thesmall intestine.Bile saltsalso act asbactericides,destroying many of the microbes that may be present in the food.^[13]

Clinical significance

In the absence of bile, fats become indigestible and are instead excreted infeces,a condition calledsteatorrhea.Feces lack their characteristic brown color and instead are white or gray, and greasy.^[14]Steatorrhea can lead to deficiencies inessential fatty acidsandfat-soluble vitamins.^[15]In addition, past the small intestine (which is normally responsible for absorbing fat from food) thegastrointestinal tractandgut floraare not adapted to processing fats, leading to problems in the large intestine.^[16]

Thecholesterolcontained in bile will occasionally accrete into lumps in the gallbladder, forminggallstones.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 aschenodeoxycholic acidandursodeoxycholic acid.^[17]^[18]

On an empty stomach – after repeatedvomiting,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.^[19]Bile may be forced into the stomach secondary to a weakened valve (pylorus), the presence of certain drugs includingalcohol,or powerful muscular contractions and duodenal spasms. This is known asbiliary reflux.^[20]

Obstruction

Biliary obstruction refers to a condition whenbile ductswhich deliver bile from the gallbladder or liver to the duodenum become obstructed. The blockage of bile might cause a buildup ofbilirubinin thebloodstreamwhich can result injaundice.There are several potential causes for biliary obstruction including gallstones, cancer,^[21]trauma,choledochal cysts,or other benign causes of bile duct narrowing.^[22]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 orcystic ductmay causecholecystitis.If the blockage is beyond the confluence of the pancreatic duct, this may cause gallstonepancreatitis.In some instances of biliary obstruction, the bile may become infected by bacteria resulting inascending cholangitis.

Society and culture

In medical theories prevalent in the West fromclassical antiquityto theMiddle Ages,the body's health depended on the equilibrium offour "humors",or vital fluids, two of which related to bile: blood,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" ).^[23]

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 wordscholera(from Greek χολήkholē,"bile" ) andmelancholia.In the former of those senses, the same theories explain the derivation of the English word bilious frombile,the meaning of gall in English as "exasperation" or "impudence", and the Latin wordcholera,derived from the Greekkholé,which was passed along into some Romance languages as words connoting anger, such ascolère(French) andcólera(Spanish).^[24]

Soap

Soap can be mixed with bile from mammals, such asox gall.This mixture, called bile soap^[25]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.^[26]

Food

Pinapaitanis a dish inPhilippine cuisinethat uses bile as flavoring.^[27]Other areas where bile is commonly used as a cooking ingredient includeLaosand northern parts ofThailand.

During theBoshin War,Satsumasoldiers of the earlyImperial Japanese Armyreportedlyate human liversboiled in bile.^[28]The practice of eating a slain enemy's liver, known ashiemondori(Lãnh え vật lấy り),was a tradition of the Satsuma people.

Bears

In regions where bile products are a popular ingredient intraditional medicine,theuse of bearsin bile-farming has been widespread. This practice has been condemned by activists, and some pharmaceutical companies have developed synthetic (non-ursine) alternatives.^[29]

Principal acids

References

^Puestow, Charles B. (1931-12-01)."The Discharge of Bile into the Duodenum".Archives of Surgery.23(6): 1013–1029.doi:10.1001/archsurg.1931.01160120127008.ISSN 0272-5533.
^Barrett, Kim E.; Barman, Susan M.; Boitano, Scott; Brooks, Heddwen L. (2012).Ganong's Review of Medical Physiology(24th ed.). New York: McGraw-Hill Medical. p. 512.ISBN 978-0-07-178003-2.
^Guyton and Hall (2011).Textbook of Medical Physiology.U.S.: Saunders Elsevier. p. 784.ISBN 978-1-4160-4574-8.
^"Bile pigments - Oxford Reference".oxfordreference.Retrieved2020-01-20.
^"Secretion of Bile and the Role of Bile Acids In Digestion".vivo.colostate.edu.Retrieved2017-03-31.
^A. Potter, Patrica (2013).Fundamentals of Nursing, 8th edition.Elsevier, Inc. p. 1000.ISBN 978-0-323-07933-4.
^Dickinson, Eric; Leser, Martin E. (2007-10-31).Food Colloids: Self-Assembly and Material Science.Royal Society of Chemistry. p. 22.ISBN 978-1-84755-769-8.
^Lowe, Mark E. (2002-12-01)."The triglyceride lipases of the pancreas".Journal of Lipid Research.43(12): 2007–2016.doi:10.1194/jlr.R200012-JLR200.ISSN 0022-2275.PMID 12454260.
^Starr, Cecie (2007-09-20).Biology: Concepts and Applications.Cengage Learning. p. 650.ISBN 978-0-495-11981-4.
^"Secretion of Bile and the Role of Bile Acids In Digestion".vivo.colostate.edu.Retrieved2016-06-05.
^"Secretion of Bile and the Role of Bile Acids In Digestion".vivo.colostate.edu.Retrieved2018-04-09.
^Sutor, D. June (1976)."Diurnal Variations in the pH of Pathological Gallbladder Bile".Gut.17(12): 971–974.doi:10.1136/gut.17.12.971.PMC1411240.PMID 14056.
^Merritt, M. E.; Donaldson, J. R. (2009-09-17)."Effect of bile salts on the DNA and membrane integrity of enteric bacteria".Journal of Medical Microbiology.58(12): 1533–1541.doi:10.1099/jmm.0.014092-0.ISSN 0022-2615.PMID 19762477.
^Barabote RD, Tamang DG, Abeywardena SN, et al. (2006). "Extra domains in secondary transport carriers and channel proteins".Biochim. Biophys. Acta.1758(10): 1557–79.doi:10.1016/j.bbamem.2006.06.018.PMID 16905115.
^Azer, Samy A.; Sankararaman, Senthilkumar (2019),"Steatorrhea",StatPearls,StatPearls Publishing,PMID 31082099,retrieved2020-01-20
^Gorbach, Sherwood L. (1971-06-01)."Intestinal Microflora".Gastroenterology.60(6): 1110–1129.doi:10.1016/S0016-5085(71)80039-2.ISSN 0016-5085.PMID 4933894.
^Bell, G. D. (1980-01-01), Dukes, M. N. G. (ed.),Drugs used in the management of gallstones,Side Effects of Drugs Annual, vol. 4, Elsevier, pp. 258–263,doi:10.1016/S0378-6080(80)80042-0,ISBN 9780444901309,retrieved2020-01-20
^Guarino, Michele Pier Luc a; Cocca, Silvia; Altomare, Annamaria; Emerenziani, Sara; Cicala, Michele (2013-08-21)."Ursodeoxycholic acid therapy in gallbladder disease, a story not yet completed".World Journal of Gastroenterology.19(31): 5029–5034.doi:10.3748/wjg.v19.i31.5029.ISSN 1007-9327.PMC3746374.PMID 23964136.
^Choices, NHS."Nausea and vomiting in adults - NHS Choices".nhs.uk.Retrieved2016-06-05.
^Iacobuzio-Donahue, Christine A.; Montgomery, Elizabeth A. (2011-06-06).Gastrointestinal and Liver Pathology E-Book: A Volume in the Series: Foundations in Diagnostic Pathology.Elsevier Health Sciences. p. 71.ISBN 978-1-4557-1193-2.
^Boulay, Brian R; Birg, Aleksandr (2016-06-15)."Malignant biliary obstruction: From palliation to treatment".World Journal of Gastrointestinal Oncology.8(6): 498–508.doi:10.4251/wjgo.v8.i6.498.ISSN 1948-5204.PMC4909451.PMID 27326319.
^Shanbhogue, Alampady Krishna Prasad; Tirumani, Sree Harsha; Prasad, Srinivasa R.; Fasih, Najla; McInnes, Matthew (2011-08-01). "Benign Biliary Strictures: A Current Comprehensive Clinical and Imaging Review".American Journal of Roentgenology.197(2): W295–W306.doi:10.2214/AJR.10.6002.ISSN 0361-803X.PMID 21785056.
^Johansson, Ingvar; Lynøe, Niels (2008).Medicine & Philosophy: A Twenty-First Century Introduction.Walter de Gruyter. p. 27.ISBN 9783110321364.Retrieved2015-04-23.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.
^Boddice, Rob (2017).Pain: A Very Short Introduction.Oxford University Press. p. 10.ISBN 978-0-19-873856-5.
^Newton, W. (1837)."The invention of certain improvements in the manufacture of soap, which will be particularly applicable to the felting of woollen cloths".The London Journal of Arts and Sciences; and Repertory of Patent Inventions.IX:289.Retrieved2007-02-08.
^Martin, Geoffrey (1951).The Modern Soap and Detergent Industry: The manufacture of special soaps and detergent compositions.Technical Press. p. 15.
^"Pinapaitan - Ang Sarap".Ang Sarap (A Tagalog word for "It's Delicious" ).2013-08-13.Retrieved2016-06-05.
^Mục nguyên Makihara, hiến phu Norio (December 26, 2008).Văn minh quốc をめざして.Japan: Tiểu học quán Shōgakukan.ISBN 4096221139.
^Hance, J. (2015)."Is the end of 'house of horror' bear bile factories in sight?".The Guardian.