Liver

Theliveris a majormetabolicorganexclusively found invertebrateanimals, which performs many essential biologicalfunctionssuch asdetoxificationof the organism, and thesynthesis of proteinsand various otherbiochemicalsnecessary fordigestionand growth.Inhumans, it is located in theright upper quadrantof theabdomen, below thediaphragmand mostly shielded by the lower rightrib cage. Its other metabolic roles includecarbohydrate metabolism, the production ofhormones, conversion and storage of nutrients such asglucoseandglycogen, and the decomposition ofred blood cells.
The liver is also anaccessory digestive organthat producesbile, analkalinefluid containingcholesterolandbile acids,  whichemulsifiesand aids thebreakdown of dietary fat. Thegallbladder, a small hollow pouch that sits just under the right lobe of liver, stores and concentrates the bile produced by the liver, which is later excreted to theduodenumto help withdigestion.The liver's highly specializedtissue, consisting mostly ofhepatocytes, regulates a wide variety of high-volume biochemical reactions, including the synthesis and breakdown of small and complex organic molecules, many of which are necessary for normal vital functions.Estimates regarding the organ's total number of functions vary, but is generally cited as being around 500.For this reason, the liver has sometimes been described as the body'schemical factory.
It is not known how to compensate for the absence of liver function in the long term, althoughliver dialysistechniques can be used in the short term.Artificial livershave not been developed to promote long-term replacement in the absence of the liver. As of 2018,liver transplantationis the only option for completeliver failure.
The liver is a dark reddish brown, wedge-shapedorganwith twolobesof unequal size and shape. A human liver normally weighs approximately 1.5 kilograms (3.3 pounds)and has a width of about 15 centimetres (6 inches).There is considerable size variation between individuals, with the standardreference rangefor men being 970–1,860 grams (2.14–4.10 lb)and for women 600–1,770 g (1.32–3.90 lb).It is both the heaviest internal organ and the largestglandin the human body. It is located in the right upper quadrant of theabdominal cavity, resting just below the diaphragm, to the right of the stomach, and overlying thegallbladder.
The liver is connected to two largeblood vessels: thehepatic arteryand theportal vein. The hepatic artery carries oxygen-rich blood from the aorta via theceliac trunk, whereas the portal vein carries blood rich in digested nutrients from the entiregastrointestinal tractand also from thespleenandpancreas.These blood vessels subdivide into small capillaries known asliver sinusoids, which then lead tohepatic lobules.
Hepatic lobules are the functional units of the liver. Each lobule is made up of millions ofhepatic cells(hepatocytes), which are the basic metabolic cells. The lobules are held together by a fine, dense, irregular,fibroelasticconnective tissue layer extending from the fibrous capsule covering the entire liver known asGlisson's capsuleafter British doctorFrancis Glisson.This tissue extends into the structure of the liver by accompanying the blood vessels, ducts, and nerves at the hepatic hilum. The whole surface of the liver, except for thebare area, is covered in aserouscoat derived from theperitoneum, and this firmly adheres to the inner Glisson's capsule.
Terminology related to the liver often starts inhepat-from ἡπατο-, from theGreekword for liver.
The liver isgrosslydivided into two parts when viewed from above – a right and a left lobe – and four parts when viewed from below (left, right,caudate, andquadrate lobes).
Thefalciform ligamentmakes a superficial division of the liver into a left and right lobe. From below, the two additional lobes are located between the right and left lobes, one in front of the other. A line can be imagined running from the left of thevena cavaand all the way forward to divide the liver and gallbladder into two halves.This line is calledCantlie's line.
Other anatomical landmarks include theligamentum venosumand theround ligament of the liver, which further divide the left side of the liver in two sections. An important anatomical landmark, theporta hepatis, divides this left portion into four segments, which can be numbered starting at the caudate lobe as I in an anticlockwise manner. From this parietal view, seven segments can be seen, because the eighth segment is only visible in thevisceralview.
On the diaphragmatic surface, apart from a triangular bare area where it connects to the diaphragm, the liver is covered by a thin, double-layered membrane, theperitoneum, that helps to reduce friction against other organs.This surface covers the convex shape of the two lobes where it accommodates the shape of the diaphragm. The peritoneum folds back on itself to form thefalciform ligamentand therightandleft triangular ligaments.
Theseperitoneal ligamentsare not related to the anatomic ligaments in joints, and the right and left triangular ligaments have no known functional importance, though they serve as surface landmarks.The falciform ligament functions to attach the liver to theposteriorportion of theanteriorbody wall.
The visceral surface or inferior surface is uneven and concave. It is covered in peritoneum apart from where it attaches the gallbladder and the porta hepatis.The fossa of gallbladder lies to the right of the quadrate lobe, occupied by the gallbladder with its cystic duct close to the right end of porta hepatis.
Several impressions on the surface of the liver accommodate the various adjacent structures and organs. Underneath the right lobe and to the right of the gallbladder fossa are two impressions, one behind the other and separated by a ridge. The one in front is a shallow colic impression, formed by thehepatic flexureand the one behind is a deeper renal impression accommodating part of the right kidney and part of thesuprarenal gland.
The suprarenal impression is a small, triangular, depressed area on the liver. It is located close to the right of thefossa, between the bare area and the caudate lobe, and immediately above the renal impression. The greater part of the suprarenal impression is devoid of peritoneum and it lodges the right suprarenal gland.
Medial to the renal impression is a third and slightly marked impression, lying between it and the neck of the gall bladder. This is caused by the descending portion of the duodenum, and is known as the duodenal impression.
The inferior surface of the left lobe of the liver presents behind and to the left of the gastric impression.This is moulded over the upper front surface of thestomach, and to the right of this is a rounded eminence, thetuber omentale, which fits into the concavity of the lesser curvature of the stomach and lies in front of the anterior layer of thelesser omentum.
Microscopically, each liver lobe is seen to be made up ofhepatic lobules. The lobules are roughly hexagonal, and consist of plates ofhepatocytes, andsinusoidsradiating from a central vein towards an imaginary perimeter of interlobular portal triads.The central vein joins to the hepatic vein to carry blood out from the liver. A distinctive component of a lobule is theportal triad, which can be found running along each of the lobule's corners. The portal triad consists of the hepatic artery, the portal vein, and the common bile duct.The triad may be seen on a liver ultrasound, as aMickey Mouse signwith the portal vein as the head, and the hepatic artery, and the common bile duct as the ears.
Histology, the study of microscopic anatomy, shows two major types of liver cell:parenchymalcells and nonparenchymal cells. About 70–85% of the liver volume is occupied by parenchymal hepatocytes. Nonparenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume.Theliver sinusoidsare lined with two types of cell,sinusoidal endothelial cells, andphagocyticKupffer cells.Hepatic stellate cellsare nonparenchymal cells found in theperisinusoidal space, between a sinusoid and a hepatocyte.Additionally, intrahepaticlymphocytesare often present in the sinusoidal lumen.
The central area orhepatic hilum, includes the opening known as the porta hepatis which carries thecommon bile ductandcommon hepatic artery, and the opening for the portal vein. The duct, vein, and artery divide into left and right branches, and the areas of the liver supplied by these branches constitute the functional left and right lobes. The functional lobes are separated by the imaginary plane, Cantlie's line, joining the gallbladder fossa to theinferior vena cava. The plane separates the liver into the true right and left lobes. The middle hepatic vein also demarcates the true right and left lobes. The right lobe is further divided into ananteriorandposteriorsegment by the right hepatic vein. The left lobe is divided into themedialandlateralsegments by the left hepatic vein.
The hilum of the liver is described in terms of threeplatesthat contain thebile ductsand blood vessels. The contents of the whole plate system are surrounded by a sheath.The three plates are thehilar plate, thecystic plateand theumbilical plateand the plate system is the site of the many anatomical variations to be found in the liver.
In the widely usedCouinaudsystem, the functional lobes are further divided into a total of eight subsegments based on a transverse plane through the bifurcation of the main portal vein.The caudate lobe is a separate structure that receives blood flow from both the right- and left-sided vascular branches.The Couinaud classification divides the liver into eight functionally independent liver segments. Each segment has its own vascular inflow, outflow and biliary drainage. In the centre of each segment are branches of the portal vein, hepatic artery, and bile duct. In the periphery of each segment is vascular outflow through the hepatic veins.The classification system uses the vascular supply in the liver to separate the functional units (numbered I to VIII) with unit 1, the caudate lobe, receiving its supply from both the right and the left branches of the portal vein. It contains one or more hepatic veins which drain directly into the inferior vena cava.The remainder of the units (II to VIII) are numbered in a clockwise fashion:
About 20,000 protein coding genes are expressed in human cells and 60% of these genes are expressed in a normal, adult liver.Over 400 genes are more specifically expressed in the liver, with some 150 genes highly specific for liver tissue. A large fraction of the corresponding liver-specific proteins are mainly expressed in hepatocytes and secreted into the blood and constitute plasma proteins andhepatokines. Other liver-specific proteins are certainliver enzymessuch asHAO1andRDH16, proteins involved in bile synthesis such asBAATandSLC27A5, and transporter proteins involved in the metabolism of drugs, such asABCB11andSLC2A2. Examples of highly liver-specific proteins includeapolipoprotein A II, coagulation factorsF2andF9,complement factor related proteins, and thefibrinogen beta chainprotein.
Organogenesis, the development of the organs, takes place from the third to the eighth week duringembryogenesis. The origins of the liver lie in both the ventral portion of theforegutendoderm(endoderm being one of the three embryonicgerm layers) and the constituents of the adjacentseptum transversummesenchyme. In the humanembryo, thehepatic diverticulumis the tube of endoderm that extends out from the foregut into the surrounding mesenchyme. The mesenchyme of septum transversum induces this endoderm to proliferate, to branch, and to form the glandular epithelium of the liver. A portion of the hepatic diverticulum (that region closest to the digestive tube) continues to function as thedrainage ductof the liver, and a branch from this duct produces the gallbladder.Besides signals from the septum transversum mesenchyme,fibroblast growth factorfrom thedeveloping heartalso contributes to hepatic competence, along withretinoic acidemanating from thelateral plate mesoderm. The hepatic endodermal cells undergo a morphological transition from columnar to pseudostratified resulting in thickening into the earlyliver bud. Their expansion forms a population of the bipotential hepatoblasts.Hepatic stellate cells are derived from mesenchyme.
After migration of hepatoblasts into the septum transversum mesenchyme, the hepatic architecture begins to be established, with liver sinusoids and bile canaliculi appearing. The liver bud separates into the lobes. The leftumbilical veinbecomes theductus venosusand the rightvitelline veinbecomes the portal vein. The expanding liver bud is colonized byhematopoietic cells. The bipotential hepatoblasts begin differentiating intobiliary epithelial cellsand hepatocytes. The biliary epithelial cells differentiate from hepatoblasts around portal veins, first producing a monolayer, and then a bilayer of cuboidal cells. In ductal plate, focal dilations emerge at points in the bilayer, become surrounded by portal mesenchyme, and undergo tubulogenesis into intrahepatic bile ducts. Hepatoblasts not adjacent to portal veins instead differentiate into hepatocytes and arrange into cords lined by sinusoidal epithelial cells and bile canaliculi. Once hepatoblasts are specified into hepatocytes and undergo further expansion, they begin acquiring the functions of a mature hepatocyte, and eventually mature hepatocytes appear as highly polarized epithelial cells with abundantglycogenaccumulation. In the adult liver, hepatocytes are not equivalent, with position along the portocentrovenular axis within a liver lobule dictating expression of metabolic genes involved in drug metabolism,carbohydrate metabolism, ammonia detoxification, and bile production and secretion.WNT/β-cateninhas now been identified to be playing a key role in this phenomenon.
At birth, the liver comprises roughly 4% of body weight and weighs on average about 120 g (4 oz). Over the course of further development, it will increase to 1.4–1.6 kg (3.1–3.5 lb) but will only take up 2.5–3.5% of body weight.
Hepatosomatic index (HSI) is the ratio of liver weight to body weight.
In the growing fetus, a major source of blood to the liver is the umbilical vein, which supplies nutrients to the growing fetus. The umbilical vein enters the abdomen at the umbilicus and passes upward along the free margin of the falciform ligament of the liver to the inferior surface of the liver. There, it joins with the left branch of the portal vein. The ductus venosus carries blood from the left portal vein to the left hepatic vein and then to the inferior vena cava, allowing placental blood to bypass the liver. In the fetus, the liver does not perform the normal digestive processes and filtration of the infant liver because nutrients are received directly from the mother via theplacenta. The fetal liver releases some blood stem cells that migrate to the fetalthymus, creating theT cells(or T lymphocytes). After birth, the formation of blood stem cells shifts to the redbone marrow. After 2–5 days, the umbilical vein and ductus venosus are obliterated; the former becomes theround ligament of liverand the latter becomes the ligamentum venosum. In thedisordersofcirrhosisandportal hypertension, the umbilical vein can open up again.
Unlike eutherian mammals, in marsupials the liver remains haematopoietic well after birth.
The various functions of the liver are carried out by the liver cells or hepatocytes. The liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs. Currently, noartificial organor device is capable of reproducing all the functions of the liver.  Some functions can be carried out byliver dialysis, an experimental treatment forliver failure. The liver also accounts for about 20% of resting total body oxygen consumption.
The liver receives a dual blood supply from the hepatic portal vein and hepatic arteries. The hepatic portal vein delivers around 75% of the liver's blood supply and carriesvenous blooddrained from the spleen, gastrointestinal tract, and its associated organs. The hepatic arteries supply arterial blood to the liver, accounting for the remaining quarter of its blood flow. Oxygen is provided from both sources; about half of the liver's oxygen demand is met by the hepatic portal vein, and half is met by the hepatic arteries.The hepatic artery also has both alpha- and beta-adrenergic receptors; therefore, flow through the artery is controlled, in part, by the splanchnic nerves of the autonomic nervous system.
Blood flows through the liver sinusoids and empties into the central vein of each lobule.  Thecentral veinscoalesce into hepatic veins, which leave the liver and drain into the inferior vena cava.
Thebiliary tractis derived from the branches of the bile ducts. The biliary tract, also known as the biliary tree, is the path by which bile is secreted by the liver then transported to the first part of the small intestine, theduodenum. The bile produced in the liver is collected inbile canaliculi, small grooves between the faces of adjacent hepatocytes. The canaliculi radiate to the edge of the liver lobule, where they merge to form bile ducts. Within the liver, these ducts are termed intrahepatic bile ducts, and once they exit the liver, they are considered extrahepatic. The intrahepatic ducts eventually drain into the right and left hepatic ducts, which exit the liver at thetransverse fissure, and merge to form the common hepatic duct. Thecystic ductfrom the gallbladder joins with the common hepatic duct to form the common bile duct.The biliary system and connective tissue is supplied by the hepatic artery alone.
Bile either drains directly into the duodenum via the common bile duct, or is temporarily stored in the gallbladder via the cystic duct. The common bile duct and the pancreatic duct enter the second part of the duodenum together at the hepatopancreatic ampulla, also known as theampulla of Vater.
The liver plays a major role in carbohydrate, protein, amino acid, and lipid metabolism.
The liver performs several roles in carbohydrate metabolism.
The liver is responsible for the mainstay of proteinmetabolism, synthesis as well as degradation. Allplasma proteinsexceptGamma-globulinsare synthesised in the liver.It is also responsible for a large part ofamino acid synthesis. The liver plays a role in the production of clotting factors, as well asred blood cellproduction. Some of the proteins synthesized by the liver includecoagulation factorsI(fibrinogen),II(prothrombin),V,VII,VIII,IX,X,XI,XII,XIII, as well asprotein C,protein Sandantithrombin. The liver is a major site of production forthrombopoietin, aglycoproteinhormone that regulates the production ofplateletsby the bone marrow.
The liver plays several roles inlipidmetabolism: it performscholesterolsynthesis,lipogenesis, and the production oftriglycerides, and a bulk of the body's lipoproteins are synthesized in the liver. The liver plays a key role in digestion, as it produces and excretesbile(a yellowish liquid) required for emulsifying fats and help the absorption of vitamin K from the diet. Some of the bile drains directly into the duodenum, and some is stored in the gallbladder. The liver producesinsulin-like growth factor 1, apolypeptideproteinhormone that plays an important role in childhood growth and continues to haveanabolic effectsin adults.
The liver is responsible for the breakdown ofinsulinand otherhormones. The liver breaks downbilirubinviaglucuronidation, facilitating its excretion into bile.
The liver is responsible for the breakdown and excretion of many waste products. It plays a key role in breaking down or modifying toxic substances (e.g.,methylation) and most medicinal products in a process calleddrug metabolism. This sometimes results intoxication, when the metabolite is more toxic than its precursor. Preferably, the toxins areconjugatedto avail excretion in bile or urine. The liver convertsammoniaintoureaas part of theornithine cycleor the urea cycle, and the urea is excreted in the urine.
Because the liver is an expandable organ, large quantities of blood can be stored in its blood vessels. Its normal blood volume, including both that in the hepatic veins and that in the hepatic sinuses, is about 450 milliliters, or almost 10 percent of the body's total blood volume. When high pressure in the right atrium causes backpressure in the liver, the liver expands, and 0.5 to 1 liter of extra blood is occasionally stored in the hepatic veins and sinuses. This occurs especially incardiac failurewith peripheral congestion. Thus, in effect, the liver is a large, expandable, venous organ capable of acting as a valuable blood reservoir in times of excess blood volume and capable of supplying extra blood in times of diminished blood volume.
Because the pores in the hepatic sinusoids are very permeable and allow ready passage of both fluid and proteins into theperisinusoidal space, thelymphdraining from the liver usually has a protein concentration of about 6 g/dl, which is only slightly less than the protein concentration of plasma. 
Also, the high permeability of the liver sinusoid epithelium allows large quantities of lymph to form. Therefore, about half of all the lymph formed in the body under resting conditions arises in the liver.
The liver is a vital organ and supports almost every other organ in the body. Because of its strategic location and multidimensional functions, the liver is prone to many diseases.The bare area of the liver is a site that is vulnerable to the passing of infection from the abdominal cavity to thethoracic cavity. Liver diseases may be diagnosed byliver function tests–blood tests that can identify various markers. For example,acute-phase reactantsare produced by the liver in response to injury or inflammation.
The most common chronic liver disease isnonalcoholic fatty liver disease, which affects an estimated one-third of the world population.
Hepatitisis a common condition of inflammation of the liver. The most usual cause of this isviral, and the most common of these infections arehepatitis A,B,C,D, andE. Some of these infections aresexually transmitted. Inflammation can also be caused by other viruses in the familyHerpesviridaesuch as theherpes simplex virus. Chronic (rather than acute) infection with hepatitis B virus or hepatitis C virus is the main cause ofliver cancer.Globally, about 248 million individuals are chronically infected with hepatitis B (with 843,724 in the U.S.),and 142 million are chronically infected with hepatitis C(with 2.7 million in the U.S.).Globally there are about 114 million and 20 million cases of hepatitis Aand hepatitis Erespectively, but these generally resolve and do not become chronic. Hepatitis D virus is a "satellite" of hepatitis B virus (it can only infect in the presence of hepatitis B), and co-infects nearly 20 million people with hepatitis B, globally.
Hepatic encephalopathyis caused by an accumulation of toxins in the bloodstream that are normally removed by the liver. This condition can result in coma and can prove fatal.Budd–Chiari syndromeis a condition caused byblockageof thehepatic veins(includingthrombosis) that drain the liver. It presents with the classical triad of abdominal pain,ascitesandliver enlargement.Many diseases of the liver are accompanied byjaundicecaused by increased levels ofbilirubinin the system. The bilirubin results from the breakup of thehemoglobinof dead red blood cells; normally, the liver removes bilirubin from the blood and excretes it through bile.
Other disorders caused by excessive alcohol consumption are grouped underalcoholic liver diseasesand these includealcoholic hepatitis,fatty liver, andcirrhosis. Factors contributing to the development of alcoholic liver diseases are not only the quantity and frequency of alcohol consumption, but can also include gender, genetics, and liver insult. Liver damage can also becaused by drugs, particularlyparacetamoland drugs used to treat cancer. A rupture of the liver can be caused by aliver shotused in combat sports.
Primary biliary cholangitisis anautoimmune diseaseof the liver.It is marked by slow progressive destruction of the smallbile ductsof the liver, with the intralobular ducts (Canals of Hering) affected early in the disease.When these ducts are damaged, bile and other toxins build up in the liver (cholestasis) and over time damages the liver tissue in combination with ongoing immune related damage. This can lead to scarring (fibrosis) andcirrhosis. Cirrhosis increases the resistance to blood flow in the liver, and can result inportal hypertension.Congested anastomosesbetween theportal venous systemand the systemic circulation, can be a subsequent condition.
There are also many pediatric liver diseases, includingbiliary atresia,alpha-1 antitrypsin deficiency,alagille syndrome,progressive familial intrahepatic cholestasis,Langerhans cell histiocytosisandhepatic hemangiomaabenign tumourthe most common type of liver tumour, thought to be congenital. A genetic disorder causing multiple cysts to form in the liver tissue, usually in later life, and usually asymptomatic, ispolycystic liver disease. Diseases that interfere with liver function will lead to derangement of these processes. However, the liver has a great capacity toregenerateand has a large reserve capacity. In most cases, the liver only produces symptoms after extensive damage.
Hepatomegalyrefers to an enlarged liver and can be due to many causes. It can bepalpatedin aliver spanmeasurement.
Consumingcaffeineregularly may help safeguard individuals fromliver cirrhosis.Additionally, it has been shown to slow the advancement of liver disease in those already affected, lower the risk of liver fibrosis, and provide a protective benefit against liver cancer for moderate coffee drinkers. A 2017 study revealed that the positive effects of caffeine on the liver were evident regardless of the coffee preparation method.
The classic symptoms of liver damage include the following:
The diagnosis ofliver diseaseis made byliver function tests, groups ofblood tests, that can readily show the extent of liver damage. Ifinfectionis suspected, then otherserologicaltests will be carried out. A physical examination of the liver can only reveal its size and any tenderness, and some form ofimagingsuch as anultrasoundorCT scanmay also be needed.
Sometimes aliver biopsywill be necessary, and a tissue sample is taken through a needle inserted into the skin just below therib cage. This procedure may be helped by a sonographer providing ultrasound guidance to an interventional radiologist.
The liver is the only human internal organ capable of naturalregenerationof losttissue; as little as 25% of a liver can regenerate into a whole liver.This is, however, not true regeneration but rathercompensatory growthin mammals.The lobes that are removed do not regrow and the growth of the liver is a restoration of function, not original form.  This contrasts with true regeneration where both original function and form are restored. In some other species, such as zebrafish, the liver undergoes true regeneration by restoring both shape and size of the organ.In the liver, large areas of the tissues are formed but for the formation of new cells there must be sufficient amount of material so the circulation of the blood becomes more active.
This is predominantly due to thehepatocytesre-entering thecell cycle. That is, the hepatocytes go from the quiescentG0 phaseto theG1 phaseand undergo mitosis. This process is activated by thep75receptors.There is also some evidence ofbipotentialstem cells, called hepatic oval cells or ovalocytes (not to be confused with oval red blood cells ofovalocytosis), which are thought to reside in thecanals of Hering. These cells can differentiate into eitherhepatocytesorcholangiocytes. Cholangiocytes are theepithelial lining cellsof thebile ducts.They are cuboidal epithelium in the small interlobular bile ducts, but become columnar and mucus secreting in larger bile ducts approaching the porta hepatis and the extrahepatic ducts. Research is being carried out on the use of stem cells for the generation of anartificial liver.
Scientific and medical works about liver regeneration often refer to the GreekTitanPrometheuswho was chained to a rock in theCaucasuswhere, each day, his liver was devoured by an eagle, only to grow back each night. The myth suggests theancient Greeksmay have known about the liver's remarkable capacity for self-repair.
Human liver transplants were first performed byThomas Starzlin theUnited StatesandRoy CalneinCambridge, England in 1963 and 1967, respectively.
Liver transplantationis the only option for those with irreversible liver failure. Most transplants are done for chronic liver diseases leading tocirrhosis, such as chronichepatitis C,alcoholism, and autoimmune hepatitis. Less commonly, liver transplantation is done forfulminant hepatic failure, in which liver failure occurs rapidly over a period of days or weeks.
Liverallograftsfortransplantusually come from donors who have died from fatalbrain injury.Living donor liver transplantationis a technique in which a portion of a living person's liver is removed (hepatectomy) and used to replace the entire liver of the recipient.  This was first performed in 1989 for pediatric liver transplantation.  Only 20 percent of an adult's liver (Couinaud segments 2 and 3) is needed to serve as a liver allograft for an infant or small child.
More recently,adult-to-adult liver transplantation has been done using the donor's right hepatic lobe, which amounts to 60 percent of the liver.  Due to the ability of the liver toregenerate, both the donor and recipient end up with normal liver function if all goes well. This procedure is more controversial, as it entails performing a much larger operation on the donor, and indeed there were at least two donor deaths out of the first several hundred cases. A 2006 publication addressed the problem of donor mortality and found at least fourteen cases.The risk of postoperative complications (and death) is far greater in right-sided operations than that in left-sided operations.
With the recent advances of noninvasive imaging, living liver donors usually have to undergo imaging examinations for liver anatomy to decide if the anatomy is feasible for donation. The evaluation is usually performed by multidetector rowcomputed tomography(MDCT) andmagnetic resonance imaging(MRI). MDCT is good in vascular anatomy and volumetry. MRI is used for biliary tree anatomy. Donors with very unusual vascular anatomy, which makes them unsuitable for donation, could be screened out to avoid unnecessary operations.
Some cultures regard the liver as the seat of thesoul.InGreek mythology, the gods punishedPrometheusfor revealing fire to humans by chaining him to a rock where avulture(or aneagle) would peck out his liver, which would regenerate overnight (the liver is the only human internal organ that actually can regenerate itself to a significant extent). Many ancient peoples of the Near East and Mediterranean areas practiced a type ofdivinationcalledharuspicyorhepatomancy, where they tried to obtain information by examining the livers of sheep and other animals.
In Plato, and in later physiology, the liver was thought to be the seat of the darkest emotions (specifically wrath, jealousy and greed) which drive men to action.TheTalmud(tractateBerakhot 61b) refers to the liver as the seat ofanger, with thegallbladdercounteracting this. ThePersian,Urdu, andHindilanguages (جگرorजिगरorjigar) refer to the liver in figurative speech to indicate courage and strong feelings, or "their best"; e.g., "ThisMeccahas thrown to you the pieces of its liver!".The termjan e jigar, literally "the strength (power) of my liver", is a term of endearment in Urdu. In Persian slang,jigaris used as an adjective for any object which is desirable, especially women. In theZulu language, the word for liver (isibindi) is the same as the word for courage. In English the term 'lily-livered' is used to indicate cowardice from the medieval belief that the liver was the seat of courage.
Spanishhígadosalso means "courage".However the secondary meaning of Basquegibelis "indolence".
In biblical Hebrew, the word for liver,כבד(Kauved, stemmedKBDorKVD, similar to Arabicالكبد), also meansheavyand is used to describethe rich("heavy"  with possessions) andhonor(presumably for the same reason). In the Book of Lamentations (2:11) it is used to describe the physiological responses to sadness by "my liver spilled to earth" along with the flow of tears and the overturning in bitterness of the intestines.On several occasions in thebook of Psalms(most notably16:9), the word is used to describe happiness in the liver, along with the heart (which beats rapidly) and the flesh (which appears red under the skin).  Further usage asthe self(similar to "your honor") is widely available throughout the old testament, sometimes compared to the breathing soul (Genesis 49:6, Psalms 7:6, etc.). An honorable hat was also referred to with this word (Job 19:9, etc.) and under that definition appears many times along withפארPe'er- grandeur.
These four meanings were used in preceding ancientAfro-Asiatic languagessuch asAkkadianand Ancient Egyptian preserved in classical EthiopicGe'ez language.
Humans commonly eat the livers of mammals, fowl, and fish as food. Domestic pig, ox, lamb, calf, chicken, and goose livers are widely available from butchers and supermarkets. In theRomance languages, the anatomical word for "liver" (Frenchfoie,Spanishhígado, etc.) derives not from theLatinanatomical term,jecur, but from the culinary termficatum, literally "stuffed withfigs", referring to the livers of geese that had been fattened on figs.Animal livers are rich in iron,vitamin Aandvitamin B12; andcod liver oilis commonly used as adietary supplement.
Liver can be baked, boiled, broiled, fried, stir-fried, or eaten raw (asbeh nayehorsawda nayeinLebanese cuisine, or liversashimiinJapanese cuisine). In many preparations, pieces of liver are combined with pieces of meat or kidneys, as in the various forms of Middle Eastern mixed grill (e.g.meurav Yerushalmi). Well-known examples includeliver pâté,foie gras,chopped liver, andleverpastej. Liversausages, such asBraunschweigerandliverwurst, are also a valued meal.Liver sausagesmay also be used as spreads. A traditionalSouth Africandelicacy,skilpadjies, is made of minced lamb's liver wrapped innetvet(caul fat), and grilled over an open fire. Traditionally, some fish livers were valued as food, especially thestingrayliver. It was used to prepare delicacies, such as poached skate liver on toast in England, as well as thebeignets de foie de raieandfoie de raie en crouteinFrench cuisine.
TheHumrare one of the tribes in theBaggaraethnic group, native to southwesternKordofaninSudanwho speakShuwa(Chadian Arabic), make a non-alcoholic drink from the liver andbone marrowof thegiraffe, which they callumm nyolokh. They claim it is intoxicating (Arabic  سكرانsakran), causing dreams and even wakinghallucinations.Anthropologist Ian Cunnison accompanied the Humr on one of their giraffe-hunting expeditions in the late 1950s, and noted that:
Cunnison's remarkable account of an apparently psychoactive mammal found its way from a somewhat obscure scientific paper into more mainstream literature through a conversation betweenW. Jamesof the Institute of Social and CulturalAnthropologyat theUniversity of Oxfordand specialist on the use ofhallucinogensand intoxicants in society, andR. Rudgley, who discussed it in a book on psychoactive drugs for general readers.He speculated that a hallucinogenic compoundN,N-Dimethyltryptaminein the giraffe liver might account for the intoxicating properties claimed forumm nyolokh.
Cunnison, on the other hand, writing in 1958 found it hard to believe in the literal truth of the Humr's assertion that the drink was intoxicating:
The study ofentheogensin general – including entheogens of animal origin (e.g.hallucinogenic fishandtoad venom) – has, however, made considerable progress in the sixty-odd years since Cunnison's report; the idea that some intoxicating substance might reside in giraffe livers may no longer be as far-fetched as it seemed to Cunnison. However, to date, proof (or disproof) still waits on detailed analyses of the organ and the beverage made from it.
CertainTungusic peoplesof northeast Asia formerly prepared a type ofarrow poisonfrom rotting animal livers, which was, in later times, also applied tobullets. Russian anthropologistS. M. Shirokogoroffwrote that:
The liver is found in allvertebratesand is typically the largest internal organ. The internal structure of the liver is broadly similar in all vertebrates, though its form varies considerably in different species, and is largely determined by the shape and arrangement of the surrounding organs. Nonetheless, in most species, it is divided into right and left lobes; exceptions to this general rule includesnakes, where the shape of the body necessitates a simple cigar-like form.
In neonatal marsupials, it is responsible for the production of blood cells.
An organ sometimes referred to as a liver is found associated with the digestive tract of the primitive chordateamphioxus. Although it performs many functions of a liver, it is not considered a "true" liver but rather ahomologof the vertebrate liver.The amphioxus hepatic caecum produces the liver-specific proteinsvitellogenin,antithrombin,plasminogen,alanine aminotransferase, andinsulin/insulin-like growth factor.