The liver is also anaccessory digestive organ that producesbile, analkaline fluid containingcholesterol andbile acids, whichemulsifies and 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 theduodenum to help withdigestion.[5] 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.[6] Estimates regarding the organ's total number of functions vary, but is generally cited as being around 500.[7] For this reason, the liver has sometimes been described as the body'schemical factory.[8][9]
It is not known how to compensate for the absence of liver function in the long term, althoughliver dialysis techniques can be used in the short term.Artificial livers have not been developed to promote long-term replacement in the absence of the liver. As of 2018[update],[10]liver transplantation is the only option for completeliver failure.
The liver, viewed from above, showing the left and right lobes separated by thefalciform ligament
The liver is a dark reddish brown, wedge-shapedorgan with twolobes of unequal size and shape. A human liver normally weighs approximately 1.5 kilograms (3.3 pounds)[11] and has a width of about 15 centimetres (6 inches).[12] There is considerable size variation between individuals, with the standardreference range for men being 970–1,860 grams (2.14–4.10 lb)[13] and for women 600–1,770 g (1.32–3.90 lb).[14] It is both the heaviest internal organ and the largestgland in 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.[5]
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,fibroelastic connective tissue layer extending from the fibrous capsule covering the entire liver known asGlisson's capsule after British doctorFrancis Glisson.[4] 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 aserous coat derived from theperitoneum, and this firmly adheres to the inner Glisson's capsule.
The liver, viewed from below, surface showing four lobes and the impressions
The liver isgrossly divided 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).[16]
Thefalciform ligament makes 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 cava and all the way forward to divide the liver and gallbladder into two halves.[17] This line is calledCantlie's line.[18]
Other anatomical landmarks include theligamentum venosum and 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 thevisceral view.[19]
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.[20] 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 ligament and theright andleft triangular ligaments.[21]
Theseperitoneal ligaments are 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.[21] The falciform ligament functions to attach the liver to theposterior portion of theanterior body 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.[20] 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 flexure and the one behind is a deeper renal impression accommodating part of the right kidney and part of thesuprarenal gland.[22]
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.[23]
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.[23]
The inferior surface of the left lobe of the liver presents behind and to the left of the gastric impression.[23] 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, andsinusoids radiating from a central vein towards an imaginary perimeter of interlobular portal triads.[24] 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.[25] The triad may be seen on a liver ultrasound, as aMickey Mouse sign with the portal vein as the head, and the hepatic artery, and the common bile duct as the ears.[26]
Histology, the study of microscopic anatomy, shows two major types of liver cell:parenchymal cells 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.[27] Theliver sinusoids are lined with two types of cell,sinusoidal endothelial cells, andphagocyticKupffer cells.[28]Hepatic stellate cells are nonparenchymal cells found in theperisinusoidal space, between a sinusoid and a hepatocyte.[27]Additionally, intrahepaticlymphocytes are often present in the sinusoidal lumen.[27]
Microscopic anatomy of the liver
Types of capillaries–sinusoid on right
3D medical animation still shot depicting parts of liver
The central area orhepatic hilum, includes the opening known as the porta hepatis which carries thecommon bile duct andcommon 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 ananterior andposterior segment by the right hepatic vein. The left lobe is divided into themedial andlateral segments by the left hepatic vein.
The hilum of the liver is described in terms of threeplates that contain thebile ducts and blood vessels. The contents of the whole plate system are surrounded by a sheath.[29] The three plates are thehilar plate, thecystic plate and theumbilical plate and the plate system is the site of the many anatomical variations to be found in the liver.[29]
Shape of human liver in animation, with eight Couinaud segments labelled
In the widely usedCouinaud system, 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.[30] The caudate lobe is a separate structure that receives blood flow from both the right- and left-sided vascular branches.[31][32] 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.[33] 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.[30] The remainder of the units (II to VIII) are numbered in a clockwise fashion:[33]
About 20,000 protein coding genes are expressed in human cells and 60% of these genes are expressed in a normal, adult liver.[34][35] 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 enzymes such asHAO1 andRDH16, proteins involved in bile synthesis such asBAAT andSLC27A5, and transporter proteins involved in the metabolism of drugs, such asABCB11 andSLC2A2. Examples of highly liver-specific proteins includeapolipoprotein A II, coagulation factorsF2 andF9,complement factor related proteins, and thefibrinogen beta chain protein.[36]
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 diverticulum is 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 duct of the liver, and a branch from this duct produces the gallbladder.[37] Besides signals from the septum transversum mesenchyme,fibroblast growth factor from thedeveloping heart also contributes to hepatic competence, along withretinoic acid emanating 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.[38] Hepatic stellate cells are derived from mesenchyme.[39]
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 vein becomes theductus venosus and the rightvitelline vein becomes the portal vein. The expanding liver bud is colonized byhematopoietic cells. The bipotential hepatoblasts begin differentiating intobiliary epithelial cells and 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 abundantglycogen accumulation. 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-catenin has now been identified to be playing a key role in this phenomenon.[38]
Adult ultrasound showing the right lobe of the liver and right kidney
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.[40]
Hepatosomatic index (HSI) is the ratio of liver weight to body weight.[41]
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 liver and the latter becomes the ligamentum venosum. In thedisorders ofcirrhosis andportal hypertension, the umbilical vein can open up again.
Unlike eutherian mammals, in marsupials the liver remains haematopoietic well after birth.[42][43][44][45]
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 organ or 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 gets its 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 blood drained 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.[46] 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 veins coalesce into hepatic veins, which leave the liver and drain into the inferior vena cava.[47]
The liver and its veins
Diagram of liver, lobule, and portal tract and their inter-relations
Thebiliary tract is 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 duct from the gallbladder joins with the common hepatic duct to form the common bile duct.[47] 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 several roles inlipid metabolism: it performscholesterol synthesis,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, apolypeptideprotein hormone that plays an important role in childhood growth and continues to haveanabolic effects in adults.
The liver is responsible for the breakdown ofinsulin and otherhormones. The liver breaks downbilirubin viaglucuronidation, 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 areconjugated to avail excretion in bile or urine. The liver convertsammonia intourea as part of theornithine cycle or the urea cycle, and the urea is excreted in the urine.[52]
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 failure with 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.[53]
Because the pores in the hepatic sinusoids are very permeable and allow ready passage of both fluid and proteins into theperisinusoidal space, thelymph draining 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.
Haemopoiesis - The formation of blood cells is called haemopoiesis. In the embryonic stage, RBCs and WBCs are formed by liver. In the first trimester fetus, the liver is the main site of red blood cell production. By the 32nd week ofgestation, thebone marrow has almost completely taken over that task.[56]
The liver helps in the purification of blood. TheKupffer cells of liver arephagocytic cells that help in the phagocytosis of dead blood cells and bacteria from the blood.[57]
The liver is responsible for immunological effects – themononuclear phagocyte system of the liver contains many immunologically active cells, acting as a 'sieve' for antigens carried to it via theportal system.
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.[58] 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 reactants are produced by the liver in response to injury or inflammation.
Hepatitis is 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 familyHerpesviridae such as theherpes simplex virus. Chronic (rather than acute) infection with hepatitis B virus or hepatitis C virus is the main cause ofliver cancer.[60] Globally, about 248 million individuals are chronically infected with hepatitis B (with 843,724 in the U.S.),[61] and 142 million are chronically infected with hepatitis C[62] (with 2.7 million in the U.S.).[63] Globally there are about 114 million and 20 million cases of hepatitis A[62] and hepatitis E[64] respectively, 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.[65]
Hepatic encephalopathy is 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 syndrome is a condition caused byblockage of thehepatic veins (includingthrombosis) that drain the liver. It presents with the classical triad of abdominal pain,ascites andliver enlargement.[66] Many diseases of the liver are accompanied byjaundice caused by increased levels ofbilirubin in the system. The bilirubin results from the breakup of thehemoglobin of 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 diseases and 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, particularlyparacetamol and drugs used to treat cancer. A rupture of the liver can be caused by aliver shot used in combat sports.
Consumingcaffeine regularly may help safeguard individuals fromliver cirrhosis.[70] 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.[71]
The classic symptoms of liver damage include the following:
Pale stools occur whenstercobilin, a brown pigment, is absent from the stool. Stercobilin is derived from bilirubin metabolites produced in the liver.
Dark urine occurs when bilirubin mixes with urine
Jaundice (yellow skin and/or whites of the eyes) This is wherebilirubin deposits in skin, causing an intenseitch. Itching is the most common complaint by people who have liver failure. Often this itch cannot be relieved by drugs.
Bruising and easy bleeding are other features of liver disease. The liver makesclotting factors, substances which help prevent bleeding. When liver damage occurs, these factors are no longer present and severe bleeding can occur.[72]
Pain in the upper right quadrant can result from the stretching of Glisson's capsule in conditions ofhepatitis andpre-eclampsia.
The diagnosis ofliver disease is made byliver function tests, groups ofblood tests, that can readily show the extent of liver damage. Ifinfection is suspected, then otherserological tests will be carried out. A physical examination of the liver can only reveal its size and any tenderness, and some form ofimaging such as anultrasound orCT scan may also be needed.
Sometimes aliver biopsy will 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.[73]
Axial CT image showing anomalous hepatic veins coursing on the liver's subcapsular anterior surface[74]
Maximum intensity projection (MIP) CT image as viewed anteriorly showing the anomaloushepatic veins coursing on the anterior surface of the liver
Lateral MIP view in the same patient as previous image
A CT scan in which the liver and portal vein are shown
The liver is the only human internal organ capable of naturalregeneration of losttissue; as little as 25% of a liver can regenerate into a whole liver.[75] This is, however, not true regeneration but rathercompensatory growth in mammals.[76] 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.[77] 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.[78]
This is predominantly due to thehepatocytes re-entering thecell cycle. That is, the hepatocytes go from the quiescentG0 phase to theG1 phase and undergo mitosis. This process is activated by thep75 receptors.[79] 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 eitherhepatocytes orcholangiocytes. Cholangiocytes are theepithelial lining cells of thebile ducts.[80] 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 GreekTitanPrometheus who was chained to a rock in theCaucasus where, each day, his liver was devoured by an eagle, only to grow back each night. The myth suggests theancient Greeks may have known about the liver's remarkable capacity for self-repair.[81]
Liver transplantation is 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.
Liverallografts fortransplant usually come from donors who have died from fatalbrain injury.Living donor liver transplantation is 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,[when?] 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.[82] 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.
MDCT image. Arterial anatomy contraindicated for liver donation
MDCT image. Portal venous anatomy contraindicated for liver donation
MDCT image. 3D image created by MDCT can clearly visualize the liver, measure the liver volume, and plan the dissection plane to facilitate the liver transplantation procedure.
Phase contrast CT image. Contrast is perfusing the right liver but not the left due to a left portal vein thrombus.
Some cultures regard the liver as the seat of thesoul.[83] InGreek mythology, the gods punishedPrometheus for 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 ofdivination calledharuspicy orhepatomancy, 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.[84] TheTalmud (tractateBerakhot 61b) refers to the liver as the seat ofanger, with thegallbladder counteracting this. ThePersian,Urdu, andHindi languages (جگر orजिगर orjigar) refer to the liver in figurative speech to indicate courage and strong feelings, or "their best"; e.g., "ThisMecca has thrown to you the pieces of its liver!".[85] The termjan e jigar, literally "the strength (power) of my liver", is a term of endearment in Urdu. In Persian slang,jigar is 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.Spanishhígados also means "courage".[86]However the secondary meaning of Basquegibel is "indolence".[87]
In biblical Hebrew, the word for liver,כבד (Kauved, stemmedKBD orKVD, similar to Arabicالكبد), also meansheavy and 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.[88] 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.[89]
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 theLatin anatomical term,jecur, but from the culinary termficatum, literally "stuffed withfigs", referring to the livers of geese that had been fattened on figs.[91] Animal livers are rich in iron,vitamin A andvitamin B12; andcod liver oil is commonly used as adietary supplement.
Liver can be baked, boiled, broiled, fried, stir-fried, or eaten raw (asbeh nayeh orsawda naye inLebanese cuisine, or liversashimi inJapanese 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 asBraunschweiger andliverwurst, are also a valued meal.Liver sausages may also be used as spreads. A traditionalSouth African delicacy,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 thestingray liver. It was used to prepare delicacies, such as poached skate liver on toast in England, as well as thebeignets de foie de raie andfoie de raie en croute inFrench cuisine.[92]
TheHumr are one of the tribes in theBaggara ethnic group, native to southwesternKordofan inSudan who speakShuwa (Chadian Arabic), make a non-alcoholic drink from the liver andbone marrow of thegiraffe, which they callumm nyolokh. They claim it is intoxicating (Arabic سكرانsakran), causing dreams and even wakinghallucinations.[93] Anthropologist Ian Cunnison accompanied the Humr on one of their giraffe-hunting expeditions in the late 1950s, and noted that:
It is said that a person, once he has drunkumm nyolokh, will return to giraffe again and again. Humr, beingMahdists, are strictabstainers [from alcohol] and a Humrawi is never drunk (sakran) onliquor or beer. But he uses this word to describe the effects whichumm nyolokh has upon him.[94]
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. James of the Institute of Social and CulturalAnthropology at theUniversity of Oxford and specialist on the use ofhallucinogens and intoxicants in society, andR. Rudgley, who discussed it in a book on psychoactive drugs for general readers.[93] He speculated that a hallucinogenic compoundN,N-Dimethyltryptamine in the giraffe liver might account for the intoxicating properties claimed forumm nyolokh.[93]
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:
I can only assume that there is no intoxicating substance in the drink, and that the effect it produces is simply a matter of convention, although it may be brought aboutsubconsciously.[94]
The study ofentheogens in general – including entheogens of animal origin (e.g.hallucinogenic fish andtoad 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.[93]
Formerly the using of poisoned arrows was common. For instance, among the Kumarčen, [a subgroup of theOroqen] even in recent times, a poison was used which was prepared from decaying liver.
[Note] This has been confirmed by the Kumarčen. I am not competent to judge as to the chemical conditions of production of poison which is not destroyed by the heat of explosion. However, the Tungus themselves compare this method [of poisoning ammunition] with the poisoning of arrows.[95]
The liver is found in allvertebrates and 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.[96]
In neonatal marsupials, it is responsible for the production of blood cells.[42][45][97][44]
^Elias, H.; Bengelsdorf, H. (1 July 1952). "The Structure of the Liver in Vertebrates".Cells Tissues Organs.14 (4):297–337.doi:10.1159/000140715.PMID14943381.
^abTortora, Gerard J.; Derrickson, Bryan H. (2008).Principles of Anatomy and Physiology (12th ed.). John Wiley & Sons. p. 945.ISBN978-0-470-08471-7.
^Maton, Anthea; Jean Hopkins; Charles William McLaughlin; Susan Johnson; Maryanna Quon Warner; David LaHart; Jill D. Wright (1993).Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall.ISBN978-0-13-981176-0.OCLC32308337.
^Zakim, David; Boyer, Thomas D. (2002).Hepatology: A Textbook of Liver Disease (4th ed.).ISBN9780721690513.
^Pocock, Gillian (2006).Human Physiology (Third ed.). Oxford University Press. p. 404.ISBN978-0-19-856878-0.
^abKawarada, Y; Das, BC; Taoka, H (2000). "Anatomy of the hepatic hilar area: the plate system".Journal of Hepato-Biliary-Pancreatic Surgery.7 (6):580–586.doi:10.1007/s005340070007.PMID11180890.
^Strunk, H.; Stuckmann, G.; Textor, J.; Willinek, W. (2003). "Limitations and pitfalls of Couinaud's segmentation of the liver in transaxial Imaging".European Radiology.13 (11):2472–2482.doi:10.1007/s00330-003-1885-9.PMID12728331.S2CID34879763.
^abOld, J.M.; Deane, E.M. (July 2000). "Development of the immune system and immunological protection in marsupial pouch young".Developmental & Comparative Immunology.24 (5):445–454.doi:10.1016/S0145-305X(00)00008-2.PMID10785270.
^abOld, J.M; Selwood, L; Deane, E.M (April 2004). "A developmental investigation of the liver, bone marrow and spleen of the stripe-faced dunnart (Sminthopsis macroura)".Developmental & Comparative Immunology.28 (4):347–355.doi:10.1016/j.dci.2003.08.004.PMID14698220.
^abOld, J. M.; Deane, E. M. (February 2003). "The lymphoid and immunohaematopoietic tissues of the embryonic brushtail possum (Trichosurus vulpecula)".Anatomy and Embryology.206 (3):193–197.doi:10.1007/s00429-002-0285-2.PMID12592570.
^Shneider, Benjamin L.; Sherman, Philip M. (2008).Pediatric Gastrointestinal Disease. Connecticut: PMPH-USA. p. 751.ISBN978-1-55009-364-3.
^abHuman Anatomy & Physiology + New Masteringa&p With Pearson Etext. Benjamin-Cummings Pub Co. 2012. p. 881.ISBN9780321852120.
^abHuman Anatomy & Physiology + New Masteringa&p With Pearson Etext. Benjamin-Cummings Pub Co. 2012. p. 939.ISBN9780321852120.
^Jelkmann, Wolfgang (2001). "The role of the liver in the production of thrombopoietin compared with erythropoietin".European Journal of Gastroenterology & Hepatology.13 (7):791–801.doi:10.1097/00042737-200107000-00006.PMID11474308.
^Human Anatomy & Physiology + New Masteringa&p With Pearson Etext. Benjamin-Cummings Pub Co. 2012.ISBN9780321852120.
^Lautt, WW; Greenway, CV (August 1976). "Hepatic venous compliance and role of liver as a blood reservoir".American Journal of Physiology. Legacy Content.231 (2):292–295.doi:10.1152/ajplegacy.1976.231.2.292.PMID961879.
^"Liver".The Lecturio Medical Concept Library. 9 September 2020. Retrieved2021-06-23.
^Schweitzer A, Horn J, Mikolajczyk RT, Krause G, Ott JJ (2015). "Estimations of worldwide prevalence of chronic hepatitis B virus infection: a systematic review of data published between 1965 and 2013".Lancet.386 (10003):1546–1555.doi:10.1016/S0140-6736(15)61412-X.PMID26231459.S2CID41847645.
^Dény, P. (2006). "Hepatitis Delta Virus Genetic Variability: From Genotypes I, II, III to Eight Major Clades?".Hepatitis Delta Virus. Current Topics in Microbiology and Immunology. Vol. 307. pp. 151–171.doi:10.1007/3-540-29802-9_8.ISBN978-3-540-29801-4.PMID16903225.
^Rajani R, Melin T, Björnsson E, Broomé U, Sangfelt P, Danielsson A, Gustavsson A, Grip O, Svensson H, Lööf L, Wallerstedt S, Almer SH (Feb 2009). "Budd-Chiari syndrome in Sweden: epidemiology, clinical characteristics and survival – an 18-year experience".Liver International.29 (2):253–259.doi:10.1111/j.1478-3231.2008.01838.x.PMID18694401.S2CID36353033.
^Sheporaitis, L; Freeny, PC (1998). "Hepatic and portal surface veins: A new anatomic variant revealed during abdominal CT".AJR. American Journal of Roentgenology.171 (6):1559–1564.doi:10.2214/ajr.171.6.9843288.PMID9843288.
^Defrances, Marie C.; Michalopoulos, George K. (2011). "Liver Regeneration and Partial Hepatectomy: Process and Prototype".Liver Regeneration. pp. 1–16.doi:10.1515/9783110250794.1.ISBN978-3-11-025078-7.
^Kumar, Vinay; Abbas, Abul K.; Fausto, Nelson (1999).Robbins and Cotran Pathologic Basis of Disease (7th ed.). Elsevier Saunders. p. 101.ISBN978-0-8089-2302-2.
^Spence, Lewis (2010).Myths and Legends of Babylonia and Assyria. Cosimo. p. 281.ISBN978-1-61640-464-2.Now among people in a primitive state of culture the soul is almost invariably supposed to reside in the liver instead of in the heart or brain.
^"hígado".Diccionario de la lengua española (in Spanish) (23.4 ed.). ASALE-RAE. 2020. Retrieved29 July 2021.Ánimo, valentía. U. m. en pl.
^Azkue, Resurrección María de (1905)."gibel".Diccionario vasco-español-francés ... Dictionnaire basque-espagnol-français . (in Spanish and French). Bilbao, Dirección del autor. p. 345. Retrieved29 July 2021.(Bc, BN-s, R)cachaza,calme
^כלו בדמעות עיני חמרמרו מעי נשפך לארץ כבדי על שבר בת עמי בעטף עולל ויונק ברחבות קריה "My eyes terminated with tears, my intestines overturned with bitterness, my liver spilled to the earth on the breaking of my nation's daughter when a suckling baby lies in the town squares" (Lamentations 2:11) this could be interpreted to be read as myhonor spilled, ormyself being spilled).
^Kavod - Honor (in Hebrew, Israeli Linguist Ruvik Rosenthal's website). Rosenthal hypothesized that the term's usage to describe heaviness comes perhaps from the liver being the heaviest of all body parts in some farm animals or in humans.
^SeeKabadu in Akkadian, (From online dictionary at Association Assyrophile de France organization website)
^"Foie".Larousse.fr.Archived from the original on 2018-06-12. Retrieved2019-04-16.
^abCunnison, Ian (1958). "Giraffe hunting among the Humr tribe".SNR.39:49–60.
^Shirokogoroff, S.M. (1935).Psychomental Complex of the Tungus. Kegan Paul, Trench, Trubner & Co. p. 89.
^Romer, Alfred Sherwood; Parsons, Thomas S. (1977).The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 354–355.ISBN978-0-03-910284-5.
^Old, J.M.; Selwood, L.; Deane, E.M. (2003). "A Histological Investigation of the Lymphoid and Immunohaematopoietic Tissues of the Adult Stripe-Faced Dunnart (Sminthopsis macroura)".Cells Tissues Organs.173 (2):115–121.doi:10.1159/000068946.PMID12649589.
^Yuan, Shaochun; Ruan, Jie; Huang, Shengfeng; Chen, Shangwu; Xu, Anlong (February 2015). "Amphioxus as a model for investigating evolution of the vertebrate immune system".Developmental & Comparative Immunology.48 (2):297–305.doi:10.1016/j.dci.2014.05.004.PMID24877655.
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