Liver

Liver

Liver
Human liver shown in abdomen
Details
Latin Jecur, iecur
Greek Hepar (ἧπαρ)
root hepat- (ἡπατ-)
Precursor Foregut
System Digestive system
Hepatic artery
Hepatic vein and hepatic portal vein
Celiac ganglia and vagus nerve[1]
Identifiers
MeSH A03.620
Anatomical terminology

The liver is a vertebrates and some other animals.[2] In the human it is located in the upper right quadrant of the abdomen, below the diaphragm. The liver has a wide range of functions, including detoxification of various metabolites, protein synthesis, and the production of biochemicals necessary for digestion.[3]

The liver is a homologous it is to the vertebrate liver.[55]

Additional images

See also

References

  1. ^ Physiology: 6/6ch2/s6ch2_30 - Essentials of Human Physiology
  2. ^
  3. ^ a b
  4. ^ a b TortoraDerrickson 2008, p. 945.
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  7. ^
  8. ^
  9. ^ a b Liver Anatomy at eMedicine
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  14. ^
  15. ^
  16. ^ a b
  17. ^ a b
  18. ^
  19. ^ a b c Dorland 2011, p. 924.
  20. ^ a b c Marieb & Hoehn 2012, p. 881.
  21. ^ a b c
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  23. ^ a b c
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  25. ^
  26. ^ a b c
  27. ^
  28. ^
  29. ^ a b
  30. ^
  31. ^
  32. ^
  33. ^
  34. ^ a b Marieb & Hoehn 2012, p. 939.
  35. ^
  36. ^ Cirrhosis Overview National Digestive Diseases Information Clearinghouse. Retrieved 2010-01-22
  37. ^
  38. ^
  39. ^
  40. ^
  41. ^ Extraintestinal Complications: Liver Disease Crohn's & Colitis Foundation of America. Retrieved 2010-01-22
  42. ^ Liver Information HealthLine. Retrieved 2010-01-22
  43. ^
  44. ^
  45. ^
  46. ^
  47. ^
  48. ^
  49. ^
  50. ^ An argument for the ancient Greek’s knowing about liver regeneration is provided by Counterarguments are provided by and by
  51. ^
  52. ^
  53. ^ The Great Battle Of Badar (Yaum-E-Furqan). Shawuniversitymosque.org (2006-07-08). Retrieved 2013-03-19.
  54. ^
  55. ^ a b

Sources

External links

An organ sometimes referred to as a liver is found associated with the digestive tract of the primitive chordate

The liver is found in all snakes, where the shape of the body necessitates a simple cigar-like form. The internal structure of the liver is broadly similar in all vertebrates.[55]

Sheep's liver

Other animals

Animal livers are rich in iron and vitamin A, and cod liver oil is commonly used as a dietary supplement. Traditionally, some fish livers were valued as food, especially the stingray liver. It was used to prepare delicacies, such as poached skate liver on toast in England, as well as the beignets de foie de raie and foie de raie en croute in French cuisine.[54]

Liver can be baked, boiled, broiled, fried, stir-fried, or eaten raw (asbeh nayeh or sawda naye in Lebanese cuisine, liver sashimi). In many preparations, pieces of liver are combined with pieces of meat or kidneys, like in the various forms of Middle Eastern mixed grill (e.g. meurav Yerushalmi). Liver is often made into spreads. Well-known examples include liver pâté, foie gras, chopped liver, and leverpastej. Liver sausages such as Braunschweiger and liverwurst are also a valued meal. Liver sausages may also be used as spreads. A traditional South African delicacy, namely Skilpadjies, is made of minced lamb's liver wrapped in netvet (caul fat), and grilled over an open fire.

The liver of mammals, fowl, and fish are commonly eaten as food by humans. Domestic pig, ox, lamb, calf, chicken, and goose livers are widely available from butchers and supermarkets.

Food

In the motion picture The Message, Hind bint Utbah is implied or portrayed eating the liver of Hamza ibn ‘Abd al-Muttalib during the Battle of Uhud. Although there are narrations that suggest that Hind did "taste", rather than eat, the liver of Hamza, the authenticity of these narrations have to be questioned.

The legend of Liver-Eating Johnson says that he would cut out and eat the liver of each man killed after dinner.

The Persian, Urdu, and Hindi languages (جگر or जिगर or jigar) refer to the liver in figurative speech to indicate courage and strong feelings, or "their best"; e.g., "This Mecca has thrown to you the pieces of its liver!".[53] The term jan 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 the Zulu language, the word for liver (isibindi) is the same as the word for courage.

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.[52] The Talmud (tractate Berakhot 61b) refers to the liver as the seat of anger, with the gallbladder counteracting this.

In divination called haruspicy, where they tried to obtain information by examining the livers of sheep and other animals.

Society and culture

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 row computed tomography (MDCT) and magnetic 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.

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 to regenerate, 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 have been at least two donor deaths out of the first several hundred cases. A recent publication has addressed the problem of donor mortality, and at least 14 cases have been found.[51] The risk of postoperative complications (and death) is far greater in right-sided operations than that in left-sided operations.

Liver transplant usually come from donors who have died from fatal brain injury. Living donor liver transplantation is a technique in which a portion of a living person's liver is removed 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.

Liver transplantation is the only option for those with irreversible liver failure. Most transplants are done for chronic liver diseases leading to cirrhosis, such as chronic hepatitis C, alcoholism, autoimmune hepatitis, and many others. Less commonly, liver transplantation is done for fulminant hepatic failure, in which liver failure occurs over days to weeks.

After resection of left lobe liver tumor

Human liver transplants were first performed by Thomas Starzl in the United States and Roy Calne in Cambridge, England in 1963 and 1967, respectively.

Liver transplantation

Scientific and medical works about liver regeneration often refer to the Greek Titan Prometheus who was chained to a rock in the Caucasus where, each day, his liver was devoured by an eagle, only to grow back each night. The myth suggests the ancient Greeks may have known about the liver’s remarkable capacity for self-repair.[50]

This is predominantly due to the hepatocytes re-entering the cell cycle. That is, the hepatocytes go from the quiescent G0 phase to the G1 phase and undergo mitosis. This process is activated by the p75 receptors.[48] There is also some evidence of bipotential stem cells, called hepatic oval cells or ovalocytes (not to be confused with oval red blood cells of ovalocytosis), which are thought to reside in the canals of Hering. These cells can differentiate into either hepatocytes or cholangiocytes. Cholangiocytes are the epithelial lining cells of the bile ducts.[49] 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.

[47] In 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.[46] The liver is the only human internal organ capable of natural

Liver regeneration

In a biopsy, a needle is inserted into the skin just below the rib cage and a tissue sample obtained. The tissue is sent to the laboratory, where it is analyzed under a microscope. Sometimes, a radiologist may assist the physician performing a liver biopsy by providing ultrasound guidance.[43]

Damage to the liver is sometimes determined with a biopsy, particularly when the cause of liver damage is unknown. In the 21st century they have been largely replaced by high-resolution radiographic scans. The latter do not require ultrasound guidance, lab involvement, microscopic analysis, organ damage, pain, or patient sedation; and the results are available immediately on a computer screen.

Biopsy / scan

Physical examination of the liver can only reveal its size and any tenderness, and some form of imaging will also be needed.[42]

The diagnosis of liver disease is made by liver function tests, groups of blood tests, that can readily show the extent of liver damage. If infection is suspected, then other serological tests will be carried out. Sometimes, an ultrasound or a CT scan is needed to produce an image of the liver.

Diagnosis

  • Pale stools occur when stercobilin, 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 where bilirubin deposits in skin, causing an intense itch. Itching is the most common complaint by people who have liver failure. Often this itch cannot be relieved by drugs.
  • Swelling of the abdomen, ankles and feet occurs because the liver fails to make albumin.
  • Excessive fatigue occurs from a generalized loss of nutrients, minerals and vitamins.
  • Bruising and easy bleeding are other features of liver disease. The liver makes substances which help prevent bleeding. When liver damage occurs, these substances are no longer present and severe bleeding can occur.[41]
  • Pain in the upper right quadrant can result from the stretching of Glisson's capsule in conditions of hepatitis and pre-eclampsia.

The classic symptoms of liver damage include the following:

Symptoms

Liver diseases may be diagnosed by liver 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.

Hepatomegaly refers to an enlarged liver and can be due to many causes. It can be palpated in a liver span measurement.

Diseases that interfere with liver function will lead to derangement of these processes. However, the liver has a great capacity to regenerate and has a large reserve capacity. In most cases, the liver only produces symptoms after extensive damage.

There are also many pediatric liver diseases, including biliary atresia, alpha-1 antitrypsin deficiency, alagille syndrome, progressive familial intrahepatic cholestasis, and Langerhans cell histiocytosis, to name but a few.

Many diseases of the liver are accompanied by jaundice caused by increased levels of bilirubin in the system. The bilirubin results from the breakup of the hemoglobin of dead red blood cells; normally, the liver removes bilirubin from the blood and excretes it through bile.

Primary biliary cirrhosis is an autoimmune disease of the liver.[38][39] It is marked by slow progressive destruction of the small bile ducts of the liver, with the intralobular ducts (Canals of Hering) affected early in the disease.[40] 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) and cirrhosis.

Budd–Chiari syndrome is a condition caused by blockage of the hepatic veins (including thrombosis) that drain the liver. It presents with the classical triad of abdominal pain, ascites and liver enlargement.[37]

Other disorders caused by excessive alcohol consumption are grouped under alcoholic liver diseases and these include alcoholic hepatitis, fatty liver, and cirrhosis. Liver damage can also be caused by drugs, particularly paracetomol and drugs used to treat cancer.

Hepatitis is a common condition of inflammation of the liver. The most usual cause of this is viral, and the most common of these infections are hepatitis A, B, C, D, and E. Some of these infections are sexually transmitted. Inflammation can also be caused by other viruses in the Herpesviridae family such as the herpes simplex virus. Infection with hepatitis B virus or hepatitis C virus is the main cause of liver cancer.

The liver supports almost every organ in the body and is vital for survival. Because of its strategic location and multidimensional functions, the liver is also prone to many diseases.[36]The bare area of the liver is a site that is vulnerable to the passing of infection from the abdominal cavity to the thoracic cavity.

Left lobe liver tumor

Disease

Clinical significance

The oxidative capacity of the liver decreases with aging and therefore any medications that require oxidation (for instance, benzodiazepines) are more likely to accumulate to toxic levels. However, medications with shorter half-lives, such as lorazepam and oxazepam, are preferred in most cases when benzodiazepines are required in regards to geriatric medicine.

Relation to medicine and pharmacology

Other functions

The liver is responsible for the breakdown of insulin and other hormones. The liver breaks down bilirubin via glucuronidation, 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 called drug metabolism. This sometimes results in toxication, when the metabolite is more toxic than its precursor. Preferably, the toxins are conjugated to avail excretion in bile or urine. The liver breaks down ammonia into urea as part of the urea cycle, and the urea is excreted in the urine.insulin-like growth factor 1 (IGF-1), a polypeptide protein hormone that plays an important role in childhood growth and continues to have anabolic effects in adults.

The liver plays a key role in digestion, as it produces and excretes bile (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 plays several roles in lipid metabolism: it performs cholesterol synthesis, lipogenesis, the production of triglycerides, and a bulk of the body's lipoproteins are synthesized in the liver.

The liver is responsible for the mainstay of protein metabolism, synthesis as well as degradation. It is also responsible for a large part of amino acid synthesis. The liver plays a role in the production of clotting factors as well as red blood cell production. Some of the proteins synthesized by the liver include coagulation factors I (fibrinogen), II (prothrombin), V, VII, VIII, IX, X and XI, as well as protein C, protein S and antithrombin. In the first trimester fetus, the liver is the main site of red blood cell production. By the 32nd week of gestation, the bone marrow has almost completely taken over that task. The liver is a major site of production for thrombopoietin, a glycoprotein hormone that regulates the production of platelets by the bone marrow.[35]

The liver performs several roles in carbohydrate metabolism: The liver synthesizes and stores approximately 100g of glycogen via glycogenesis, the formation of glycogen from glucose. When needed, the liver releases glucose into the blood by performing glycogenolysis, the breakdown of glycogen into glucose.[34] The liver is also responsible for gluconeogenesis, which is the synthesis of glucose from certain amino acids, lactate or glycerol. Adipose and liver cells produce glycerol by breakdown of fat, which the liver uses for gluconeogenesis.[34]

The liver plays a major role in carbohydrate, protein, amino acid, and lipid metabolism.

Synthesis

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 the ampulla of Vater.

The biliary 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, the duodenum. The bile produced in the liver is collected in bile 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 the transverse fissure, and merge to form the common hepatic duct. The cystic duct from the gallbladder joins with the common hepatic duct to form the common bile duct.[20]

Biliary tract

Biliary flow

The liver receives a dual blood supply from the arterial blood to the liver, accounting for the remaining quarter of its blood flow. Oxygen is provided from both sources; approximately half of the liver's oxygen demand is met by the hepatic portal vein, and half is met by the hepatic arteries.[32]
Blood flows through the liver sinusoids and empties into the central vein of each lobule. The central veins coalesce into hepatic veins, which leave the liver and drain into the inferior vena cava.[20]

Blood supply

The various functions of the liver are carried out by the liver cells or liver dialysis, an experimental treatment for liver failure.

Physiology

At birth the liver comprises roughly 4% of body weight and is at average 120g. Over the course of development, it will increase to 1,4–1,6 kg but will only take up 2.5–3.5% of body weight.[31]

During childhood

After birth, the umbilical vein and ductus venosus are completely obliterated in two to five days; the former becomes the ligamentum teres and the latter becomes the ligamentum venosum. In the disease state of cirrhosis and portal hypertension, the umbilical vein can open up again.

In the fetus, the liver develops throughout normal gestation, and does not perform the normal filtration of the infant liver. The liver does not perform digestive processes because the fetus does not consume meals directly, but receives nourishment from the mother via the placenta. The fetal liver releases some blood stem cells that migrate to the fetal thymus, so initially the lymphocytes, called T-cells, are created from fetal liver stem cells. Once the fetus is delivered, the formation of blood stem cells in infants shifts to the red bone marrow.

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.

Fetal blood supply

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 left umbilical vein becomes the ductus venosus and the right vitelline vein becomes the portal vein. The expanding liver bud is colonized by hematopoietic cells. The bipotential hepatoblasts begin differentiating into biliary 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 sinudoidal 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 abundant glycogen 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.[29]

human embryogenesis. The origins of the liver lie in both the ventral portion of the foregut endoderm (endoderm being one of the 3 embryonic germ layers) and the constituents of the adjacent septum transversum mesenchyme. In the human embryo, the hepatic 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 the drainage duct of the liver, and a branch from this duct produces the gallbladder.[28] Besides signals from the septum transversum mesenchyme, fibroblast growth factor from the developing heart also contributes to hepatic competence, along with retinoic acid emanating from the lateral plate mesoderm. The hepatic endodermal cells undergo a morphological transition from columnar to pseudostratified resulting in thickening into the early liver bud. Their expansion forms a population of the bipotential hepatoblasts.[29] Hepatic stellate cells are derived from mesenchyme.[30]

Development

  • unit V is the most medial and inferior
  • unit VI is located more posteriorly
  • unit VII is located obove unit VI
  • unit VIII sits above unit V in the superio-medial position

Units V to VIII make up the right hemiliver:[26]

  • units II and III lie lateral to the falciform ligament with II superior to the portal venous supply and III inferior
  • unit IV lies medial to the falciform ligament and is subdivided into IVa (superior) and IVb (inferior)

The remainder of the units (II to VIII) are numbered in a clockwise fashion:[26]

  • Unit I is the caudate lobe and is situated posterior l and it may receive its supply from both the right and the left branches of portal vent. It contains one or more hepatic veins which drain directly into the IVC.[23]

The classification system uses the vascular supply in the liver to separate the functional units (numbered I to VIII):

The fissure for the [23]

Couinaud classification system

The central area or hilum, known as the porta hepatis is where the common bile duct, hepatic portal vein, and the hepatic artery proper enter the liver. 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 the inferior 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 an anterior and posterior segment by the right hepatic vein. The left lobe is divided into the medial and lateral segments by the left hepatic vein.

Functional anatomy

Histology, the study of microscopic anatomy, shows two major types of liver cell: parenchymal cells and non-parenchymal cells. 70–85% of the liver volume is occupied by parenchymal hepatocytes. Non-parenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume.[21] The liver sinusoids are lined with two types of cell, sinusoidal endothelial cells, and phagocytic Kupffer cells.[22] Hepatic stellate cells are non-parenchymal cells found in the space of Disse, between a sinusoid and a hepatocyte.[21] Additionally, intrahepatic lymphocytes are often present in the sinusoidal lumen.[21]

Microscopically, each liver lobe is seen to be made up of hepatic lobules. The lobules are roughly hexagonal, and consist of plates of hepatocytes radiating from a central vein.portal triad, which can be found running along each of the lobule's corners. The portal triad, misleadingly named, consists of five structures: a branch of the hepatic artery, a branch of the hepatic portal vein, and a bile duct, as well as lymphatic vessels and a branch of the vagus nerve.[20] Between the hepatocyte plates are liver sinusoids, which are enlarged capillaries through which blood from the hepatic portal vein and hepatic artery enters via the portal triads, then drains to the central vein.

Types of capillaries–sinusoid on right
Microscopic anatomy of the liver
Cells, ducts and blood vessels

Microscopic anatomy

The inferior surface of the left lobe of the liver presents behind and to the left the gastric impression.[19] This is moulded over the upper front surface of the stomach, and to the right of this is a rounded eminence, the tuber omentale, which fits into the concavity of the lesser curvature of the stomach and lies in front of the anterior layer of the lesser omentum.

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.[19]

The suprarenal impression is a small triangular depressed area on the liver. It is located close to the right of the fossa 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.[19]

There are several impressions on the surface of the liver which 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 the hepatic flexure and the one behind is a deeper renal impression accommodating part of the right kidney and part of the suprarenal gland.[18]

Impressions of the liver

Impressions

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.[16]

These peritoneal 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.[17] The falciform ligament functions to attach the liver to the posterior portion of the anterior body wall.

[17].left triangular ligaments and right triangular ligament and the falciform ligament folds back on itself to form the peritoneum This surface covers the convex shape of the two lobes where it accommodates the shape of the diaphragm. The [16], apart from a large triangular diaphragmatic surface On the

Surfaces

Other anatomical landmarks exist, such as the ligamentum venosum and the round ligament of the liver (ligamentum teres), which further divide the left side of the liver in two sections. An important anatomical landmark, the porta hepatis, also known as the transverse fissure of the liver, divides this left portion into four segments, which can be numbered starting at the caudate lobe as I in an anticlockwise manner. From this visceral view, seven segments can be seen, because the eighth segment is only visible in the parietal view.[15]

The falciform ligament, visible on the front of the liver, divides the liver into a left lobe and a much larger right lobe. From the visceral surface, 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 the vena cava and all the way forward to divide the liver and gallbladder into two halves.[13] This line is called Cantlie's line.[14]

Gross anatomy traditionally divided the liver into two portions– a right and a left lobe, as viewed from the front (diaphragmatic) surface; but the underside (the visceral surface) shows it to be divided into four lobes and includes the caudate and quadrate lobes.[12]

Visceral surface showing four lobes and the impressions
The upper surface of the liver showing two lobes

Lobes

Gross anatomy

Lobules are the functional units of the liver. Each lobule is made up of millions of hepatic cells (hepatocytes) which are the basic metabolic cells. The lobules are held together by fine areolar tissue which extends into the structure of the liver, by accompanying the vessels (veins and arteries) ducts and nerves through the hepatic portal, as a fibrous capsule called Glisson's capsule.[11] The whole surface of the liver is covered in a serous coat derived from peritoneum and this has an inner fibrous coat (Glisson's capsule) to which it is firmly adhered. The fibrous coat is of areolar tissue and follows the vessels and ducts to support them.

The liver is connected to two large blood vessels, the hepatic artery and the portal vein. The hepatic artery carries oxygen-rich blood from the aorta, whereas the portal vein carries blood rich in digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas.[9] These blood vessels subdivide into small capillaries known as liver sinusoids, which then lead to a lobule.

The liver is a reddish brown wedge-shaped organ with four gland in the human body. Located in the right upper quadrant of the abdominal cavity, it rests just below the diaphragm, to the right of the stomach and overlies the gallbladder.[4]

Structure

Contents

  • Structure 1
    • Gross anatomy 1.1
      • Lobes 1.1.1
      • Surfaces 1.1.2
      • Impressions 1.1.3
    • Microscopic anatomy 1.2
    • Functional anatomy 1.3
    • Couinaud classification system 1.4
  • Development 2
    • Fetal blood supply 2.1
    • During childhood 2.2
  • Physiology 3
    • Blood supply 3.1
    • Biliary flow 3.2
    • Synthesis 3.3
    • Breakdown 3.4
    • Other functions 3.5
    • Relation to medicine and pharmacology 3.6
  • Clinical significance 4
    • Disease 4.1
    • Symptoms 4.2
    • Diagnosis 4.3
    • Biopsy / scan 4.4
    • Liver regeneration 4.5
    • Liver transplantation 4.6
  • Society and culture 5
    • Food 5.1
  • Other animals 6
  • Additional images 7
  • See also 8
  • References 9
  • Sources 10
  • External links 11

There is currently no way to compensate for the absence of liver function in the long term, although liver dialysis techniques can be used in the short term.[9] Liver transplantation is the only option for complete liver failure.

Terminology related to the liver often starts in hepar- or hepat- from the Greek word for liver, hēpar (ἧπαρ, root hepat-, ἡπατ-).[7][8]

[6]