liver

Dictionary: liv·er1   (lĭv'ər)

Also from Answers.com... Cancer Treatments Learn about current and promising cancer treatments.

(Click to enlarge)

liver1

A. liver B. hepatic vein C. hepatic artery D. portal vein E. common bile duct F. stomach G. cystic duct H. gallbladder (Carlyn Iverson)

1. Anatomy. A large, reddish-brown, glandular vertebrate organ located in the upper right portion of the abdominal cavity that secretes bile and is active in the formation of certain blood proteins and in the metabolism of carbohydrates, fats, and proteins.
2. An organ in invertebrates that is similar to the vertebrate liver.
3. The bile-secreting organ of an animal, used as food.
4. A dark reddish brown.

1. Made of or flavored with liver: liver pâté; liver sandwiches.
2. Of a dark reddish brown.

[Middle English, from Old English lifer.]

One who lives in a specified manner: a high liver.

A large gland found in all vertebrates. It consists of a continuous parenchymal mass arranged to form a system of walls through which venous blood emanating from the gut must pass. This strategic localization between nutrient-laden capillary beds and the general circulation is associated with hepatic regulation of metabolite levels in the blood through storage and mobilization mechanisms controlled by liver enzymes.

Function

The large size of the liver is matched by its functional complexity and involvement in a diverse array of regulatory mechanisms. The liver plays a key role in assuring carbohydrate homeostasis (dynamic steady-state conditions) by removing simple sugars from the general circulation after ingestion of food and storing them as glycogen. In the intervals between ingestion of food, liver glycogen is broken down. This process tends to maintain blood sugar levels between 80 and 100 mg per 100 ml of blood. Under conditions of prolonged fast, where glycogen stores are exhausted, the liver is capable of converting noncarbohydrate metabolites such as amino acids and fats into glucose to maintain blood sugar levels. The complex steps involved in maintaining carbohydrate metabolism are subject to endocrine control, with the liver serving as a particularly sensitive target organ of hormone regulators such as insulin. See also Carbohydrate metabolism; Glucose; Glycogen; Insulin.

The liver is key in the interconversion of many metabolites. It is a major site of production of fatty acids, triglycerides, phospholipids, ketone bodies, and cholesterol. Steroid hormones are degraded in the liver. See also Cholesterol; Ketone; Lipid; Steroid.

The liver is the sole source of such necessary constituents of the blood as fibrinogen, serum albumin, and cholinesterase. In the embryonic stage of most vertebrates the liver serves as the major manufacturing site of erythrocytes, a process known as erythropoiesis. The liver also removes toxins from the systemic circulation and degrades them, as well as excess hormones. Particulate material may be removed through a phagocytic action of specialized cells (Kupffer cells) lining the lumen of the hepatic “capillary spaces,” or sinusoids. In addition to the products which the liver delivers directly to the general circulation (endocrine function), it secretes bile through a duct system which, involving the gallbladder as a storage chamber, eventually passes into the duodenum (exocrine function). Bile functions as an emulsifier of fats to facilitate their digestion by fat-splitting lipases, and may also activate the lipase directly. See also Gallbladder.

Anatomy

The human liver is a massive wedge-shaped organ divided into a large right lobe and a smaller left lobe. Its anterior surface underlies the diaphragm. The upper portion of the liver is partially covered ventrally by the lungs, whereas the lower portion overhangs the stomach and intestine. The entire liver is covered by Glisson's capsule, an adherent membranous sheet of collagenous and elastic fibers.

Venous blood from the intestine, and to a lesser extent from spleen and stomach, converges upon a short broad vessel, called the hepatic portal vein, which enters the liver through a depression in the dorsocaudal surface termed the porta hepatis. There the hepatic portal vein divides into a short right branch and a longer left branch. These vessels then ramify into the small branches which actually penetrate the functional parenchymal mass as the inner tubes of the portal canals.

The hepatic artery also enters at the porta hepatis and ramifies into smaller branches, which flank the portal venules within the portal canals. The branches of the portal vein and hepatic artery then empty into sinusoids, which are major regions of hepatovascular exchange. They communicate with small branches of the hepatic veins and, through the hepatic vein, the blood is returned to the heart by way of the vena cava.

The tiny bile canaliculi, which lie between grooves in adjacent parenchymal cells, communicate with tiny intralobular bile ducts. These intralobular bile ducts empty into increasingly larger interlobular bile ducts which lie within the portal canals and make up the third element of the so-called portal triad.

The concept that certain organs, such as the liver, brain, and heart, enjoyed a higher status than others was first proposed and accepted in the earliest days of medical thought. Indeed, the Babylonians considered the liver to be the seat and mirror of the soul and, as a consequence, this organ became the focus of divination ceremonies, in which the livers of sacrificial animals were carefully inspected by priests for signs of damage prior to being offered as gifts to the gods. The observed condition of the excised organ was taken to portend the future and, especially, to predict whether or not conditions were favourable for battle. Prayers at these solemn ceremonies were even inscribed on tablets shaped like livers, many of which were subsequently recovered from countries bordering the Mediterranean, far beyond the limits of Babylon.

It was the Greeks who first abandoned superstition in favour of an approach to the understanding of the body based on anatomy and physiology, and it is in the writings of Aristotle where the first attempts to describe animals' livers based on dissection are to be found. However, because of his great influence, Aristotle also helped to perpetuate the notion that human emotions were controlled by four cardinal ‘humours’, two of which — yellow bile and black bile — emanated from the liver. These liver-derived humours were held to be responsible for choleric and melancholic moods, respectively. The coming of the Renaissance age and the scientific revolution put paid to the notion that body organs exist under a hierarchical structure, and the fallacy of the four humour theory was exposed. Rather than denigrate the importance of the liver, however, advances in anatomy and physiology over the years have instead highlighted how important the liver is for normal bodily function.

Anatomy

The liver — the largest internal organ of the body — weighs approximately 1200-1500 g or, on average, one fiftieth of the total adult body weight. It is relatively larger in the infant, comprising approximately one twentieth of the birth weight. Situated in the upper abdomen, beneath the right rib cage and separated from the chest cavity by the diaphragm, the upper border of the liver lies approximately at the level of the nipples. Largely composed of cells known as hepatocytes, which are involved in a multiplicity of synthetic, metabolic, and biotransformatory processes, the liver is unusual in that it is perfused with a dual blood supply. The portal vein carries blood from the spleen and intestines and accounts for approximately 75% of the liver's blood supply, whilst the hepatic artery, which arises indirectly from the aorta, delivers the remaining 25%. Owing to the higher oxygen content of arterial blood, oxygen delivery to the liver is about equally derived from the portal vein and hepatic artery. There is continuous exchange between hepatocytes and the perfusing blood, as various chemicals delivered to the liver from elsewhere in the body by the bloodstream are taken up for degradation and further metabolism, whilst others produced by the liver are, conversely, exported from it. An alternative pathway for dispersal of substances produced in the liver is through secretion into an extensive system of minute canals which eventually form the bile ducts draining into the intestine.

Functions

A multitude of functions of the liver have already been well described, and there are many more of which relatively little is currently known. One of the most important — and easily recognizable when deranged — is the metabolism of the pigment, bilirubin, a chemical predominantly derived from products released during the normal destruction of senescent red blood cells. Yellow discolouration of the eyes and the skin (jaundice) ensues when overproduction of bilirubin exceeds the liver's metabolic capability or when hepatic metabolism of bilirubin is impaired.

Another important function of the liver is the synthesis of bile acids, which are then transported via the bile ducts into the intestine to aid in the digestion of fatty foods and the absorption of certain fat-soluble vitamins, particularly vitamins A, D, E, and K. These vitamins are important for night vision, building strong bones and maintaining normal skin integrity and nerve function, as well as for ensuring normal clotting of the blood. Cholesterol and phospholipids — each of which are important constituents of all cell membranes — and triglycerides — which contain a variety of fatty acids and act as an important storage form of energy — are also synthesized in the liver.

The liver is the main site for the metabolism of a vast range of chemical substances produced as a result of the digestion of food in the intestine. For example, ammonia, produced by digestive processes and by the action of intestinal bacteria on dietary protein, is absorbed into the bloodstream. Ammonia in high quantities interferes with normal brain function — an eventuality prevented by its conversion in the liver to the non-toxic compound, urea. Many other amino acids — the building blocks for protein synthesis — which are derived from the diet and from tissue degradation, are also carried by the bloodstream to the liver. Once there they are metabolized to various proteins with a wide range of important functions, including the prevention of fluid accumulation within the tissues and the binding of potentially toxic compounds, such as copper and iron. The liver has a remarkable capacity for such tasks. Under experimental conditions, at least 85% of the liver must be removed or damaged before protein synthesis is substantially impaired.

The liver also plays a key role in carbohydrate metabolism, resulting in the synthesis of glucose for energy and the generation of body heat. Excess quantities are stored as glycogen, which can subsequently be mobilized as required. There is also a complex system of enzymes which function to convert a myriad of drugs and other toxins, including alcohol, to non-toxic metabolites. The activity of these enzyme systems may be modified by various factors. For example, the capacity of the liver to metabolize alcohol is increased by a steady high level of drinking but markedly impaired by alcohol binges.

Another important function of the liver is performed by so-called ‘phagocytic’ Kupffer cells, which line the vascular networks. These cells play an important role in the prevention of systemic infection and inflammation, by extracting and destroying particulate matter, such as pro-inflammatory bacterial cell walls, as it passes through the liver via the bloodstream.

Advancing age has various effects on the liver. Liver weight and blood supply are each reduced in the healthy elderly subject, but most functions of the liver are well maintained. However, the metabolism of certain drugs may be impaired and this may be at least partly responsible for the increased sensitivity to drugs and possibly also for the high prevalence of adverse drug reactions in this group, especially when multiple drugs are ingested.

Disorders

Any or all of the various liver functions outlined above may be disturbed to varying extents in acute liver disorders, such as acute viral hepatitis. Most such episodes resolve spontaneously without sequelae, owing to the great capacity of liver cells to regenerate. Chronic liver disorders, such as cirrhosis, in which fibrosis and nodule formation occur as the common end result of many disorders causing destruction of hepatocytes, may have more serious consequences. Over the past thirty-five years, liver transplantation has grown from a largely experimental procedure to become a well-established treatment option, not only for that subgroup of patients who have advanced cirrhosis and an otherwise poor prognosis, but also for those patients with the less commonly encountered acute liver failure or liver-based metabolic disorders. Over 650 liver transplantations are performed annually in the UK alone, with over 70% of recipients making a full recovery.

It is clear that, even though ancient cultures were mistaken as to the functions of the liver, they were certainly correct in attaching so much importance to it. Indeed, the maxim that ‘life depends on the liver’ is as pertinent today as ever before.

— Stephen M. Riordan, Roger Williams

See alimentary system. See also bile; gall bladder; jaundice.

Usually from calf, pig, ox, lamb, or poultry; a 150-g portion (fried or stewed) is an exceptionally rich source of iron and vitamins A, D, B₂, B₆, and B₁₂; a rich source of protein, zinc, copper, selenium, niacin, and vitamin B₁; also, unusually for meat, a good source of vitamin C; contains 10 g of fat, of which one-third is saturated; supplies 300-380 kcal (1250-1600 kJ). The vitamin A content of liver is high enough for it to pose a possible hazard to unborn children, and pregnant women have been advised not to eat liver. See vitamin A toxicity. Fish liver is a particularly rich source of vitamins A and D, and fish liver oils (especially cod and halibut) are used as sources of these vitamins as nutritional supplements.

The largest and one of the most important organs, liver has immense nutritional value . . . Providing, that is, that it comes from a fairly young animal. Because liver acts as a clearinghouse for substances that enter the body, it tends to store and absorb unwanted chemicals, medicines and hormones that an animal might be fed. Naturally, the older the animal the greater the accumulation of these unwanted substances, which, according to some, offset liver's nutritional value. For this very reason, many people choose the more expensive calf's liver over beef liver. There are several ways to distinguish between the two. The color of beef liver is reddish-brown, compared to the paler pinkish-brown of calf's liver. Liver from a mature animal also has a stronger odor and flavor than that from a youngster. Additionally, it will be less tender. Besides beef and calf's, the most common animal livers used in cookery are lamb, pork, poultry and goose, the latter used mainly to produce foie gras. The strongest-flavored and least tender of the livers is pork, while poultry livers are the most mild and tender of the lot. All livers are usually available fresh-beef and chicken livers may also be purchased frozen (though the quality of frozen liver is considerably lower than that of fresh). While chicken livers are sold whole, most of those from other animals are marketed sliced. Look for liver that has a bright color and moist (not slick) surface. It should have a fresh, clean smell. Refrigerate loosely wrapped for no more than a day. Liver can be prepared in a variety of ways though quick sautéing is the most popular. It toughens quickly with overcooking. Liver is rich in iron, protein and vitamin A. See also variety meats.

The largest gland of the body and one of the body’s most complex organs. More than 500 functions of the liver have been identified. It is divided into four lobes, contains as many as 100,000 lobules, and is served by two distinct blood supplies. The hepatic artery conveys oxygenated blood to the liver, and the hepatic portal vein conveys nutrient-filled blood from the stomach and the intestines. At any given moment the liver holds about one pint of blood or approximately 13% of the total blood supply of the body.

For more information on liver, visit Britannica.com.

One of the largest organs of the body. The liver has many functions including detoxication, glucose metabolism, urea formation, bile production, storage of fat-soluble vitamins and some minerals (e.g. iron), and the manufacture of the clotting agents, prothrombin and fibrinogen. The liver also plays an important role in thermoregulation; changes in metabolism of its cells varies the heat produced by the body.

A large organ, located on the right side of the abdomen and protected by the lower rib cage, that produces bile and blood proteins, stores vitamins for later release into the bloodstream, removes toxins (including alcohol) from the blood, breaks down old red blood cells, and helps maintain levels of blood sugar in the body.

1. the large, dark-red organ located in the cranial portion of the abdomen, just behind the diaphragm. Its functions include storage and filtration of blood; secretion of bile; detoxication of noxious substances; conversion of sugars into glycogen; synthesis and breakdown of fats and temporary storage of fatty acids; and synthesis of serum proteins such as certain of the alpha and beta globulins, albumin, which helps regulate blood volume, and fibrinogen and prothrombin, which are essential blood clotting factors. See also hepatic.
2. a rich red-brown coat color in dogs that resembles the color of the organ.

• l. abscess — causes toxemia, possibly local signs of subacute abdominal pain, pain on percussion or palpation over the liver if peritoneal inflammation is present, when there may also be a positive paracentesis sample.
• l. damage — damage to the liver parenchyma causing some degree of hepatic insufficiency.
• l. displacement — may be because of a diaphragmatic hernia with the liver protruding into the thoracic cavity. Usually accompanied by dyspnea.
• l. dullness — dullness on percussion over the right rib cage, used to help in defining the size of the liver which must be grossly enlarged to register a recognizable change.
• l. dysfunction — the result of diffuse damage to the liver, e.g. in hepatitis. There may be clinical signs including photosensitization, jaundice, hepatic encephalopathy in the form of the dummy syndrome, dullness and anorexia, or there may be subclinical disease detectable by clinicopathological tests, e.g. hypoglycemia, hypoproteinemia, hyperammonemia. All of the functions of the liver will be affected at the one time.
• l. enlargement — may be caused by neoplasia, congestion (as with heart failure), and infiltration by fat or inflammatory cells.
• l. enzyme — when there is acute, diffuse damage to the liver some of its enzymes are liberated into the blood, where they can be measured. An indication of the severity of the damage can be obtained in this way. Different enzymes are used in each animal species.
• l. failure — when liver function is inadequate to sustain life; the end-stage of liver dysfunction.
• fatty l. — one affected with fatty infiltration.
• fatty l. syndrome — see fat cow syndrome.
• l. fluke — fasciola hepatica.
• l. fluke disease — see hepatic fascioliasis.
• l. function — summation of the functions of the liver.
• l. function tests — biochemical tests capable of demonstrating that the liver's functions are, or are not, at full capacity. The sulfobromophthalein clearance test is the most commonly used in veterinary medicine.
• l. inflammation — see hepatitis.
• inherited l. insufficiency — occurs in several breeds of sheep and is characterized by the appearance of photosensitive dermatitis when the lambs begin to eat green feed. There is an accumulation of phylloerythrin in the blood and other biochemical indications of insufficiency, but the liver is histologically normal. Called also inherited photosensitization.
• l. injury — damage to the hepatic parenchyma, possibly by massive trauma, but usually by an hepatic toxin. A common cause of hepatic insufficiency.
• l. insufficiency — see liver dysfunction (above).
• l. lobe torsion — see liver torsion (below).
• l. melanosis — see hepatic lipofuscinosis.
• l. meridian points — acupuncture points along the liver meridian.
• l. necrobacillosis — a disease characterized by multiple liver abscesses, usually containing Fusobacterium necrophorum and resulting from infection from a chemical rumenitis which originated from carbohydrate engorgement and lactic acid rumenitis.
• l. protectant — substance used for the treatment of liver failure. The important ones are choline, methionine, betaine, lecithin, vitamin B₁₂, selenium-vitamin E, essential phospholipids, glucose, fructose, vitamins E and B complex, and glucuronic acid.
• l. rot — see acute hepatic fascioliasis.
• l. rupture — is usually the result of severe trauma to the abdomen. In most cases there is massive hemorrhage into the peritoneal cavity, acute hemorrhagic anemia and mucosal pallor. Abdominal paracentesis recovers whole blood.
• l. torsion — is usually restricted to a single lobe. Causes severe abdominal pain and severe vomiting.

n.

A large red organ thoughtfully provided by nature to be bilious with. The sentiments and emotions which every literary anatomist now knows to haunt the heart were anciently believed to infest the liver; and even Gascoygne, speaking of the emotional side of human nature, calls it "our hepaticall parte." It was at one time considered the seat of life; hence its name -- liver, the thing we live with. The liver is heaven's best gift to the goose; without it that bird would be unable to supply us with the Strasbourg pate.

Dreaming about liver can be a dream about one's health: either we need a diet change or perhaps we are hurting our liver with alcohol or prescription drugs. Also note the expression "lily-livered," which refers to cowardice.

This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations where appropriate. (June 2008)

Liver
Liver of a sheep: (1) right lobe, (2) left lobe, (3) caudate lobe, (4) quadrate lobe, (5) hepatic artery and portal vein, (6) hepatic lymph nodes, (7) gall bladder.
Anterior view of the position of the liver (red) in the human abdomen.
Latin	jecur, iecur
Gray's	subject #250 1188
Vein	hepatic vein, hepatic portal vein
Nerve	celiac ganglia, vagus[1]
Precursor	foregut
MeSH	Liver

The liver is a vital organ present in vertebrates and some other animals; it has a wide range of functions, a few of which are detoxification, protein synthesis, and production of biochemicals necessary for digestion. The liver is necessary for survival; there is currently no way to compensate for the absence of liver function.

The liver plays a major role in metabolism and has a number of functions in the body, including glycogen storage, decomposition of red blood cells, plasma protein synthesis, hormone production, and detoxification. It lies below the diaphragm in the thoracic region of the abdomen. It produces bile, an alkaline compound which aids in digestion, via the emulsification of lipids. It also performs and regulates a wide variety of high-volume biochemical reactions requiring highly specialized tissues, including the synthesis and breakdown of small and complex molecules, many of which are necessary for normal vital functions.^[2]

Medical terms related to the liver often start in hepato- or hepatic from the Greek word for liver, hēpar (ήπαρ).^[3]

Contents 1 Anatomy 1.1 Blood flow 1.2 Biliary flow 1.3 Surface anatomy 1.3.1 Peritoneal ligaments 1.3.2 Lobes 1.4 Functional anatomy 2 Physiology 2.1 Synthesis 2.2 Breakdown 2.3 Other functions 3 Diseases of the liver 4 Regeneration 5 Liver transplantation 6 Development 6.1 Fetal blood supply 7 As food 7.1 Poisoning 8 Cultural allusions 9 Gallery 10 See also 11 References 12 Further reading 13 External links

Anatomy

An adult human liver normally weighs between 1.4-1.6 kg (3.1-3.5 lb),^[4] and is a soft, pinkish-brown, triangular organ. Averaging about the size of an American football in adults, it is both the largest internal organ and the largest gland in the human body (not considering the skin).

It is located in the right upper quadrant of the abdominal cavity, resting just below the diaphragm. The liver lies to the right of the stomach and overlies the gallbladder.

Blood flow

The liver receives a dual blood supply consisting of the hepatic portal vein and hepatic arteries. Supplying approximately 75% of the liver's blood supply, the hepatic portal vein carries venous blood drained from the spleen, gastrointestinal tract, and its associated organs. The hepatic arteries supply arterial blood to the liver, accounting for the remainder 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.^[5]
Blood flows through the sinusoids and empties into the central vein of each lobule. The central veins coalesce into hepatic veins, which leave the liver and empty into the inferior vena cava. it occupies most of the right+ hypochondriac region,epigastric region and left hypochondriac region

Biliary flow

The bile produced in the liver is collected in bile canaliculi, which merge to form bile ducts. Within the liver, these ducts are called intrahepatic bile ducts, and once they exit the liver they are considered extrahepatic. The extrahepatic ducts eventually drain into the right and left hepatic ducts, which in turn 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. The term biliary tree is derived from the arboreal branches of the bile ducts. The intrahepatic bile ducts form the most distant branches of this tree.

Bile can either drain directly into the duodenum via the common bile duct or be temporarily stored in the gallbladder via the cystic duct. The common bile duct and the pancreatic duct enter the duodenum together at the ampulla of Vater.

The Biliary Tree.

Surface anatomy

Peritoneal ligaments

Apart from a patch where it connects to the diaphragm (the so-called "bare area"), the liver is covered entirely by visceral peritoneum, a thin, double-layered membrane that reduces friction against other organs. The peritoneum folds back on itself to form the falciform ligament and the right and left triangular ligaments.

These "ligaments" are in no way related to the true anatomic ligaments in joints, and have essentially no functional importance, but they are easily recognizable surface landmarks.

Lobes

Traditional gross anatomy divided the liver into four lobes based on surface features. The falciform ligament is visible on the front (anterior side) of the liver. This divides the liver into a left anatomical lobe, and a right anatomical lobe.

If the liver flipped over, to look at it from behind (the visceral surface), there are two additional lobes between the right and left. These are the caudate lobe (the more superior), and below this the quadrate lobe.

From behind, the lobes are divided up by the ligamentum venosum and ligamentum teres (anything left of these is the left lobe), the transverse fissure (or porta hepatis) divides the caudate from the quadrate lobe, and the right sagittal fossa, which the inferior vena cava runs over, separates these two lobes from the right lobe.

Each of the lobes is made up of lobules; a vein goes from the centre of each lobule which then joins to the hepatic vein to carry blood out from the liver.

On the surface of the lobules there are ducts, veins and arteries that carry fluids to and from them.

Functional anatomy

Correspondence between anatomic lobes and Corinaud segments

Segment*	Couinaud segments
Caudate	1
Lateral	2, 3
Medial	4a, 4b
Right	5, 6, 7, 8
* or lobe in the case of the caudate lobe. Each number in the list corresponds to one in the table. Caudate Superior subsegment of the lateral segment Inferior subsegment of the lateral segment Superior subsegment of the medial segment Inferior subsegment of the medial segment Inferior subsegment of the anterior segment Inferior subsegment of the posterior segment Superior subsegment of the posterior segment Superior subsegment of the anterior segment

The central area where the common bile duct, hepatic portal vein, and hepatic artery proper enter is the hilum or "porta hepatis". The duct, vein, and artery divide into left and right branches, and the portions of the liver supplied by these branches constitute the functional left and right lobes.

The functional lobes are separated by an imaginary plane 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. The fissure for the ligamentum teres also separates the medial and lateral segments. The medial segment is also called the quadrate lobe. In the widely used Couinaud (or "French") 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. The caudate lobe is a separate structure which receives blood flow from both the right- and left-sided vascular branches.^[6][7]

Physiology

The various functions of the liver are carried out by the liver cells or hepatocytes. Currently, there is no artificial organ or device capable of emulating all the functions of the liver. Some functions can be emulated by liver dialysis, an experimental treatment for liver failure.

Synthesis

Further information: Proteins produced and secreted by the liver

• A large part of amino acid synthesis
• The liver performs several roles in carbohydrate metabolism:
  • Gluconeogenesis (the synthesis of glucose from certain amino acids, lactate or glycerol)
  • Glycogenolysis (the breakdown of glycogen into glucose)
  • Glycogenesis (the formation of glycogen from glucose)(muscle tissues can also do this)
• The liver is responsible for the mainstay of protein metabolism, synthesis as well as degradation
• The liver also performs several roles in lipid metabolism:
  • Cholesterol synthesis
  • Lipogenesis, the production of triglycerides (fats).
• The liver produces coagulation factors I (fibrinogen), II (prothrombin), V, VII, 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 produces and excretes bile (a greenish liquid) required for emulsifying fats. Some of the bile drains directly into the duodenum, and some is stored in the gallbladder.
• The liver also produces 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 is a major site of thrombopoietin production. Thrombopoietin is a glycoprotein hormone that regulates the production of platelets by the bone marrow.

Breakdown

• The breakdown of insulin and other hormones
• The liver breaks down hemoglobin, creating metabolites that are added to bile as pigment (bilirubin and biliverdin).
• The liver breaks down toxic substances 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 converts ammonia to urea.

Other functions

• The liver stores a multitude of substances, including glucose (in the form of glycogen), vitamin A (1–2 years' supply), vitamin D (1–4 months' supply), vitamin B12, iron, and copper.
• The liver is responsible for immunological effects- the reticuloendothelial system of the liver contains many immunologically active cells, acting as a 'sieve' for antigens carried to it via the portal system.
• The liver produces albumin, the major osmolar component of blood serum.
• The liver synthesizes angiotensinogen, a hormone that is responsible for raising the blood pressure when activated by renin, a kidney enzyme that is released when the juxtaglomerular apparatus senses low blood pressure.

Diseases of the liver

Main article: Liver disease

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.

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.

Liver diseases may be diagnosed by liver function tests, for example, by production of acute phase proteins.

Regeneration

The liver is the only internal human organ capable of natural regeneration of lost tissue; as little as 25% of a liver can regenerate into a whole liver. A human liver is known to grow back in no less than 8 years, due to hyptochronatin cells in the remaining liver.^{[citation needed]}

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.^[8] There is also some evidence of bipotential stem cells, called ovalocytes or hepatic oval cells, which are thought to reside in the canals of Hering. These cells can differentiate into either hepatocytes or cholangiocytes, the latter being the cells that line the bile ducts.

Liver transplantation

Main article: Liver transplantation

Human liver transplants were first performed by Thomas Starzl in the United States and Roy Calne in Cambridge, England in 1963 and 1965 respectively.

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.

Liver allografts for transplant usually come from non-living 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% 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% 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 2 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.^[9] The risk of postoperative complications (and death) is far greater in right sided hepatectomy than left sided operations.

With the recent advances of non-invasive 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 multi-detector 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.

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.

Development

Fetal blood supply

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 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.

After birth, the umbilical vein and ductus venosus are completely obliterated two to five days postpartum; 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.

As food

Liver sandwiches in Alexandria, Egypt.

Fardel, a pork liver product from Aragon.

Cornmeal mush with chicken liver, Cuisine of Moldova.

Fegato alla veneziana; liver venetian style.

Pork liver Nutritional value per 100 g (3.5 oz)
Energy 130 kcal   560 kJ
Carbohydrates     2.5 g Fat 3.7 g Protein 21 g Vitamin A equiv.  6500 μg  722% Riboflavin (Vit. B2)  3 mg   200% Niacin (Vit. B3)  15 mg   100% Vitamin B6  0.7 mg 54% Folate (Vit. B9)  212 μg  53% Vitamin B12  26 μg   1083% Iron  23 mg 184% Sodium  87 mg 4%
Calf liver and chicken liver are comparable. Percentages are relative to US recommendations for adults. Source: USDA Nutrient database

Mammal, bird and fish livers are commonly eaten as food by humans. Livers from calf, chicken, and goose are widely available in supermarkets.

Liver can be baked, boiled, broiled, fried or eaten raw (liver sashimi). The most widespread liver dish is liver and onions. In many preparations pieces of liver are combined with pieces of meat or kidneys, like in mixed grill or in Meurav Yerushalmi. Liver is also often made into spreads; well-known examples include liver pâté, foie gras, chopped liver, and leverpostej. Liver sausages such as Braunschweiger and liverwurst are also a valued meal; liver sausages may also be used as spreads.

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.^[10]

Poisoning

Very high doses of Vitamin A have the potential to be toxic and can cause hypervitaminosis A, a dangerous disorder. Russian sailor Alexander Konrad, who accompanied explorer Valerian Albanov in a tragic ordeal over the arctic ice in 1912 wrote about the awful effects of consuming polar bear liver.^[11] Also, in 1913, Antarctic explorers Douglas Mawson and Xavier Mertz were both poisoned, the latter fatally, from eating husky liver. In the US, the USDA specifies 3000 μg per day as a tolerable upper limit, which amounts to about 50 g of raw pork liver. ^[12]

Poisoning will less likely result from consuming oil-based vitamin A products and liver than from consuming water-based and solid preparations.^[13]

Inuit will not eat the liver of polar bears (a polar bear's liver contains so much Vitamin A as to be poisonous to humans), or seals.^[14]

Cultural allusions

“	The liver has always been an important symbol in occult physiology. As the largest organ, the one containing the most blood, it was regarded as the darkest, least penetrable part of man's innards. Thus it was considered to contain the secret of fate and was used for fortunetelling. In Plato, and in later physiology, the liver represented the darkest passions, particularly the bloody, smoky ones of wrath, jealousy, and greed which drive men to action. Thus the liver meant the impulsive attachment to life itself.	”
—James Hillman[15]

In Greek mythology, Prometheus was punished by the gods for revealing fire to humans, by being chained to a rock where a vulture (or an eagle) 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 practised a type of divination called haruspicy, whereby they tried to obtain information from examining the livers of sheep and other animals.

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

In the Persian, Urdu, and Hindi languages, the liver (جگر or जिगर or jigar) refer to the liver in figurative speech to refer to courage and strong feelings, or "their best," e.g. "This Mecca has thrown to you the pieces of its liver!" ^[16]. 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.

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

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.

Gallery

Accessory digestive system.	Digestive organs.	The liver and the veins in connection with it, of a human embryo, twenty-four or twenty-five days old, as seen from the ventral surface.	Transverse section through the middle of the first lumbar vertebra, showing the relations of the pancreas.
Front of abdomen, showing surface markings for liver, stomach, and great intestine	Topography of thoracic and abdominal viscera.	Portal triad	View of the superior ("top") surface from Gray's Anatomy (1918)
View of the inferior ("bottom") surface from Gray's Anatomy (1918)	Human Liver taken from Autopsy

See also

Look up liver in Wiktionary, the free dictionary.

• Artificial liver
• Bile
• Bile canaliculus
• Hepatocyte
• Liver function tests
• Liver shot (martial arts strike)

References

1. ^ Physiology at MCG 6/6ch2/s6ch2_30
2. ^ 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. ISBN 0-13-981176-1. OCLC 32308337. 
3. ^ The Greek word "ήπαρ" was derived from hēpaomai (ηπάομαι): to mend, to repair, hence hēpar actually means "repairable", indicating that this organ can regenerate itself spontaneously in the case of lesion.
4. ^ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease. St. Louis, Mo: Elsevier Saunders. pp. 878. ISBN 0-7216-0187-1. 
5. ^ Benjamin L. Shneider; Sherman, Philip M. (2008). Pediatric Gastrointestinal Disease. Connecticut: PMPH-USA. pp. 751. ISBN 1-55009-364-9. 
6. ^ "Three-dimensional Anatomy of the Couinaud Liver Segments". http://dpi.radiology.uiowa.edu/nlm/app/livertoc/liver/liver.html. Retrieved on 2009-02-17. 
7. ^ "Prof. Dr. Holger Strunk - Homepage". http://www.uni-bonn.de/~umm705/quiz0403.htm. Retrieved on 2009-02-17. 
8. ^ Suzuki K, Tanaka M, Watanabe N, Saito S, Nonaka H, Miyajima A (July 2008). "p75 Neurotrophin receptor is a marker for precursors of stellate cells and portal fibroblasts in mouse fetal liver". Gastroenterology 135 (1): 270–281.e3. doi:10.1053/j.gastro.2008.03.075. PMID 18515089. http://linkinghub.elsevier.com/retrieve/pii/S0016-5085(08)00571-4. 
9. ^ Bramstedt K (2006). "Living liver donor mortality: where do we stand?". Am J Gastrointestinal 101 (4): 755–9. doi:10.1111/j.1572-0241.2006.00421.x. PMID 16494593. 
10. ^ Calvin W. Schwabe Unmentionable Cuisine (English)
11. ^ Valerian Albanov. In the Land of White Death. Appendix; A. Konrad's notes.
12. ^ A. Aggrawal, Death by Vitamin A
13. ^ Myhre et al., "Water-miscible, emulsified, and solid forms of retinol supplements are more toxic than oil-based preparations", Am. J. Clinical Nutrition, 78, 1152 (2003)
14. ^ Man's best friend? - Student BMJ
15. ^ Krishna, Gopi; Hillman, James (commentary) (1970). Kundalini – the evolutionary energy in man. London: Stuart & Watkins. pp. 77. SBN 7224 0115 9. http://www.scribd.com/doc/7577310/KUNDALINI-the-evolutionary-energy-in-man. 
16. ^ THE GREAT BATTLE OF BADAR (Yaum-e-Furqan)

Further reading

The following are standard medical textbooks:

• Eugene R. Schiff, Michael F. Sorrell, Willis C. Maddrey, eds. Schiff's diseases of the liver, 9th ed. Philadelphia : Lippincott, Williams & Wilkins, 2003. ISBN 0-7817-3007-4
• Sheila Sherlock, James Dooley. Diseases of the liver and biliary system, 11th ed. Oxford, UK ; Malden, MA : Blackwell Science. 2002. ISBN 0-632-05582-0
• David Zakim, Thomas D. Boyer. eds. Hepatology: a textbook of liver disease, 4th ed. Philadelphia: Saunders. 2003. ISBN 0-7216-9051-3

These are for the lay reader or patient:

• Sanjiv Chopra. The Liver Book: A Comprehensive Guide to Diagnosis, Treatment, and Recovery, Atria, 2002, ISBN 0-7434-0585-4
• Melissa Palmer. Dr. Melissa Palmer's Guide to Hepatitis and Liver Disease: What You Need to Know, Avery Publishing Group; Revised edition May 24, 2004, ISBN 1-58333-188-3. her webpage.
• Howard J. Worman. The Liver Disorders Sourcebook, McGraw-Hill, 1999, ISBN 0-7373-0090-6. his Columbia University web site, "Diseases of the liver"

External links

This article's external links may not follow Wikipedia's content policies or guidelines. Please improve this article by removing excessive or inappropriate external links.

Wikimedia Commons has media related to: Liver

Information

• UC Berkeley anatomy lecture on the liver
• Electron microscopic images of the liver (Dr. Jastrow's EM-atlas)
• Elevated liver enzymes information
• "It's Dangerous to Ignore Your Liver" by the American Liver Foundation
• "The Liver and its Diseases" — information at h2g2
• Autoimmune immune liver disease
• VIRTUAL Liver - online learning resource

v • d • e Anatomy of torso, digestive system: accessory digestive glands Liver by region: Left lobe (Caudate lobe, Quadrate lobe) • Right lobe • Transverse fissure of liver • Bare area of the liver by function: Fibrous capsule of Glisson • Hepatocyte • Space of Disse • Space of Mall • Kupffer cell • Liver sinusoid • Hepatic stellate cell • Hepatic lobule Biliary tract Bile ducts intrahepatic: Bile canaliculus • Canals of Hering • Interlobular bile ducts • Intrahepatic bile ducts • Left and Right hepatic ducts extrahepatic: Common hepatic duct • Cystic duct • Common bile duct Gallbladder by region: Body • Fundus • Neck Pancreas by region: Tail • Body • Neck • Head • Uncinate process by function: Islets of Langerhans • Exocrine pancreas ducts: Pancreatic duct • Accessory pancreatic duct Common Hepatopancreatic ampulla • Sphincter of Oddi

This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)

Dansk (Danish)
1.
n. - lever
adj. - lever-

2.
n. - en som bor et nærmere angivet sted, en som lever på en bestemt måde

Nederlands (Dutch)
lever, leverkleur, persoon die op bepaalde wijze leeft

Français (French)
1.
n. - (Culin, Méd) foie
adj. - de/relatif au foie

2.
n. - quelqu'un qui vit d'une certaine façon (bon vivant, noceur, etc)

Deutsch (German)
1.
n. - Leber
adj. - dunkles rotbraun

2.
n. - solider Mensch

Ελληνική (Greek)
n. - (ανατ.) ήπαρ (κν. συκώτι), έμβια οντότητα, άνθρωπος που ζει

Italiano (Italian)
fegato

Português (Portuguese)
n. - fígado (m) (Anat.), vivente (m) (f)

Русский (Russian)
печень, (живой) человек, обитатель

Español (Spanish)
1.
n. - hígado
adj. - de hígado

2.
n. - viviente, residente, morador

Svenska (Swedish)
n. - lever (anat. o. kok.), person som för ett ... liv, (isht. Am.) invånare

中文（简体）(Chinese (Simplified))
1. 肝脏, 肝, 肝脏的, 肝的

2. 过着...生活的人, 居住者, 居民

中文（繁體）(Chinese (Traditional))
1.
n. - 肝臟, 肝
adj. - 肝臟的, 肝的

2.
n. - 過著...生活的人, 居住者, 居民

한국어 (Korean)
1.
n. - 간 , 간장색 , 응결물
adj. - 간의 , 간장색의

2.
n. - 생활자, 주민

日本語 (Japanese)
n. - 肝臓, レバー, 生活をする人

العربيه (Arabic)
‏(الاسم) لبد, العائش بطريقه معينه, الساكن أو المقيم‏

עברית (Hebrew)
n. - ‮אדם החי בצורה מסוימת‬
adj. - ‮חי (בצורה מסוימת)‬
n. - ‮כבד‬

If you are unable to view some languages clearly, click here.

To select your translation preferences click here.