liver

(lĭv'ər)

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.]

(lĭv'ər)

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calf liver

An edible red variety meat from butchered animals, poultry, game and certain fish (cod, monkfish, skate). The liver of young animals is tastier and more tender; the most sought after is calf's liver. Lamb, heifer, poultry and rabbit livers are highly regarded for their tenderness and delicate flavor. Beef, sheep, pig and poultry livers have a stronger flavor and a pastier texture after cooking.

Buying

Choose: a liver that glistens, does not have a strong smell and is not sitting in a large quantity of liquid.
The color of liver varies from pinkish brown to reddish brown, depending on the particular animal and its age.

Preparing

Remove the fine membrane that covers the liver so that it keeps its shape during cooking, and remove the tubes. Soak beef and pig livers in milk for 1-2 hr in the fridge to soften their flavor. Dry well. Cut the liver into slices of equal size so that they cook evenly.

Serving Ideas

Liver is sautéed, grilled or broiled, pan-fried or marinated; it is accompanied by mushrooms, wine, cream or onions. Pig liver especially is used for charcuterie products (pâtés and terrines). 
Cod liver is often smoked.

Storing

Liver is highly perishable. 

In the fridge: 1-2 days.

In the freezer: 3-4 months.

Cooking

Liver should not be eaten rare; it is tastier if it is slightly pink in the middle.

Grilled, broiled or sautéed: tender liver 
(5-8 min). 

Use as little fat as possible to avoid increasing its fat content. Cook less tender liver slowly and in a small amount of liquid.

Nutritional Information

Browse other variety meats: Introduction | Heart | Liver | Sweetbreads | Tongue | Brains | Kidneys | Tripe

Browse other foods: Vegetables | Legumes | Fruits | Nuts and Seeds | Seaweeds | Mushrooms | Cereals and Grains | Fish | Crustaceans | Mollusks | Herbs, Spices and Seasonings | Meats | Variety Meats | Delicatessen Meats | Poultry | Dairy Products | Sugars, Cocoa and Carob | Fats and Oils | Binders and Leavenings | Coffee, Tea and Herbal Teas

For more information on liver, visit Britannica.com.

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.

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 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.

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.

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.

LearnThatWord.com is a free vocabulary and spelling program where you only pay for results!

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.

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.

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.

• Endocrine System and Glands - liver: large gland that secretes bile and stores glycogen
• Meats and Cuts of Meat
• Painting Tools and Techniques - liver: oil paint that has thickened into an insoluble, rubbery mass inside tube
• Reddish Brown

For other uses, see Liver (disambiguation).

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.
Surface projections of the organs of the trunk, showing liver in center
Latin	jecur, iecer
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, including 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 long term, although liver dialysis can be used short term.

This organ 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 abdominal-pelvic region of the abdomen. It produces bile, an alkaline compound which aids in digestion via the emulsification of lipids. The liver's highly specialized tissues regulate a wide variety of high-volume biochemical reactions, 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 (ἡπαρ).

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 1.5 In other animals 2 Physiology 2.1 Synthesis 2.2 Breakdown 2.3 Other functions 3 Diseases of the liver 4 Disease symptoms 5 Diagnosis 6 Biopsy 7 Regeneration 8 Liver transplantation 9 Development 9.1 Fetal blood supply 10 As food 11 Cultural allusions 12 See also 13 References 14 External links

Anatomy

Liver of 8 weeks human embryo

The liver is a reddish brown organ with four lobes of unequal size and shape. A human liver normally weighs 1.44–1.66 kg (3.2–3.7 lb),^[3] and is a soft, pinkish-brown, triangular organ. It is both the largest internal organ (the skin being the largest organ overall) and the largest gland in the human body. 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. It is connected to two large blood vessels, one called the hepatic artery and one called the portal vein. The hepatic artery carries blood from the aorta, whereas the portal vein carries blood containing digested nutrients from the entire gastrointestinal tract and also from the spleen and pancreas. These blood vessels subdivide into capillaries, which then lead to a lobule. Each lobule is made up of millions of hepatic cells which are the basic metabolic cells.

Blood flow

The liver gets a dual blood supply from 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.^[4]
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.

Liver

Liver

Biliary flow

The biliary tree

The term biliary tree is derived from the arboreal branches of the bile ducts. 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 (within the liver) bile ducts, and once they exit the liver they are considered extrahepatic (outside the liver). The intrahepatic ducts eventually drain into the right and left hepatic ducts, which 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.

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 second part of the duodenum together at the ampulla of Vater.

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.

Dissection of portal vein in right lobe of liver

These "lits" are in no way related to the true anatomic ligaments in joints, and have essentially no known functional importance, but they are easily recognizable surface landmarks. An exception to this is the falciform ligament, which attaches the liver to the posterior portion of the anterior body wall.

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 is 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 the quadrate lobe (the more inferior).

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, 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 Couinaud 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. 1. Caudate 2. Superior subsegment of the lateral segment 3. Inferior subsegment of the lateral segment 4a. Superior subsegment of the medial segment 4b. Inferior subsegment of the medial segment 5. Inferior subsegment of the anterior segment 6. Inferior subsegment of the posterior segment 7. Superior subsegment of the posterior segment 8. 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.^[5][6]

In other animals

The liver is found in all vertebrates, and is typically the largest visceral organ. 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 include 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.^[7]

An organ sometimes referred to as a liver is found associated with the digestive tract of the primitive chordate Amphioxus. However, this is an enzyme secreting gland, not a metabolic organ, and it is unclear how truly homologous it is to the vertebrate liver.^[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. The liver is thought to be responsible for up to 500 separate functions, usually in combination with other systems and organs.

Synthesis

Further information: Proteins produced and secreted by the liver

A CT scan in which the liver and portal vein are shown.

• 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).
  • A bulk of the lipoproteins are synthesized in the liver.
• 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 yellowish 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 glucoronidates bilirubin, facilitating its excretion into bile.
• The liver breaks down or modifies 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 converts ammonia to urea (urea cycle)

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 (1–3 years' supply), 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, an enzyme that is released when the kidney senses low blood pressure.

Diseases of the liver

Main article: Liver disease

Left lobe liver tumor

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.^[8]

The most common include: Infections such as hepatitis A. B, C, E, alcohol damage, fatty liver, cirrhosis, cancer, drug damage (especially acetaminophen (also known as paracetamol) and cancer drugs)

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.

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.

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

Disease symptoms

The classic symptoms of liver damage include the following:

• 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.^[9]

Diagnosis

The diagnosis of liver function is made by blood tests. Liver function tests can readily pinpoint the extent of liver damage. If infection is suspected, then other serological tests are done. Sometimes, one may require an ultrasound or a CT scan to produce an image of the liver.

Physical examination of the liver is not accurate in determining the extent of liver damage. It can only reveal presence of tenderness or the size of liver, but in all cases, some type of radiological study is required to examine it.^[10]

Biopsy

The ideal way to determine damage to the liver is with a biopsy. A biopsy is not required in all cases, but may be necessary when the cause is unknown. A needle is inserted into the skin just below the rib cage and a biopsy is 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.^[11]

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. This is, however, not true regeneration but rather compensatory growth.^[12] 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.

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.^[13] 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, the latter being the cells that line the bile ducts.

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. Some think the myth indicates the ancient Greeks knew about the liver’s remarkable capacity for self-repair, though this claim has been challenged.^[14]

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.

After resection of left lobe liver tumor

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 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.

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.^[15] 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 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.

• 

  Phase contrast CT image. Contrast is perfusing the right liver but not the left due to a left portal vein thrombus.

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 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.

As food

Main article: Liver (food)

Cultural allusions

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 practiced a type of divination called haruspicy, 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.^[16] The Talmud (tractate Berakhot 61b) refers to the liver as the seat of anger, with the gallbladder counteracting this.

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!".^[17] 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.

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. Although there are narrations that suggest that Hind did "taste", rather than eat, the liver of Hamza, the authenticity of these narrations has to be questioned.

See also

Look up liver in Wiktionary, the free dictionary.

• Artificial liver
• Bile
• Bile canaliculus
• Hepatic cyst (liver cyst)
• Hepatocyte
• Liver function tests
• Liver shot (martial arts strike)
• Polycystic liver disease
• Porto-Systemic anastomosis

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. ^ Cotran, Ramzi S.; Kumar, Vinay; Fausto, Nelson; Nelso Fausto; Robbins, Stanley L.; Abbas, Abul K. (2005). Robbins and Cotran pathologic basis of disease (7th ed.). St. Louis, MO: Elsevier Saunders. p. 878. ISBN 0-7216-0187-1. 
4. ^ Benjamin L. Shneider; Sherman, Philip M. (2008). Pediatric Gastrointestinal Disease. Connecticut: PMPH-USA. pp. 751. ISBN 1-55009-364-9. 
5. ^ "Three-dimensional Anatomy of the Couinaud Liver Segments". http://dpi.radiology.uiowa.edu/nlm/app/livertoc/liver/liver.html. Retrieved 2009-02-17. 
6. ^ "Prof. Dr. Holger Strunk". http://www.uni-bonn.de/~umm705/quiz0403.htm. Retrieved 2009-02-17. 
7. ^ ^{a b} Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. pp. 354–5. ISBN 0-03-910284-X. 
8. ^ Cirrhosis Overview National Digestive Diseases Information Clearinghouse. Retrieved on 2010-01-22
9. ^ Extraintestinal Complications: Liver Disease Crohn's & Colitis Foundation of America. Retrieved on 2010-01-22
10. ^ Liver Information HealthLine. Retrieved on 2010-01-22
11. ^ Liver.. The largest gland in the body MedicineNet. Retrieved on 2010-01-22
12. ^ Robbins and Cotran Pathologic Basis of Disease (7th ed.). 1999. p. 101. ISBN 0-8089-2302-1. 
13. ^ 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. 
14. ^ An argument for the ancient Greek’s knowing about liver regeneration is provided by Chen T and Chen P (1994). "The Myth of Prometheus and the Liver". Journal of the Royal Society of Medicine 87(12): 754-755. A counterargument is provided by Power C and Rasko J (2008). "Whither Prometheus' Liver? Greek Myth and the Science of Regeneration". Annals of Internal Medicine 149(6): 421-426.
15. ^ 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. 
16. ^ 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. 
17. ^ THE GREAT BATTLE OF BADAR (Yaum-e-Furqan)

External links

Wikimedia Commons has media related to: Livers

• Liver at the Open Directory Project.
• VIRTUAL Liver - online learning resource
• Liver enzymes

v d e Human systems and organs TA 2–4: MS Skeletal system Bone (Carpus · Collar bone (clavicle) · Thigh bone (femur) · Fibula · Humerus · Mandible · Metacarpus · Metatarsus · Ossicles · Patella · Phalanges · Radius · Skull (cranium) · Tarsus · Tibia · Ulna · Rib · Vertebra · Pelvis · Sternum) · Cartilage Joints Fibrous joint · Cartilaginous joint · Synovial joint Muscular system Muscle · Tendon · Diaphragm TA 5–11: splanchnic/ viscus mostly Thoracic Respiratory system URT (Nose, Nasopharynx, Larynx) · LRT (Trachea, Bronchus, Lung) mostly Abdominopelvic Digestive system+ adnexa Mouth (Salivary gland, Tongue) · upper GI (Oropharynx, Laryngopharynx, Esophagus, Stomach) · lower GI (Small intestine, Appendix, Colon, Rectum, Anus) · accessory (Liver, Biliary tract, Pancreas) GU: Urinary system Kidney · Ureter · Bladder · Urethra GU: Reproductive system Female (Uterus, Vulva, Ovary, Placenta) · Male (Scrotum, Penis, Prostate, Testicle, Seminal vesicle) Endocrine system Pituitary · Pineal · Thyroid · Parathyroid · Adrenal · Islets of Langerhans TA 12–16 Circulatory system Cardiovascular system peripheral (Artery, Vein, Lymphatic vessel) · Heart Lymphatic system primary (Bone marrow, Thymus) · secondary (Spleen, Lymph node) Nervous system (Brain, Spinal cord, Nerve) · Sensory system (Ear, Eye) Integumentary system Skin · Subcutaneous tissue · Breast (Mammary gland) Blood (Non-TA) Myeloid Myeloid immune system Lymphoid Lymphoid immune system General anatomy: systems and organs, regional anatomy, planes and lines, superficial axial anatomy, superficial anatomy of limbs

v d e Anatomy of torso, digestive system: accessory digestive glands (TA A05.8–9, TH H3.04.05-07, GA 11.1188) Liver diaphragmatic surface: Bare area of the liver • Ligamentum venosum visceral surface: Gastric impression • Duodenal impression • Colic impression • Renal impression • Suprarenal impression • Porta hepatis • Round ligament of liver lobes: Left lobe  • Right lobe (Caudate lobe, Quadrate lobe) Fibrous capsule of Glisson • Perisinusoidal space • Liver sinusoid • Periportal space • Portal triad • Lobules of liver cells: Hepatocyte · Hepatic stellate cell · Kupffer cell Biliary tract Bile ducts intrahepatic (from Bile canaliculus and Canals of Hering): Interlobular bile ducts • Left hepatic duct • Right hepatic duct extrahepatic: Common hepatic duct Gallbladder by region: Body • Fundus • Neck Cystic duct • Common bile duct Hepatopancreatic ampulla (Sphincter of ampulla) cells: Cholecystocyte Pancreas by region: Tail • Body • Neck • Head (Uncinate process) ducts: Pancreatic duct • Accessory pancreatic duct by function: Islets of Langerhans • Exocrine component of pancreas cells: Centroacinar cell · Pancreatic stellate cell M: DIG anat(t, g, p)/phys/devp/enzy noco/cong/tumr, sysi/epon proc, drug(A2A/2B/3/4/5/6/7/14/16), blte

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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

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