gallbladder

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A hollow muscular organ, present in humans and most vertebrates, which receives dilute bile from the liver, concentrates it, and discharges it into the duodenum. It also participates in the entero-hepatic (re)circulation of bile, and in secretion and removal of conjugated xenobiotics, including radiopaque substances taken orally or intravenously for diagnostic purposes. Although not a vital organ, it stores bile, regulates biliary tract pressures, and, when diseased, enhances precipitation of various constituents of the bile as gallstones.

The system of bile ducts lying outside the liver is known as the extrahepatic biliary tract. In humans (Illus.) right and left hepatic ducts empty into the common hepatic duct, which continues to the duodenum as the common bile duct, or ductus choledochus. The gallbladder and cystic duct thus appear to be accessory organs and therefore are removable. However, they are converted into main-line structures by the presence of a sphincter (sphincter of Oddi) at the choledochoduodenal junction. Tonic contraction of this sphincter between meals forces the bile to back up into the gallbladder.

Extrahepatic biliary tract in humans.

In most other vertebrates essentially similar relations exist except when the gallbladder is absent, but there is considerable variation in proportion and arrangement of ducts, including the pancreatic ducts. See also Liver; Pancreas.

In humans, evacuation of the gallbladder is accomplished by a trigger mechanism which is set off by the presence of fatty foods, meat, and hydragogue cathartics in the duodenum and upper jejunum. Absorption of these substances by the mucous membrane results in the release of cholecystokinin (CCK), a hormone which rapidly circulates in the bloodstream and simultaneously produces contraction of the gallbladder and relaxation of the sphincter of Oddi. The most effective food is egg yolk, which contains certain l-amino acids. Resorption of bile salts by the intestine stimulates secretion of bile for hours after a meal. See also Digestive system.

The organ situated in the liver which stores the bile formed in the liver before its secretion into the small intestine. See gastro-intestinal tract.

A small sac lying beneath the right lobe of the liver. It stores bile.

The gall bladder receives bile from the liver, stores and concentrates it, and delivers it to the intestine as required. It is a slate-blue sac, partly sunken in a groove on the under surface of the right lobe of the liver. It is 7-10 cm long, 3 cm in maximum breadth and, under usual circumstances, has a 30-50 ml capacity. Bile acids and other constituents of bile produced in the liver are carried to the gall bladder via the hepatic and cystic ducts. A 10-fold concentration effect is achieved by the transport of water from the bile to the bloodstream within the gall bladder wall. When fatty food passes from the stomach into the intestine, the gall bladder is stimulated to contract by cholecystokinin, a hormone released from the lining of the intestine. Concentrated bile is then released into the intestine via the cystic and common bile ducts. The high concentration of bile acids turns fat in the diet into an emulsion which is easily digested by the action of the enzyme lipase from the pancreas, and absorbed across the intestinal wall. The efficiency of this system is enhanced by the reabsorption of bile acids from the intestine, minimizing the quantity lost in the faeces. Reabsorbed bile acids are then carried by the bloodstream back to the liver, where they are available for further recycling into the bile. If the gall bladder has to be removed, unconcentrated bile drains directly into the intestine from the liver, but in most people digestion of fatty food can still occur quite adequately.

The formation of gallstones within the gall bladder represents the most common cause of gall bladder disease. Gallstones were first described by Gentile da Foligno in Padua in 1341, who noted many stones within the post-mortem gall bladder of a woman whose viscera had been removed so that the body could be embalmed. Gallstones occur commonly in people of all races and at all ages (even in the teens). Although their prevalence varies, there is some truth in the well-known aphorism that the typical patient with gallstones is a fat, fair, fertile woman in her forties.

Bernard Naunyn's classic monograph published in 1892 is credited as containing the first discussion of the chemical composition of gallstones. It is now common to speak of three types of gallstone: pigment, cholesterol, and mixed. Patients with excessive breakdown of their red blood cells, resulting in increased production of bilirubin, are at increased risk of the formation of pigment gallstones, which are predominantly composed of calcium bilirubinate, carbonate, phosphate, and palmitate. Conversely, supersaturation of bile with insoluble cholesterol, as a result of metabolic defects, promotes the formation of cholesterol gallstones.

Autopsy series suggest that gallstones are formed in at least 15% of the adult population, the majority of whom have never experienced symptoms. Indeed, it has been estimated that only about 1% of people with gallstones will develop complications of them each year. These occur when gallstones obstruct either the cystic or the common bile ducts. The most common symptom is abdominal pain, which may be due to inflammation of the gall bladder (cholecystitis), bile duct obstruction (biliary colic), or inflammation of the pancreas (pancreatitis). Partial obstruction of the common bile duct by a gallstone is the commonest cause of cholangitis (inflammation of the bile ducts), marked by the appearance of ‘Charcot's triad’ of abdominal pain, fever, and jaundice (named after the Parisian professor who described ‘biliary fever’ in 1876, although he was mainly famed as a neurologist).

‘Acalculous’ cholecystitis, in which gall bladder inflammation occurs in the absence of gallstones, accounts for about 10% of all cases of acute cholecystitis and also a proportion of those with chronic gall bladder inflammation. Gall bladder inflammation may occur during the course of typhoid fever. In a minority of cases, the responsible bacterium, Salmonella typhi, even persists in the gall bladder after the acute illness has resolved, and is intermittently excreted in the faeces. After a year, about 2-5% of individuals still excrete this organism and some, mostly females, continue to do so indefinitely. These ‘chronic carriers’ may spread the infection to others if their personal hygiene is careless, by the faecal-oral route. The most notorious carrier was ‘typhoid Mary’ who, in her capacity as cook to many households and institutions in the early 1900s, left a trail of typhoid victims across the US and Canada.

— Stephen M. Riordan, Roger Williams

See also alimentary system; bile; jaundice; liver.

A small, muscular sac located under the liver. Bile is stored in the gallbladder until it is needed by the small intestine for digestion. (See digestive system.)

The pear-shaped reservoir for bile attached to the visceral surface or between the lobes of the liver in all domestic animal species except the horse. It serves as a storage place for bile. The gallbladder may be subject to such disorders as inflammation and the formation of gallstone.

• g. cystic mucosal hyperplasia — hyperplasia of the mucus-secreting glands in the gallbladder and larger bile ducts.
• g. edema — a gross lesion in many cases of infectious canine hepatitis.
• g. inflammation — cholecystitis.
• g. meridian points — acupuncture points on the gallbladder meridian.
• g. paralysis — a specific abnormality in lantadene poisoning. The gallbladder is grossly distended and full of viscid, pale bile.
• porcelain g. — intramural mineralization of the gallbladder.
• g. radiography — see cholecystography.

• Endocrine System and Glands - gallbladder: small vessel near liver for bile storage

For other uses, see Gallbladder (disambiguation).

This article's lead section may not adequately summarize its contents. Please consider expanding the lead to provide an accessible overview of the article's key points. (April 2010)

Gallbladder
Diagram of Stomach
Surface projections of the organs of the trunk, with gallbladder labeled at the transpyloric plane
Latin	vesica fellea; vesica biliaris
Gray's	subject #250 1197
System	Digestive system (GI Tract)
Artery	Cystic artery
Vein	Cystic vein
Nerve	Celiac ganglia, vagus[1]
Precursor	Foregut

1. Bile ducts: 2. Intrahepatic bile ducts, 3. Left and right hepatic ducts, 4. Common hepatic duct, 5. Cystic duct, 6. Common bile duct, 7. Ampulla of Vater, 8. Major duodenal papilla
9. Gallbladder, 10-11. Right and left lobes of liver. 12. Spleen.
13. Esophagus. 14. Stomach. Small intestine: 15. Duodenum, 16. Jejunum
17. Pancreas: 18: Accessory pancreatic duct, 19: Pancreatic duct.
20-21: Right and left kidneys (silhouette).
The anterior border of the liver is lifted upwards (brown arrow). Gallbladder with Longitudinal section, pancreas and duodenum with frontal one. Intrahepatic ducts and stomach in transparency.

In vertebrates the gallbladder (cholecyst, gall bladder, biliary vesicle) is a small organ that aids mainly in fat digestion and concentrates bile produced by the liver. In humans the loss of the gallbladder is usually easily tolerated.

Contents 1 Human anatomy 2 Microscopic anatomy 3 Function 4 In animals 5 See also 6 References 7 External links

Human anatomy

The gallbladder is a hollow system that sits just beneath the liver.^[2] In adults, the gallbladder measures approximately 8 centimetres (3.1 in) in length and 4 centimetres (1.6 in) in diameter when fully distended.^[3] It is divided into three sections: fundus, body and neck. The neck tapers and connects to the biliary tree via the cystic duct, which then joins the common hepatic duct to become the common bile duct. At the neck of the gall bladder is a mucosal fold called Hartmann's pouch, where gallstones commonly get stuck. The angle of the gallbladder is located between the costal margin and the lateral margin of the rectus abdominis muscle.

Microscopic anatomy

Micrograph of a normal gallbladder wall. H&E stain.

The different layers of the gallbladder are as follows:^[4]

• The epithelium, a thin sheet of cells closest to the inside of the gallbladder
• The lamina propria, a thin layer of loose connective tissue (the epithelium plus the lamina propria form the mucosa)
• The muscularis, a layer of smooth muscular tissue that helps the gallbladder contract, squirting its bile into the bile duct
• The perimuscular ("around the muscle") fibrous tissue, another layer of connective tissue
• The serosa, the outer covering of the gallbladder that comes from the peritoneum, which is the lining of the abdominal cavity

Unlike elsewhere in the intestinal tract, the gallbladder does not have a muscularis mucosae.

Function

When food containing fat enters the digestive tract, it stimulates the secretion of cholecystokinin (CCK). In response to CCK, the adult human gallbladder, which stores about 50 millilitres (1.7 U.S. fl oz; 1.8 imp fl oz) of bile, releases its contents into the duodenum. The bile, originally produced in the liver, emulsifies fats in partly digested food.

During storage in the gallbladder, bile becomes more concentrated which increases its potency and intensifies its effect on fats.

In 2009, it was demonstrated that the gallbladder removed from a patient expressed several pancreatic hormones including insulin.^[5] This was surprising because until then, it was thought that insulin was only produced in pancreatic β-cells. This study provides evidence that β-like cells do occur outside the human pancreas. The authors suggest that since the gallbladder and pancreas are adjacent to each other during embryonic development, there exists tremendous potential in derivation of endocrine pancreatic progenitor cells from human gallbladders that are available after cholecystectomy.

In animals

Most vertebrates have gallbladders, whereas invertebrates do not. However, its precise form and the arrangement of the bile ducts may vary considerably. In many species, for example, there are several separate ducts running to the intestine, rather than a single common bile duct, as in humans. Several species of mammals (including horses, deer, rats, and various lamoids^[6]) and several species of birds lack a gallbladder altogether, as do lampreys.^[7]

Gallbladder

See also

• Gallbladder disease
• Gallbladder polyp
• Gallstone
• Cholelithiasis

References

1. ^ Ginsburg, Ph.D., J.N. (2005-08-22). "Control of Gastrointestinal Function". In Thomas M. Nosek, Ph.D.. Gastrointestinal Physiology. Essentials of Human Physiology. Augusta, Georgia, United State: Medical College of Georgia. pp. p. 30. http://www.lib.mcg.edu/edu/eshuphysio/program/section6/6ch2/6ch2line.htm. Retrieved 2007-06-29. 
2. ^ http://www.buzzle.com/articles/where-is-the-gallbladder-located-in-the-body.html
3. ^ Jon W. Meilstrup (1994). Imaging Atlas of the Normal Gallbladder and Its Variants. Boca Raton: CRC Press. pp. 4. ISBN 0-8493-4788-2. 
4. ^ "Staging of Gallbladder Cancer". http://www.cancer.org/Cancer/GallbladderCancer/DetailedGuide/gallbladder-staging. 
5. ^ Sahu S, Joglekar MV, Dumbre R, Phadnis SM, Tosh D, Hardikar AA. (2009) Islet-like cell clusters occur naturally in human gall bladder and are retained in diabetic conditions. J Cell Mol Med. 2009 May;13(5):999-1000
6. ^ C. Michael Hogan. 2008. Guanaco: Lama guanicoe, GlobalTwitcher.com, ed. N. Strömberg
7. ^ Romer, Alfred Sherwood; Parsons, Thomas S. (1977). The Vertebrate Body. Philadelphia, PA: Holt-Saunders International. p. 355. ISBN 0-03-910284-X. 

External links

Wikimedia Commons has media related to: Gall bladder

• Diagram of Human Stomach and Gallbladder – Human Anatomy Online, MyHealthScore.com.
• www.newchronicles.webs.com/f/gastrointestinalphysiology – Gastrointestinal Physiology Review.

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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