gallbladder

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gallbladder

(Carlyn Iverson)

A small, pear-shaped muscular sac, located under the right lobe of the liver, in which bile secreted by the liver is stored until needed by the body for digestion.

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 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.

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.

For more information on gallbladder, visit Britannica.com.

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.

Gall Bladder
Gall bladder is #5
Diagram of Stomach
Latin	vesica fellea
Gray's	subject #250 1197
System	Digestive system (GI Tract)
Artery	Cystic artery
Vein	Cystic vein
Nerve	Celiac ganglia, vagus[1]
Precursor	Foregut

The gallbladder (or cholecyst, sometimes gall bladder) is a small non-vital organ which aids in the digestive process and concentrates bile produced in the liver.

Contents 1 Human anatomy 2 Microscopic anatomy 3 Function 4 Abnormal conditions 5 References 6 External links

Human anatomy

The gallbladder is a hollow organ that sits in a concavity of the liver known as the gallbladder fossa. In adults, the gallbladder measures approximately 10 cm in length and 4 cm in diameter when fully distended.^[2] 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.

Microscopic anatomy

The different layers of the galbladder are as follows:^[3]

• The gallbladder has a simple columnar epithelial lining characterized by recesses called Aschoff's recesses, which are pouches inside the lining.
• Under the epithelium there is a layer of connective tissue (lamina propria).
• Beneath the connective tissue is a wall of smooth muscle (muscularis externa) that contracts in response to cholecystokinin, a peptide hormone secreted by the duodenum.
• There is essentially no submucosa separating the connective tissue from serosa and adventitia, but there is a thin lining of muscular tissue to prevent infection.

Function

This section does not cite any references or sources. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2008)

The gallbladder stores about 50 mL (1.7 US fluid ounces / 1.8 Imperial fluid ounces) of bile, which is released when food containing fat enters the digestive tract, stimulating the secretion of cholecystokinin (CCK). The bile, produced in the liver, emulsifies fats in partly digested food.

After being stored in the gallbladder, the bile becomes more concentrated than when it left the liver, increasing its potency and intensifying its effect on fats. Most digestion occurs in the heat.

Most vertebrates have gallbladders (exceptions include the horse, cervids, and the rat), while invertebrates do not.

The human gallbladder is shaped like a pear, although the organ's shape and function vary considerably among other mammalian species; in fact, in some species, such as the lamoids, the gallbladder is absent.^[4]

Abnormal conditions

Gallstones may develop in the gallbladder as well as elsewhere in the biliary tract. If gallstones in the gallbladder are symptomatic and cannot be dissolved by medication or broken into small pieces by ultrasonic waves, surgical removal of the gallbladder, known as cholecystectomy, may be indicated.

Other indications for this procedure include porcelain gallbladder and gallbladder cancer.

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 on 2007-06-29. 
2. ^ Jon W. Meilstrup (1994). Imaging Atlas of the Normal Gallbladder and Its Variants. Boca Raton: CRC Press. pp. 4. ISBN 0-8493-4788-2. 
3. ^ "Slide 5: Gall Bladder". JayDoc HistoWeb. University of Kansas. http://www.kumc.edu/instruction/medicine/anatomy/histoweb/epithel/epith05.htm. Retrieved on 2007-06-29. 
4. ^ C. Michael Hogan. 2008. Guanaco: Lama guanicoe, GlobalTwitcher.com, ed. N. Strömberg

External links

• Diagram of Human Stomach and Gallbladder – Human Anatomy Online, MyHealthScore.com.

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

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