|Diagram of Stomach|
|Surface projections of the organs of the trunk, with gallbladder labeled at the transpyloric plane|
|Latin||Vesica biliaris, vesica fellea|
|Gray's||subject #250 1197|
|Nerve||Celiac ganglia, vagus|
In vertebrates the gallbladder (cholecyst, gall bladder or biliary vesicle) is a small organ where bile is stored, before it is released into the small intestine. Humans can live without a gallbladder. The surgical removal of the gallbladder is called a cholecystectomy.
The gallbladder is a hollow system that sits just beneath the liver. In adults, the gallbladder measures approximately 8 centimetres (3.1 in) in length and 4 centimetres (1.6 in) in diameter when fully distended. 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 gallbladder 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. The fundus is at the same level as the transpyloric plane; the body is attached to the liver.
The different layers of the gallbladder are as follows:
- 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.
Early in development, the human embryo has three layers and abuts an embryonic yolk sac. During the second week of embryological development, as the embryo grows, it begins to surround and envelop portions of this sac. The enveloped portions form the basis for the adult gastrointestinal tract. Sections of this gut begin to differentiate into the organs of the gastrointestinal tract, such as the oesophagus, stomach, and intestines. 
During the fourth week of embryological development, the stomach rotates. The stomach, originally lying in the midline of the embryo, rotates so that its body is on the left. This rotation also affects the part of the gastrointestinal tube immediately below the stomach, which will go on to become the duodenum. By the end of the fourth week, the developing duodenum begins to spout a small outpouching on its right side, which will go on to become the liver biliary tree. Just below this is a second outpouching, known as the cystic diverticulum, that will eventually develop into the gallbladder.
Anatomical variants of the gallbladder occur very rarely, although a range of abnormalities have been documented.
The number and structure of the gallbladder may vary. Occasionally two or even three gallbladders may coexist, either as separate bladders draining into the cystic duct, or sharing a common branch that drains into the cystic duct. Additionally, the gallbladder may fail to form at all. Gallbladders with two lobes separated by a septum may also exist. These abnormalities are not likely to affect function and are generally asymptomatic.
The location of the gallbladder with regard to the liver may also vary, with documented variants including gallbladders found within, above, on the left side of, behind, and detached from the liver. Such variants are very rare: from 1886 to 1998, only 110 cases of left-lying liver, or less than one per year, were reported in scientific literature.
The main purpose of the gallbladder is to store bile, or gall. The gallbladder is part of the biliary system and serves as a reservoir for bile, which is produced by the liver. The liver produces the bile and then it flows through the bile ducts into the gallbladder. The gallbladder releases the bile in response to a hormone called cholecystokinin, which is released from the small intestine. When the bile is released, it is released into the small intestine and its purpose is to break down large fat molecules into smaller ones. After the fat is absorbed, the bile is also absorbed and transported back to the liver for reuse.
When food containing fat (and amino acids) enters the digestive tract, it stimulates the secretion of cholecystokinin (CCK) from I cells of the duodenum and jejunum. 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, contracts and 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.
"By far, the most common gallbladder problem is Gallstones" (Rodriguez). The gallbladder is supposed to store bile in a natural, semi-liquid form at all times. Hydrogen ions secreted from the inner lining of the gallbladder are supposed to keep the bile acidic enough to prevent hardening. To dilute the bile, water and electrolytes from the digestion system are added. Also, salts attach themselves to cholesterol molecules in the bile to keep them from crystallizing. Sometimes there can be too much cholesterol or bilirubin in the bile, or the gallbladder doesn't empty like it should and the systems listed above fail. This is how gallstones form. All it takes is a tiny bit of calcium to get coated with either cholesterol or bilirubin and crystallization of the bile, to form a gallstone. Gallstones are dangerous because they may never cause any pain or symptoms until they are causing a problem in the biliary system.
The recurrence rate of gallstone related issues is very high, so elective surgical resection of the gallbladder is the standard of care after such issues. This is fine because the digestive system will still be able to function properly . The gallbladder does not produce anything needed for digestion, it simply stores bile until digestion, when it is released into the small intestine. With no gallbladder, bile will just continuously drip from the liver during digestion for the breakdown of fats. Patients undergoing a cholecystectomy seldom have long-term post-surgical issues with the function of their digestive system .
A traditional cholecystectomy is most commonly performed from the infundibulum to the fundus.
Society and culture
Numerous words in the English language relate to the gallbladder and the bile that it stores. To have 'gall' is associated with bold behaviour, whereas to have 'bile' is associated with bitterness. 
In the Chinese language, the gallbladder (Chinese: 胆) is associated with courage and a plethora of related idioms, including using terms such as "a body completely [of] gall" (Chinese: 浑身是胆) to describe a brave person, and "single gallbladder hero" (Chinese: 孤胆英雄) to describe a lone hero. 
In other 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 laminis) and several species of birds lack a gallbladder altogether, as do lampreys.
- 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. Retrieved 2007-06-29.
- "Where is the Gallbladder Located in the Body". Buzzle.com. 2013-02-28. Retrieved 2013-08-18.
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- Larsen's human embryology (4th ed., Thoroughly rev. and updated. ed.). Philadelphia: Churchill Livingstone/Elsevier. 2009. pp. "Development of the Gastrointestinal Tract". ISBN 9780443068119.
- Leeuw, Th.G.; Verbeek, P.C.M.; Rauws, E.A.J.; Gouma, D.J. (September 1995). "A double or bilobar gallbladder as a cause of severe complications after (laparoscopic) cholecystectomy". Surgical Endoscopy 9 (9). doi:10.1007/BF00188459.
- Dhulkotia, A; Kumar, S; Kabra, V; Shukla, HS (1 March 2002). "Aberrant gallbladder situated beneath the left lobe of liver". HPB: Official Journal of The International Hepato Pancreato Biliary Association 4 (1): 39–42. doi:10.1080/136518202753598726.
- Naganuma, S.; Ishida, H.; Konno, K.; Hamashima, Y.; Hoshino, T.; Naganuma, H.; Komatsuda, T.; Ohyama, Y.; Yamada, N.; Ishida, J.; Masamune, O. (6 March 2014). "Sonographic findings of anomalous position of the gallbladder". Abdominal Imaging 23 (1): 67–72. doi:10.1007/s002619900287.
- Sahu, S.; Joglekar, M. V.; Dumbre, R.; Phadnis, S. M.; Tosh, D.; Hardikar, A. A. (2009). "Islet-like cell clusters occur naturally in human gall bladder and are retained in diabetic conditions". Journal of Cellular and Molecular Medicine 13 (5): 999–1000. doi:10.1111/j.1582-4934.2008.00572.x. PMID 19175681.
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- The Oxford English dictionary. (2nd ed. ed.). Oxford: Clarendon Press. 1989. p. gall, bile. ISBN 9780198611868.
- Yu, Ning (1 January 2003). "Metaphor, Body, and Culture: The Chinese Understanding of Gallbladder and Courage". Metaphor and Symbol 18 (1): 13–31. doi:10.1207/S15327868MS1801_2.
- C. Michael Hogan. 2008. Guanaco: Lama guanicoe, GlobalTwitcher.com, ed. N. Strömberg
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|Wikimedia Commons has media related to Gall bladder.|
- Diagram of Human Stomach and Gallbladder – Human Anatomy Online dd, MyHealthScore.com.
- www.newchronicles.webs.com/f/gastrointestinalphysiology – Gastrointestinal Physiology Review.
- Anatomy photo:38:14-0100 at the SUNY Downstate Medical Center - "Stomach, Spleen and Liver: The Gallbladder and the Bile System"
- Rodriguez, D. (2010, Jan. 25). What Is the Gallbladder?. Everyday Health, Retrieved Mar. 20, 2011, from http://www.everydayhealth.com/gallbladder/what-is-the-...
- (2009, Jan.). Life Without a Gallbladder. Digestive Disorders, 30-31. Retrieved n.d., from Health Source - Consumer Edition (9780929661674).