| 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 |
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 |
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.
The different layers of the gallbladder are as follows:[4]
Unlike elsewhere in the intestinal tract, the gallbladder does not have a muscularis mucosae.
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.
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]