Gall-Bladder

For other uses, see Gallbladder (disambiguation).

Gallbladder
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
System Digestive system
Artery Cystic artery
Vein Cystic vein
Nerve Celiac ganglia, vagus[1]
Precursor Foregut

Template:Bile ducts and pancreas

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. In humans, the loss of the gallbladder, in most cases, is easily tolerated by the body. The surgical removal of the gallbladder is called a cholecystectomy.

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 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.

Microscopic anatomy

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 (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.

In 2009, it was proposed that the gallbladder can produce several pancreatic hormones, including insulin.[5]

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[6]) and several species of birds lack a gallbladder altogether, as do lampreys.[7]

See also

References

External links

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

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