150 The Gallbladder
The Gallbladder
The gallbladder stores bile produced by the liver.
Learning Objectives
Describe the gallbladder
Key Takeaways
Key Points
- The gallbladder has a muscular wall that contracts in response to cholecystokinin, a peptide hormone that is synthesized by the small intestine.
- When food containing fat enters the digestive tract, the secretion of cholecystokinin is stimulated and the gall bladder releases the bile into the small intestine.
Key Terms
- gallbladder: In vertebrates, a small organ that aids mainly in fat digestion and concentrates bile produced by the liver.
The gallbladder is a pear-shaped organ that stores about 50 ml of the bile produced by the liver until the body needs it for digestion. It is about 7–10cm long in humans and is dark green in color.
The gallbladder has a muscular wall that contracts in response to cholecystokinin, a peptide hormone that is synthesized by the small intestine.
Bile and the Gallbladder
When food containing fat enters the digestive tract, the secretion of cholecystokinin (CCK) is stimulated, and the gallbladder releases the bile into the small intestine. The bile emulsifies fats and neutralizes acids in partly digested food. After being stored in the gallbladder, the bile becomes more concentrated to increase its potency and intensify its effect in fats.
Anatomy of the Gallbladder
The gallbladder, a hollow organ that stores bile, is located under the liver.
Learning Objectives
Detail the anatomy of the gallbladder
Key Takeaways
Key Points
- The gallbladder is a hollow organ that sits beneath the liver and stores bile that is made in the liver.
- The gallbladder is divided into three sections: the fundus, body, and neck. The neck connects to a system of ducts.
Key Terms
- gallstones: Small, hard objects, in the shape of a pebble, that sometimes form in the gallbladder or bile duct that are composed of cholesterol, bile pigments, and calcium salts.
Anatomy of the Gallbladder
The gallbladder is a hollow organ that sits beneath the liver and stores bile made in the liver. In adults, the gallbladder measures approximately eight centimeters (3.1 in) in length and four centimeters (1.6 in) in diameter when fully distended.
The gallbladder, labeled: An illustration of the gallbladder from Gray’s Anatomy with each section labeled.
The gallbladder is divided into three sections:
- The fundus.
- The body.
- The 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 where gallstones commonly get stuck.
Layers of the Gallbladder
There are several different layers of the gallbladder: the mucosa ( epithelium and lamina propria), the muscularis, the perimuscular, and the serosa.
- The epithelium is a thin sheet of cells that is closest to the inside of the gallbladder.
- The lamina propria is a thin layer of loose connective tissue, which together with the epithelium, forms the mucosa.
- The muscularis is a layer of smooth muscular tissue that helps the gallbladder contract and squirt its bile into the bile duct.
- The perimuscular (meaning around the muscle) is a fibrous connective tissue layer that surrounds the muscularis.
- The serosa is a smooth membrane that is the outer covering of the gallbladder.
Layers of the gallbladder: A micrograph of the layers of a gallbladder.
