During a meal, bile enters the duodenum from the common bile duct through the Sphincter of Oddi. Between meals, this sphincter is closed to prevent bile from entering the small intestine. As a result, much of the bile secreted from the liver is backed up the common bile duct into the cystic duct and the gallbladder. The gallbladder is located on the inferior surface of the liver. Within the gallbladder, sodium is actively removed from the bile. Chloride follows the sodium down its electrical gradient and water follows osmoti-cally. As a result, the organic constituents of bile are concentrated 5- to 10-fold. During a meal, when bile is needed for digestion, the gallbladder contracts and the bile is squeezed out and into the duodenum. Contraction is elicited by cholecystokinin, an intestinal hormone released in response to the presence of chyme, especially lipids, in the duodenum.

Essentials of Human Physiology

Essentials of Human Physiology

This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.

Get My Free Ebook

Post a comment