Final answer:
Cholecystokinin (CCK) is produced by cells in the duodenum's intestinal mucosa, where it helps in the digestion and metabolism of lipids by stimulating pancreatic lipase secretion and gallbladder contraction to release bile salts.
Step-by-step explanation:
Cholecystokinin (CCK) is a hormone produced by the cells in the intestinal mucosa, specifically within the duodenum, which is the first section of the small intestine. The release of CCK occurs when food, particularly fatty chyme, enters the duodenum. This hormone plays a pivotal role in digestive secretions and the regulation of lipid metabolism. CCK's functions include stimulating the pancreas to produce pancreatic lipase—an enzyme that breaks down fats—and inducing the contraction of the gallbladder to release bile salts into the intestine. Additionally, CCK acts as a hunger suppressant by sending signals to the brain.