Master Cholecystokinin (CCK) with Picmonic for Medicine

CCK-containing cells (known as I-cells) are most concentrated in the duodenum and jejunum. It has been hypothesized that these cells connect with enteric nerves, offering a direct connection between the nervous system and the gut.

CCK is secreted by I cells, which are located in the duodenum and jejunum.

One of the actions of CCK is to increase the secretion of pancreatic juices into the GI tract. These juices contain various enzymes that aid in the breakdown of ingested food. This process is crucial for the digestion of fats, proteins, and carbohydrates.

CCK induces gallbladder contraction, which promotes emptying of bile into the GI tract and aids in digestion. This function is especially important in emulsifying dietary fats for absorption.

CCK acts to release the sphincter of Oddi, which is the sphincter that controls the opening of the common bile duct into the duodenum. Relaxation of the sphincter of Oddi allows the emptying of pancreatic and gallbladder secretions into the intestine, allowing them to aid in digestion.

CCK reduces gastric emptying through multiple mechanisms. One of these is stimulating vagal afferent nerve fibers, which causes a feedback mechanism that slows gastric emptying and induces satiety. This slowing effect is important in ensuring adequate time for digestion and nutrient absorption.

Acts on vagal afferents and brain centers to induce feelings of satiety, reducing further food intake.

Ingestion of amino and fatty acids in meals stimulates secretion of CCK, which in turn stimulates secretion of various digestive enzymes by the pancreas and gallbladder to aid in the breakdown of the very same amino and fatty acids.