Your body needs to digest the food you eat before nutrients from the food can be absorbed into the blood and carried to cells. Although there are more than two dozen hormones found in the gastrointestinal system, gastrin, secretin and cholecystokinin, also known as CCK, are the primary hormones that affect the process of digestion. These hormones stimulate the digestive juices responsible for breaking down food into simple molecules that will fuel the body's cells.
Digestive Process
Food in the stomach is partially digested into a semi-fluid known as chyme. Glands in the mucosa of the mouth, stomach and small intestine produce juices that help the body digest food. Mucosa is moist tissue that lines the digestive organs and digestive tract and is where the cells are located that release the digestive hormones. Digestive juices produced in the liver and pancreas mix with food once the stomach empties its contents into the small intestine. As food dissolves in these juices, enzymes in the juices go to work breaking down carbohydrate, fat and protein. The process continues as the stomach contents move along the digestive tract. Bile acids stored in the gall bladder also help to break down fat.
Function of Hormones
Gastrin is the hormone that stimulates the stomach to secrete gastric acid, of which hydrochloric acid and pepsin enzymes are components. It also contributes to the production of pancreatic enzymes and liver bile -- both of which play important roles in digestion. Secretin signals the pancreas to produce a digestive juice that contains a bicarbonate base to help neutralize the acidic stomach contents before they move on through to the small intestine. Another function of the hormone secretin is to signal the stomach to produce pepsin -- an enzyme that digests protein. CCK is a hormone that aids in producing the enzymes in pancreatic juice that digest fat and protein. The hormone also stimulates the release of bile from the gallbladder.
Production of Hormones
Cells in the stomach and duodenum -- the first part of the small intestine -- secrete gastrin. Cells in the duodenum also produce secretin once the stomach empties its contents. The hormone secretin stimulates the pancreas to secrete sodium bicarbonate into the pancreatic fluid. This helps to raise the pH of the chyme. Cells in the duodenum and jejunum also secrete CCK. This hormone then stimulates the release of digestive enzymes into the pancreatic fluid and causes the gallbladder to contract forcing bile into the intestine.
Absorbing Nutrients
Most nutrients are absorbed into the bloodstream through the small intestine. Digestion of carbohydrates basically takes place in the intestine, where enzymes in the digestive juices break down nutrients into smaller molecules. Protein digestion begins in the stomach and then continues in the small intestine. Carbohydrates are usually digested the most quickly, followed by proteins and then fats. Nutrients are absorbed in the ileum -- the lower and longest section of the small intestine. Water-soluble vitamins are absorbed more quickly than fat-soluble vitamins. Once absorbed, nutrients travel through the bloodstream to the liver. This is where they are processed and then stored or sent out to other parts of the body.
