Gastrointestinal hormones are chemical messengers produced by the cells in the gastrointestinal tract. They play a crucial role in regulating digestion, appetite, and metabolism. These hormones are released in response to food intake and help coordinate various digestive processes, such as the secretion of digestive enzymes and the movement of food through the intestines. Some key gastrointestinal hormones include gastrin, which stimulates stomach acid production, and cholecystokinin (CCK), which promotes the release of bile from the gallbladder. Other important hormones include secretin and glucose-dependent insulinotropic peptide (GIP), which help regulate the digestive process and maintain blood sugar levels.