Final answer:
Secretin is a hormone released in the small intestine to aid in digestion by stimulating the release of bicarbonate-rich pancreatic juice.
Step-by-step explanation:
Secretin is a hormone released in the small intestine in response to acidic chyme entering the duodenum. It stimulates the release of bicarbonate-rich pancreatic juice from the duct cells, which helps neutralize the pH of the food from the stomach. This hormone aids in digestion by promoting the production of a fluid that neutralizes stomach acid.