Final answer:
The hormone secretin stimulates the pancreas to secrete a bicarbonate-rich solution, which is high in sodium bicarbonate, to neutralize the acidic chyme in the small intestine.
Step-by-step explanation:
The hormone secretin stimulates the pancreas to secrete a solution high in sodium bicarbonate. The primary role of sodium bicarbonate is to neutralize the highly acidic chyme that enters the small intestine from the stomach. This neutralization is essential for the proper functioning of the digestive enzymes and creating an optimal environment for digestion in the small intestine. Secretin, together with cholecystokinin (CCK), regulates pancreatic secretions during the digestive process. While secretin prompts the pancreas to release bicarbonate-rich juice, CCK causes the pancreas to secrete enzyme-rich juices and stimulates the gallbladder to release bile.