What is the primary action of secretin on the pancreas and stomach?

• A. Secretin has no effect on digestion.
• B. Secretin stimulates pancreatic bicarbonate secretion and inhibits gastric acid secretion, also slowing gastric emptying.
• C. Secretin stimulates gastric acid secretion and inhibits pancreatic bicarbonate.
• D. Secretin stimulates bile acid synthesis in the liver.

Answer: (B)

Secretin’s primary role is to neutralize acid as it enters the small intestine. It is released in response to the acidic chyme in the duodenum and acts to protect the intestinal lining. In the pancreas, secretin stimulates the ductal cells to secrete a bicarbonate-rich fluid, which raises the pH of the chyme and provides a more favorable environment for digestive enzymes to work. At the same time, secretin dampens gastric acid secretion from the stomach and can slow gastric emptying, giving the duodenum time to neutralize the incoming acid. It does not increase bile acid synthesis, and its main digestive effect is the bicarbonate secretion paired with reduced acid load. That combination is why this option is the best description of secretin’s action on the pancreas and stomach.