What is a primary effect of secretin on digestion?

What is a primary effect of secretin on digestion?

• A. Inhibits pancreatic enzyme secretion.
• B. Delays intestinal glucose absorption.
• C. Stimulates pancreatic bicarbonate-rich fluid secretion and inhibits gastric acid secretion.
• D. Stimulates gallbladder contraction.

Answer: (C)

Secretin’s main job in digestion is to protect the small intestine from acidity and set the stage for proper digestion. When acidic chyme enters the duodenum, S cells release secretin. The key action is to signal the pancreas to release a bicarbonate-rich fluid, which neutralizes the stomach acid as it mixes with digestive enzymes. This neutralization is crucial because pancreatic enzymes work best at a higher pH, and a less acidic environment protects the intestinal mucosa. At the same time, secretin helps limit further acid exposure in the stomach by reducing gastric acid secretion. It does this in part by acting on the stomach’s cells and by dampening the stimulatory effects of gastrin. This combination—pancreatic bicarbonate secretion and inhibition of gastric acid secretion—is why the correct description is the one that emphasizes neutralizing acid and reducing acid secretion. The other choices don’t fit: secretin is not primarily about stimulating pancreatic enzyme secretion (that’s more of a role for CCK), it doesn’t slow glucose absorption in the intestine as a main action, and it does not trigger gallbladder contraction (that’s CCK).

Secretin’s main job in digestion is to protect the small intestine from acidity and set the stage for proper digestion. When acidic chyme enters the duodenum, S cells release secretin. The key action is to signal the pancreas to release a bicarbonate-rich fluid, which neutralizes the stomach acid as it mixes with digestive enzymes. This neutralization is crucial because pancreatic enzymes work best at a higher pH, and a less acidic environment protects the intestinal mucosa.

At the same time, secretin helps limit further acid exposure in the stomach by reducing gastric acid secretion. It does this in part by acting on the stomach’s cells and by dampening the stimulatory effects of gastrin.

This combination—pancreatic bicarbonate secretion and inhibition of gastric acid secretion—is why the correct description is the one that emphasizes neutralizing acid and reducing acid secretion. The other choices don’t fit: secretin is not primarily about stimulating pancreatic enzyme secretion (that’s more of a role for CCK), it doesn’t slow glucose absorption in the intestine as a main action, and it does not trigger gallbladder contraction (that’s CCK).