Advanced Dental Admission Test (ADAT)

What is the effect of secretin produced by S Cells?

1. Increase gastric motility

2. Stimulate HCl secretion

3. Increase pancreatic HCO3 secretion

4. Enhance fat absorption

The correct answer is: Increase pancreatic HCO3 secretion

Secretin, produced by S cells in the duodenum, plays a crucial role in the digestive process, particularly in response to the acidic chyme that enters the small intestine from the stomach. Its primary function is to stimulate the pancreas to secrete bicarbonate (HCO3-), which helps neutralize stomach acid. This increase in pancreatic bicarbonate secretion is essential as it creates a more alkaline environment in the small intestine, facilitating the activity of digestive enzymes that function optimally at a higher pH. This bicarbonate also protects the intestinal mucosa from the harmful effects of excessive acidity. Additionally, the neutralization of acid supports the optimal absorption of nutrients further down the digestive tract. While secretin has other roles, such as modestly inhibiting gastric motility and acid secretion, its most significant effect and the primary reason for its secretion is the increase in pancreatic bicarbonate secretion, making it a critical component of digestive health.