Secretin
A) is stimulated by the alkalinity of secretions from the pancreas.
B) regulates secretion from the islets of Langerhans in the pancreas.
C) operates as an antagonist of gastrin.
D) is secreted by S cells in the duodenum in response to a fall in pH and is controlled by a negative feedback mechanism.
E) is secreted into the intestine to stimulate digestion.

Question

Quizplus · Accepted Answer

Secretin is indeed secreted by S cells in the duodenum in response to a fall in pH (acidic chyme entering from the stomach) and operates through a negative feedback mechanism to regulate the pH by stimulating the pancreas to release bicarbonate-rich fluids. This helps neutralize the acidic chyme.