Which intestinal segment is a primary site for cholecystokinin and secretin secretion?

Which intestinal segment is a primary site for cholecystokinin and secretin secretion?

• A. Stomach
• B. Duodenum
• C. Jejunum
• D. Ileum

Answer: (B)

Cholecystokinin and secretin are hormones produced by enteroendocrine cells in the lining of the small intestine to coordinate digestion. Secretin is released by S cells in the proximal small intestine in response to acidic chyme, triggering bicarbonate secretion from the pancreas and bile ducts to neutralize acid. Cholecystokinin is released by I cells in response to fats and amino acids, prompting pancreatic enzyme release and gallbladder contraction to help digest fats. The duodenum is the primary site because it is the first segment to encounter chyme and contains a high density of these S and I cells, enabling timely hormonal signaling. While other portions of the small intestine can contribute, the duodenum is the main source of secretion for these hormones.

Cholecystokinin and secretin are hormones produced by enteroendocrine cells in the lining of the small intestine to coordinate digestion. Secretin is released by S cells in the proximal small intestine in response to acidic chyme, triggering bicarbonate secretion from the pancreas and bile ducts to neutralize acid. Cholecystokinin is released by I cells in response to fats and amino acids, prompting pancreatic enzyme release and gallbladder contraction to help digest fats. The duodenum is the primary site because it is the first segment to encounter chyme and contains a high density of these S and I cells, enabling timely hormonal signaling. While other portions of the small intestine can contribute, the duodenum is the main source of secretion for these hormones.