THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -S cells in the small intestine emit secretin. Gastric acid stimulates secretin release, allowing movement into the duodenal lumen. Secretin causes an increase in pancreatic and biliary bicarbonate secretion and a decrease in gastric H+ secretion. Secretin stimulates the secretion of bicarbonate-rich pancreatic fluid.

Detailed explanation-2: -The mechanism underlying bicarbonate secretion is essentially the same as for acid secretion by parietal cells in the stomach and is dependent on the enzyme carbonic anhydrase. In pancreatic duct cells, the bicarbonate is secreted into the lumen of the duct and hence into pancreatic juice.

Detailed explanation-3: -In mammals the pancreatic juice is secreted as the result of stimulation of the exocrine pancreas cells by peptide hormones produced by cells in the anterior intestine and the stomach.

Detailed explanation-4: -secretin, a digestive hormone secreted by the wall of the upper part of the small intestine (the duodenum) that regulates gastric acid secretion and pH levels in the duodenum.