Question

Secretin and cholecystokinin are digestive hormones. They are secreted in
A. Esophagus
B. Ilem
C. Duodenum
D. Pyloric

Answer 1

Hint: (i) Digestive hormones control the release of secretions from the digestive glands. These hormones are released by epithelium of certain regions of the alimentary canal. Then these hormones are carried and by the blood to digestive glands which then release their secretions.
(ii) These hormones control digestive secretions and are known as gastrointestinal hormones.
(iii) Secretin by duodenal epithelium.

Complete Answer:
Due to the entry of acidic chyme into the duodenum, the duodenal epithelium secretes hormones.
(a) Secretin: It is secreted in duodenum epithelium bicarbonates in the pancreatic juice.
(ii) It also steps up secretion of bile.
(iii) It inhibits secretion of gastrin. Secretin targets the pancreas, liver and stomach.
(b) Cholecystokinin:
(i) It is also secreted by epithelium of duodenum. It causes release of bile by contraction of the gallbladder.
(ii) It also brings about the secretion of enzymes in the pancreatic juice.
(iii) Presence of fat in duodenum stimulates its secretion.

The correct option is (C), Duodenum.

Note: Some other gastrointestinal hormone are:
(i) Gastrin: Secreted by pyloric stomach. It stimulates the gastric glands to release the gastric juice. Distension of stomach on the entry of food into it, stimulates the epithelium of the pyloric stomach to secrete gastrin.
(ii) Enterogastrone: It is secreted by duodenal epithelium. The duodenum epithelium is stimulated as chyme enters into duodenum. It slows gastric contractions to delay its emptying and it also stops the secretion of gastric juice.
(iii) Duocrinin: Secreted by the intestinal epithelium, it causes the release of mucus from Brunner’s gland into the intestinal juice.
(iv) Enterocrinin: Also secreted by intestinal epithelium when acidic chyme enters the intestine. It brings about the release of enzymes from the crypts of Lieberkuhn into the intestinal juice.
(v) Villikinin: Also secreted by intestinal epithelium. It accelerates movements of villi.