Question

Fill in the blank-
If pH of duodenum decreases below 5 then secretion of ______ stop.

Answer 1

The acid in the stomach is neutralized in the duodenum because the environment in the duodenum is alkaline. Secretin helps in the regulation of ph of the duodenum by inhibiting the secretion of a component that is from the parietal cells of the stomach.

Complete answer:
Duodenum consist of two main hormones which are secretin and cholecystokinin.
Function of secretin-
- It inhibits the secretion of gastric acid in order to regulate pH of the duodenum
- It stimulates the production of bicarbonate from the ductal cells of the pancreas
- It stimulates bile production by the liver
Secretin is present in the unusable form called prosecretin and is activated by the gastric acid. This results in the neutralization of the pH in duodenum which prevents damage to the small intestine.
Secretin is released in the intestinal lumen in response to very low or low duodenal pH ranges from 2 and 4.5.
The release of secretion is inhibited by H2 antagonists which are reducing the gastric acid secretion.
Hence the pH of the duodenum increases above the 5 or 4.5 the secretin is no longer released.
Basically in the duodenum gastric acid is neutralized by sodium bicarbonate and also blocking the gastric enzymes.
Gastric Acid- It is made up of digestive enzymes and HCl and other substances. The per day production of gastric acid is 3 to 4 litres.
So the correct answer is GASTRIC ACID.

Note: Here the secretin and gastric acid act inversely. In order to stop gastric acid which is lowering the pH of the duodenum then the release of secretin hormone takes place in the duodenum.