Library · Physiology
Pancreatic secretion
Make it clearer
The pancreas does not secrete at random. It waits to be told, and what tells it is the intestine, with two different messages that ask for different things.
The first message is triggered by acid. When food leaves the stomach for the duodenum, the first stretch of the small intestine, it arrives bathed in gastric acid. The duodenal mucosa detects it and releases a hormone called secretin, which travels to the pancreas and asks it for bicarbonate and water. The bicarbonate neutralizes that acid and brings the environment to a pH of 6 to 8. That is not a cosmetic detail, it is the pH at which the digestive enzymes can work.
The second message is sent by some intestinal cells called I cells, and the hormone is called cholecystokinin. This one goes straight to the acinar cells of the pancreas, the ones that store the enzymes, and tells them to release those that break down fats, proteins and carbohydrates.
When this machinery breaks down, you notice. In cystic fibrosis, a genetic disease, the pancreas barely responds to secretin, and without that water and that bicarbonate the secretions come out dehydrated and thick.
In brief
Secretin, made in the duodenal mucosa, asks the pancreas for bicarbonate and water.
Stomach acid triggers its release, and that bicarbonate neutralizes the acid to a pH of 6 to 8.
That pH is what lets the digestive enzymes work.
Cholecystokinin, from the intestine's I cells, tells the acinar cells to release the enzymes for fats, proteins and carbohydrates.
Two different orders to the same organ: one for fluid, one for tools.
In cystic fibrosis this response drops sharply and secretions come out thick.
Sources (2)
- National Center for Biotechnology Information, StatPearls PublishingPhysiology, Secretin, StatPearlsPublished
- National Center for Biotechnology Information, StatPearls PublishingBiochemistry, Cholecystokinin, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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