Control of Digestion by the

Endocrine System

By David Sharpe (aged 17 and ¾) and Jo Ford (aged 18 and ¼)

The secretion of digestive juices by the stomach and pancreas, and the release of bile from the gall bladder are controlled by hormones.

The hormones which cause the secretion for digestion are released even before food reaches the stomach. This is because the action potential (triggered by the medulla oblongata) that causes the secretion is sent as soon as food is sensed in the mouth.

Sensory nerves in mouth

The medulla oblongata

Goblet cells, from which Gastrin is produced.

Action potential

Action potential

The hormone that causes the gastric glands to release digestive juices is called gastrin. It is secreted by some of the cells in the mucosa, that lines the entire gastrointestinal tract.

The gastrin is released into the blood and causes the gastric glands to release large amounts of gastric juice into the digestive system. This process is caused by sensory nerves in the mouth detecting the presence of food and by the presence of food in the stomach.

As the process is begun when food is in the mouth it ensures there are some digestive juices in the stomach when food is swallowed, and when it is, the quantity of gastric juices increase dramatically.

The stomach, showing the mucous membrane from which gastrin is released.

The secretion of pancreatic juice is largely controlled by the arrival of food in the duodenum. Contact with the acidic substances stimulates a hormone called secretin. This, like all hormones, is released into the blood, which distributes it to its target cells in the pancreas.

A section Monkey pancreas. Delicious.

Secretin stimulates the exocrine cells in the pancreas to release a juice rich in Hydrogen-carbonate ions, into the pancreatic duct.A simple diagram showing the secretion of

pancreatic juice. Very simple.

The cells lining the duodenum also respond to the arrival of food containing the products of fat and protein digestion. In these circumstances they secrete a different hormone, cholecystokinin or CCK for short. CCK, like secretin, acts on the exocrine cells of the pancreas, except that this time it stimulates the secretion of a juice rich in enzymes.

The products which cause CCK release.

CCK also affects the gall bladder, causing smooth muscles in its walls to contract and force bile along the bile duct into the duodenum.Both the gall bladder and Pancreas are affected

by CCK.

This is CCK. The entire structure shown here must be completely memorised at A2 level.

Haha, only kidding. …Or am I?

This diagram shows the entire process of digestion control by the endocrine system. If you as a student find learning diagrams is a more efficient method of revision than learning text, memorizing this relatively simple diagram will be extremely beneficial when it comes to your A2 examinations.