The Digestive System In A Nutshell- Part Three

So far in this series we’ve spoken about the main structures involved in digestion as well as the ever important organs. And while we know what each is responsible for, you may be wondering how they know what to do & when… in come…. HORMONES! That’s right, it’s the endocrine system that is responsible for controlling this well orchestrated system.

hormone system

The endocrine system is a chemical messaging system that responds to any changes within the body and sends out messengers (hormones!) telling the body how to respond. While there are many more hormones throughout the body, we’re going to take a look at the ones specifically helping out the digestive system.


Secreted from the stomach as food enters through the LES. It begins the digestive process by signaling for the release of hydrochloric acid and pepsin. In turn, this promotes the wave like contractions through the stomach, keeps the LES closed, causes gallbladder contractions and promotes the release of the alkaline solution from the pancreas.


When the bacteria killing acids (hydrochloric) reach the small intestine, secretin is released. This hormone then travels to the pancreas and bile ducts to produce the pancreatic fluid to help neutralize acids. On top of that, this hormone inhibits gastrin (to slow down the stomach process) and enhances CCK (see below)

CCK (cholecystokinin)

Secreted as partially digested proteins and fats enter the small intestine. CCK signals to the pancreas that it is ready for the pancreatic enzymes to aid in digestion. It plays a role in inhibiting gastrin as well since acids from the stomach are no longer needed).

It is also CCK that stimulates the release of bile into the small intestine with the enzymes. Lastly, it shoots up a quick signal to your brain telling you you’re full and to wait a bit to eat.


GIP (gastric inhibitory polypeptide)

Released from the small intestine as CCK is working.. this hormone Enhances release of insulin and prepares body for appearance of glucose. It also ceases gastric secretions and movement as it is no longer needed.

GLP-1 B(Glucagon Like Peptide)

This messenger enhances the release of insulin and slows gastric emptying (similar to GIP). After you ingest your meal, the small intestine determines the amount of carbohydrates it contained and helps your pancreas create an insulin response.

This is why you get a bigger response from ingesting glucose instead of shooting it into your veins.


hungerSecreted from the small intestine as the alkaline solution enters. It promotes GI muscle contraction which helps move the partially digested food along. It is also released at regular intervals between meals which is what creates the “growling” sound when hungry.



Secreted by the stomach, intestine and pancreas when the alkaline solution enters. It is responsible for slowing gastric emptying, reducing smooth muscle contractions, reducing blood flow and casing enzyme release. In other words, it reduces digestive activity.

Peptide YY

This hormone comes from both intestines in the hours following a meal as it helps suppress appetite. It is released in direct proportion to the calorie content of the meal. It then inhibits stomach movement while it increases water and electrolyte absorption in the colon.


Released by the stomach, pancreas, kidney’s, pituitary & hypothalamus (in case we didn’t get the message??) in response to low food intake. It is the hunger hormone. It encourages appetite and stimulated growth hormone and after meals its concentrations decrease. Regulating ghrelin is key to long term energy balance.


Wow! Are your eyes glazed over yet? All of these hormones are necessary to function optimally. It is the endocrine system that acts a coordinator for the entire digestive process. While you may not know it, your body is constantly sending signals, responding and working at all times… so reward it with the fuel it needs to do its job. Contact me for help in how to optimally fuel your body.