Your food is digested in a complex process, and that process also involves a wide variety of hormones.
This lesson goes over some of the more commonly known gastrointestinal hormones and their major actions.
What Are Gastrointestinal Hormones?
Besides water and air, what else do you need in order to live a healthy life? Nope, not your phone, but good guess. It’s food. Your body needs food as a source of fuel to power all of its processes.But the food doesn’t magically enter your body’s cells.
It needs to be digested thanks to the gastrointestinal system, a collection of cells, tissues, organs, and biochemicals that allow for the digestion and absorption of food into the body.Those biochemicals, at least some of them, are what this lesson is about. We’ll be taking a look specifically at gastrointestinal hormones, which are biological molecules that help your body digest and absorb the food that you eat.
Gastrin, Secretin, & CCK
Let’s pretend you’re eating a hamburger. As you swallow a piece of it, it moves from your mouth, into the esophagus (food tube), and down into the stomach. Some of the stomach’s cells release a hormone called gastrin. Gastrin is released in order to tell the stomach to secrete hydrochloric acid.
This acid is an important component of your stomach acid.What’s stomach acid good for? Well, two major things. First, the stomach acid helps to break the food apart a bit chemically. Second, the acid is deadly. Not to you, thankfully (at least not usually). It’s deadly to all sorts of potentially harmful microorganisms that may be found in that probably not-very-well-cooked piece of hamburger meat.
The partially digested bite of hamburger moves on to the intestines. The first part of the intestines is called the duodenum. It is attached directly to the stomach.
The cells of the duodenum release a hormone called secretin. Secretin has a bunch of different roles:
- It tells the stomach to stop making so much stomach acid.
- It helps promote the release of bicarbonate from the bile ducts. Bicarbonate is something that neutralizes the stomach acid that was just flushed into the duodenum from the stomach. Think of bicarbonate as pouring water on the fire that is stomach acid.
- It tells the pancreas to start secreting bicarbonate juice as well, for much the same reason.
On the note of the pancreas, this is an organ that also secretes digestive enzymes. And, what do you know? There’s a gastrointestinal hormone that tells the pancreas to do this. That hormone is called cholecystokinin.
Thankfully it’s abbreviated as CCK. CCK is also released by the cells of the duodenum, and besides stimulating the pancreas to release digestive enzymes, it also tells the gallbladder to release a substance called bile, which is essential for the digestion and absorption of fat.
GIP, Ghrelin, ; Motilin
The duodenal cells also release a compound called glucose-dependent insulinotropic polypeptide, also known as gastric inhibitory polypeptide, and thankfully just GIP for short. This hormone has two main roles. First, it tells the stomach to stop making stomach acid and to stop moving around so much, which it normally does to help mechanically digest your food and pass it along into the intestines.
Second, GIP helps the pancreas release a hormone called insulin, which is the hormone that drives blood sugar into your body’s cells.Another pretty well-known gastrointestinal hormone is called ghrelin, which is made by the stomach. Ghrelin levels increase before a meal and decrease after a meal. So, one of its functions is to increase a person’s hunger.It is also during the fasted state, when a person is more likely to be hungry, that a hormone called motilin is secreted by the small intestine.
Motilin is like a housekeeper. It tells the digestive tract to contract to sweep undigested food down the digestive system so you’re ready to eat another meal.
Of course, there are plenty of other hormones related to digestion and even other functions attributed to the hormones covered in this lesson. We can’t cover all of them in a short lesson, but do be aware of some examples of other hormones involved in digestion:
- Vasoactive intestinal peptide (VIP), a hormone that has many functions, including the relaxation of gastrointestinal smooth muscles
- Glucagon-like peptide-1 (GLP), which helps to promote insulin release
- Somatostatin, which helps decrease stomach acid secretion
There were a ton of hormones to learn about and a lot of functions as well.
Let’s summarize everything like this for our lesson.The gastrointestinal system is a collection of cells, tissues, organs, and biochemicals that allow for the digestion and absorption of food into the body. Those biochemicals include gastrointestinal hormones, which are biological molecules that help your body digest and absorb the food that you eat.
There are many such hormones, and almost all of them have many different functions.Remember, there’s:
- Gastrin, which tells the stomach to secrete hydrochloric acid
- Secretin, which promotes the release of bicarbonate
- Cholecystokinin, which tells the pancreas to release digestive enzymes
- Glucose-dependent insulinotropic polypeptide, also called gastric inhibitory polypeptide (GIP), which helps release insulin
- Ghrelin, which stimulates your appetite
- Motilin, which clears your digestive tract of undigested food so it’s ready for another meal