You hear a lot about the digestive system —- from reflux to the gallbladder to the gut microbiome. But how does the digestive system work? And how does the digestive system work with other systems of the body to keep you functioning and healthy? Read on to find out more.

How Does the Digestive System Work?

Digestion refers to the process of breaking down food so that your body can absorb the nutrients and eliminate what it doesn’t need. When it comes to digestion, many people think of the stomach and intestines. But there’s a lot more to the digestive system than that. In addition to the gastrointestinal tract, there is also a complex accessory organ system. The process of digestion begins the moment you put food in your mouth and ends, well, you know — where it ends.

Here is a chart of the major parts of the digestive system. How does the digestive system work? We will cover everything you need to know.

The gastrointestinal tract

The gastrointestinal tract starts at the mouth, believe it or not:

Teeth, tongue, and mouth

The function of these parts is pretty straightforward. The body takes in food and drink through the mouth. The teeth pulverize the food, making it ready to swallow. In addition to being a sense organ, the muscular tongue helps move food from the mouth to the esophagus.


The esophagus, or throat, is a muscular tube that takes food from the mouth to the stomach. It does this through a process of peristaltic contractions or peristalsis. The intestines also use peristalsis to move food along the digestive tract.


organ system - diagram of the stomach for How Does the Digestive System Work article

Image: Public Domain CC by 0, by Henry Gray, via Wikimedia Commons.

The stomach is where the magic happens, or so to speak. The stomach, too, is a muscular organ. And it is very tough. The gastric acid inside the stomach is about as strong as battery acid. In fact, if you were to put a drop of stomach acid on a piece of wood, it would eat right through it! Sometimes the stomach produces too much acid, and it causes problems such as reflux or ulcers.

Small intestine function

About one hour after food has entered the stomach, it goes to the small intestine. At this point, it is no longer food, but chyme, a highly acidic substance containing nutrients. The small intestine function is mainly about absorbing those nutrients. In order to do this, the body needs to make the chyme less acidic. It does this by adding bile from the gallbladder, bicarbonate secretions from the pancreatic duct, and secretions of bicarbonate-rich mucus from the Brunner’s glands.

Large intestine function

After most of the nutrients have been absorbed into the bloodstream, the food moves to the large intestine. It will remain in the large intestine for between 12 and 50 hours. While there, the material will ferment, and the large intestine will absorb the remaining nutrients. When no further nutrients remain, the body will expel the waste matter as feces.

Dietary fiber plays an important role in moving waste matter out of the large intestine and out of your body. Dietary fiber is found in most fruits and vegetables. A diet poor in dietary fiber can lead to constipation, hemorrhoids, and other problems.

The accessory organ system

A number of organs aid in digestion and waste removal. You have probably heard the names. But have you ever wondered what it is, exactly, that each of them does? (We already know you want to know how does the digestive system work, so it makes sense that you would have wondered.)

Salivary glands

The salivary glands produce saliva, which helps to break down food in the mouth. Humans have three sets of major salivary glands and hundreds of minor ones.

The salivary glands: how does the digestive system work with other systems

Image is CC by A 3.0 Unported (CC BY 3.0), by Blausen Medical Communications, Inc., via Wikimedia Commons.


The pancreas is a glandular organ that sits behind the stomach. This organ does double duty. First, as a gland, it produces several essential hormones, including insulin. Insulin helps your body to digest carbohydrates, proteins, and fats by encouraging your body to absorb glucose. The pancreas is also a digestive organ. It secretes pancreatic juice into the small intestine. This juice helps to neutralize the acidic chyme so that nutrients can be absorbed in the small intestine. The pancreas also secretes various digestive enzymes into the small intestine.


How Does the Digestive System Work article diagram of bile system and liver showing gall bladder

Image: CC by 0 Public Domain, by Henry Gray, via Wikimedia Commons.

The liver has two primary functions. First, it secretes bile, which helps to break down fats so that your body can absorb them. Second, it helps your body to get rid of toxins, like alcohol. Too much of certain toxins, such as alcohol and some drugs, can cause serious liver problems like cirrhosis.


The gallbladder is a small, hollow organ that stores and concentrates bile before releasing it into the small intestine. The gallbladder is located beneath the liver and receives bile from the liver. The gallbladder’s main function is helping your body to digest fats. Gallstones are caused by concentrations of indigestible matter — cholesterol or bilirubin — in the gallbladder. If gallstones cause pain or other complications, it is common to remove it. In general, loss of the gallbladder has little effect on digestion, though some people may experience indigestion after the operation.

How Does the Digestive System Work with Other Systems?

All of the systems of the body work together, supporting one another. The job of the digestive system is to provide the nutrients the body needs to function. It does this by breaking down foods and converting them into forms that different parts of the body can absorb and use. In addition, here are some specific ways that the digestive system and certain bodily systems work together.

How Does the Digestive System Work article image is a cross stitch image of the internal digestive organs from esophagus to anus

Image: Attribution 2.0 Generic (CC BY 2.0), by Hey Paul Studios, via Flickr.

The nervous system

The nervous system alerts the body to the fact that the body needs fuel. This results in the sensation of hunger. Hunger is the signal to the brain that the body needs to eat. In addition, the nervous system regulates the speed at which food passes through the digestive tract.

The muscular system

Muscles move food through the digestive tract. There are three layers of muscle in the stomach, and two each in the large and small intestines. These muscles help to digest the food and move it along in a process called peristalsis.

The circulatory system

Once the body has broken down the food you eat, the digestive organs break it down further into something your body can absorb. As it passes through the intestines, the intestines absorb the fats, carbohydrates, and nutrients, and then transfer them to the bloodstream. Then the blood distributes these nutrients to other parts of the body. The heart pumps the blood, which moves it throughout your body.

The excretory system

Excretion is the process of getting rid of waste. After your body has broken down the food you’ve eaten, it separates it into nutrients and waste. The body absorbs the nutrients, then pushes out the waste. The kidneys process liquid waste and send it to the bladder, where it becomes urine. Solid waste travels through the intestines and leaves the body through the anus as feces.

What Is the Gut Microbiome, and Why Is It so Important?

The gut microbiome is a complex ecosystem of organisms that live in our digestive tract. These organisms include bacteria, yeasts, fungi, viruses, and protozoans. These organisms play a number of vital roles in our health. They help us to digest food. And they help to break down toxins. In addition, they help to train our immune system. Some scientists also think that the gut microbiome may play roles in such diverse functions as mental health, acne, and weight gain. So, to answer you question about how does the digestive system work, it is essential to understand your gut biome.

Certain medications may affect your gut microbiome, including antibiotics. In addition, your diet can affect your gut microbes, both positively and negatively. Stress can also have an impact on your intestinal flora. You can learn more about your gut microbiome and how to care for it here.

How Does the Digestive System Work? Now You Know

Digestion is a complicated dance of organs, muscles, fluids, and microorganisms. An upset in the digestive system is more than just a belly ache. It can have repercussions for your entire body. On the other hand, good digestive health can help you to keep your whole body healthy and fit. If you take care of your digestive tract, it will take care of you.


Featured Image: CC by 0, by Silviarita, via Pixabay.