How does the digestive system work step by step? Pathway of food explained

Heather Campbell
 min read

How does the digestive system work step by step? Often referred to as the “second brain,” it is important to know how it works.

How does the digestive system work step by step? Pathway of food explainedYour digestion tells you everything about your health. And did you know that good health starts in your gut?

The digestive system is a complex structure that assimilates food and drink and decides what is needed and what isn’t. Its functions start at the mouth, and can encompass as many as eight organs until the waste is ready to be discarded. It hosts trillions of bacteria essential to our well-being.

Listening carefully to your gut will help you know what your digestive system needs. This is important because your digestion is vital, just like your heart, lungs, and brain.

So in reality, how does the digestive system work step by step? Learn all about your digestive system below and find out exactly how it works and how best to take care of it.

How does the digestive system work step by step? Introduction

Each bite you take makes a trip through your digestive system of about 26 feet in length.

Before your bite ends up in the toilet, it takes as many as eight different organs to help turn your food into poop.

The esophagus, stomach, small intestine, colon, and microbiome extract nutrients from your food.

What your body can’t use, your digestion keeps apart. So that later forms your stool.

The pancreas, gallbladder, and liver make digestive juices that help digest your food.

In total, your complete digestion takes 24 to 48 hours, depending on precisely what you ate and how much.

Your food travels: Chronological trajectory from mouth to butt

Smelling, seeing, hearing, and even thinking about food can make your mouth water.

This is also called salivating (or drooling), which is the start of your digestion.

At these moments of saliva production, signals are sent from the brain to your organs so that the body can prepare in advance for digestion.

How does the digestive system work step by step? Check it out via the chronological timeline below.


When you see, smell or even think about something delicious, your brain sends signals to your organs.

Think of a juicy apple. If the water runs into your mouth at such a moment, the digestion has already started.

In any case, chewing well is very important. It triggers saliva production and makes you feel full faster. Producing more saliva in the mouth also makes it easier to swallow the food.

When your food is finely chewed, you then push it into the esophagus with your tongue.


The esophagus can be thought of as a muscular tube. With squeezing and pushing motions, also called peristaltic movements, that tube sends the chewed food to your stomach.

At the same time, the esophagus protects you from rising stomach acid. Namely, there is a sphincter opening and closing like a valve where your esophagus goes through the diaphragm to enter your stomach.

This sphincter allows the food to pass through while stopping the stomach acid from traveling back up.


Your stomach contents shake back and forth. Thus, the chewed food becomes smaller and finer and is now mixed with the acidic gastric juice.

This juice contains all sorts of substances that make for good digestion. Most food sits in your stomach for 2 to 3 hours. Fatty food usually sits in your stomach a little longer than that.

Once your stomach has processed everything, the food is passed in pieces to the first part of the small intestine.

Small intestine

At the beginning of the small intestine, digestive enzymes further cut the mouthful of food into pieces.

The bite of food now consists of nutrients so small that they are absorbed into the blood through the intestinal wall.


Once the nutrients are absorbed by the small intestine, they travel from the intestinal wall through the portal vein to the liver.

The liver is best compared to a factory that receives about 0.4 liquid gallons of blood every minute.

By filtering the blood, this organ controls the nutrients that enter in tiny particles. Good nutrients are allowed to pass while toxins are stopped and broken down.


If we call the liver a factory, the gallbladder is the warehouse. Bile is made by the liver and stored here (in the gallbladder warehouse).

It is a yellow-green sac that sits under your liver. The bite of food on the way through your body may contain fats. In such a case, the gallbladder comes into action.

In fact, bile plays an important role in breaking down fats. The gallbladder receives a signal to send bile fluid to the small intestine.


This gland makes the digestive juices to cut carbohydrates, fats, and proteins into pieces at the beginning of the small intestine.

This pancreas also regulates your blood sugar levels by making the hormones insulin and glucagon.

Insulin lowers blood sugar, and glucagon raises blood sugar.

Did you know that only if your pancreas is working properly, will thesse hormones (insulin and glucagon) be in balance.

Large intestine

That one bite of food is now nearing the end of its journey through your body.

Your colon extracts some more moisture and salt from it, so the whole thing becomes thicker and thicker.

The poop is pushed to the end of the intestine with squeezing motions. The fiber from your snack has arrived in your colon and helps keep stools flexible.


This is the very last stage of your digestion. Is your rectum full? Then a signal is sent to your brain. You will feel urges, and a toilet visit is about to become urgent.


Your gut is home to trillions of bacteria that make up your microbiome, along with viruses, yeasts, and fungi.

These bacteria have a significant impact on your life and how you feel. And they do a tremendous job because, for example, they help digest food and stimulate bowel movement!

The microbiome also helps keep your gut wall healthy. It also trains your immune system, making you less likely to get sick and heal faster.

What does your microbiome look like?

  • All those bacteria together weigh as much as 3.3 pounds. Scientists are getting to know more and more what goes on in our inner ecosystem. New techniques are mapping our microbiome in detail. As a result, we know that our microbiome is as unique as a human fingerprint. What your microbiome looks like depends on several factors such as your age, birth, environment, genes, and use of medications. Indeed all of these factors affect your microbiome.
  • The composition of your microbiome is partly in your control. Getting enough exercise, sleeping well, and relaxing enough all contribute to a healthy microbiome. But nutrition is the most decisive factor because what we eat is also on the menu for our bacteria in the intestinal system.
  • The bacteria in your gut absolutely love fiber. Fiber is found in vegetables, fruits, legumes, and whole-grain products. By eating a lot of this, you help the good bacteria to do their job. It is good to have many different strains of bacteria in your gut. Eating many fiber types is the best way to take care of your microbiome and take control of your own health. In contrast, a diet high in sweet and fatty processed foods makes the microbiome a lot less versatile. In addition, by doing this, you are feeding the bad bacteria.

What does the microbiome do for you?

The influence of our microbiome is huge. You feed it daily with what you eat, and in return, the bacteria go to work for you.

But what exactly do they do in your body? What role do they have, and what benefits do you get from them?

The microbiome helps your digestion

The bacteria in your gut digest sugars and extract nutrients from your food. For example, they break down indigestible pieces of fiber to extract energy as needed.

All kinds of useful substances are released during that process. These keep the intestinal wall in shape and encourage smooth bowel movements.

The microbiome works together with your immune system

The bacteria are in constant contact with your immune system. Together they respond to incoming pathogens and viruses. So the microbiome regulates the immune system.

The immune system must react alertly to invaders but not too fanatically, or an allergic reaction may occur.

Good to know: A healthy and diverse microbiome reduces the risk of chronic inflammation, allergic reactions, and autoimmune diseases.

Related postHow does the digestive system prevent infection? Why gut health is important

The microbiome talks to your brain

The bacteria in your gut affect your behavior, illnesses, and mood. This is because they send signals to the nervous system.

By the way, that contact with the brain is a two-way street.

For example, stress hormones (such as cortisol) also affect the microbiome’s composition. Think about constipation or diarrhea in anticipation of experiencing an exciting moment or delivering a performance.

Related postConstipation in adults: Insights & tips to stimulate a bowel movement

Your gut is your second brain

Your brain is connected to your gut by the body’s longest cranial nerve, the vagus nerve.

The intestines and brain communicate with each other through this nerve and that’s why your gut is also called your second brain.

We are finding out more and more about the direct relationship between the microbiome, the gut, and the brain.

Your gut and your brain are constantly communicating about your well-being. For example, when:

  • you are hungry,
  • your stomach is full, or
  • you’re experiencing stress, and
  • when to go to the bathroom.

The intestines can also sound the alarm, for example, when eating spoiled food.

When the bacteria recognize the wrong food, they want to get rid of it quickly. The vagus nerve lets the brain know this directly.

And in response, the gut gets a signal to contract. With any luck, you’ll just be able to sprint to the bathroom in that time!

In short, the microbiome is a vital digestive organ. If your microbiome stays in good shape, those billions of bacteria can take the best care of you.

How does the digestive system work step by step? Conclusion

The digestive system is often underrated.

Starting at the mouth and ending up at the rectum, the “second brain” is responsible for our well-being mentally and physically.

That is why it is so important to keep it going with the right fuel – food and drink.

About Heather Campbell

As a nutritionist, my field of specialization is science-based nutritional advice but more importantly, it is my goal to share capturing and inspiring stories, examples and solutions which can help plus-size individuals overcome their specific difficulties. Read More