The Human Digestive System

NOM, NOM, NOM! Lunch sure was delicious! But, do you know what happens to food once it enters your body?

The human body can do a lot of amazing things. One of the coolest things it can do is digest food into energy.

After you take a bite of food, your teeth work to grind it up. You swallow, and it travels into your stomach. Strong acids and other chemicals slowly break it down into smaller and smaller pieces.

The food is passed into your small intestine, which pulls out the nutrients it needs to make you strong and give you energy. The leftovers pass into the large intestine, which sucks up all the extra water to keep you hydrated. Then it eliminates the parts your body can’t use (yes… we are talking about poop).

Here’s how your amazing digestive system works.

Digestion begins in your mouth

Digestion starts as soon as you take a bite of food. Chewing breaks food into smaller pieces. This helps the rest of the process by allowing the acids and chemicals your body makes to easily surround each piece and dissolve it more quickly.

When you swallow, that bite of food travels from your mouth to your stomach through a tube called the esophagus. The esophagus squeezes food forward by contracting and relaxing, like squeezing toothpaste out of a tube! Scientists call this movement “peristalsis”.

Human Digestive System

Your Intestines Suck up the Good Stuff

Next, muscles in the stomach wall squeeze your food even more and keep it moving down your digestive tract. You can not feel these muscles, but they are slowly squeezing the food around your stomach to make sure each piece of food gets covered in acid and digestive juices.

The next stop is the small intestine, where your body starts to separate food from waste. Your body absorbs nutrients in the small intestine, transferring them to your bloodstream. The nutrients can travel around your body to where they are needed. Waste products continue on the journey through your digestive tract.

It all comes out in the end

Waste management ends in the large intestine, which is also called the colon. In the large intestine, your body removes the water from the leftovers that are moving through it. The large intestine compacts this waste into stool, which your body then disposes of (yes, stool is poop).

The stool keeps moving by peristalsis (muscle contractions) into the rectum. This is the final section of your large intestine. It is also the end of your digestive tract. From the rectum, your body pushes out waste (hopefully into a toilet!).

Turning food into energy

All along the digestive journey, your bite of food is being broken down by mechanical and chemical processes. The mechanical processes include chewing, peristalsis or squeezing, and mixing the food up with various digestive juices.

The digestive juices take care of the chemical breakdown. In addition to saliva and stomach acid, your body uses bile for digestion. Bile is kind of like soap, as it helps break apart oils and fats. The liver makes bile and sends it to the gall bladder to be stored. When digested food arrives in the small intestine, the gall bladder releases bile to digest all the fats and oils.

The pancreas is an organ that also plays an important role in turning the food you eat into energy. When food is passing through your small intestine, all the sugar is dumped into your bloodstream. Your pancreas makes a chemical called insulin. Insulin is like a signal to your cells that tells them to suck up this sugar. Cells can turn this sugar into energy. That’s how each cell in your body gets the energy it needs to function.

How bacteria help with digestion

Did you know you have tons of microscopic organisms living inside of you?

The human digestive system wouldn’t work without trillions of microscopic helpers: bacteria and other single-celled organisms. Helpful bacteria that live in your digestive system break down tough fibers and other undigestable food particles. These helpful microbes also kill harmful bacteria and strengthen your immune system.

We have a symbiotic relationship with these bacteria: we need them as much as they need us!

Written by Laura McCamy

Edited by Gabriel Buckley, MS Professional Natural Sciences