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The Digestive System: Turning Food Into Fuel · The digestive system breaks food down so the body can absorb nutrients and remove waste. · MS-LS1-3

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Prerequisite: Complete or review The Digestive System: How We Eat and Digest Food; Use with parent or guardian controls for child learners

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The Digestive System: Turning Food Into Fuel

with Atlas

Atlas the friendly guide stands beside a giant glowing see-through body map, pointing along a winding tube from mouth to belly while a cheerful apple travels through it.

Name the main stops food makes on its journey: mouth, esophagus, stomach, small intestine, and large intestine.
Explain that digestion breaks big food into tiny pieces the body can absorb.
Describe how the body absorbs nutrients and removes leftover waste.
Put the steps of digestion in the correct order from start to finish.

Key terms

digestion: breaking food into tiny pieces to use
saliva: the watery spit inside your mouth
esophagus: the tube from mouth to stomach
small intestine: where nutrients pass into your blood
waste: leftover food the body cannot use

A Bite of Apple's Trip

A bite of apple starts its trip in your mouth. Your teeth chew it into mushy bits, and your spit, called saliva, softens it and begins breaking it down. You swallow, and the apple slides down a long tube called the esophagus. The esophagus carries the food straight down into your stomach, where the next step of digestion is ready to begin.

Fuel In, Waste Out

Your stomach is a stretchy bag that squishes the food into a thick soup. The soup moves into your small intestine, a long coiled tube. There the tiny food bits, called nutrients, pass into your blood. Your blood carries that fuel all over you. Leftovers go to the large intestine, which soaks up water and packs the waste to leave your body.

Worked examples

What happens to a bite of apple first?

Your teeth chew the apple into mushy bits.
Your saliva softens it and starts breaking it down.
You swallow and it slides down the esophagus.
The apple lands in your stomach.

Answer: The mouth chews and softens it, then it goes to the stomach.

Hi, I'm Atlas! Let's follow a bite of apple on its amazing trip. It all starts in your mouth, where your teeth chew the apple into mushy bits and your spit (called saliva) softens the food and begins breaking it down. You swallow, and the food slides down a long tube called the esophagus straight into your stomach. Your stomach is like a stretchy mixing bag. It squishes and churns the food with special juices until it turns into a thick soup. Then the soup moves into your small intestine, a long, coiled tube. This is where the magic happens! The tiny bits of food, called nutrients, pass through the walls and into your blood. Your blood carries that fuel all over your body to give you energy to run, think, and grow. Not everything can be used. The leftover parts your body cannot absorb move into the large intestine, which soaks up water and packs the rest into waste that leaves your body when you go to the bathroom. So your digestive system does two big jobs: it pulls out the good fuel, and it gets rid of what's left over. If you ever feel stuck, remember the order: mouth → esophagus → stomach → small intestine → large intestine.

Activity

Put these stops in the order a bite of food actually travels through the body.

Practice

What is the main job of the digestive system?

Where do nutrients pass into your blood?

Common mistakes to avoid

Food turns into blood in the stomachThe stomach makes soup; nutrients enter blood in the small intestine.
Food is absorbed in the mouthFood is chewed in the mouth, not absorbed into the blood there.

Check your understanding

What is the main job of the digestive system?

Where does food go right after you chew and swallow it?

A friend says, 'Your stomach is where food turns into blood.' Why is that not quite right?

What happens to the leftover parts of food the body cannot use?

Recap

Your digestive system breaks food into tiny pieces and pulls out the good fuel. Food travels from mouth to esophagus to stomach to small intestine to large intestine, where leftover waste leaves the body.

Reflect

Imagine following a bite of your favorite snack inside you!