Have you ever wondered how we breathe? Or have your kids ever asked you? The obvious, easy answer is “with our lungs”, but what does that really mean? What does that process look like? How does the air get into our lungs? These are all pretty valid questions! Let’s build a model of our lungs and see if we can figure it out.

I originally looked into building this model when I wrote the activity packs for The Gingerbread Girl Goes Animal Crackers. The main character is on a chase throughout the book and I wanted to tie in a science experiment that was related to running. I don’t know about you, but when I run, my two main thoughts are:

  1. I’m probably going to die soon. Please let the sweet release of death take me quickly.
  2. Why am I breathing so hard? Is this normal?

I should add that there’s usually an afterthought of “man, I really regret those last 3 Oreos”, but that’s a different video for a different day.

So, last 3 oreos aside, why am I breathing so hard? Let’s look at the model


  • A 1 Liter Soda Bottle
    • I actually used a 1 1/4 liter bottle, which was the larger “single serve” soda bottle. A 2 liter bottle is too big for our balloons to fit and a true “single serve” soda bottle won’t be large enough for our lungs to expand.
  • 2 Straws
    • I used bendy straws, but you don’t have to get that fancy. Regular straws will work just fine. Ask if you can get extra next time you hit the drive through.
  • 2 Balloons
    • Regular sized balloons that you can get anywhere. I used some with polka dots because I thought it was reminiscent of alveoli, but I assure you, I am the only person who made that connection.
  • Tape
    • Masking tape or painters tape will work great. You probably need something tougher than regular scotch tape.
  • Clay or Playdough
    • We need something to seal off the top of the soda bottle. I used homemade pumpkin spice playdough (you can get the base recipe here and if you follow me on social media, I occasionally drop seasonal recipes). Obviously, any type of commercial playdoh or clay would be fine!
  • A Punch Balloon
    • We need a slightly larger balloon to fit over the bottom of the soda bottle. I like the punch balloon because it fits great and there’s a rubber band already attached to make pulling down our diaphragm easy.
  • A Box Cutter
    • Something that will easily cut through the soda bottle

Step 1: Make The Lungs

Image shows author taping a balloon onto the end of a straw.

The first thing we’re going to do is turn our balloons into lungs. We do this by sliding one of the balloons over the end of a straw and taping around the top of the balloon. We’re looking to completely seal off the balloon so that the only air that enters is through the straw.

Repeat that with the second balloon and straw.

Step 2: Make The Trachea

Image shows author holding up two straws with balloons attached to the end of each.

Now that you have two “lungs”, tape the two straws together about mid way up the straw. These two straws are going to form our trachea.

Step 3: Create The Torso

Image shows the author with an empty soda bottle.  The end has been cut off the bottle.

Cut the bottom 1/4 off the soda bottle. I did this with a box cutter. I originally tried to cut it with scissors, then I tried to saw it off with a knife. Neither worked for beans. Trust me, just start with the box cutter. Be careful and try to cut a fairly straight line.

Step 4: Put The Lungs In The Torso

Image shows the author sliding the set of straws and balloons into the empty soda bottle.

Take your pair of lungs and pop it into the torso. Go in through the bottom so that the “trachea” or taped straws can come out the neck of the bottle.

Step 5: Seal Off The Top

Author is wrapping playdough around the neck of the soda bottle.

Use your clay or playdough to seal off the top of the bottle. Wrap the playdough around the straws and down onto the threads for the lid. Really smoosh it to make sure no air can get in the top except through the straws.

Step 6: Make The Diaphragm

Author is cutting the end off a punch balloon.

Make the diaphragm by cutting the open end off a punch balloon. This will leave you with a rubber bowl with a rubber band on the end. This bowl will be our diaphragm.

Step 7: Add The Diaphragm

Author is pulling a balloon over the cut off end of a soda container

This part is easier if you have a partner. Have one person hold the bottle with the open bottom facing out. The other person should pull the rubber bowl of the diaphragm over the end of the soda bottle. It really is easier with two hands to pull on the balloon, so if you have a partner, use them! Once the diaphragm is on, tape it to the bottle around the edge. This step probably isn’t necessary, but it doesn’t hurt to add a little security.

Ta Da: Our Model Is Finished!

Image shows the completed lung model

How Does It Work?

Pull down on the rubber band. If everything is sealed up, you’ll hear air rush into the balloons and see them fill with air. When you let go of the rubber band, it’ll pop back up and your balloons will deflate and you’ll hear the air come out.

Author pulling down on the balloon to simulate a diaphragm pulling down

Why? What’s happening?

When the diaphragm pulls down, it’s creating extra space in the torso and making a vacuum in the process. The only way air can get in to fill the vacuum is by rushing in to the lungs and filling them up. As the diaphragm relaxes and comes back up, it takes the space the air was occupying and pushes the air out of the lungs and back through the trachea. I have a degree in anatomy and this simple model is probably the best visual I’ve ever seen for how the diaphragm facilitates breathing!

What about when we run?

A couple things happen when we run and our body is processing oxygen faster. In order to get more air into our lungs, our diaphragm pulls down farther, allowing more air to enter the lungs. Also, it starts to move faster. That panting/hard breathing situation when we’re “out of breath” is our diaphragm working harder to pull in larger volumes of air more quickly.

Try it with the model.

Image shows retracted diaphragm on the model

Pull the diaphragm down slightly. See how the lungs inflate, but not to their full volume? That’s kind of “typical” breathing. Now pull the diaphragm down all the way. The lungs fill up much more noticeably. By pulling down further on the diaphragm, we’ve created more space and the lungs can fill more.

Now pull down and release the diaphragm more quickly and repeatedly. It sounds like our model is breathing hard, right? It’s bringing in and releasing more air as it pulls and releases quickly.

Pretty amazing, right?

Isn’t our body phenomenal? The way it works will never cease to amaze me! If you want to see more science videos or activities to accompany your favorite picture books, follow me on social media and YouTube. New stuff comes out weekly, so there’s always something different to try. I hope to see you again soon!