How Do Your Lungs Work

Name: ______________________________
How Do Your Lungs Work?
What parts of the body are involved in the breathing process?
For each student
20 ounce or 2 liter plastic bottle
piece of plastic from a trash bag or shopping bag (cut in a 30-cm-diameter circle)
rubber band
poster or reference books with lung diagrams
masking tape
For teacher's use only
craft knife
Advance Preparation
Collect plastic bottles. Cut a small starter slit in the bottle about one-fourth of the way up from the bottom and
parallel to the bottom. Collect enough plastic trash and shopping bags to supply each student with a 30 cm
diameter circle of plastic.
1. Using scissors, carefully cut off the bottom of the plastic bottle starting at the precut slit.
2. Push the end of the balloon through the mouth of the bottle. Stretch the mouth of the balloon over the mouth
of the bottle.
3. Fold the 30-cm-diameter circle in half twice. Twist about 2.5 cm of the folded corner around and secure it
with a short piece of masking tape to make a handle.
4. Cover the open bottom of the bottle with the plastic circle so the handle is on the outside of the bottle.
Secure the plastic tightly to the bottle with a rubber band. There should be some slack in the plastic. The rubber
band may need to be doubled if using the smaller plastic bottle. See diagram below.
5. Gently push and pull on the handle to move the plastic in and out. What do you observe?
6. Hold the bottle so the mouth is near your cheek and move the surface of the plastic in and out. What do you
7. Describe what happens to the balloon as the plastic moves in and out. Explain your observations.
8. Using posters or reference books, compare the lung model to that of the human lung. Stimulate discussion by
asking students to discuss which parts of the model represent the lungs, chest cavity, and diaphragm? (Answer:
The balloon represents the lung, the bottle represents the chest cavity, and the plastic represents the diaphragm).
1. Extra mucus that forms in the lungs during a cold and with some respiratory diseases has an effect on the
function of the lungs. To explore this, add one spoonful of water to the balloon. Push and pull on the plastic and
observe what happens. How has the addition of water affected the ability of the lungs to function properly?
How does the extra "mucus" affect the amount of air that can be inhaled?
As you breathe in, your diaphragm contracts and flattens out. This allows it to move down, so your lungs have
more room to grow larger as they fill up with air. "Move over, diaphragm, I'm filling up!" is what your lungs
would say. And the diaphragm isn't the only part that gives your lungs the room they need. Your rib muscles
also lift the ribs up and outward to give the lungs more space.
At the same time, you inhale air through your mouth and nose, and the air heads down your trachea, or
windpipe. On the way down the windpipe, tiny hairs called cilia (say: sill-ee-uh) move gently to keep mucus
and dirt out of the lungs. The air then goes through the series of branches in your lungs, through the bronchi and
the bronchioles.
When it's time to exhale (breathe out), everything happens in reverse: Now it's the diaphragm's turn to say,
"Move it!" Your diaphragm relaxes and moves up, pushing air out of the lungs. Your rib muscles become
relaxed, and your ribs move in again, creating a smaller space in your chest.
One 1-liter or 1-quart clear plastic bottle*
One large balloon
One small balloon
Two rubber bands
One straw
Modeling clay
Cut off the bottom of the bottle. You can use a serrated knife, a utility knife, or scissors.
Cut the neck off of the large balloon.
Stretch this balloon over the bottom of the bottle.
Put a rubber band around it to hold it in place.
Insert the straw into the neck of the balloon.
Tie the balloon to the straw using the other rubber band.
Put the balloon end of the straw into the bottle so that the balloon is all the way into the bottle but does not
touch the balloon over the bottom of the bottle.
Secure the straw in the bottle by using the modeling clay.
Make sure the clay completely covers the mouth of the bottle, but does not crimp the straw.
1. Push on the rubber at the bottom of the bottle. What happens? Is this like breathing in or out?
2. Pull the rubber down. Which way would you be breathing now?
What happens?
The stretched balloon across the bottom of the bottle acts like a diaphragm. This is the flat muscle at the bottom
of the chest cavity. This muscle forces air in and out of your lungs. Your lungs do not inflate or deflate by
themselves ... a muscle, your diaphragm, is pulling or pushing so that you can breathe. 
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