Working Lung Model

Food and air both enter your body through your mouth, diverging when they reach the esophagus and trachea. Food goes to the gastrointestinal tract through your esophagus and air travels to your lungs via the trachea, or windpipe.

You will be making a model of how your lungs work in this lab. It will include the trachea, lungs, and the diaphragm, which expands and contracts as it fills and empties your lungs.

Here’s what you need

    1. 1 2-liter soda bottle, emptied and cleaned
    2. 1 pair of scissors
    3. 1”Y” valve hose connector
    4. 3 round, 9-inch balloons
    5. 1 #3 one-hole stopper
    6. 1 length of hose, 8-inch
    7. 2 rubber bands
    8. 1 jar of petroleum jelly


Here’s what you do

  1. Cut off the bottom of the 2-liter bottle. Ask an adult for help.
  2. Take the “Y” valve and secure the two balloons to the top branches with the rubber bands.
  3. Put a tiny bit of petroleum jelly on the end of the hose to make it easier to insert into the #3 stopper. Pull 6 inches of hose through the stopper and then thread the hose through the bottle’s neck. Insert the stopper into the top of the bottle.
  4. Put the end of the hose (that is now inside the bottle) into the base of the “Y” valve (which now has balloons on its other branches). Pull the hose through the stopper a bit. Also, pull the lungs up toward the top of the bottle.
  5. Tie a knot in the third, unused balloon. Cut it in half and stretch the part with the knot over the open bottom of the soda bottle. Make sure the bottom balloon is as tight as it can be.
  6. Grab the bottle with one hand, the knot at the bottom of the balloon with the other. Carefully pull the knot on the balloon down. What happens to the balloons in the bottle? Now let go of the knot and observe how this affects the balloons. Note your observations in the experiment’s data.
  7. Sketch your model and label its trachea, lungs, and diaphragm.

What’s going on?

By placing a stopper in the top of the bottle and putting the stretched rubber balloon on the bottom, you have created an enclosed system. The tube at the top of the bottle is the only way for air to enter or exit the model’s lungs. Pulling down on the balloon’s knot reduced the air pressure inside the lungs. As compensation, air was pushed down into the tube to equalize the pressure. This caused the balloon lungs to expand. When you released the knot, the air pressure forced the air out of the balloons.

If you need more help with identification, the tube acts as the trachea, the balloons are the lungs, and the balloon with the knot at the bottom is the diaphragm.

Did you know that an average person breathes about 24,000 times each day? If you live to be 70 years old, that means about 600,000,000 breaths. Make them count!