How To Make a Model of the Lungs

Lung Model
This image shows an inflating model of the lungs.

Dave King/Dorling Kindersley/Getty Images

Constructing a lung model is an excellent way to learn about the respiratory system and how the lungs function. The lungs are respiratory organs that are vital to the breathing process and necessary to acquire life giving oxygen. They provide a place for gas exchange between air from the outside environment and gases in the blood.

Gas exchange occurs at lung alveoli (tiny air sacs), as carbon dioxide is exchanged for oxygen. This oxygen is then delivered to the tissues and cells of the body by the circulatory system. Breathing is an involuntary process that is regulated by a region of the brain called the medulla oblongata.

Building your own lung model will help you to gain a better understanding of how the lungs work!

What You Need

  • Scissors
  • 3 Large balloons
  • 2 Rubber bands
  • Electrical tape
  • Plastic 2-liter bottle
  • Flexible plastic tubing - 8 inches
  • Y-shaped hose connector

Here's How

  1. Gather together materials listed under the What You Need section above.
  2. Fit the plastic tubing into one of the openings of the hose connector. Use the tape to make an airtight seal around the area where the tubing and the hose connector meet.
  3. Place a balloon around each of the remaining 2 openings of the hose connector. Tightly wrap the rubber bands around the balloons where the balloons and hose connector meet. The seal should be air tight.
  4. Measure two inches from the bottom of the 2-liter bottle and cut the bottom off.
  5. Place the balloons and hose connector structure inside the bottle, threading the plastic tubing through the neck of the bottle.
  6. Use the tape to seal the opening where the plastic tubing goes through the narrow opening of the bottle at the neck. The seal should be air tight.
  7. Tie a knot at the end of the remaining balloon and cut the large part of the balloon in half horizontally.
  8. Using the balloon half with the knot, stretch the open end over the bottom of the bottle.
  9. Gently pull down on the balloon from the knot. This should cause air to flow into the balloons within your lung model.
  1. Release the balloon with the knot and watch as the air is expelled from your lung model.

Tips

  1. When cutting the bottom of the bottle, make sure to cut it as smoothly as possible.
  2. When stretching the balloon over the bottom of the bottle, make sure it is not loose but fits tightly.

Process Explained

The purpose of assembling this lung model is to demonstrate what happens when we breathe. In this model, structures of the respiratory system are represented as follows:

  • plastic bottle = chest cavity
  • plastic tubing = trachea
  • Y-shaped connector = bronchi
  • balloons inside bottle = lungs
  • balloon covering bottom of bottle = diaphragm

The chest cavity is the body chamber (bounded by the spine, rib cage, and breast bone) that provides a protective environment for the lungs. The trachea, or windpipe, is a tube the extends from the larynx (voice box) down into the chest cavity, where it splits into two smaller tubes called bronchi. The trachea and bronchi function to provide a pathway for air to enter into and exit the lungs. Within the lungs, air is directed into tiny air sacs (alveoli) that serve as the sites of gas exchange between the blood and external air. The breathing process (inhalation and exhalation) relies heavily on the muscular diaphragm, which separates the chest cavity from the abdominal cavity and works to expand and contract the chest cavity.

What Happens When I Pull Down on the Balloon?

Pulling down on the balloon at the bottom of the bottle (step 9) illustrates what happens when the diaphragm contracts and the respiratory muscles move outward. Volume increases in the chest cavity (bottle), which lowers air pressure in the lungs (balloons inside the bottle). The decrease of pressure in the lungs causes air from the environment to be drawn through the trachea (plastic tubing) and bronchi (Y-shaped connector) into the lungs. In our model, the balloons within the bottle expand as they fill with air.

What Happens When I Release the Balloon?

Releasing the balloon at the bottom of the bottle (step 10) demonstrates what happens when the diaphragm relaxes. Volume within the chest cavity decreases, forcing air out of the lungs. In our lung model, the balloons within the bottle contract to their original state as the air within them is expelled.