Daddy made us a model of our diaphragm and lungs today. He needed a 1 liter soda bottle with the bottom cut off. Two balloons and two rubber bands.
Cut the neck off of one balloon and attach it with a rubber band to the bottom of the bottle. This is the diaphragm.
Next put a balloon into the top of the bottle. Use a rubber band to secure it. This balloons represents the lungs.
Now slowly pull the bottom balloon downward...this is inhaling, the top balloon enlarges. When you push the bottom balloon up (exhaling) the lung gets smaller.
Science is fun!