Unit Size each
Show how the lungs are emptied and filled with air by relaxation and contraction of the diaphragm. Two balloons attached to a Y-tube simulate the lungs. The chest cavity is represented by a plastic bell jar (approximately 2L in volume) with an open top and a stout rubber sheet that acts as the diaphragm. As the diaphragm is pulled downward, the atmospheric pressure is lowered inside the chamber causing the lungs to expand as they take in air. When the diaphragm is released the lungs deflate.