8.6: Activity 5

How Breathing Occurs: Exploring with a Bell Jar Model

The bell jar balloon model is a classic hands-on demonstration to visualize how breathing works. It simulates the human respiratory system using simple materials, clearly showing how changes in pressure and volume allow air to move in and out of the lungs. This activity directly illustrates Boyle’s Law: when the volume of a closed space increases, the pressure inside decreases, drawing air in—just as in real breathing.

Figure \(\PageIndex{1}\) showcases the Bell jar model, a straightforward, airtight setup that illustrates the mechanics of human breathing through Boyle's Law principles. The model simulates how changes in thoracic volume and pressure, influenced by diaphragm movement, result in air moving into and out of the lungs. Component Parts of the Model shown:

• Bell Jar: Represents the rib cage or chest cavity, acting as a rigid, transparent enclosure.
• Y-shaped Tube: Symbolizes the trachea (windpipe) and the two bronchi leading to the lungs, passing through an airtight stopper at the top of the bell jar.
• Two Balloons: Mimic the lungs, attached to the ends of the Y-shaped tube inside the bell jar.
• Rubber Sheet: Represents the diaphragm, stretched and sealed across the open bottom of the bell jar.