Answer:
The plastic at the bottom of the balloons act like diaphragm , as it expands air move in throw the straw which represent trachea and when it contract, the air move out the balloons.
Step-by-step explanation:
In the lung ballin model, the plastic at the bottom acts as the diaphragm. Diaphragm is a strong muscle that expand and contracts that cause air to flow in and out of the lungs. The movement of the balloon matches with breathing. When someone breathe in, air moves into the lungs like the balloons and it is because the diaphragm/plastic expands and these make air to enter through the straw which represent trachea and when you breathe out, the diaphragm contracts which allow air to move out.