Respiratory system

We have learnt more about the human body: the respiratory system. To understand the way it works and why we can fill the lungs using our diaphragm, we did this experiment.
The pressure inside the plastic glass doesn't change because it is isolated. But the pressure inside the ballon (fake lung) changes because it is connected to the outside by a straw. When you pull the outside ballon, you reorder the particles inside the plastic glass, reducing the pressure, so the inside ballon takes air from the outside and get wider.
This is the result: