Examine how contraction and relaxation of the diaphragm leads to inspiration and expiration of air from the lungs:

(a) Explain scientifically what happened when you pulled downwards on the diaphragm in the models. Relate what you visualized with respect to changes in volume and pressure of the air and indicate how this relates to inspiration and expiration in our bodies. How does the pleura assist with this process? [4 marks]

(b) What happened when you put a pin hole in your ‘lung’ balloon? Why did you see this effect? [1 mark]

(c) Is the diaphragm the only muscle that affects the volume of the thoracic cavity and therefore breathing in the human lung? [0.5 mark]