Answer:
1) The diaphragm contracts
2) External inter coastal muscles contract--- raise the rib cage
3) Thoratic cavity and lungs expand causing pressure inside the lungs and aleoil to drop
4) Air the rushes in the lungs
Pathway of the Air = Nasal Cavity ---> Pharynx -----> Glottis -----> Larynx ----> Bronchi ----> bronchioles -----> alveoli
5) Oxygen diffuses across the alveolar membrane into the pulmonary capillaries
*** remember air inside the lungs must be lower than that of the external atmosphere .. air flows from high to low .