The composition of inhaled and exhaled air are compared and the anatomy of the respiratory surface is described. Using an animation, the presenters describe how gaseous exchange takes place. The function and importance of the alveoli are explained: large surface area, moist, thin walls, good blood supply.

First broadcast:
21 November 2008

Students could draw lungs with a magnified section to show the branching bronchioles and alveoli, and the gaseous exchange between the alveoli and the blood.