A powerpoint from the OLD syllabus, much is still relevant.
Fantastic animated tutorials from McGraw Hill Education – alveolar pressure changes during breathing & gas exchange during respiration (breathing).
How do the Lungs work? – a three and a half minute lesson from TED-Ed:
Paul Andersen describes The Respiratory System in an 8m 46s tutorial.
In Crash Course Biology #27 – Circulatory & Respiratory Systems, Hank takes us on a trip around the body – we follow the circulatory and respiratory systems.