Scientific Eye – Energy for Life – a 19m 9s video:
Science in Action – Respiration – a 19m 13s video.
Want2TlkScience? –Respiration – a 6m 27s video.
Scientific Eye – Breathing – a 14m 18s video.
KS3 Bitesize foundation level – Humans as Organisms part 1 – a video covering nutrition & the digestive system, the skeletal system & how muscles work, then finally the process of Respiration and the Respiratory System.
A nice simplied powerpoint and here’s a 4m 25 s video: The Human Body – Heart & Circulation .