PRESENTER:'Ella has P.E. today, and her circulatory system is going to have some exceptional challenges to overcome.' BOTH:Bye mum! PRESENTER:'We are going to follow the action in extreme detail.' ...

Circulatory system: Blood vessels Laid end-to-end, an adult's arteries, veins and capillaries would stretch for about 100,000 miles - enough to wrap around the world nearly four times.