BBC8 个月
KS2 Science: How do muscles and bones work?
PRESENTER:'It's quiet and everyone is fast asleep.' PRESENTER:Muscles and bones keep us moving 24 hours-a-day, even when we're asleep. Without muscles or bones, we wouldn't even be able to get out ...
BBC1 年
How do your muscles work?
Really? They don't look much use. When a muscle contracts (bunches up), it gets shorter and so pulls on the bone it is attached to. When a muscle relaxes, it goes back to its normal size.