Muscles move bones

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Q1: How do the muscles in your arm work?

[Answer]

Muscles are the soft parts of the body below the skin. We call this flesh. They are the materials that give your body its shape. The skin is just a thin layer draped over the muscles.

There are more than 600 muscles in your body.

Muscles can only tighten or relax. They are told to do this by the brain. This is why, to move a joint, you need a pair of muscles.