 Bones are living, changing things that need the right nutrients and exercise to grow and stay strong. Bones are made up of living tissues, like blood vessels and nerves, and also of certain minerals like calcium. Calcium is a mineral that is found in dairy foods like milk, cheese, and yogurt. We need to eat foods with calcium because it helps our bones to stay strong.
Bones also work with our muscles to help us move. Our bodies have 650 muscles that work with bones to help our bodies move. Muscles also do other things that keep our bodies working. Muscles move our jaws so we can chew food or talk. Muscles help to move food through our bodies. Our heart is a muscle, and it pumps blood through our bodies. Muscles also help us to breathe and to stay warm.
A muscle can pull a bone to move it, but that same muscle cannot push the bone back to where it came from. So, muscles work in pairs to move bones back and forth. In your arm, the top muscle flexes to bring your arm bone closer to your body. The lower muscle in the pair is relaxed. Then, when you want to put your arm down, the lower muscle flexes and the top muscle relaxes.
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