Bones make a body frame — Biology, 4–6 years
Bones give our bodies a firm frame, help us stand and protect some delicate parts. Muscles pull on bones, so bones and muscles work together when we move.
Bones are the body’s frame
Bones are hard parts inside your body. Together they make a frame that gives shape to your head, chest, arms and legs. Bones can also shield delicate parts: the skull surrounds the brain, and the ribs help protect the heart and lungs.
Why do we need a frame?
A soft body without support would sag and could not hold its shape well. Bones solve this problem by making a strong inside frame. They also give muscles something firm to pull against, which helps your body bend, reach, walk and jump instead of simply flopping down.
Bending an arm
1. Your upper-arm bone and forearm bones make a frame for the arm. 2. At the elbow, the bones meet at a joint. 3. A muscle pulls on a forearm bone. 4. The forearm moves closer to the upper arm, so the elbow bends. The bone does not pull itself; the muscle pulls it.
The trap: bones move by themselves
It is reasonable to think bones move themselves, because they are the parts we feel when an arm or leg changes position. But bones are more like levers in a frame: muscles pull them, and joints let them move in particular ways. A bone is essential for movement, but it does not choose or pull on its own.
Bones in everyday life
Your bones help you sit, stand, hold a cup, climb steps and play. A helmet and a bicycle frame also show the idea of a hard structure protecting or supporting something. Looking at a chicken wing or a medical picture can reveal bones, but never cut or break an animal or your own body to investigate.
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