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Skeletons and muscles

Many animals have skeletons to support and protect their body and to help it move.

Illustration of a horse skeletonIllustration of a fish skeleton

The human skeleton is made of bone and grows as we grow. Our skull protects our brain and our ribs protect our heart and lungs.

Illustration of the human skeleton

The skeleton bends at joints such as knees and ankles. Joints are where two or more bones join together.

Muscles are attached to bones. When a muscle contracts (bunches up), it gets shorter and so pulls up the bone it is attached to. When a muscle relaxes, it goes back to its normal size. This is how skeletons move.

Illustration of humans arms showing the muscles relaxed and showing muscles contracting (side by side)

Some animals, such as insects, crabs and lobsters, have a skeleton outside their body. Such skeletons are called exoskeletons.

Illustration of an ant skeleton

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