1.3 Muscles and bones (musculo-skeletal system)

Together, muscles, bones and joints are referred to as the musculo-skeletal system; this system provides support and enables the body to move.

Muscles are groups of long fibre cells that have the ability to contract and relax, meaning that they shorten and lengthen. Bones are rigid structures that maintain the structure of the body and protect its organs. Joints are the areas where two or more bones meet, allowing the body to move. Muscles, bones and joints are attached to one another by ligaments and tendons.

There are over 300 bones in a baby’s body, although when babies are born some of their bones are soft like cartilage. As babies grow older, their bones begin to fuse and become more solid until they are strong enough to enable a baby to start moving independently.

Listen to Audio 1, which describes how opposite groups of muscles work with bones and joints to allow you to move.

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Transcript: Audio 1

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How does the musculoskeletal system work?

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Muscles, bones, and joints work together to enable us to move. They keep us moving 24 hours a day, even when we're asleep. Bones are rigid. They maintain the structure of the body and protect its organs. Because bones are rigid, they can only move at a joint.

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Muscles can only pull. They can't push. This is why our joints are controlled by more than one muscle. It is important young children are physically active to make sure of healthy bone development. It is critical for their growth, development, and physical wellbeing.

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There are over 300 bones in a baby's body. When babies are born, their bones are soft, like cartilage. As babies grow older, bones fuse and become more solid.

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Until they are strong enough to enable a baby to stand.

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They support their weight.

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Bones are made of calcium and other minerals. This makes them strong, but slightly flexible, and this property helps protect and support the body.

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Bones protect vital organs. The ribs protect the heart and lungs. The skull protects the brain and eyes. The largest bone is the leg bone, or femur, whilst the smallest bones are those in our ears. There are six types of freely-movable joint.

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But it's the muscles that are responsible for all movement. They are in every part of the body. Muscles move joints by contracting and relaxing, meaning that they get shorter and longer.

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Each of our joints is controlled by sets of muscles. Our elbow joint has two muscles.

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The biceps pull the forearm up.

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And the triceps pull the forearm down.

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Our muscles are a little bit like elastic bands. They can get longer...

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...or shorter. Often, muscles work in pairs.

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In our leg, if the muscle in the back of our thigh contracts and shortens, it bends our leg at our knee joint.

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To extend our leg, the muscle on the front of our thigh contracts and gets shorter.

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Muscles develop as they are used, and waste away if under used. To do all the things that most of us take for granted, like standing up and walking around, our bones, muscles, and joints must all work together.

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So it's the bones, joints, and muscles that let children move. Unrestricted floor-based movement helps children maintain a healthy weight and develop good posture and balance.

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And active play develops essential movement skills, builds strength, health, and launches children into positive social learning.

End transcript: Audio 1

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Audio 1

Muscles that are used frequently develop and grow strong; those that are not used fail to develop, or waste away. Therefore, movement is crucial for babies and young children’s growth, health and physical development.