The human skeleton

The human skeleton is made up of more than 200 bones of different shapes and sizes.

Bones are made of collagen (a type of protein) and minerals such as calcium and phosphate. The combination of collagen and minerals makes the bones strong.

Bones do lots of important things:

• They support our bodies. The joints at the end of bones act as levers. This is so we can move around.
• They protect parts of our bodies from injury. For example, the ribs protect the heart and lungs, and the skull protects the brain.
• They store important minerals that our bodies use, such as calcium.
• Some bones are filled with a soft, spongy material called bone marrow. This makes blood cells.

The joints at the end of bones are covered in cartilage. This allows joints to move smoothly.

Our bones are constantly breaking down and being replaced with new bone. This helps keep their strength and shape. There are 2 main types of cell that break down and replace bone:

• Osteoclasts – these break down and remove old bone.
• Osteoblasts – these cells make new bone.