Grade 4 · Unit 1: Humans and animals

The human skeleton

206 bones, from your skull to your toes.

Explore the bones of the body in the Inside My Body lab.

206 bones

An adult human skeleton has 206 bones. Some bones are long, like the bones in your arms and legs. Some are flat, like the skull. Some are tiny, like the bones in your ear. More than half of your bones are in your hands and feet!

Your hand alone has 27 bones and your foot has 26. Doctors use X-ray photographs to look at bones without cutting the skin.

Head and chest

Your skull is made of bones joined tightly together. It protects your brain. Your ribs curve round your chest like a cage. The ribcage protects your heart and lungs.

The only bone in your skull that moves is your lower jaw. It moves up and down when you talk and eat.

Your backbone

Your spine is made of 33 small bones called vertebrae. Because it is made of many small bones, you can bend and twist. The spine also protects the spinal cord, which carries messages between your brain and body.

Between the vertebrae are soft pads called discs. They work like cushions so the bones do not rub, and they let your back bend and twist.

Arms and legs

The pelvis (hip bones) joins your spine to your legs. The femur, or thigh bone, is the longest and strongest bone in your body. Your arms have a long upper arm bone and two bones in the lower arm.

Your thigh bone is about a quarter of your height. Scientists who study old skeletons can even estimate how tall a person was from the femur alone.

What I learnt