Skeleton system!
What are bones?
We all have bones. If we didn’t, we would be like jellyfish!
Bones make up the framework of our bodies. We call this framework the skeleton.
Bones are living, growing and changing parts of our bodies. Babies’ skeletons are made up from more than 300 parts, but by the time we become adults we only have 206 bones!
No, we haven’t lost any! It’s just that some of our baby bones are made, partly or completely, of cartilage. As we grow bigger and heavier, cartilage is slowly replaced by harder bone. Some smaller bones join together to make one bigger bone.
By the time we have finished growing, at about 25 years old, our bones are as big as they are going to get.
Most bones have 4 parts:
- The outside part of bone is called the periosteum . This is a thin but very dense layer that has the nerves and blood vessels which nourish the bone.
- Compact bone is next. It is smooth and very hard.
- Cancellous bone comes next, and this looks a bit like a sponge but is much stronger.
- On the very inside of many bones is the bone marrow. It looks a bit like a jelly and it makes new blood cells for the body
The bones of the skeleton give us our shape and our posture. Without our spine (backbone) and leg bones we would be unable to stand erect.
Bones also protect the softer parts of our bodies.
- The skull is like a natural helmet which protects the brain.
- The spine protects the nerves in the spinal column.
- The ribs make a shield around our lungs, heart and liver
Bones are great team players!
- They act as a base for muscles, ligaments and tendons. Ligaments connect bones to bones, and tendons connect muscles to bones. Our topic ‘Your muscles’ will tell you more.
- They all work together to help us move around.
