Explanation Writing: The Skeletal System

Discovering the Skeletal System

The skeletal system is really an amazing thing. Did you know that you are born with 300 bones but as you grow you only have 206? Also that your bones are made up of four parts. Your skeletal system Allows you to grow, move and this is the reason.

Bones are made up of four parts. The centre of the bone is the bone marrow. This is a like thick blob of jelly, it’s job is to create new blood cells for the body. Over top of that is the cancellous. This looks a bit like a sponge but is much stronger. Next is the cancellous is the compact bone. This is the part you see when you look at skeletons, it is very smooth and very hard. Finally on the top is the Periosteum,  a thin dense layer that contains nerves and blood vessels that nourish the bone. That’s the ‘Bone’ as such but another thing is Cartilage. Cartilage is a softer more flexible ‘bone’ as such. Cartilage sits inside most of our joints and part of our nose is made from cartilage.

You are born with three hundred bones but as you grow into an adult you will have 206. No, you don’t lose any! It’s just that some of your smaller bones fuse or join together to create bigger bones. Bones are a network of calcium made up by cells. As we grow, these cells add new calcium to the network of bone. At the end of childrens’ bone they have layers of the cells in the shape of plates. These are called “growth plates” . When we get to full height these close up.

Your bones move by using joints. Joints are ways that two bones can ‘clip’ together to move around. There are two types of joints, hinge and ball and socket. The hinge joint works like a door hinge. With this joint the bone can only move side to side or up and down, like your knee. The ball and socket can move around. It works like a ball in a cup. The ball can move almost everywhere around.

Bones are flexible, but not that flexible! Once too much pressure is put on them, they will snap or crack. A bit like a wooden pencil. When a bone gets broken it is called a fracture. There are lots of different types of fractures. A complete fracture is when the bone has broken or snapped into two pieces. A greenstick fracture is when the bone cracks in one place only, not all the way through. A single fracture is when the bone is broken in one place. A comminuted fracture is when the bone is broken into more than two pieces, crushed or shattered. A bowing fracture, which only happens in children, is when the bone bends but doesn't break. An open fracture is when the bone sticks through the skin. When a bone gets fractured it heals all by itself. Bones heal like they grow. The cells add more calcium to where it is broken until it is all filled in.

Just like the whole human body, the skeletal system is amazing. Breaking a bone especially when you're young, is just part of human life. And to think that your bones are made up of a whole network, is really cool!