Head and back bones
When you pat the top of your head, you can feel the bones of your brain case. When you rub your chin, you feel your jawbone and when you scratch the top of your nose, you feel your nasal bone. Most of your head is made from bone but there are two places on the outside that are not. Rub the end of your nose and it feels soft and wobbly. Bend your ear and let it go and your ear springs back into place. The end of your nose and the outer part of your ear are made from cartilage, or gristle.

Inside your head is a large grey structure, which has a wrinkled surface like a walnut. This structure is your brain, which is made from nerves. They gather messages from your body, store information in your memory and send commands to your muscles to make them work. If this part of the body is damaged the rest can die. The bones on the top of the skull perform a very important task. They form a protective covering around the brain. Although this covering may seem hard and strong, it can be broken. If this happens the brain can be damaged. In normal conditions the bones can protect the brain safely but if a person falls from a bicycle, motorcycle or a horse without head protection there could be serious damage to the brain.

If you look at the front of a skull you can see two hollows called eye sockets. At the back of each socket is a hole, which carries a nerve from the eye to the brain. Under the nasal bone are smaller bones that are so thin they are almost like paper. They make the passageways that air flows through as you breathe in and out. Below the nose is the upper jaw which holds the top set of teeth. Beneath this is the lower jaw. It is the only large bone in the skull which can move. It carries the bottom set of teeth. Underneath the skull are two round pieces of bone. They form 'rockers' which allow the skull to rock on the top of the spine. They let you nod your head. There is also a large hole underneath the skull. It allows the brain to connect to the spinal cord, a huge collection of nerves, which runs down inside the bones of the spine.

There are twenty six bones in the spine. The top one has grooves on its upper surface. They hold the 'rockers' at the base of the skull that let the head nod. The second bone in the spine has a peg, which sticks up through a hole in the bone above it. This peg lets you turn your head from side to side and also shake your head.

Most bones in the spine have a hole in their centre. This lets the spinal cord pass through. The bones in the neck have two more holes in them. They let tubes called blood vessels pass through. The blood vessels carry blood from the heart straight to the brain. The main tasks of the neck bones are to allow movement of the head and to protect the spinal cord and blood vessels entering the head.

Below the neck bones are twelve back bones which are in the chest region. Each one has a hole in its centre to protect the spinal cord but it also has lumps on its sides, which help form joints with the ribs. There are muscles between the ribs, which move them up and down. This movement allows you to breathe in and out. The ribs join together to make a structure called the rib cage. This protects the heart and the lungs.

Below the backbones in the chest are five very large backbones. They are strong and sturdy to carry the weight of the body above them. They also have bony arms sticking out from them, which help back muscles attach to them.

The remaining bones in the backbone are stuck or fused together. Some are joined to the hipbone to help support the lower part of the body while four tiny bones fuse together at the end of the backbone. In other animals these bones help to form a tail.

Now we have taken a journey from the top of your head to the end of the spine there is just one more part to consider. In between many of the backbones are discs of cartilage. They act as cushions and prevent the bones rubbing on each other. During the night when you are asleep, water from your blood enters them and they swell up a little. During the day as you walk around you squash some of the water out of the discs. This means that they get thinner and the bones in your back come closer together. It also means that when you go to bed you are slightly shorter than when you got up.

Do other animals have backbones?
Yes, some of them do. Each bone in the back is called a vertebra. The plural of vertebra is vertebrae. Animals which have vertebrae are called vertebrates. There are five kinds of animals in this group. They are fish, amphibians, reptiles, birds and mammals.

What are animals without backbones called?
These animals do not have vertebrae so they are called invertebrates. The main groups of invertebrates are worms, snails, slugs, clams, insects, spiders, crabs, lobsters and starfish.

What are the smallest bones in the skull?
They are the ear bones. In fact the ear bones are the smallest bones in the body. They do not support or protect like other bones but they do move. The movement of the ear bones helps you to hear.

Are all skulls and backbones made from bone?
No. Sharks and rays have skeletons made out of cartilage, or gristle (the substance in your nose end or that makes the outside of your ears).

Animal skulls are different but do they have different spines?
Yes, they do. A fish has a spine made from many small backbones. The ends of the backbones make joints, which allow the spine to bend easily. The muscles pull on the backbone in such a way that the body makes curves, which pass from head to tail, and help the fish swim forwards. The rabbit and many four-legged animals have their backbone in the shape of an arch. This gives the backbone extra strength to support the other parts inside the body. A bird's backbone is short and rigid. If it bent like a fish backbone, the bird's body would bend when the wings flapped and this would probably prevent the bird from flying.

Is the human backbone different from other backbones?
Yes, it is. The reason for this is that we are the only animals to walk all the time on two legs. We have a curve in our spine. It helps to bring the weight of our shoulders over our hips so we can move easily. This explains why people may tell you to stand up straight when you are walking. If you walk with your head forwards you make your spine bend forwards too. This can cause backache and in time it can make a person have round shoulders. If you walk by sticking out your stomach you bend your spine backwards and this too can cause backache.

What is a slipped disc?
This is a condition when a disc between two of the backbones has burst. This causes the bones to come so close together that they rub on each other and cause pain. A slipped disc generally occurs in older people. It can be cured.