The Hard Stuff! All About Bones

The Hard Stuff! All About Bones

Body Shapers Lizards have one. Elephants have one. Even fish have one. You have one, too! What is it? A skeleton! Skeletons are the bones inside animals' bodies. The skeleton is the frame that muscles and skin wrap around. Skeletons give all vertebrates, including humans, their shape. You can probably name many animals just by looking at their skeletons.

The human skeleton has 206 bones, starting at the top with the skull and ending at the bottom with the toe bones. Many bones have muscles attached to them by tendons. These bones help us move. Some bones protect soft organs inside our bodies, such as the heart and brain. And many big bones have special areas in the center that make blood cells. Tissues called ligaments connect all the bones together to form the skeleton. To learn how bones work, let's take a closer look at different areas of the body.

Heads Up Press your hand against your forehead- the part of your face above your eyebrows. You can feel your skull, or cranium, under the skin. The cranium is one set of bones in your body. It protects your brain, a very important and very soft organ. The cranium is like a crash helmet, but it is not as strong. For that reason, you should wear a helmet for sports such as biking and skating.

If you feel your head, your skull seems to be one piece. In fact, the skull is made up of many bones. The bones join at special joints called sutures. Unlike other joints, the sutures cannot move much. Your skull has twenty-two bones, not counting the six in your ears and one in your throat. Under your cheeks, you can feel your cheekbones. Your jaw is made up of two bones.

If you look at a skeleton, you might see something missing from its face--a nose. The part of your nose that sticks out is not bone. Your nose is made of a tissue called cartilage (CAR-tih-ledj). Touch your nose and move it around. Cartilage can bend. Your bones cannot. You also have cartilage at the ends of bones. Cartilage keeps bones from rubbing against each other. Skeletons also have teeth, but teeth are not bones. Teeth are harder than bones. The outside of a tooth is made of enamel. Enamel is the hardest thing in the body.