Your skeletal system consists of all the bones in the body and the tissues such as tendons, ligaments and cartilage that connect them. A typical bone has an outer layer of hard or compact bone, which is very strong, dense and tough. Inside this is a layer of spongy bone, which is like honeycomb, lighter and slightly flexible. In the middle of some bones is jelly-like bone marrow, where new cells are constantly being produced for the blood.
The skeleton also has over 200 joints, where bones come together. Here there is a cushion of cartilage that helps protect the bones. Cartilage helps to prevent the bones from rubbing against each other and wearing down the bone. As we age, bones become more brittle and cartilage can deteriorate.