Bone
Although the human skeleton seems rigid and unchanging, it is actually undergoing change constantly. The skeleton's primary purposes are to protect the body and provide mobility and structural support. In childhood, the skeleton undergoes a process called modeling, the primary purpose of which is to build new bone. In adulthood, a different strategy begins as damage occurs. Damaged bone is removed and replaced at the same site in a process called remodeling. In fact, the skeleton replaces itself every 10 years via this remodeling process. As long as bone remodeling remains balanced (i.e., as long as old bone is removed and new bone is laid down at the same rate), the skeleton remains healthy. However many factors can upset this balance, and, when they do, bone disease may occur.
