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It's very easy for most of us to take our skeletal systems for granted. Like much of our anatomy, if it's working fine and isn't something we can fixate on in the mirror, then out of sight is truly out of mind. View a few photographs of decayed human remains, and you can quickly fall into the trap of perceiving our skeletons as fixed, permanent structures on which our flesh grows, lives and dies.

While the skeleton's main functions include supporting the body and protecting vital organs, our skeletal system is as much a living system as any other part of our anatomy. The red marrow inside our bones produces red blood cells. Yellow marrow stores fat, and the bone itself is home to various minerals. Your body constantly breaks down old bone cells and replaces them with new ones.

But, just as our bones are ruled by constant cellular activity, there are plenty of diseases, disorders and other conditions that can disrupt the intended process. One such condition is osteogenesis imperfecta (OI), Latin for "imperfectly formed bone."

Also known as brittle bone disease, OI is a genetic disorder. A person either inherits the condition from a parent or develops it spontaneously in the womb. OI disrupts the body's ability to form strong connective tissue. This, in turn, affects the body's ability to grow new bone tissue. Instead of creating strong, compact bones capable of withstanding normal stress, the cells of a person afflicted with OI produce weaker skeletal tissue. In addition to other symptoms, the bones can break easily under everyday levels of stress.

On the next page, learn exactly how OI leads to the production of brittle bones.