Problems with the skeleton that makes up the hard but resilient framework of the body, vital for the ability to move at will. In general, bone consists of three main layers. On the outside is a thin membrane (periosteum) containing blood vessels and nerves; below that is the dense hard shell we normally think of as bone, which gets its rigidity from large amounts of calcium and phosphate; inside the shell is spongy tissue, including the bone marrow, where vital blood cells are produced.
Bone is a living, dynamic organ, being continuously remodelled in response to external mechanical and chemical influences and acting as a large reservoir for calcium and phosphate.