bone

bone The hard connective tissue that forms the skeleton of the body. It is composed chiefly of collagen fibers that contain calcium phosphate and calcium carbonate. Bones also serve as a storage area for calcium, playing a large role in calcium balance in the blood. The 206 bones in the human body serve a wide variety of purposes. They support and protect internal organs; for example, the ribs protect the lungs. Muscles pull against bones to make the body move. See also bone marrow.