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Bone is a hard substance that makes up the skeleton, which supports
the body and provides protection for the organs. Bone is composed of minerals,
mainly calcium and phosphate, which it stores and provides to the body as they
Bone consists of three layers: the outside covering of the bone
(periosteum); the hard middle (compact) bone; and the inner spongy (cancellous)
bone. The covering of the bone contains nerves and blood vessels that feed the
hard bone. Holes and channels run through the hard bone to supply oxygen and
nutrients to the inner bone cells. The spongy bone contains bone marrow, which
produces red and white blood cells and platelets.
Normal bone is constantly dissolving and being absorbed into the
body and then being rebuilt in a process called remodeling. This allows bones
to react to changes in body weight and structure and to increase bone strength
in areas of stress.
Current as of:
May 22, 2015
Anne C. Poinier, MD - Internal Medicine & Jennifer Hone, MD - Endocrinology, Diabetes and Metabolism
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