What is Bone Fracture
(Broken Bone)?

Bones form the skeleton of the body and allow the body to be supported against gravity to move and function in the world. Bones also protect some body parts, and bone marrow is the production center for blood products. Bone is not a stagnant organ. It is the body's reservoir of calcium and is always undergoing change under the influence of hormones. Parathyroid hormone increases blood calcium levels by leeching calcium from bone, while calcitonin has the opposite effect, allowing bone to accept calcium from the blood.

Source: http://www.emedicinehealth.com