Hormonal regulation of Calcium, .

The increase in thickness of compact bone on its superficial face is counteracted by the resorption of bone by osteoclasts on its internal surface. An osteoid seam is an unmineralized band of bony matrix that is about 10–12 micrometers wide. Between this seam and older bone is an abrupt transition called a calcification front. The osteoid seam always stays the same width, indicating that osteoid tissue must mature before it can be calcified. This area then changes quickly from an unmineralized matrix to a mineralized matrix. Two control loops regulate bone remodeling. One is a negative feedback hormonal mechanism that maintains blood Ca2+, and the other involves mechanical and gravitational forces acting on the skeleton.