A process in which old bone is removed to make way for new bone that forms. This occurs during the process of bone remodelling, just like the remodelling of a house, when old things are removed and new things are put in.
Bone resorption is the process by which osteoclasts break down bone and release the minerals, resulting in a transfer of calcium from bone fluid to the blood. The osteoclasts are multi-nucleated cells that contain numerous mitochondria and lysosomes. These are the cells responsible for the resorption of bone.