Osteoclast pit

This image shows a 3D model of the pit caused by the reabsorption of bone by mouse osteoclast cells. There are two types of cells that work together in the formation of bone tissue: osteoblasts and osteoclast cells. The latter actively reabsorbs old or fatigued bone so that the osteoblast cells may replace it with new bone. This is a normal process in the regeneration of bone, however, on the rare occasions that osteoclast cells reabsorb bone faster than the osteoblast cells can produce it, then osteoporosis (bone loss) may occur.