Osteoblasts

Osteoblasts are the bone-building cells. Osteoblasts secrete collagen that is mineralized to form new bone tissue. They lay down bone in an orderly manner after the osteoclasts dissolve old bone creating pits or holes on the surface of the bone. Osteoblasts take 3 months to fill in the pits that osteoclasts took about 2 weeks to make.

The process of bone breakdown and formation called bone turnover replaces the tissue of the skeleton many times during your life. Your entire skeleton is replaced about every 10 years.

Bone turnover is equally balanced when new bone made by osteoblasts matches the amount of old bone broken down by osteoclasts. With loss of estrogen in menopause and aging, osteoblasts are unable to keep up with increased bone breakdown activity and deeper pits made by osteoclasts. This imbalance results in a deficit of new bone. Over time bone microstructure becomes thinner and fragile.