Function of Osteoblasts and Osteoclasts for Bone Health

Although it seems like your bones are solid as a rock and never changing, the fact is they are continuously being remodelled. Bone remodelling is a complex process of reabsorption and formation. Osteoblasts and osteoclasts are the two primary cell types used to create or absorb bone. Generally, normal bone health is maintained when these two activities are in balance.

Function of Osteoblasts

Osteoblasts are cells that create bone by producing and depositing a matrix into small cavity sites, which were created  by a previous break down. This matrix primarily consists of collagen fibers. New bone hardens with the mineralization of calcium and phosphate, which can take 3 to 6 months.

Function of Osteoclasts

The function of osteoclasts is to break down and absorb, what’s referred to as bone reabsorption. Osteoclasts secrete enzymes that dissolve the matrix and acids that dissolve salts containing calcium and phosphate ions, which are then released into your bloodstream. This absorption process takes about three weeks. After a period of rest, osteoclasts convert into osteoblasts to form new bone in that cavity.

The process of bone resorption followed by formation is controlled by hormones, particularly vitamin D, parathyroid hormone, calcitonin, estrogen and testosterone.

There are some instances for which maintaining bone health may require osteoblast and osteoclast function to be out of balance, for instance during childhood growth period, bone fracture repair or performing routine weight bearing activities that cause an increase in bone density. However, there are some circumstances for which an imbalance of bone remodelling function is not advantageous, resulting in postmenopausal osteoporosisosteopetrosis and hypercalcemia.