An osteoblast (from the Greek words for "bone" and "to build") is a cell that secretes a protein called osteoid which, when it mineralizes, becomes bone. Osteoid is primarily composed of collagen.

 

Bone is a dynamic tissue that is constantly being reshaped by osteoblasts, which are responsible for the production of matrix and mineral, and osteoclasts, which break down the tissue.

 

When there is insufficient mineral or osteoblast dysfunction, the osteoid does not mineralize properly, and it accumulates in a process called osteomalacia.