An osteoblast (from the Greek words for "bone" and "germ" or embryonic)'s a mononucleate cell that's responsible for bone formation. Osteoblasts produce osteoid, which's composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix. Bone's a dynamic tissue that's constantly being reshaped by osteoblasts, which build bone, and osteoclasts, which resorb bone. Osteoblast cells tend to decrease as individuals become elderly, thus decreasing the natura… (More on Osteoblast)