An osteoblast (from the Greek words for "bone" and "germ" or embryonic) is a mononucleate cell that's responsible for bone formation. Osteoblasts produce osteoid, which is composed mainly of Type I collagen. Osteoblasts are also responsible for mineralization of the osteoid matrix. Bone is 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 nat… (More on Osteoblast)