ANTH 336 Lecture Notes - Intramembranous Ossification, Osteogenesis Imperfecta, Ossification Center
Document Summary
Bone is formed when osteoprogenitor cells differentiate into osteoblasts that lay down osteoid: hydroxyapatite then mineralizes the organic matrix. Bone always grows by replacing a preexisting tissue. The main difference between these two types of ossification is the preexisting tissue that the bone replaces - the type of bone that is produced is the same. Certain diseases target one type of bone more than the other. Bone is deposited on tissue within an embryonic tissue membrane. Most of the skull bones (except the base and parts of the face) and other flat bones ossify this way. Bone growth occurs between the periosteum (outer layer) and an inner fibrous layer containing osteoprogenitor cells that become osteoblasts. During cell differentiation, the cells get organized and form the membranes that will be replaced by bone matrix. Earliest endochondral bone formation begins in the embryo in what will become the long bones of the limbs.
