As cartilage enlarges, chondrocytes near center of shaft (diaphysis) increase in size and surrounding matrix begins to calcify. Deprived of nutrients chondrocytes begin to die. perichondrium surrounding the cartilage differentiate into osteoblasts. Perichondrium converts to periosteum and the osteogenic layer produces a bony collar around shaft of cartilage. Capillaries and osteoblasts migrate into the heart of the cartilage, into spaces left by chondrocytes. The calcified matrix breaks down and osteoblasts replace with spongy bone. This becomes Primary Ossification Center in the shaft (diaphysis). The entire diaphysis is filled with spongy bone but as it enlarges, osteoclasts erode the central portion to create Medullary Cavity. Growth involves increase in length and diameter. Centers of the epiphyses now begin to calcify. Capillaries and osteoblasts migrate to these areas, creating Secondary Ossification Centers. The epiphyses eventually become filled with spongy bone. A thin cap of cartilage remains exposed to join cavity as Articular Cartilage. At metaphysis, the epiphyseal plate separates the epiphysis from the diaphysis.
An ossification center occurs within the embryonic tissue where mesenchymal cells cluster together, differentiate into osteoblasts, and secrete bone matrix. Some of the osteoblasts become trapped in the bone matrix and become osteocytes. Blood vessels grow into the area to supply the cells and matrix with oxygen and nutrients. These blood vessels get trapped within the developing bone. The bone assumes a foundation of spongy bone. Remodeling creates compact bone and the finalized form of the bone.
As cartilage enlarges, chondrocytes near center of shaft (diaphysis) increase in size and surrounding matrix begins to calcify. Deprived of nutrients chondrocytes begin to die. perichondrium surrounding the cartilage differentiate into osteoblasts....