This essay focuses on The replacement of chondrocytes. retained instead of being broken down to form a medullary cavity. When secondary ossification

The replacement of chondrocytes

process of bone formation.The cartilage in the epiphyses continues to grow so the developing bone increases in length. Later, usually after birth, secondary ossification centers form in the epiphyses. Ossification in the epiphyses is similar to that in the diaphysis except that the spongy bone is retain instead of being broke down to form a medullary cavity. When secondary ossification is complete, the hyaline cartilage is totally replace by bone except in two areas. A region of hyaline cartilage remains over the surface of the epiphysis.

During the third phase of endochondral ossification, the chondrocytes proliferate rapidly to form the model for the bone. As they divide, the chondrocytes secrete a cartilage-specific extracellular matrix. In the fourth phase, the chondrocytes stop dividing and increase their volume dramatically, becoming hypertrophic chondrocytes. These large chondrocytes alter the matrix they produce (by adding collagen X and more fibronectin) to enable it to become mineralized by calcium carbonate. The fifth phase involves the invasion of the cartilage model by blood vessels. The hypertrophic chondrocytes die by apoptosis.

the cartilage tissue serves as a model for the bone that follows. The skeletal components of the vertebral column, the pelvis, and the. It is limbs are first formed of cartilage and later become bone.

The replacement of chondrocytes by bone cells is dependent on the mineralization of the extracellular matrix. This is clearly illustrated in the developing skeleton. It isof the chick embryo, which utilizes the calcium carbonate of the eggshell as its calcium source