Histogenesis - Hyaline Cartilage

3. Histogenesis, All cartilage derives from embryonic mesenchyme. During the development of hyaline cartilage, mesenchymal cells retract their cytoplasmic extensions and assume a rounded shape, becoming chondroblasts; at the same time, they become more tightly packed, forming a mesenchymal condensation, or precartilage condensation. The increased cell-to-cell contact stimulates cartilage differentiation, which progresses from the center outward. Chondroblasts at the core of the condensation are the first to secrete cartilaginous matrix materials, which separate the cells again. When it is completely surrounded by cartilage matrix, a chondroblast is termed a chondrocyte. Peripheral mesenchyme condenses around the developing cartilage mass to form the fibroblast-containing. dense, regular connective tissue of the perichondrium.


4. Growth. Cartilage grows by 2 distinct processes. Both involve mitosis and the deposition of additional matrix. Matrix synthesis is enhanced by growth hormone, thyroxine, and testesterone and is inhibited by estradiol and excess cortisone.
a. Interstitial growth involves the division of existing chondrocytes and gives rise to the isogenous groups, It is important in the formation of the fetal skeleton and continues in the epiphyseal plates and articular cartilages.
b. Appositional growth involves the differentiation into chondrocytes by chondroblasts and stem cells on the inner surface of the perichondrium. It is responsible for continued increase in the girth of the cartilage masses.