BMS 250 Chapter Notes - Chapter 7: Medullary Cavity, Epiphyseal Plate, Osteoclast
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7. 4b endochondral ossification: endochondral ossification begins with a hyaline cartilage model and produces most bones of the skeleton, including those of the upper and lower limbs, the pelvis, the vertebrae, and the ends of the clavicle. Long bone development in the limb is a good example of this process, which takes place in the following six steps: (cid:327). The fetal hyaline cartilage model develops: during the eighth to twelfth week of development, chondroblasts secrete cartilage matrix and a hyaline cartilage model forms. Chondrocytes are trapped within lacunae, and a perichondrium surrounds the cartilage. (cid:328). Cartilage calcifies, and a periosteal bone collar forms. Within the center of the cartilage model, chondrocytes start to hypertrophy and resorb some of the surrounding cartilage matrix, producing larger holes in the matrix. As these chondrocytes enlarge, the cartilage matrix begins to calcify. Chondrocytes in this region die and disintegrate because nutrients cannot diffuse to them through this calcified matrix.
