Diaphysis

zone of hypertrophy zone of calcified cartilage zone of resorption bone osteoclast blood vessel osteoblasts from the diaphysis, elongating the bone. The events that follow this incremental growth, namely, hypertrophy, calcification, resorption, and ossification, simply involve the mechanism by which the newly formed cartilage is replaced by bone tissue during development. • Bone increases in width or diameter when appositional growth of new bone occurs between the cortical lamellae and the periosteum. The marrow cavity then enlarges by resorption of bone on the endosteal surface of the cortex of the bone.

As bones elongate, remodeling is required

Remodeling consists of preferential resorption of bone in some areas and deposition of bone in other areas, as described above and outlined in Figure 8.17.

When an individual achieves maximal growth, proliferation of new cartilage within the epiphyseal plate terminates

When proliferation of new cartilage ceases, the cartilage that has already been produced in the epiphyseal plate continues to undergo the changes that lead to the deposition of new bone until, finally, there is no remaining cartilage. At this point, the epiphyseal and diaphyseal marrow cavities become confluent. The elimination of the epiphyseal plate is referred to as epiphyseal closure. In illustration 9 of Figure 8.14, the lower epiphyseal cartilage is no longer present, and in illustration 10, both epiphyseal cartilages are gone. Growth is now complete, and the only remaining cartilage is found on the articular surfaces of the bone. Vestigial evidence of the site of the epiphyseal plate is reflected by an epiphyseal line consisting of bone tissue (see Fig. 8.2).

epiphysis enlarges by growth of cartilage and replacement by bone resorbed growing shaft is remodeled by bone being...

added bone added inside tunnels here shaft elongates because rtilage grows here and is replaced by bone here resorbed here

OLDER BONE YOUNGER BONE

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