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PART 2 Support and Movement

broken bone. In modern medical practice, applying a cast orsurgically implanting metal supports can help stabilize the bone.3. Callus ossification (figure 6.20 b , step 3 ). Like the cartilagemodels formed during fetal development, the cartilage in theexternal callus is replaced by woven spongy bone throughendochondral ossification. The result is a stronger external

callus. Even as the internal callus is forming and replacingthe hematoma, osteoblasts from the periosteum and endos-teum enter the internal callus and begin to produce bone.Eventually, the fibers and cartilage of the internal callus arereplaced by woven spongy bone, which further stabilizes thebroken bone.

Diseases and Disorders

TABLE 6.3

Skeletal System