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If you were an osteoclast in a callus near the cortex
of the right tibial diaphysis of a skier sitting in the lodge
because of a tibial fracture, what would you want to do?

O (A) Form collagen
O (B) Resorb bone
O © Synthesize osteoid
O (D) Elaborate cytokines
12) (E) Divide

b?

. (B) Bone remodeling is accomplished when osteo-
blasts produce new bone and osteoclasts resorb it. This is
an ongoing process in all bones, but the process is speeded
up in fracture callus. Collagen is produced by fibroblasts.
Osteoid is produced by osteoblasts. Cytokines can be elab-
orated by macrophages and other inflammatory cells within
the callus. Osteoprogenitor cells give rise to osteoblasts.
Osteoclasts are derived from the same hematopoietic pro-
genitor cells that give rise to macrophages and monocytes.