T. Clark Brelje, Ph.D.
University of Minnesota
Department of Genetics, Cell Biology and Development
6-160 Jackson Hall
321 Church St SE
Minneapolis, MN 55455
Robert L. Sorenson, Ph.D.
University of Minnesota
Department of Genetics, Cell Biology and Development
6-160 Jackson Hall
321 Church St SE
Minneapolis, MN 55455
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MH 046 Bone Development
Endochondral Bone Formation
Endochondral bone formation occurs at the epiphyseal plate of long bones. It can be identified by the layer of basophilic hyaline cartilage.
(The initial zones are easier to see in MH 029B Bone.)
Resting Zone - thin layer of non-dividing chondrocytes.
Proliferative Zone - rapidly dividing chondrocytes (basophilic) that organize into distinct columns ("stacks of coins").
Zone of Hypertrophy - chondrocytes (basophilic) cease dividing and grow in size. The cartilage matrix forms (lightly basophilic) linear bands between the columns of hypertrophied cells.
Zone of Calcification - the cartilage matrix becomes calcified inhibiting the diffusion of nutrients. The dying chondrocytes are removed leaving longitudinal spicules of calcified cartilage (intensely basophilic).
Zone of Ossification - osteoprogenitor cells migrate into the cavities with the new blood vessels. New bone (eosinophilic) forms on the scaffold of calcified cartilage (basophilic).
Osteoblasts - condense on the spicules of calcified cartilage and produce new bone (osteoid).
Osteoclasts (#1 and #2) - large, multinucleated cells that remove bone tissue.
