Page 271 - Atlas of Histology with Functional Correlations
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Osteoblasts (6, 20) line up along remaining plates of calcified cartilage (5,
17) and lay down a layer of osteoid (19) and bone. Osteoblasts trapped in the
osteoid or bone become osteocytes (9, 21). Capillaries (8, 18) from the marrow
cavity (10) invade the newly ossified area.
The developing marrow cavity (10) contains numerous megakaryocytes
(13, 24) and pluripotent stem cells that give rise to erythrocytic and granulocytic
blood cells (23). Multinucleated osteoclasts (11, 22) lie in shallow depressions
called Howship lacunae (11, 22) and are adjacent to the bone that is being
resorbed.
The left side of the illustration shows periosteal bone (7) with osteocytes (9)
in their lacunae. The new bone is added peripherally by osteoblasts (6), which
develop from osteoprogenitor cells of the inner periosteum (12). The outer
layer of connective tissues around the cartilage remains as the perichondrium
(3).
FIGURE 7.20 ■ Endochondral ossification: zone of ossification. Stain:
hematoxylin and eosin. Medium magnification.
FIGURE 7.21 | Endochondral Ossification: Zone
of Ossification
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