Hard tissue formation and destruction. Hard tissue associated with the functioning tooth: cementum, dentin, and enamel Specialized connective tissues (except enamel) Collagen (esp. type I) plays a role in determining their structure.
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Fig. 1-81 illustrates an osteon with osteocytes (OC) residing in osteocyte lacunae in the lamellar bone. The osteocytes connect via canaliculi (can) which contain cytoplasmatic projections of the osteocytes. A Haversian canal (HC) is seen in the middle of the osteon.
Fig. 1-82 illustrates an area of the alveolar bone in which bone formation occurs. The osteoblasts (arrows), the bone-forming cells, are producing bone matrix (osteoid) consisting of collagen fi bers, glycoproteins, and proteoglycans. The bone matrix or the osteoid undergoes mineralization by the deposition of minerals such as calcium and phosphate, which are subsequently transformed into hydroxyapatite.
Fig. 1-83 The drawing illustrates how osteocytes, present in the mineralized bone, communicate with osteoblasts on the bone surface through canaliculi.
Mononuclear-phagocyte lineage are the most likely candidates to differentiate into osteoclasts.
May occur at the promonocyte stage, but monocytes and macrophages, already commited to their own lineage, might still be able to form osteoclasts under the right circumstances.
Remodeling of the trabecular bone starts with resorption of the bone surface by osteoclasts (OCL) as seen in Fig. 1-90a. After a short period, osteoblasts (OB) start depositing new bone (Fig. 1- 90b) and fi nally a new bone multicellular unit is formed, clearly delineated by a reversal line (arrows) as seen in Fig. 1-90c.