Fundamentals of Oral Histology and Physiology by Hand Arthur R.; Frank Marion E.; & Marion E. Frank

Author:Hand, Arthur R.; Frank, Marion E.; & Marion E. Frank [Hand, Arthur R. & Frank, Marion E.]
Language: eng
Format: epub
Publisher: John Wiley & Sons, Incorporated
Published: 2014-11-20T00:00:00+00:00

Osteoclasts are large multinucleated cells (Fig. 6.28) that arise from fusion of bone marrow-derived precursors of the monocyte-macrophage lineage, under the control of specific cell surface ligands found on other cell types (e.g., osteoblasts, bone marrow stromal cells, certain immune cells) and receptors found on osteoclast precursors. The fusion of osteoclast precursors and their development into active osteoclasts requires interaction of the receptor activator of nuclear factor kappa B ligand (RANKL) on osteoblasts or bone marrow stromal cells with the receptor activator of nuclear factor kappa B (RANK) on the osteoclast precursors, and macrophage colony stimulating factor (M-CSF) on osteoblasts with colony stimulating factor 1 receptor on osteoclast precursors. Osteoblasts and bone marrow stromal cells also secrete osteoprotegerin, which binds to RANKL and prevents its interaction with RANK. The ratio of osteoprotegerin to RANKL is an important determinant of bone mass and skeletal integrity.

Figure 6.28 Osteoclasts. (a) Light micrograph of developing bone, showing two osteoclasts with multiple nuclei, osteoblasts, and osteocytes. The resorptive activity of the osteoclast on the right has created a Howship’s lacuna. Ruffled border (RB). (b) Low magnification electron micrograph of an osteoclast on the surface of alveolar bone. Two nuclei (N) are present in this section; numerous mitochondria (M) and several small vacuoles (Vac) are seen in the cytoplasm. (c) Higher magnification of the ruffled border region of a similar osteoclast. The ruffled border is encircled by the sealing zone (SZ), seen as two broad cell processes filled with actin filaments. The cytoplasm contains numerous mitochondria (M), several small rough endoplasmic reticulum (rER) cisternae, and many small vacuoles (Vac) and vesicles.

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