Biology of Bone Tissue: Structure, Function, and Factors That Influence Bone Cells

Figure 4

Light (a and c) and electron micrographs (b and d) of portions of alveolar bone of rats. In (a) tartrate-resistant acid phosphatase (TRAP) activity (in red color) is observed in the cytoplasm of osteoclasts (OC) adjacent to the alveolar bone (B) surface. Note that in the opposite side of the bony trabecula B is covered by large and polarized osteoblasts (Ob). Ot, osteocytes (Ot); BV: blood vessel. Bar: 40 μm. (b) Multinucleated osteoclast (OC) shows evident ruffled border (RB) adjacent to the excavated bone surface (arrows). Several vacuoles (V) are observed in the cytoplasm adjacent to ruffled border (RB). N: nucleus. Bar: 4 μm. (c) Portions of TRAP-positive osteoclasts (Oc and Oc₁) are observed in a resorbing bone lacuna. A round cell (Ap) with condensed irregular blocks of chromatin, typical apoptotic cell, is observed inside a large vacuole of the Oc₁. B: bone matrix; Ot: osteocyte. Bar: 15 μm. (d) An osteoclast (Oc) showing ruffled border (RB) and clear zone (CZ) is in close juxtaposition to the excavation of the bone surface (arrows), that is, Howship lacuna. Vacuoles (V) with varied size are present next to the ruffled border (RB); one of them contains a round cell with masses of condensed chromatin (Ap), typical of cell undergoing apoptosis. B: bone matrix; N: nucleus. Bar: 3 μm.

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