Correlation between the structure of the wall of the bone lacuna and the localization of the osteocyte within this lacuna. Electron-microscopic studies.

A correlation between the structure of the wall of the bone lacuna and the localization of the osteocyte within this lacuna was the object of investigation under light and electron microscopes. On the basis of the structural divergences detected, the author distinguished zones A and B in the osteocyte situated in the lacuna. Zone B is characterized by a parallel, compact system of collagen fibrils which form a characteristic ridge in the lacunar wall, a continuous demarcating line bordering this wall, the osteocyte cytoplasm in this part lying far from the lacuna wall and surrounding the nucleus with a narrow band, and the pericellular space which is wide here and containing a large number of mucopolysaccharides. This picture may correspond to the area of temporary non-reactivity of the osteocyte. Zone A is characterized by a loosened and disordered system of collagen fibrils forming the lacunar wall. These fibrils being exposed in this place by nature, the demarcating line bordering the lacunar wall is broken in some places, the osteocyte cytoplasm is considerably concentrated around the nucleus and contains a large number of organelles. It also lies closer to the lacunar wall, which results in a decreased width of the pericellular space and a diminished mucopolysaccharide content in this part of the lacuna. Structural variations in the lacuna wall and its space (zones A and B) observed in the images obtained with a normal bone in the light and electron microscopes show their immediate dependence on the position of the osteocyte in the lacuna, which may be associated with the osteocyte activity. On the other hand, the occurrence of significant changes in a definite zone (zone A) of the lacuna only points to the oriented character of this activity.