The bone-destroying function of the osteoclasts; Koelliker's brush border

Kroon, D.B.

Acta Anatomica 21(1): 1-18


ISSN/ISBN: 0001-5180
PMID: 13170937
Document Number: 3185
A description is given with illustrations of the variations in structure of the well developed striated borders of the osteoclasts in parathyroid hormone-treated pigeons in which the formation of medullary bone was previously induced by injections of oestradiol. These striated borders, known in the literature as Koelliker's brush borders, are of a different nature from the cuticular and brush borders which are found in absorptive epithelia, and it is equally incorrect to regard them as more fringe-like projections formed by collagen fibrils which project from the bone substance for a certain distance at places where destruction of the latter is going on. These striated structures are formed by the penetration of protoplasmic projections from the osteoclast into the bone substance; the bone substance trapped in the border is broken down and liquefied in vacuoles, the number of which in the border, and also in the other protoplasm of the osteoclast, increases steadily throughout the process. The contents of the vacuoles finally lose all staining properties. These borders in their varying morphological aspects must be regarded as representing functional states of the osteoclast in the process of osteoclasis.

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The bone-destroying function of the osteoclasts; Koelliker's brush border