General histomorphology and pathology

Abstract

Marrow-containing bone may be regarded as one organ because of the combined properties of its tissues, its common blood and nerve supply and because of similar tasks of its components; this in spite of being divided in numerous sectors over large regions of the body and the diverse purpose of the tissues united in it. The interest shown in this performance by various clinical and medico-scientific disciplines was the reason for considering these according to the requirements of particular branches. In consequence certain connecting features which form the basis of the existence of the whole have been studied less thoroughly than the more specialized tissues of bone or bloodforming parenchyma. The stroma producing both these salient elements consists of blood vessels and a reticular tissue consisting of small cells. Both originate from the mesoderm, particularly from the medial portions of the embryonal primitive segments. A primary mesenchyme (O. Hertwig) is formed in its sclerotomes which matures to embryonal connective tissue, the germinal tissue of all later differentiated connective tissues. Here arise the buds of capillaries from an undifferentiated “mesenchymal” reticular connective tissue. In their immediate surroundings, possibly from primitive capillary endothelia, islands develop from actively dividing cells which mature to red blood corpuscles.