Electronmicroscopic studies on arterial blood vessels of the spleen, especially their relation to the reticuloendothelial system.

Abstract

1) Electron-microscopic findings of the vascular system of the spleen and its relationship to the reticuloendothelial system are described. 2) In the white pulp, fine arterial blood vessels branch from the follicular artery and form a rich plexus of slender capillaries. The follicular arterioles are essentially similar in their fine structure to the arterioles of other organs. 3) The marginal zone of the white pulp is composed of phagocytic reticulum cells. Perifollicular sinusoids are poorly developed in the mouse spleen, but in the dog spleen wide perifollicular spaces form a boundary between the white and red pulp. Its basement membrane is broken in places and the wall is infiltrated by lymphoid cells, thrombocytes and erythrocytes. 4) Sheathed artery is found in the dog spleen. Sheath cells can be regarded as one of the phagocytic reticulum cells, which are differentiated from adventitial cells. 5) A large part of the terminal branches of the vascular system in the red pulp seem to end in a structure resembling a so-called finger-like extension. The basement membrane disappears abruptly and the edge of the vascular channel is structurally open. The open ending is protected by thrombocytes and reticulum cells.