The Abscence of Direct Permeability Pathways in Continuous Capillaries and the Internal Nature of Endothelial Vesicles

Abstract

The paired rete mirabile (red bodies) of the eel swim bladder consist of counterparallel venous and arterial capillary segments which function in countercurrent exchange of gases. The arterial capillaries are thick-walled and continuous and the venous capillary walls have thin, fenestrated endothelium. This permits one type of capillary to serve as a control for the other in differential permability studies. The capillaries are unbranched and of similar length which allows for the perfusion of each of them at the same flow rate and under the same hydrostatic and osmotic pressure.</jats:p