Fracture faces of fenestrations and junctions of endothelial cells in human choroidal vessels.

Replicas of freeze-fractured endothelial cells of human choroidal capillaries show fenestrations with a central thickening, as described in thin-section studies. Between the endothelial cells there are discontinuous zonulae occludentes (i.e., maculae or fasciae occludentes), composed of ridges on face A and grooves on face B of the split-cell membrane. They are also present along the sutures of the endothelial cells of venules. Close to the intercellular suture gap junctions, probably connecting capillary endothelial cells and pericytes, are found.