Water-soluble substances, like ions, cross the capillary wall through either water-filled spaces, called clefts, between the endothelial cells, or through large pores in the walls of fenestrated capillaries.

水溶，如离子，通过内皮胞间的充水空间（），过毛血管壁或由有孔毛血管壁的小孔过。