The depths of the intercellular clefts, measured from the luminal to the abluminal openings, vary among different types of capillaries, but the average is about 0.7 μm. The width of the intercellular clefts is about 20 nm outside the junctional region (i.e. in the larger part of the clefts). In intercellular clefts of capillaries, it has been calculated that the fractional area of the capillary wall occupied by the intercellular cleft is 20m/cm2 x 20 nm (length x width)= 0.004 (0.4%).