Fig. 2

Mechanisms of intestinal barrier functions. Traverse of intraluminal content occurs across tight junctions by two different routes termed pore and the leak pathways. The pore pathway is a high-capacity, charge-selective route that regulates the passage of small molecules less than 8 Å in diameter. The leak pathway is a low-capacity, non-charge selective route traversed by molecules up to 100 Å in diameter. When epithelial damage occurs, the tight junction-independent, size-nonselective, charge-nonselective unrestricted pathway becomes the dominant route of intestinal permeability