How do tight junctions contribute to the function of epithelial tissues?

Tight junctions (zonula occludens) are specialized intercellular junctions in animal cells that form a continuous seal around cells, preventing the leakage of fluid across a layer of epithelial cells. They consist of strands of transmembrane proteins (like claudins and occludins) that tightly bind adjacent cells. Their contribution to epithelial tissue function is crucial for creating barriers, such as in the lining of the stomach, intestines, and bladder, where they prevent the passage of substances between cells, ensuring selective absorption and preventing pathogen entry.