Tight junctions form a continuous seal around epithelial cells, creating a barrier that prevents the passage of fluids and solutes between adjacent cells. This function is crucial for maintaining distinct compartments and controlling paracellular transport. Unlike gap junctions (which allow communication), desmosomes and adherens junctions (which provide mechanical strength), tight junctions specifically regulate permeability and maintain cell polarity.

Reference:
Ross & Wilson, *Anatomy and Physiology in Health and Illness*, 13th Edition, Chapter 3, Page 54