Epithelial barriers are the body's first line of defense against invading pathogens. The skin, for instance, is a tough, impermeable barrier that prevents the entry of microorganisms. Mucous membranes in the respiratory, gastrointestinal, and urogenital tracts produce mucus that traps pathogens. Additionally, these barriers are often equipped with antimicrobial peptides and enzymes like lysozyme that can destroy bacterial cell walls.
