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secretions from epithelial cells in the mucosa of respiratory, digestive, and urogenital tracts, as well as from the submaxillary and sublingual salivary glands. Mucins are mixtures of the carbohydrate-protein compounds known as glycoproteins and impart moisture and elasticity to the mucosa. Salivary mucins promote the moistening and adhesion of food particles for smooth passage through the esophagus. Covering the gastrointestinal mucosa, mucins provide protection from the action of proteolytic enzymes in gastric and intestinal juices. Mucins perform an overall protective function in the organism; for example, they inhibit the erythrocyte agglutination caused by the influenza virus.