The Structure and Function of Gastrointestinal Mucus

Gastrointestinal Mucus is secreted as a viscoelastic gel that adheres to the mucosal surfaces and is resistant to aqueous solubilization. The major function attributed to gastrointestinal mucus is one of protection. Throughout the gastrointestinal tract mucus will protect the underlying epithelial cells from mechanical damage by the passage of food or feces and the vigorous forces of the digestive processes. The interactions of mucus and proteolytic enzymes, e.g., pepsin are more complex than that of just permeability. Proteolytic enzymes will degrade and solubilize mucous gel. The gel-forming components of mucous secretions are glycoproteins of large molecular weight. Proteolysis by a variety of enzymes including pepsin, papain, and trypsin, also cleaves the native pig gastric mucous glycoproteins into an average of four subunits, essentially the same size as those obtained by reduction, and without loss of any carbohydrate. Mucous gels are weak, viscoelastic gels with properties well suited to forming a continuous protective cover over the mucosal surface.