Mucus Gel Layer

A secreted, viscoelastic extracellular matrix dominated by high‑molecular‑weight mucin glycoproteins, together with salts, lipids and other macromolecules; it overlies the epithelium, provides lubrication, creates a diffusion barrier that limits particulate and microbial access to the epithelial surface, and forms a habitat and nutrient matrix for the resident microbiota.