mucous membrane

Thin skin lining all animal body cavities and canals that come into contact with the air (for example, eyelids, breathing and digestive passages, genital tract). It contains goblet cells that secrete mucus, a moistening, lubricating, and protective fluid. In the air passages mucus captures dust and bacteria. In the gut it helps food slip along, and protects the epithelial cells from being damaged by digestive enzymes. Mucous membranes line the air passages from the mouth to the lungs and to the gut. The layer of cells next to the space in the tubes is an epithelium. In the air passages many of these cells have hair-like projections called cilia and the epithelium is then called a ciliated epithelium.