ABSTRACT
Mucus, the viscous secretion of epithelial glands, is a ubiquitous substance found in even the most primitive life forms. In mammals, mucus is secreted as a protective barrier between the epithelium and the environment by several organs: in the stomach it inhibits diffusion of secreted HCl (1); in the intestine it prevents damage from bacteria, viruses, and parasites (2); in the cervix it restricts passage of sperm to fertile period (3); and in the eye it helps to keep the corneal surface from drying (4). One of the main functions of bronchial mucus is to protect the lung from airborne particles by trapping them and facilitating their clearance by the ciliary movement (5).
