what do glands in the mucous membranes that line the stomach secrete
Membranes. 1  Mucous membranes line cavities that open to the outside of the body (digestive, respiratory, excretory, and reproductive tracts). 2  They contain glands and secrete mucus. 3  Serous membranes line trunk cavities that do not open to the outside of the body (pleural, pericardial, and peritoneal cavities).