Mucous membranes line parts of the body that lead to the outside and are exposed to air. Examples of mucous membranes are the lining of the digestive tract (including the mouth), the lining of the urogenital tract, and the lining of the respiratory tract (including the nose). Other mucous membranes include the eyes (conjunctival membranes).
Mucous membranes are made up of epithelial (skin) tissue that usually covers and protects underlying connective tissue. Mucous membranes are rich with mucous glands to help keep them moist. Dry mucous membranes are a sign of dehydration and can cause various health problems. For example, dry mucous membranes in the lining of the nose can cause frequent bloody noses. Keeping mucous membranes moist involves drinking a lot of fluids. You can also use a humidifier, preferably a cool mist humidifier.
National Cancer Institute. SEER Training Modules: Membranes. Accessed: December 14, 2010 from http://training.seer.cancer.gov/anatomy/cells_tissues_membranes/membranes.html