Mucous membrane is the general name given to the mucous-lubricated tissues lining passages and cavities in the body. They are usually composed of three layers of tissues: epithelium, a supporting lamina propria, and a thin, usually double layer of smooth muscle. Cells which secrete mucus, a watery fluid containing mucin, salts and other substances, may be present.
Mucous membranes provide protection for and support of blood vessels and lymphatics by forming a lining for the passages which connect to the exterior. The membranes also provide a large surface for various secretions and absorptions.
Kimber, D.C., C.E. Grey & C.E. Stackpole. Anatomy and Physiology, 15th ed. MacMillan Co., New York. 1966.