Mucous membranes line the digestive, respiratory and reproductive tracts and are the primary barrier between the external world and the interior of the body; in an adult human the total surface area of the mucosa is about 400 square meters while the surface area of the skin is about 2 square meters.[4]: 1 Along with providing a physical barrier, they also contain key parts of the immune system and serve as the interface between the body proper and themicrobiome.[2]: 437
One of its functions is to keep the tissue moist (for example in the respiratory tract, including the mouth and nose).[2]: 480 It also plays a role in absorbing and transformingnutrients.[2]: 5, 813 Mucous membranes also protect the body from itself. For instance, mucosa in the stomach protects it from stomach acid,[2]: 384, 797 and mucosa lining the bladder protects the underlying tissue from urine.[8] In theuterus, the mucous membrane is called theendometrium, and it swells each month and is then eliminated duringmenstruation.[2]: 1019
^abcdefgGuyton, Arthur C.; Hall, John E. (2006).Textbook of Medical Physiology, 11th Edition. Philadelphia: Elsevier Saunders.ISBN9780721602400.OCLC56661571.
^Schoenwolf, Gary C.; Bleyl, Steven B.; Brauer, Philip R.; Francis-West, Philippa H. (2014-12-01).Larsen's Human Embryology. Elsevier Health Sciences. p. 372.ISBN9781455727919.
