View source for Mucous membrane

{{Short description|Protective layer that lines the interior of hollow organs}}{{Human-centric|date=May 2022}}
{{Infobox microanatomy
| Name        = Mucous membrane
| Latin       = tunica mucosa
| Image       = Normal gastric mucosa intermed mag.jpg
| Caption     = [[Histology|Histological]] section taken from the [[gastric antrum]], showing the mucosa of the stomach
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{{Gastrointestinal wall series}}
A '''mucous membrane''' or '''mucosa''' is a [[biological membrane|membrane]] that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of [[Epithelium|epithelial cells]] overlying a layer of [[loose connective tissue]]. It is mostly of [[endoderm]]al origin and is continuous with the skin at [[body orifice|body openings]] such as the [[eye]]s, [[eyelid]]s, [[ear]]s, [[Mucous membrane of nose|inside the nose]], [[Oral mucosa|inside the mouth]], [[lip]]s, the [[Sex organ|genital area]]s, the [[Urinary meatus|urethral opening]] and the [[anus]]. Some mucous membranes secrete [[mucus]], a thick protective fluid. The function of the membrane is to stop [[pathogen]]s and dirt from entering the body and to prevent bodily tissues from becoming dehydrated.

==Structure==
The mucosa is composed of one or more layers of [[epithelial cells]] that secrete [[mucus]], and an underlying [[lamina propria]] of [[areolar connective tissue]].<ref name="britan">{{cite encyclopedia|url=https://www.britannica.com/science/mucous-membrane|title=Mucous membrane|encyclopedia=Encyclopædia Britannica|access-date=1 August 2015}}</ref> The type of cells and type of mucus secreted vary from organ to organ and each can differ along a given tract.<ref name=Guyton2005>{{cite book|last1=Guyton|first1=Arthur C.|last2=Hall|first2=John E.|title=Textbook of Medical Physiology, 11th Edition|date=2006|isbn=9780721602400|oclc=56661571|publisher=Elsevier Saunders|location=Philadelphia}}</ref><ref>{{Cite book|last=Stuart-Low|first=William|url=https://books.google.com/books?id=nURIAAAAMAAJ|title=Mucous Membranes Normal & Abnormal Including Mucin & Malignancy|date=1905|publisher=Bailliére, Tindall & Cox|oclc=643969757|language=en}}</ref>

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.<ref name="Sompayrac2012">{{cite book|last1=Sompayrac |first1=Lauren|url=https://books.google.com/books?id=oRsGFRKypn4C|title=How the Immune System Works, 4th Edition|date=30 January 2012|publisher=[[Wiley Publishing]]|isbn=9780470657294|location=Chichester, England|oclc=1036250938}}</ref>{{rp|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 the [[microbiome]].<ref name=Guyton2005/>{{rp|437}}

===Examples===
Some examples include:{{cn|date=July 2024}}
* [[Endometrium]]: the mucosa of the [[uterus]]
* [[Gastric mucosa]]
* [[Intestinal mucosa]]
* [[Nasal mucosa]]
* [[Olfactory mucosa]]
* [[Oral mucosa]]
* [[Preputial mucosa|Penile mucosa]]
* [[Respiratory mucosa]]
* [[Vaginal mucosa]]
* [[Frenulum of tongue]]
* [[Anal canal]]
* [[Conjunctiva]]

===Development===
Developmentally, the majority of mucous membranes are of [[endoderm]]al origin.<ref>{{Cite web|url=http://discovery.lifemapsc.com/library/review-of-medical-embryology/chapter-25-germ-layers-and-their-derivatives|title=Chapter 25. Germ Layers and Their Derivatives - Review of Medical Embryology Book - LifeMap Discovery|website=discovery.lifemapsc.com|access-date=2017-02-18|archive-url=https://web.archive.org/web/20170109185535/http://discovery.lifemapsc.com/library/review-of-medical-embryology/chapter-25-germ-layers-and-their-derivatives|archive-date=2017-01-09|url-status=dead}}</ref> Exceptions include the [[palate]], [[cheek]]s, floor of the [[Mouth#Mouth cavity|mouth]], [[gums]], [[lips]] and the portion of the [[anal canal]] below the [[pectinate line]], which are all [[ectoderm]]al in origin.<ref>{{Cite book|chapter-url=https://books.google.com/books?id=1caiau37J8kC&q=mucosa+is+of+ectodermal+origin&pg=PT81|title=Human Oral Mucosa: Development, Structure and Function|page=81|last1=Squier|first1=Christopher|last2=Brogden|first2=Kim|date=2010-12-29|publisher=John Wiley & Sons|isbn=9780470959732|language=en|chapter=Chapter 7, Development and aging of the oral mucosa}}</ref><ref>{{Cite book|url=https://books.google.com/books?id=XQuqBAAAQBAJ&q=pectinate+line+embryology&pg=PA372|title=Larsen's Human Embryology|last1=Schoenwolf|first1=Gary C.|last2=Bleyl|first2=Steven B.|last3=Brauer|first3=Philip R.|last4=Francis-West|first4=Philippa H.|date=2014-12-01|publisher=Elsevier Health Sciences|isbn=9781455727919|pages=372|language=en}}</ref>

==Function==
One of its functions is to keep the tissue moist (for example in the respiratory tract, including the mouth and nose).<ref name=Guyton2005/>{{rp|480}}  It also plays a role in absorbing and transforming [[nutrients]].<ref name=Guyton2005/>{{rp|5,813}}   Mucous membranes also protect the body from itself. For instance, mucosa in the stomach protects it from stomach acid,<ref name=Guyton2005/>{{rp|384,797}}  and mucosa lining the bladder protects the underlying tissue from urine.<ref name=Fry2016rev>{{cite journal|last1=Fry|first1=CH|last2=Vahabi|first2=B|title=The Role of the Mucosa in Normal and Abnormal Bladder Function.|journal=Basic & Clinical Pharmacology & Toxicology|date=October 2016|volume=119 Suppl 3|issue=Suppl 3 |pages=57–62|doi=10.1111/bcpt.12626|pmid=27228303|pmc=5555362}}</ref> In the [[uterus]], the mucous membrane is called the [[endometrium]], and it swells each month and is then eliminated during [[menstruation]].<ref name=Guyton2005/>{{rp|1019}}

===Nutrition===
[[Niacin (nutrient)|Niacin]]<ref name=Guyton2005/>{{rp|876}} and [[vitamin A]] are [[essential nutrient]]s that help maintain mucous membranes.<ref>{{cite web|title=Vitamin A|url=https://medlineplus.gov/ency/article/002400.htm|publisher=MedlinePlus Medical Encyclopedia|access-date=16 February 2017|language=en|date=February 2, 2015}}</ref>

==See also==
{{col div|colwidth=30em}}
* [[Alkaline mucus]]
* [[Mucin]]
* [[Mucociliary clearance]]
* [[Mucocutaneous boundary]]
* [[Mucosal immunology]]
** [[Mucosal-associated invariant T cell]]
* [[Mucosal melanoma]]
* [[Rete pegs]]
* [[Epimysium]]
{{colend}}

==References==
{{Reflist}}

{{Digestive tract}}
{{Urinary system anatomy}}
{{Authority control}}

[[Category:Anatomy]]
[[Category:Membrane biology]]