Editing Vagina (section)

===Microanatomy===
{{Main|Vaginal epithelium}}
[[File:Vagina (mucosa).JPG|thumb|alt=Micrograph of vaginal wall|Medium-power magnification [[micrograph]] of a [[H&E stain]]ed slide showing a portion of a vaginal wall. [[Stratified squamous epithelium]] and underling connective tissue can be seen. The deeper muscular layers are not shown. The black line points to a fold in the mucosa.]]
The '''vaginal wall''' from the lumen outwards consists firstly of a [[mucosa]] of [[stratified squamous epithelium]] that is not [[Stratified squamous epithelium#Keratinized|keratinized]], with a [[lamina propria]] (a thin layer of [[connective tissue]]) underneath it. Secondly, there is a layer of [[smooth muscle]] with bundles of circular fibers internal to longitudinal fibers (those that run lengthwise). Lastly, is an outer layer of connective tissue called the [[adventitia]]. Some texts list four layers by counting the two sublayers of the mucosa (epithelium and lamina propria) separately.<ref name="Brown">{{cite book|vauthors=Brown L|title=Pathology of the Vulva and Vagina|year=2012|publisher=[[Springer Science+Business Media]]|isbn=978-0-85729-757-0|pages=6–7|url=https://books.google.com/books?id=Yv2CMHoVR9wC&pg=PA6|access-date=October 27, 2015|archive-date=April 25, 2016|archive-url=https://web.archive.org/web/20160425014619/https://books.google.com/books?id=Yv2CMHoVR9wC&pg=PA6|url-status=live}}</ref><ref name="Arulkumaran">{{cite book|vauthors=Arulkumaran S, Regan L, Papageorghiou A, Monga A, Farquharson D|title=Oxford Desk Reference: Obstetrics and Gynaecology|year=2011|publisher=[[Oxford University Press]]|isbn=978-0-19-162087-4|page=471|url=https://books.google.com/books?id=lRaWcRYx_7YC&pg=PA471|access-date=October 27, 2015|archive-date=May 6, 2016|archive-url=https://web.archive.org/web/20160506160720/https://books.google.com/books?id=lRaWcRYx_7YC&pg=PA471|url-status=live}}</ref>

The smooth [[muscular layer]] within the vagina has a weak contractive force that can create some pressure in the lumen of the vagina. Much stronger contractive force, such as during childbirth, comes from muscles in the [[pelvic floor]] that are attached to the adventitia around the vagina.<ref name=Bitzer>{{cite book|vauthors=Bitzer J, Lipshultz L, Pastuszak A, Goldstein A, Giraldi A, Perelman M |title=Management of Sexual Dysfunction in Men and Women |date=2016 |publisher=Springer New York |isbn=978-1-4939-3099-9 |page=202 |language=en |chapter=The Female Sexual Response: Anatomy and Physiology of Sexual Desire, Arousal, and Orgasm in Women|doi=10.1007/978-1-4939-3100-2_18 }}</ref>

The lamina propria is rich in blood vessels and lymphatic channels. The muscular layer is composed of smooth muscle fibers, with an outer layer of longitudinal muscle, an inner layer of circular muscle, and oblique muscle fibers between. The outer layer, the adventitia, is a thin dense layer of connective tissue and it blends with loose connective tissue containing blood vessels, [[lymphatic vessel]]s and nerve fibers that are between pelvic organs.<ref name="Mulhall" /><ref name="Arulkumaran" /><ref name="Wylie">{{cite book|vauthors=Wylie L|title=Essential Anatomy and Physiology in Maternity Care|year=2005|publisher=Elsevier Health Sciences|isbn=978-0-443-10041-3|pages=157–158|url=https://books.google.com/books?id=QgpOvSDxGGYC&pg=PA157|access-date=October 27, 2015|archive-date=May 5, 2016|archive-url=https://web.archive.org/web/20160505063932/https://books.google.com/books?id=QgpOvSDxGGYC&pg=PA157|url-status=live}}</ref> The vaginal mucosa is absent of glands. It forms folds (transverse ridges or [[rugae]]), which are more prominent in the outer third of the vagina; their function is to provide the vagina with increased surface area for extension and stretching.<ref name="Snell"/><ref name="Dutta"/>

[[File:Rugae vaginales.jpg|thumb|alt=Close-up photograph of vagina|Folds of mucosa (or [[vaginal rugae]]) are shown in the front third of a vagina.]]
The epithelium of the ectocervix (the portion of the uterine cervix extending into the vagina) is an extension of, and shares a border with, the vaginal epithelium.<ref name="Junctions">{{cite journal|vauthors=Blaskewicz CD, Pudney J, Anderson DJ |title=Structure and function of intercellular junctions in human cervical and vaginal mucosal epithelia.|journal=Biology of Reproduction|date=July 2011|volume=85|issue=1|pages=97–104|doi=10.1095/biolreprod.110.090423|pmid=21471299|pmc=3123383}}</ref>  The vaginal epithelium is made up of layers of cells, including the [[Stratum basale|basal cells]], the parabasal cells, the superficial [[squamous cell|squamous flat cells]], and the intermediate cells.<ref name="Mayeaux">{{cite book|title=Modern Colposcopy Textbook and Atlas |vauthors=Mayeaux EJ, Cox JT |publisher=[[Lippincott Williams & Wilkins]]|year=2011|isbn=978-1-4511-5383-5|url=https://books.google.com/books?id=3lEtAxpNLewC&pg=SA2-PA29-IA2}}</ref> The basal layer of the epithelium is the most mitotically active and reproduces new cells.<ref name="Blaustein2002">{{cite book|url=https://books.google.com/books?id=tuKGMxGRKa8C|title=Blaustein's Pathology of the Female Genital Tract|publisher=Springer|year=2002|veditors=Kurman RJ|edition=5th|page=154|isbn=978-0-387-95203-1|access-date=October 27, 2015|archive-date=July 3, 2019|archive-url=https://web.archive.org/web/20190703220003/https://books.google.com/books?id=tuKGMxGRKa8C|url-status=live}}</ref> The superficial cells [[desquamation|shed]] continuously and basal cells replace them.<ref name="Dutta"/><ref name="Beckmann"/><ref name="Robboy">{{cite book|url=https://books.google.com/books?id=ab545XL-MBEC&pg=PA111|title=Robboy's Pathology of the Female Reproductive Tract|vauthors=Robboy SJ|publisher=[[Elsevier Health Sciences]]|year=2009|isbn=978-0-443-07477-6|page=111|access-date=December 15, 2017|archive-date=July 4, 2019|archive-url=https://web.archive.org/web/20190704043208/https://books.google.com/books?id=ab545XL-MBEC&pg=PA111|url-status=live}}</ref> [[Estrogen]] induces the intermediate and superficial cells to fill with [[glycogen]].<ref name="Robboy" /><ref>{{Cite journal |vauthors=Nunn KL, Forney LJ |date=September 2016 |title=Unraveling the Dynamics of the Human Vaginal Microbiome |journal=The Yale Journal of Biology and Medicine|volume=89|issue=3|pages=331–337|issn=0044-0086|pmc=5045142|pmid=27698617}}</ref> Cells from the lower basal layer transition from active metabolic activity to death ([[apoptosis]]). In these mid-layers of the epithelia, the cells begin to lose their [[mitochondria]] and other [[organelle]]s.<ref name="Blaustein2002"/><ref>{{cite book|title=Reproductive and developmental toxicology|vauthors=Gupta R |publisher=Academic Press|year=2011|isbn=978-0-12-382032-7|location=London|pages=1005}}</ref> The cells retain a usually high level of glycogen compared to other epithelial tissue in the body.<ref name="Blaustein2002" />

Under the influence of maternal estrogen, the vagina of a newborn is lined by thick stratified squamous epithelium (or mucosa) for two to four weeks after birth. Between then to [[puberty]], the epithelium remains thin with only a few layers of cuboidal cells without glycogen.<ref name="Robboy"/><ref name="G and H">{{cite book|vauthors=Hall J |title=Guyton and Hall textbook of medical physiology|date=2011|publisher=Saunders/Elsevier|location=Philadelphia |isbn=978-1-4160-4574-8|page=993|edition=12th}}</ref>  The epithelium also has few rugae and is red in color before puberty.<ref name="Dalton" /> When puberty begins, the mucosa thickens and again becomes stratified squamous epithelium with glycogen containing cells, under the influence of the girl's rising estrogen levels.<ref name="Robboy"/> Finally, the epithelium thins out from [[menopause]] onward and eventually ceases to contain glycogen, because of the lack of estrogen.<ref name="Dutta"/><ref name="Beckmann">{{cite book|vauthors=Beckmann CR|title=Obstetrics and Gynecology|publisher=[[Lippincott Williams & Wilkins]]|isbn=978-0-7817-8807-6|pages=241–245|year=2010|url=https://books.google.com/books?id=0flWgd3OJLEC&pg=PA241|access-date=October 27, 2015|archive-date=July 3, 2019|archive-url=https://web.archive.org/web/20190703211259/https://books.google.com/books?id=0flWgd3OJLEC&pg=PA241|url-status=live}}</ref><ref name="Gad">{{cite book|vauthors=Gad SC|title=Pharmaceutical Manufacturing Handbook: Production and Processes|publisher=[[John Wiley & Sons]]|isbn=978-0-470-25980-1|page=817|year=2008|url=https://books.google.com/books?id=4c0Hp3AOi8UC&pg=PA817|access-date=October 27, 2015|archive-date=May 6, 2016|archive-url=https://web.archive.org/web/20160506171159/https://books.google.com/books?id=4c0Hp3AOi8UC&pg=PA817|url-status=live}}</ref>

Flattened squamous cells are more resistant to both abrasion and infection.<ref name="G and H"/> The permeability of the epithelium allows for an effective response from the [[immune system]] since [[antibodies]] and other immune components can easily reach the surface.<ref name="Anderson">{{Cite journal |vauthors=Anderson DJ, Marathe J, Pudney J |date=June 2014 |title=The Structure of the Human Vaginal Stratum Corneum and its Role in Immune Defense |journal=American Journal of Reproductive Immunology|language=en|volume=71|issue=6|pages=618–623|doi=10.1111/aji.12230|pmid=24661416 |issn=1600-0897|pmc=4024347}}</ref> The vaginal epithelium differs from the similar tissue of the skin. The [[epidermis]] of the skin is relatively resistant to water because it contains high levels of lipids. The vaginal epithelium contains lower levels of lipids. This allows the passage of water and water-soluble substances through the tissue.<ref name="Anderson" />

Keratinization happens when the epithelium is exposed to the dry external atmosphere.<ref name="Dutta"/> In abnormal circumstances, such as in [[Female genital prolapse|pelvic organ prolapse]], the mucosa may be exposed to air, becoming dry and keratinized.<ref name="Dutta2">{{cite book|vauthors=Dutta DC|title=DC Dutta's Textbook of Gynecology|year=2014|publisher=JP Medical Ltd|isbn=978-93-5152-068-9|page=206|url=https://books.google.com/books?id=40yVAwAAQBAJ&pg=PA206|access-date=October 27, 2015|archive-date=May 6, 2016|archive-url=https://web.archive.org/web/20160506172128/https://books.google.com/books?id=40yVAwAAQBAJ&pg=PA206|url-status=live}}</ref>