Editing Cervix (section)

=== Cervical mucus ===
Several hundred glands in the endocervix produce 20–60&nbsp;mg of cervical [[mucus]] a day, increasing to 600&nbsp;mg around the time of ovulation. It is viscous because it contains large proteins known as [[mucin]]s. The viscosity and water content vary during the [[menstrual cycle]]; mucus is composed of around 93% water, reaching 98% at midcycle. These changes allow it to function as a barrier or a transport medium to spermatozoa. It contains electrolytes such as calcium, sodium, and potassium; organic components such as glucose, amino acids, and soluble proteins; trace elements including zinc, copper, iron, manganese, and selenium; free fatty acids; enzymes such as [[amylase]]; and [[prostaglandins]].<ref name=CERVIX2006>{{cite book| vauthors = Sharif K, Olufowobi O |title=The Cervix|url=https://archive.org/details/cervixndedition00jord|url-access=limited| veditors = Jordan J, Singer A, Jones H, Shafi M |publisher=Blackwell Publishing|location=Malden, MA | date=2006|edition=2nd|pages=[https://archive.org/details/cervixndedition00jord/page/n171 157]–68 |chapter=The structure chemistry and physics of human cervical mucus|isbn=978-1-4051-3137-7}}</ref><!-- cites four previous sentences --> Its consistency is determined by the influence of the hormones estrogen and progesterone. At midcycle, around the time of [[ovulation]]—a period of high estrogen levels— the mucus is thin and serous to allow sperm to enter the uterus and is more alkaline and, hence, more hospitable to sperm.<ref name=BRANNIGAN2008 /> It is also higher in electrolytes, which results in the "ferning" pattern that can be observed in drying mucus under low magnification; as the mucus dries, the salts crystallize, resembling the leaves of a fern.<ref name = Weschler/> The mucus has a stretchy character described as ''Spinnbarkeit'' most prominent around ovulation.<ref name="pmid15775876">{{cite journal | vauthors = Anderson M, Karasz A, Friedland S | title = Are vaginal symptoms ever normal? a review of the literature | journal = MedGenMed | volume = 6 | issue = 4 | pages = 49 | date = November 2004 | pmid = 15775876 | pmc = 1480553 }}</ref>

At other times in the cycle, the mucus is thick and more acidic due to the effects of progesterone.<ref name=BRANNIGAN2008 /> This "infertile" mucus acts as a barrier to keep sperm from entering the uterus.<ref>{{cite book | vauthors = Westinore A, Billings E |title=The Billings Method: Controlling Fertility Without Drugs or Devices |publisher=Life Cycle Books |location=Toronto, ON |year=1998 |page=37 |isbn=0-919225-17-9}}</ref> Women taking an [[oral contraceptive pill]] also have thick mucus from the effects of progesterone.<ref name=BRANNIGAN2008 /> Thick mucus also prevents [[pathogen]]s from interfering with a nascent pregnancy.<ref name="pmid7431318">{{cite journal | vauthors = Wagner G, Levin RJ | title = Electrolytes in vaginal fluid during the menstrual cycle of coitally active and inactive women | journal = Journal of Reproduction and Fertility | volume = 60 | issue = 1 | pages = 17–27 | date = September 1980 | pmid = 7431318 | doi = 10.1530/jrf.0.0600017 | doi-access = free }}</ref>

A [[cervical mucus plug]], called the operculum, forms inside the cervical canal during pregnancy. This provides a protective seal for the uterus against the entry of pathogens and leakage of uterine fluids. The mucus plug is also known to have antibacterial properties. This plug is released as the cervix dilates, either during the first stage of childbirth or shortly before.<ref>{{cite journal | vauthors = Becher N, Adams Waldorf K, Hein M, Uldbjerg N | title = The cervical mucus plug: structured review of the literature | journal = Acta Obstetricia et Gynecologica Scandinavica | volume = 88 | issue = 5 | pages = 502–513 | date = May 2009 | pmid = 19330570 | doi = 10.1080/00016340902852898 | s2cid = 23738950 }}</ref> It is visible as a blood-tinged mucous discharge.<ref>{{cite book| vauthors =  Lowdermilk DL, Perry SE |title=Maternity Nursing|year=2006|publisher=Elsevier Mosby|location=Edinburgh, United Kingdom|isbn=978-0-323-03366-4|page=[https://archive.org/details/maternitynursing00deit/page/394 394]|edition=7th|url=https://archive.org/details/maternitynursing00deit/page/394}}</ref>