Cervix 5738 225729540 2008-07-15T03:10:34Z Acroterion 1839637 Reverted edits by [[Special:Contributions/76.214.131.10|76.214.131.10]] ([[User talk:76.214.131.10|talk]]) to last version by Makeemlighter {{Refimprove|date=November 2007}} {{Infobox Anatomy | Name = Cervix | Latin = cervix uteri | GraySubject = 268 | GrayPage = 1259 | Image = Scheme_female_reproductive_system-en.svg | Caption = Schematic frontal view of female anatomy | Image2 = Female_reproductive_system_lateral_nolabel.png | Caption2 = 1: [[fallopian tube]], 2: [[urinary bladder|bladder]], 3: [[pubic bone]], 4: [[g-spot]], 5: [[clitoris]], 6: [[urethra]], 7: [[vagina]], 8: [[ovary]], 9: [[sigmoid colon]], 10: [[uterus]], 11: [[Fornix vaginae|fornix]], 12: cervix, 13: [[rectum]], 14: [[anus]] | Precursor = [[Müllerian duct]] | System = | Artery = [[vaginal artery]], [[uterine artery]] | Vein = | Nerve = | Lymph = | MeshName = Cervix+uteri | MeshNumber = A05.360.319.679.256 | DorlandsPre = c_22 | DorlandsSuf = 12229212 | }} The '''cervix''' (from [[Latin]] "neck") is the lower, narrow portion of the [[uterus]] where it joins with the top end of the [[vagina]]. It is cylindrical or conical in shape and protrudes through the upper anterior vaginal wall. Approximately half its length is visible with appropriate medical equipment; the remainder lies above the vagina beyond view. It is occasionally called "cervix uteri", or "neck of the uterus". == Anatomy == ===Ectocervix=== The portion projecting into the vagina is referred to as the [[Vaginal portion of cervix|''portio vaginalis'']] or ectocervix. On average, the ectocervix is 3 cm long and 2.5 cm wide. It has a convex, elliptical surface and is divided into anterior and posterior lips. ====External os==== The ectocervix's opening is called the [[External orifice of the uterus|external os]]. The size and shape of the external os and the ectocervix varies widely with age, hormonal state, and whether the woman has had a vaginal birth. In women who have not had a vaginal birth the external os appears as a small, circular opening. In women who have had a vaginal birth, the ectocervix appears bulkier and the external os appears wider, more slit-like and gaping. ===Endocervical canal=== The passageway between the external os and the uterine cavity is referred to as the [[Canal of the cervix|endocervical canal]]. It varies widely in length and width, along with the cervix overall. Flattened anterior to posterior, the endocervical canal measures 7 to 8 mm at its widest in reproductive-aged women. ===Internal os=== The endocervical canal terminates at the [[Internal orifice of the uterus|internal os]] which is the opening of the cervix inside the uterine cavity. === Cervical crypts === There are pockets in the lining of the cervix known as ''cervical crypts.'' They function to produce cervical fluid.<ref name ="Weschler">Weschler, Toni, MPH, ''Taking Charge of Your Fertility'', Second Edition, 2002, pp. 59, 64.</ref> ==Histology== The [[epithelium]] of the cervix is varied. The ectocervix (more distal, by the vagina) is composed of nonkeratinized [[stratified squamous epithelium]] The endocervix (more proximal, within the uterus) is composed of [[simple columnar epithelium]].<ref>{{BUHistology|19404loa}}</ref><ref>{{USCHistology|rep/c_48}}</ref> The area adjacent to the border of the endocervix and ectocervix is known as the 'transformation zone. The Transformation zone undergoes [[metaplasia]] numerous times during normal life. When the endocervix is exposed to the harsh acidic environment of the vagina it undergoes [[metaplasia]] to squamous epithelium which is better suited to the vaginal environment. Similarly when the ectoocervix enters the less harsh uterine area it undergoes [[metaplasia]] to become columnar epithelium. Times in life when this [[metaplasia]] of the transformation zone occurs: - puberty; when the endocervix everts (moves out) of the uterus - with the changes of the cervix associated with the normal menstrual cycle - post-menopause; the uterus shrinks moving the transformation zone upwards All these changes are normal and the occurrence is said to be [[physiological]]. However all this metaplasia does increase the risk of cancer in this area - the transformation zone is the most common area for cervical cancer to occur. At certain times of life, the columnar epithelium is replaced by metaplastic squamous epithelium, and is then known as the transformation zone. [[Nabothian cyst]]s are often found in the cervix.<ref>Weschler, pp. 227–228.</ref> ==Cervical mucus== [[Image:Gray34.png |thumb|Mucus plug]] After a [[Menstrual cycle|menstrual period]] ends, the external os is blocked by [[mucus]] that is thick and acidic. This "infertile" mucus blocks spermatozoa from entering the [[uterus]].<ref>{{cite book |author=Ann Westinore; Evelyn, Dr Billings |title=The Billings Method: Controlling Fertility Without Drugs or Devices |publisher=Life Cycle Books |location=Toronto |year=1998 |pages=37 |isbn=0-919225-17-9}}</ref> For several days around the time of [[ovulation]], "fertile" types of mucus are produced: they have a higher water content, are less acidic, and have a ferning pattern that helps guide [[Spermatozoon|spermatozoa]] through the cervix.<ref name="w59">Weschler, pp. 58–59.</ref> This ferning is a branching pattern seen in the mucus when observed with low magnification. Some methods of [[fertility awareness]] involve estimating a woman's periods of fertility and infertility by observing changes in her body. Among these changes are several involving the quality of her cervical mucus: the sensation it causes at the vulva, its elasticity ([[spinnbarkeit]]), its transparency, and the presence of ''ferning''.<ref name="w59" /> [[Image:cervical_mucus1.jpg|thumb|left|125px|Cervical mucus]] Most methods of [[hormonal contraception]] work primarily by preventing ovulation, but their effectiveness is increased because they prevent the fertile types of cervical mucus from being produced. Conversely, methods of thinning the mucus may help to achieve pregnancy. One suggested method is to take [[guaifenesin]] in the few days before ovulation.<ref>Weschler, p. 173.</ref> During pregnancy the cervix is blocked by a special antibacterial mucosal plug which prevents infection, somewhat similar to its state during the infertile portion of the [[menstrual cycle]].<!-- is it the same, or not? --> The mucus plug comes out as the cervix dilates in labor or shortly before. ==Cervical position== After menstruation and directly under the influence of [[estrogen]], the cervix undergoes a series of changes in position and texture. During most of the menstrual cycle, the cervix remains firm, like the tip of the nose, and is positioned low and closed. However, as a woman approaches ovulation, the cervix becomes softer, and rises and opens in response to the high levels of estrogen present at ovulation.<ref name="Weschler" /> These changes, accompanied by the production of fertile types of cervical mucus, support the survival and movement of sperm. ==Functionality== During [[menstruation]] the cervix stretches open slightly to allow the [[endometrium]] to be shed. This stretching is believed to be part of the [[cramp]]ing pain that many women experience. Evidence for this is given by the fact that some women's cramps subside or disappear after their first vaginal birth because the cervical opening has widened. During [[childbirth]], contractions of the uterus will [[cervical dilation|dilate the cervix]] up to 10 cm in diameter to allow the fetus to pass through. During [[orgasm]], the cervix convulses and the [[external os]] dilates. Dr. R. Robin Baker and Dr. Mark A. Bellis, both at the [[University of Manchester]], first proposed that this behavior worked in such a way as to draw any [[semen]] in the [[vagina]] into the [[uterus]], increasing the likelihood of [[conception]]. Later researchers, most notably Elisabeth A. Lloyd, have questioned the logic of this theory and the quality of the experimental data used to back it. ==Cervical cancer== In humans the cervix may be affected by [[cervical cancer]], a particular form of [[cancer]] which is detectable by [[cytology|cytological]] study of [[epithelium|epithelial]] [[cell (biology)|cells]] removed from the cervix in a process known as the [[pap smear]]. Evidence now shows that those with exposure to HPV ([[human papilloma virus]]) are at increased risk for cervical cancer. These viruses are related to the viruses that causes [[wart]]s. The incidence of new cases of cervical cancer in the United States was observed to be 7 per 100,000 women in 2004.<ref name ="SEER Cancer Fast Stats">[http://canques.seer.cancer.gov/cgi-bin/cq_submit?dir=delay2004&db=1&rpt=TAB&sel=^12^0^2^0^&dec=4&title=SEER%20Age-Adjusted%20Incidence%20Rate%20Comparison~Delay-Adjusted%20and%20Observed%20Rates~For%20Cervix%20Uteri%20Cancer,%20All%20Races,%20Females,%20All%20Ages~SEER%209%20Registries%20for%201975-2004~Age-Adjusted%20to%20the%202000%20US%20Std%20Population&template=faststats&x=Year%20of%20diagnosis^0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29&y=Statistic%20type^0,2 SEER cancer statistics]</ref> ==Lymphatic drainage== The [[Lymphatic system|lymphatic drainage]] of the cervix is along the [[uterine artery|uterine arteries]] and cardinal [[ligament]]s to the parametrial, [[external iliac vein]], [[internal iliac vein]], and [[obturator]] and presacral [[lymph node]]s. From these pelvic lymph nodes, drainage then proceeds to the [[paraaortic lymph node]]s. In some women, the lymphatics drain directly to the paraaortic nodes. ==Additional images== <gallery> Image:Illu repdt female.jpg|Organs of the female reproductive system. Image:Illu ovaryb.jpg|Ovary Image:Illu cervix.jpg|Uterus and uterine tubes. Image:Gray1167.svg|Posterior half of uterus and upper part of vagina. </gallery> ==References== <references/> {{Female reproductive system}} {{Menstrual cycle}} [[Category:Female reproductive system]] [[Category:Gynecology]] [[Category:Reproductive system]] [[ar:عنق الرحم]] [[bg:Маточна шийка]] [[cs:Děložní hrdlo]] [[cy:Ceg y groth]] [[da:Livmoderhals]] [[de:Cervix uteri]] [[es:Cuello uterino]] [[fr:Col de l'utérus]] [[it:Cervice]] [[he:צוואר הרחם]] [[lt:Gimdos kaklelis]] [[nl:Baarmoederhals]] [[ja:子宮頸部]] [[no:Livmorhals]] [[pl:Szyjka macicy]] [[pt:Cérvix]] [[ru:Шейка матки]] [[simple:Cervix]] [[sv:Livmoderhals]] [[zh:子宮頸]]