The cervix (technically cervix uteri , from Latin cervīx , neck, and uterus, German for uterus ), also simply referred to as the cervix or cervix , is the lower, narrow part of the uterus. It connects the body of the uterus with the vagina .
The cervix is the connection between the uterus and the vagina. The opening is surrounded by thick mucous membrane that protrudes approx. 3 cm into the roof of the vagina. The opening is usually narrow to prevent germs from entering the uterus. During birth , the cervix becomes softer under the influence of the hormone prostaglandin F 2α , it opens during labor and has a diameter of over 10 cm when the baby's head passes through.
The cervix is in the of squamous epithelium covered portio vaginalis uteri (the part of the cervix, projects into the sheath) and of schleimbildendem epithelium lined cervical canal divided. The boundary between the two epithelial forms changes depending on the age and the number of births. With increasing age, the limit moves further and further up into the cervical canal. The shape of the cervix is typically dimple-shaped before the first birth, and after pregnancy it is usually split across.
As cervix ( latin ostium uteri cervix ) those openings of the uterus are referred to with those of the cervical canal itself - as outer cervix - in the vagina, or - as inner cervix into the uterine cavity (- uterine cavity opens).
The external cervix - the ostium uteri externum - is a round dimple with a short, transverse opening in a nullipara , i.e. a woman who has not yet given birth. The distinction between a posterior and an anterior cervical lip is particularly useful in women who have already given birth: Here the opening shows up as a transverse gap. During the woman's orgasm , the external cervix dips peristaltically into the spilled semen in order to induce or support the transmission of the sperm to the tubes.
The inner cervix - the ostium uteri internum - is also known as the "isthmus narrow" and represents the inner end of the cervical canal. The inner cervix is important in those cases in which the placenta completely covers it as placenta previa totalis during pregnancy thus represents an obstacle to birth .
During pregnancy , the length of the cervix is measured at every check-up. The length should be greater than 25 mm until birth.
If it is shorter, cervical insufficiency ( cervical weakness with the risk of premature widening of the cervix) can occur. The shortening of the cervix can lead to premature birth and threatens the opening of the cervix without labor. It is a cause of (also repeated) late abortions and premature births. If a shortening detected early, can be attempted with a wrap of the cervix with a thread ( " Shirodkar - or McDonald cerclage ') or with a total cervical occlusion extend the reach anticipated duration of pregnancy, these methods are controversial. If the previous pregnancy ended prematurely, prophylactic treatment in the form of an operative cervical occlusion (cerclage) should rather be considered. There is evidence that the risk of premature birth can be reduced by long-term administration of progestins .
Little is known about the physiological processes that lead to the softening of the cervix and the onset of labor.
The cervix secretes mucus, which is subject to characteristic changes in the course of the menstrual cycle : on infertile days it is viscous to sticky, of a cardboard consistency and acts as a natural barrier to the cervix. Under the microscope you can see the mucin threads lying confused and disorganized, neither sperm nor bacteria can penetrate them.
On the other hand, on the days around ovulation , the mucus becomes thin, crystal clear and stringy. The mucin threads are aligned parallel and allow the sperm to ascend into the uterus. The contraception of the so-called minipill is based, among other things, on the effect of the gestagens on the cervical mucus. This becomes more impermeable to sperm.
The cervical mucus forms the mucus plug of the cervical canal and is formed by the cervical glands ( glandulae cervicis uteri ). It is a secretion that is slightly alkaline and the consistency and quantity of which changes during the cycle. The cervical mucus may settle. a. together from mucins, amino acids , sugars , enzymes , electrolytes and water (up to 90%). The function of the cervical mucus is to prevent sperm and pathogens from entering the uterus.
Under the influence of estrogen , the cervical mucus becomes so thin that it can be pulled out into a thread and becomes spinnable. Shortly before ovulation (ovulation), the spinnability is greatest (6–15 cm long threads), the secretion for sperm is maximally permeable and the fern phenomenon (see below) is positive. In the second half of the menstrual cycle, under the influence of progestin, there is a reduced formation of non-stringy cervical mucus. The fern phenomenon is then negative and the permeability for sperm is greatly reduced or even completely eliminated. The cervix score is a point system that allows an estimation of the hormonal status based on various parameters.
The Symptothermal and Billings methods use the differences in mucus quality to determine the fertile and infertile days (→ natural family planning ).
The fern phenomenon (also called arborization phenomenon) is a very characteristic formation of fern-like NaCl crystals in the dried cervical mucus that occurs under the influence of estrogen . This phenomenon occurs particularly clearly just before the follicle rupture, but disappears under the influence of progesterone in the second half of the menstrual cycle.
A colposcopy can detect defects in the superficial epithelium of the cervix ( erosio vera ), portioectopy , inflammation of the cervix ( cervicitis ), cervical polyps (due to excessive tissue growth ), bleeding and cervical tears or cervical anomalies . If the findings are not clearly harmless, a smear cytology or tissue removal is usually carried out.
A laceration sectropion occurs after a tear in the cervix during childbirth, with subsequent scarred healing and bulging of the cervical lips.
A cytological smear for staining according to Papanicolaou and diagnosis is used for early cancer detection. In the case of unclear findings or serious cell atypia or a carcinoma in situ , a conization (a conical tissue removal) is connected.
In guinea pigs, the mucous glands can develop and thus endocervical hyperplasia .
- ↑ Eduardo B. Fonseca, Ebru Celik a. a .: Progesterone and the Risk of Preterm Birth among Women with a Short Cervix. In: New England Journal of Medicine , 357, 2007, p. 462, doi: 10.1056 / NEJMoa067815 .
- ↑ Alison Kodjak: Scientific Duo Gets Back To Basics To Make Childbirth Safer. In: npr. February 18, 2019, accessed February 18, 2019 .
- ^ Image of the bracken phenomenon. wunschkinder.net; Retrieved July 29, 2016
- ↑ Christof A. Bergmann et al .: Increase in the circumference of the cervix uteri in a guinea pig . In: Kleintierpraxis Volume 65, 2020, Issue 7, pp. 400–403.