Menstrual cycle
The menstrual cycle , menstrual cycle or woman's cycle is a monthly (about every 20 to 35, on average every 27 days) occurring process in the woman's body , which ranges from puberty (with menarche ) to menopause (with menopause ) occurs approximately 400 times and is characterized by hormonal changes aimed at different physical levels, primarily in the ovary (see also ovarian cycle) and on the uterus to create favorable conditions for fertilization and pregnancy. The first day of menstrual bleeding has been set as the start of a menstrual cycle because bleeding is the clearest and most visible symptom of the cycle. The cycle ends, by definition, the day before the onset of bleeding.
In the course of a cycle, if conception has not taken place, the uterine lining is shed ( desquamation ) and then rebuilt ( proliferation and secretion ). In the meantime, an egg cell has matured in one of the two ovaries ( follicle maturation ), which reaches the fallopian tube during ovulation and is made available there for fertilization over the next 12-18 hours . These processes are controlled by the hypothalamus , pituitary gland and ovary via various hormones : estrogen and progesterone trigger the changes in the uterine lining. Chemically modified estrogen and progesterone analogs are the main ingredients in birth control pills . With their help, the body is simulated that it is in the luteal phase, in which there is no further egg maturation or ovulation . The body's own cycle with egg maturation, ovulation and luteal phase is replaced by a cyclical sequence of external hormones.
The cycle is divided into two phases:
- The period between the onset of menstruation and the next ovulation is called the desquamation and proliferation phase or follicular phase or egg maturation phase and its duration is variable. It can last a few days or many weeks.
- The phase between ovulation and the start of menstruation is known as the secretion or luteal phase . It lasts, relatively constant, between ten and 16 days. If it lasts less than ten days, one speaks of "luteal weakness" or "luteal insufficiency". In such a cycle fertilization can take place, but the fertilized egg cell cannot implant itself. A corpus luteum phase over 16 days indicates the onset of pregnancy.
Cycles lasting 23 to 35 days are considered “normal”. 5% of healthy women's cycles are longer than 35 days.
The first menstrual cycle in a woman's life begins before the first menstrual period (menarche) with the preparation for the first ovulation, the last one ends with the last menstrual period (menopause). Between the first and the last one cycle follows the previous one, if this sequence is not interrupted by pregnancy , certain illnesses or hormonal contraception.
Processes before sexual maturity
With the menstrual cycle development continues, which starts as early as the third week in the human embryo: primordial germ cells migrate to the female gonad one, differentiate themselves in the context of oogenesis to oogonia and partly to further oocytes , the actual egg that still before the birth of the girl in the first meiotic division occur. These oocytes, as so-called primary oocytes, together with the surrounding epithelium, form the so-called primordial follicle .
Further development is now interrupted until the onset of puberty and the oocytes enter a state of rest, the dictyotene . Most oocytes perish again during this resting phase. At the time of menarche - the first menstrual period - around 400,000 of the original 700,000 to 2 million primordial follicles are still present.
The stages of the menstrual cycle
When a woman reaches sexual maturity , the fertile phase begins.
Desquamation and proliferation phase, follicular phase
The first day of menstruation marks the beginning of a new cycle. In the first phase of the cycle, the old mucous membrane layer of the uterus is shed and flushed out with the menstrual period ( desquamation phase ) and, after the bleeding has ended, it is rebuilt under the influence of the estrogen formed in the ovary ( proliferation phase ). At the same time, an ovarian follicle containing the egg matures in the ovary ( follicular phase ):
Under the influence of the follicle-stimulating hormone (FSH), 5 to 15 primordial follicles grow in each ovary at the beginning of the individual ovarian cycle. Both the follicle and theca cells of the ovary multiply .
The multiplying follicle cells produce progesterone and release it into the follicular cavity, which supports egg maturation. The granulosa cells produce estrogen , which enters the bloodstream and, among other things, brings the uterine lining into the proliferation phase (preparation for implantation).
A primordial follicle grows and matures through primary and secondary follicles to form the tertiary follicle. As a rule, only one of the primordial follicles develops into a mature and ready-to-jump tertiary follicle, the others perish and become connective tissue .
With the rupture of the follicle , an egg cell is expelled, which after many years of rest in the dictyotian stage has now completed the first meiotic division .
The progesterone- forming follicle cells of Graaf's follicle are now permeated with blood vessels, which causes an increase in progesterone in the blood.
Ovulation and fertile cycle phase
The ovulation (also called ovulation or follicle) itself is not referred to as phase, but only marks the change between the follicular and luteal phase.
Ovulation takes place - depending on the length of the follicle maturation phase - at different times, in only 25% of cases on the 14th or 15th day of the cycle. In 60% of cases, ovulation does not take place until after the 14th day of the cycle, in 5% already on the 11th day of the cycle or even earlier. The concentration of estrogen in the blood is highest just before ovulation . Although there are two ovaries, only one egg is usually developed per cycle. Which ovary becomes the follicle supplier is essentially random, as there is no right-left coordination. If the level of the follicle-stimulating hormone (FSH) increases, the maturation of the follicle is stimulated. The follicle secretes inhibin , which prevents the FSH level from rising and thus another follicle from maturing. So every time it is different whether the left or right ovary produces the follicle, after the loss of one ovary, the other is usually able to carry out the tasks on its own. In some women, the rupture of the follicle is accompanied by a characteristic pain , the so-called middle pain , which can last for several hours. The egg cell has a diameter of about 0.1 mm. After ovulation, the egg cell can be fertilized by a sperm in the outer third of the fallopian tube for 12-18 hours. If this does not happen, it dies and dissolves. If it is fertilized, it will migrate through the fallopian tubes to the uterus over the next 3-4 days.
The estrogens formed in the follicular phase in the ovary not only build up the uterine lining, but also cause the so-called cervical mucus to form in the glands of the cervix. This cervical mucus enables the sperm to survive in the woman's body for up to 5 days, so that - together with the egg cell's ability to fertilize for almost one day - one speaks of a "fertile window" of 6 days. Various natural family planning methods are used to try to determine this fertile window as precisely as possible on the basis of body signs such as cervical mucus and basal temperature.
Yellow body or luteal phase, secretion phase and sterile cycle phase
After ovulation, the action of the luteinizing hormone (LH, lutropin) forms the corpus luteum (corpus luteum ) from the cells of Graaf's follicle , which also under the influence of LH produces the hormone progesterone and causes various changes:
In the uterine lining, the combination of estrogen and progesterone effects leads to a further expansion of the vascular supply and the release of nutrient- containing secretions from the glands of the mucous membrane ( decidualization ). The mucous membrane is about a week after ovulation for implantation ( nidation ) of the fertilized prepared ovum.
At the cervical glands in the cervix, the progesterone leads to the thickening of the cervical mucus and thus to the formation of a plug of mucus that is impervious to sperm.
At the hypothalamus and pituitary gland, the progesterone has a negative feedback mechanism that stops the release of FSH and thus prevents any further egg maturation or renewed ovulation during the luteal phase. Since there are neither sperm nor a fertile egg cell in the female body, no (renewed) fertilization can occur during the luteal phase; it is an infertile phase of the cycle.
If pregnancy does not occur, the corpus luteum in the ovary perishes and becomes a white body ( corpus albicans ) through a scarred transformation . Progesterone production dries up. Without the hormonal support, the mucous membrane cannot be maintained and is rejected, bleeding occurs, which at the same time marks the beginning of the next cycle. The negative feedback mechanism is eliminated by the drop in progesterone and new egg maturation can begin.
The corpora albicantia consist only of connective tissue and give the senile ovary its scarred appearance. The process described here is repeated around 400 times until the last menstrual period , the menopause .
Pregnancy and childbirth
When fertilization occurs, there is a 25 to 30 percent chance that the egg will implant itself in the wall of the uterus ( nidation ) and pregnancy will begin. The ovarian cycle is interrupted, superfetatio cannot occur - the renewed fertilization of an egg during an existing pregnancy, which is almost impossible due to the nature of the cervical mucus during pregnancy and its impenetrability for sperm . Depending on whether and how was breastfed, the ovarian cycle continues after birth then again, if the concentration of milk production promoting hormone prolactin is sunk so far that they FSH and LH is no longer suppressed release. After pregnancy, in 50% of breastfeeding women ovulation occurs before the bleeding recurs, so women can get pregnant again before their first menstrual period. The breastfeeding can suppress ovulation, the effect is not safe and provides only under special, very strict conditions specified protection from a subsequent pregnancy; see: Breastfeeding and Contraception and Lactation Menorrhea Method .
Bleeding
During regular bleeding of normal duration (three to five days) and severity ( called eumenorrhea ), approximately 30 to 60 milliliters of blood are lost (values between 10 and 80 ml are considered normal, the bleeding maximum is usually on the second day). Depending on the author, the limit to hypermenorrhea (unhealthy heavy menstruation) is given as 150 ml or 200 ml. The clotting of the blood is prevented by the enzyme plasmin , which is contained in the lining of the uterus. In many women menstruation is accompanied by various unpleasant symptoms, so-called menstrual cramps (medical dysmenorrhea ), which can also precede menstruation. They are caused by the hormones involved and the contracting uterus. However, some women also experience the period of menstruation as positive, accompanied by an increased body awareness.
Menstrual irregularities
| Classification according to ICD-10 | |
|---|---|
| N91 | Missed, weak or infrequent menstruation |
| N92 | Menstruation that is too heavy, too frequent, or irregular |
| N93 | Other abnormal uterine or vaginal bleeding |
| N94 | Pain and other conditions related to the female genital organs and the menstrual cycle |
| ICD-10 online (WHO version 2019) | |
Menstrual disorders are deviations from the normal menstrual cycle.
A distinction is made (according to Kaltenbach ) between abnormalities in the bleeding rhythm ( regular pace disorders ) and bleeding intensity ( regular type disorders ), additional bleeding, bleeding if a follicle persists (failure to ovulate), and the complete absence of menstruation ( amenorrhea ).
- The tempo anomalies include oligomenorrhea , a bleeding that is too rare, and polymenorrhea , a bleeding that is too frequent.
- Type anomalies are called hypermenorrhea (excessive menstrual bleeding), hypomenorrhea (too weak bleeding) and menorrhagia (prolonged bleeding). For example, if ovulation has not occurred, i.e. if the follicle persists, it can lead to permanent bleeding; it is a form of dysfunctional bleeding. The metrorrhagia is characterized by normally at strong but occurring without rhythm and often long lasting bleeding.
- Extra bleeding is all bleeding in addition to normal menstruation in a two-phase cycle. According to their temporal occurrence, a distinction is made between pre- and post-bleeding as well as intermenstrual bleeding. Depending on the cause, it can be hormone-related ( dysfunctional ) bleeding (ovulation bleeding), but also organically caused additional bleeding, for example in the case of mucosal polyps or endometritis . Fibroids and endometriosis of the uterine muscles (adenomyosis uteri) tend to cause increased and / or prolonged bleeding. Extra bleeding can also be a sign of cervical or endometrial cancer .
Bleeding during pregnancy
Menstruation does not occur during pregnancy. In some women, however, menstrual periods are said to have occurred during pregnancy, individual bleeding, even excessive bleeding, can occur, especially between the 6th and 10th week of pregnancy ( impending miscarriage ) and are misinterpreted as menstrual bleeding, whereby the pregnancy is mostly preserved. The bleeding in late pregnancy, which either, as described, has no further meaning or can indicate a miscarriage , but is not dangerous in both cases, is to be distinguished from bleeding in late pregnancy : this can either be harmless or serious Indicate illnesses and, if left untreated, may lead to the death of mother and child. The birth marks (if not breastfed) the beginning of a new cycle, which then ends with the following menstrual bleeding or a new pregnancy, see above. The resumption of menstrual cycles varies from woman to woman and is related, among other things, to the length of breastfeeding, although breastfeeding itself does not provide sufficient protection against a new pregnancy.
Synchronization of menstruation in women living together
It has been argued over and over that women who live together synchronize their cycle so that they menstruate together. This effect is known as the McClintock effect or dormitory effect . However, older studies that found this association could not be clearly confirmed. Even if there is a connection, the correlation is not particularly strong.
Other living things
A regular menstrual cycle occurs only in the higher primates . In other female mammals, there are also cyclical changes in the female genital organs, but the lining of the uterus is only remodeled, but not broken down, and consequently no menstrual bleeding occurs. Therefore the term sexual cycle and rut is used for these processes .
See also
literature
- Lois Jovanovic, Genell J. Subak-Sharpe: Hormones. The medical manual for women. (Original edition: Hormones. The Woman's Answerbook. Atheneum, New York 1987) From the American by Margaret Auer, Kabel, Hamburg 1989, ISBN 3-8225-0100-X , p. 381 and passim.
Web links
- Information on facts and half-knowledge of the cycle and the fertile days (results of the NRP research project)
- Menstruation (www.netdoktor.at)
- "The female hormones and the menstrual cycle" (Homepage of Dr. Peter Hintermüller)
- Menstrual cycle (Archive for Sexology of the Humboldt University of Berlin)
Remarks
- ^ Elisabeth Raith-Paula: Dangerous half-knowledge about the fertile time . In: Business magazine for the gynecologist 3/2016, p. 3
- ↑ The maturation time of an egg cell is about eight weeks. The two ovaries work against each other by about 4 weeks, so that in total a mature egg is available about every 4 weeks.
- ^ A b c Elisabeth Raith-Paula, Petra Frank-Hermann, Günter Freundl, Thomas Strowitzki: Natural family planning today: Modern cycle knowledge for advice and application. 4th edition. Springer Verlag, 2008, p. 131ff.
- ↑ U. Sottong, M. Bremme, G. Freundl: Lactationalamenorrhoea and lactational anovulation in 109 breastfeeding women . Ed .: Adv Contracept. tape 8 , 1992, pp. 269-270 .
- ↑ David L. Healy: Menorrhagia Heavy Periods. ( Memento from April 8, 2014 in the web archive archive.today )
- ↑ Wolfgang Legrum: Fragrances, between stench and fragrance - occurrence, properties and use of fragrances and their mixtures . 2nd revised and expanded edition. Springer Spectrum, 2015, ISBN 978-3-658-07309-1 , pp. 24 .
- ↑ Julia Merlot, Anna van Hove: Myth or Medicine: Do girlfriends get their days at the same time? In: Spiegel Online. April 2016.