See also: Rules
The menstruation is the most visible demonstration of the menstrual Cycle of the woman. She consists of the disintegration of the functional layer of the Endomètre in the absence of Grossesse, conveyed by more or less abundant losses of Sang, evacuated by the Vagin. She is specific to the mankind and some higher species of primates, other than the Primate S of the New World. The females of other species of mammal Placentaires know a Estrus (or period of heats), in which the Endomètre is reabsorbed by the animal at the end of sound menstrual Cycle.
General information
The term menstruation comes from the Latin word mensis “month” (near to the Greek carries out , the the Moon) which evokes a relationship with the monthly lunar cycles. The aspect of the moon was also evoked to explain this etymology.
The menstruation, which one often calls a period or the rules , is the transformation of the Utérus each month when it eliminates, by the Vagin, the fabrics (endometer) which were in place to accommodate a egg fertilized. The bleeding generally lasts two to three days but this period can go up to seven or eight days. The bleeding can be absorbed by hygienic protections.
When women live together, there is a tendency to the synchronization of the rules, which would be due to the emission by the glands axillaires of volatile substances. The possible action of the Phéromone S in the mankind is the subject of controversies, since the Organe voméronasal does not exist in the adult. However, in the mouse, some phéromones can activate receivers present in the olfactive epithelium.
Pains
Among certain women, a Pain of the basin called Dysmenorrhoea which can last several hours, had with a cramp of the uterus, can precede and accompany the period by the rules. It lies within the scope of the premenstrual syndrome, which associates pains, faintnesses, modifications behavioral.
Certain women can also feel headaches or a tension of the centres.
These pains, very strong, do not last more few hours but, generally, the women have these pains during the first two days of their menstruations and it can even happen that these pains perdurent all their menstrual period. This is completely normal because in fact the uterus contracts to evacuate blood.
Fertile period
The Spermatozoïde S can survive in the body of the woman up to 3 days. The period of Co Fécondation (the Zygote is the meeting of the two gamètes) thus begins six days before and finishes two or three days after the Ovulation: indeed, the Ovule did not see that approximately 24 hours. The methods of natural family Planification use this principle, either to support a pregnancy, or to avoid it.
Hormonal control
The function of reproduction, i.e. the production of the Gamète S and the gonadic hormones, is controlled by the hypothalamo-hypophyseal axis. The Hypothalamus synthesizes and releases in a pulsatory way a peptide hormone (GnRH = hormone gonadolibérine) which stimulates the release by the former Hypophyse of two hormones FSH and LH. The principal hormones ovariennes implied in the control of the menstrual cycle are the estrogen S, the Progestérone and the Inhibine. At the beginning of the cycle, the former pituitary gland (pituitary gland) releases FSH (hormone stimulating the folliculogenèse) announcing to the immature follicule to grow in the ovaries. The follicule is a bag containing the ovocyte. Normally, only one ovule is produced by cycle. There is no left/right coordination. The same ovary can thus theoretically emit a Ovule several months of continuation. In fact, the presence of a yellow body in an ovary strongly disturbs the selection of the follicule dominating, so that at 88% of the women, ovulation occurs alternatively in an ovary, then in the other. The first follicule to be developed secretes inhibine. The levels of estrogens go up as the hormone is secreted by the follicule which develops. Ovulation takes place the 14th day of the cycle, approximately 36h after the peak of LH (hormone lutéotrophe) released by the former pituitary gland. During ovulation, the follicule and the wall of the ovary break releasing the egg; the level of estrogens is maximum.After ovulation, estrogens and progesterone each one are secreted by the Corpus luteum (or yellow body) which develops starting from the broken follicule and remains in the ovary. The role of progesterone is to prepare the body for a possible pregnancy. In particular, the progesterone causes an increase in the basal temperature of approximately 0,3 °C. This increase in the temperature can be used to detect ovulation.
If no pregnancy intervenes the corpus luteum degenerates and the level of the hormones falls brutally, which causes the elimination of the endometer at the time of the menstruation.
If there is a pregnancy, the Placenta produces the hormones to stop the menstrual cycle:
- HCG (human hormone gonadotrophine chorionic) to keep the corpus luteum;
- Inhibine to prevent another ovulation.
Internal bonds
External bonds
- Free Software to watch the menstrual cycle etc http://www.perimon.com/calendrier_fr.htm (in English)
- menstrual Cycle animated http://www.doctissimo.fr/html/sexualite/education/se_1357_cycle_menstruel.htm
Simple: Menstruation
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