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Cervical cycle
Last reviewed: 23.04.2024
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[Cervical by the day of the cycle
To begin with, the menstrual cycle - as a regular monthly process for the preparation of the woman's genital system for possible fertilization and conception - consists of a cycle of ovaries (including the follicular, ovulatory and luteal phases) and the uterine cycle, which also has three stages - menstrual, proliferative and secretory . In this case, the cervix in different cycles behaves in full accordance with its functions (drainage and barrier). By the way, the ovaries and uterus are also different, but everyone is controlled by steroid hormones, and both cycles are synchronous.
Thus, the cycle of the cervix from the point of view of physiology is expressed in cyclic changes in its tone, position in the vagina, the condition of the flat epithelium, the diameter of the external pharynx, the level of acidity, the intensity of the production of nerve glands by cervical mucus and its consistency.
Before menstruation, the cervix is elastic, the outer yoke is closed, the cervical mucus is thick and sticky, but there is not much of it; the pH of the mucus is below 6.5. While monthly, the tone of the cervix is reduced, the outer throat is slightly opened (providing the exit of the rejected functional endometrial layer of the uterus), the volume of mucus is average, the pH is within the range of 6.9-7. In addition, there is a partial debridement of the dead cells of the surface layer of the flat epithelium, which covers the cervix externally.
The cervix in the second phase of the cycle (at the beginning of postmenstrual recovery of the endometrium of the uterus and the follicular phase of the ovaries) also begins to prepare for the next exit of the oocyte, which is expressed in a slight thickening of the endocervix; accumulation of cells by the mucous membrane of glycogen; a gradual increase in the production of cervical secretion (mucus while sufficiently thick and viscous), and pH increase to a level of 7.3.
Usually ovulation occurs 14 days before the beginning of the next regul, that is, falls on the middle of the cycle. And the cervix in the middle of the cycle, due to the increase in the level of estrogens during the fertile phase, becomes softer, its outer cusp opens as much as possible, the cervical canal becomes wider, and the volume of the produced mucus secretion increases sharply. At the same time, the mucus very much liquefies and becomes watery (which facilitates the passage of spermatozoa), its acidity level also sharply shifts to the alkaline side - to pH 7.6-8, which creates the most favorable conditions for conception.
It is characteristic that the position of the cervix on the days of the cycle changes only in the phase of ovulation, becoming higher in relation to the entrance to the vagina. In the remaining phases of the cycle (including during menstruation) the position of the vaginal part of the cervix is low.
The cervix at the end of the cycle, after ovulation, under the action of progesterone again comes a calm state and falls down, the cervical channel narrows, the yoke closes, the mucus becomes sour and thicker and forms a cork (until another menstruation).
Cervix on days of cycle during pregnancy
The menstrual cycle during the period of gestation is known to be interrupted, so that the cycle of the cervix during this period is also absent. But this does not mean that there are no changes.
First of all, thick cervical mucus completely blocks access to the cavity of the pregnant uterus, and the outer yawn tightly closes. Until the 6th week of pregnancy, the enlarged body of the uterus softens, and the cervix remains dense and located high. But then it becomes softer and a bit longer.
In addition, under the influence of a complex of sex hormones, approximately from the 15th week of the gestational age, the structure of the connective tissue (stroma) of the cervix begins to change: its cells retain more water, and in the intercellular matrix of the mucosa increases the level of protective cells (in particular, obese and leukocytes).
Due to increased vascularization, the blood supply of tissues increases, causing the color of the mucous cervix to become bluish-violet. And closer to the birth begins to change and the composition of collagen fibers of the stroma, which will provide stretching of the cervix during the passage of the child through the birth canal.
For those who want to specify on which day of the cycle it is possible to make a biopsy, we inform you: in clinical gynecology, this diagnostic procedure is performed from the fifth to the eighth day after the end of menstruation, that is, the proliferative phase of the uterus cycle and the follicular phase of the ovarian cycle.