The menstrual cycle is what happens in the body. Everything you need to know about the menstrual cycle. Types of menstrual disorders

Hello.

Today we are starting a big and exciting topic of female physiology.

Everything in nature is subject to cycles. Morning replaces night, then day begins, evening follows, night comes after it. We constantly observe the change of seasons, we have the opportunity to observe how the moon "lives" its cycles.

A woman's body is subject to changes that occur one after another with a certain pattern, and this is called the menstrual cycle.

What is the main point of the menstrual cycle?

The female body prepares for a possible pregnancy at regular intervals.

In the ovary, the egg matures, the inner layer - the endometrium - increases in the uterus, metabolic processes in the body are aimed at the "supply of nutrients".

If the pregnancy did not take place, then the body ends this cycle, menstruation comes, and then everything starts all over again.

ThiscyclicalprocessnotIt hasnorstartnorend... One event will replace another. As the water cycle in nature, as day replaces night, as summer comes after spring.

These periodically recurring changes in the body of a girl, a woman are called the menstrual cycle.

On average, the cycle lasts about a month.

Cyclic changes in the female body occur throughout the woman's childbearing age, this is approximately 35 years.

Weoftenhearthe words, whatfemale- mystery, whatshechangeable, windy, vulnerable, asometimesandHorseon thegallopingwill stop "

What is the reason for such inconstancy.

As I delved deeper into this topic, I was pleasantly surprised. It turns out that "female inconstancy" is justified by cyclical changes in female hormones.

Want to know more about this?

I inviteTofascinatingcognitionmyself.

A little about the physiology of the menstrual cycle: in a woman, two main sex hormones are produced in the ovaries: estrogen and progesterone. The main event of the menstrual cycle is ovulation. This is the exit from the ovary of an egg ready for fertilization.

The role of female sex hormones interconnectedly affects the physiological state of a woman: mood, appetite (the desire to eat something special), sexual desire, stamina, etc.

I'll tellaboutthismore details:

Conventionally, the phases of the menstrual cycle are divided into two periods:

the first phase (from the first day of menstrual flow to ovulation),

the second phase (after ovulation before menstruation).

Vthe firstphasethe menstrual cycle occursmaturationegg cellsvovary.

At the time of the maturation of the egg, the amount of estrogen in a woman increases. The maximum amount of this hormone before ovulation.

In the second phase menstrual cycle the main hormone is progesterone. It is produced in the ovary, in the place from which the egg came out. This is called the corpus luteum.

The role of female hormones in different phases of the cycle

In this picture, you can see the green color - the level of the hormone estrogen. Orange - progesterone, throughout the menstrual cycle.

These hormones are the "governing" of our physiological and mental state.

At the time of menstruation (see the picture above), the level of sex hormones is minimal. A woman can feel weak these days, gets tired quickly, and the mood is not cheerful. I want to cry more often. Eating habits change. I want to be alone.

The amount of estrogen is slowly increasing - hormonefemininity. This period in life can be compared to spring. Nature wakes up from sleep, and the woman comes to life.

The mood rises, the activity increases, a new hope appears in the soul. I would like to communicate. And as the hormone of femininity increases, we become more feminine and attractive.

Closer to ovulation - this hormone is at its maximum level! And the woman is unrecognizable. The eyes shine, the skin is soft velvety, the mood is playful. Even the most difficult cases are within reach. These days we easily achieve success with men and in everyday affairs. The woman's sexual desire increases.

But then ovulation has occurred, and we see how the amount of progesterone increases. Thishormonemotherhood, it is necessary for carrying a pregnancy. If conception has occurred, then in the prevailing amount it remains until the very birth.

The hormone of "motherhood" makes us reasonable, balanced. A woman turns into a hostess, loves to be at home, to bring comfort, to cook a delicious dinner. To a lesser extent, I want to communicate at parties. Men evoke more desire - to feed them than to flirt.

Ifpregnancynottook place, then closer to menstruation, the level of hormones decreases. At this time, the body is cleansed, resting, gaining new strength. And everything is repeated from the beginning.

Do you want to learn how to observe hormonal changes and be able to independently recognize the norm and pathology of the menstrual cycle?

Turns out, ourorganismworkingclearly, howclock, but unlike men, we have several "regimes". Sometimes we are playful girls (despite our age), sometimes sensible wise ladies, caring mothers.

Before, I was very worried that my mood so often changed dramatically. Either I am ready to promise my husband to go on a winter hike with him, then it is difficult for me to part with my household chores. Sometimes I can do a huge job in a matter of hours, sometimes I can stretch it out for many days. At a certain time, I do not want intimacy at all - it turns out and this is very natural.

How to understand yourself well and live in harmony with yourself.

Which is what I sincerely wish you.

Irina Zhgaryova.

P.S. For more information on the physiology of the menstrual cycle, watch the free webinar "What you need to know about your cycle if you are a girl-woman-mom."

In this analysis, the “ideal” 28-day cycle is taken as an example.

Day 1

The day of the onset of menstrual bleeding is the first day of the cycle. Bleeding occurs due to rejection of the endometrium - the layer of the uterine mucosa, "feather bed". This happens against the background of a decrease in the concentration of the main "female" hormones - progesterone and estrogen. During this period, the number of prostaglandins (pain mediators), which stimulate the contractility of the uterus, increases. What is good for the body (the uterus contracts, getting rid of the old endometrium), for a woman becomes an extremely unpleasant moment in everyday life, because the first day of menstruation in most cases is accompanied by pain and heaviness in the lower abdomen. Painkillers, often taken during this period, have serious side effects - they irritate the stomach lining, and, as a result, contribute to the development of peptic ulcer disease. That is why the best approach to solving the problem of menstrual pain is to take natural drugs.

Day 2
The body begins to develop the most "important" follicle that bears the egg. Discomfort and soreness may persist, while pain sensitivity is still high. I really want to be beautiful, but at this very moment hormones work against us. Due to the low production of estrogen, the activity of the sweat and sebaceous glands becomes more intense. It's important to pay more attention to your skin, such as using soft makeup. It should be remembered that now hair changes its chemical structure and is less amenable to styling, and hair coloring done during menstruation lasts less. During this period, a visit to the dentist, epilation and other unpleasant manipulations should be postponed for 4-5 days.

Day 3

In the uterus, after rejection of the mucous membrane, a wound surface is formed, in addition, the cervix is ​​maximally ajar these days. Due to these factors, there is a high probability of infection, which means it is advisable to abstain from sex, or, at least, to protect yourself with barrier contraception methods.

Day 4

"Critical days" are coming to an end, and therefore the mood is significantly lifted, but you should not overestimate yourself. At this time, any activity associated with heavy physical exertion is contraindicated, however, light morning exercises help to reduce the duration of menstruation and the volume of blood loss.

Day 5

The healing process in the uterus is complete. On average, during normal menstruation, a woman loses about 100 ml of blood, which is not so much, but if menstruation lasts more than 5 days, and the discharge is abundant, then the woman may develop iron deficiency anemia.

Days 6 and 7

In the renewed body, the metabolism is accelerated - excess calories are burned more intensively, protein for muscles is synthesized more actively, fat is broken down, the general tone of the body, endurance and strength increases. The "important" follicle that grows every day produces more and more estrogens. At the same time, the level of testosterone begins to increase, which is responsible in the female body for the qualities usually attributed to men: a sharp mind, good working capacity, excellent memory and the ability to concentrate. Estrogen and testosterone together drive away habitual drowsiness, give vigor and freshness of thoughts better than any coffee.

Day 8

Now, every day, the concentration of estrogen in the blood is increasing - the main hormone of femininity. Skin, hair and nails become the most susceptible to various cosmetic procedures and simply shine with health. After depilation on these days, the skin remains smooth and soft longer than usual.

Days 9 and 10

There is nothing left until ovulation. These days, the chances of getting pregnant are much higher. If you are dreaming of having a girl, your time has come! There is a theory according to which sperm with the X chromosome (which determine the female sex of the unborn child) are able to "wait" longer for the release of the egg from the ovary in the woman's genital tract, so you have about 4-5 days in stock. On the day of ovulation and immediately after it, the ability to conceive a boy increases.

Days 11 and 12

By this day, thoughts about work are more and more receding, and about love truly absorb all of your consciousness. The main hormones responsible for female sexuality and libido are in the lead. In a woman, the excitability and sensitivity of the erogenous zones increases, and a special smell appears that can attract male attention.

Days 13 and 14

Under the influence of estrogen, the wall of the mature follicle bursts, and the egg is released into the abdominal cavity. At the same time, a small amount of blood is poured into the abdominal cavity, and some women may even feel soreness in the lower abdomen on the right or left (depending on which ovary ovulated). When it enters the abdominal cavity, the egg is captured by the fallopian tube and sent towards the “male principle”. On the day of ovulation, a woman has the highest libido and is able to experience the most vivid sensations from intimacy with a man. Sexologists argue that if a woman regularly abstains from sex on ovulation days (fearing an unwanted pregnancy) and does not experience an orgasm, then her libido can steadily decrease over time. For the sperm to reach the egg as quickly as possible, the mucus, which protects the entrance to the uterus, is diluted, and casual sex these days is fraught with sexually transmitted diseases.

Day 15

At the site of the bursting follicle, a yellow body begins to form. This is a special formation, and, regardless of whether fertilization has occurred or not, it will prepare the body for pregnancy within 7-8 days. The corpus luteum begins to produce the hormone progesterone - the main hormone of pregnancy, its goal is to turn an active and carefree girl into a future mother.

Day 16

Progesterone begins the preparation of the uterine lining for egg implantation. Be especially careful with carbohydrates, as appetite increases during this phase of the cycle, and weight gain occurs the fastest.

Day 17 and 18

The body is actively stocking up on nutrients for future use, as a result of which fat metabolism changes. Excess fat significantly spoils the figure and creates an increased load on the heart and blood vessels. Therefore, in this phase of the cycle, try to increase the proportion of vegetable fats in your daily diet, add garlic and red fish to your diet, enrich your diet with fermented milk products and fiber.

Day 19

Although ovulation is over, during the second phase of the cycle, the body maintains a fairly high level of testosterone, which increases libido. Higher testosterone production in the morning - fill the dawn hours with passion and tenderness.

Day 20

The flowering of the corpus luteum and the concentration of progesterone in the blood reaches its maximum value. At this time, the egg, moving along the fallopian tube, approaches the uterus. It is believed that from this day on, the likelihood of pregnancy is significantly reduced.

Days 21 and 22

Against the background of increased levels of progesterone, which acts as an antidepressant, we become "impenetrable" for troubles and other stressful situations.

Day 23

There are changes in the structure of the connective tissue: hypermobility appears in the joints, the ligaments become more extensible. The greatest number of injuries, especially those related to sports, are suffered by women on these days.

Day 24

These days, due to the difference in hormone levels, there can be problems with the work of the intestines. The activity of the sebaceous glands increases, pores expand, acne may appear. Try to pay more attention to your diet these days.

Day 25

A woman develops a special scent that allows the man to feel that a forced period of abstinence is coming. There is a possibility that this very fact is the reason for the synchronization of cycles in several women living together for a long time.

Days 26 to 28

A woman becomes sensitive and vulnerable, at this time she needs support. Are the mammary glands rough and painful, daytime sleepiness, headache, anxiety, lethargy and irritability - is that enough to ruin your mood? Experts believe that chocolate and sex can be an excellent medicine these days.

Reproductive system responsible for the reproduction (reproduction) of a person. The main links of this system are the hypothalamus, pituitary gland, ovaries and uterus. Outside of pregnancy, a woman's reproductive system works in a cyclical manner. The most striking manifestation of its cyclical function is regular menstruation.

Menses- This is a regular monthly bleeding from the vagina of a woman. Menstruation is one of the most striking features inherent only in the female body.

All processes in the reproductive system of a mature woman proceed cyclically, i.e. with a certain frequency, recurrence, and the most striking manifestation of the end of one cycle and the beginning of another is menstruation.

Menstrual cycle- This is the period from one menstruation to another and it is considered from the first day of the previous menstruation to the first day of the next.

Normally, the duration of the menstrual cycle is 21-35 days. In addition to duration, regularity is very important here. Ideally, when the duration of the individual cycle does not change from month to month. Variations within 3 days are permissible. Consider a typical 28-day cycle. Normally, in a healthy woman, the menstrual cycle has 2 phases. With a 28-day cycle, the first and second phases each have 14 days. In the first 14 days, a woman's body prepares for a possible pregnancy. In the brain, the pituitary gland produces two main hormones that affect a woman's menstrual cycle: follicle-stimulating hormone (FSH) and luteinizing hormone (LH).

Under the influence of FSH, an egg matures in one of the ovaries, and the inner membrane thickens in the uterus in order to receive a fertilized egg. The main hormone released into the blood is estrogen... It contributes to the fact that the woman looks good, is active and cheerful.

After 2 weeks occurs ovulation- the release of a mature egg from the ovary.

This process occurs due to a sharp increase in the level of LH in the blood, which reaches its peak. At this point, some women experience a slight pulling sensation in the lower abdomen. Very rarely, there may be spotting spotting from the genital tract. After the release of the egg into the abdominal cavity, it is captured in the ampulla of the fallopian tube and very slowly begins to move along it. If at this moment sperm cells meet on her way, fertilization will occur and pregnancy will occur.

From the moment of ovulation, the second phase of the cycle begins, its main hormone - progesterone... At this time, at the site of the release of the egg in the ovary, under the influence of LH, the corpus luteum matures, which, in the event of pregnancy, will at first ensure its safety. In the uterus, the inner lining is loosened to accommodate the fertilized egg. If the egg is not fertilized, the level of hormones drops sharply, and the inner lining of the uterus is gradually rejected along with a small amount of blood - menstruation begins. This ends one menstrual cycle and begins the next.

The "ideal" menstrual cycle is considered to be an ovulatory, fully hormonally provided menstrual cycle lasting 28-30 days.

Many gynecological and serious therapeutic diseases can cause a "breakdown" of the reproductive system, which will be reflected in all kinds of menstrual irregularities (bleeding, irregular menstruation, their absence) and infertility.

Types of menstrual disorders

Primary amenorrhea- lack of independent menstruation in a woman's life

Secondary amenorrhea- lack of independent menstruation for 6 months or more

Polymenorrhea- frequent periods (cycle less than 21 days)

Oligomenorrhea- rare periods (cycle more than 35 days)

Dysmenorrhea- painful periods

Metrorrhagia- irregular uterine bleeding

Menometrorrhagia- heavy, frequent, prolonged menstruation

Dysfunctional uterine bleeding- abnormal uterine bleeding due to hormonal disorders of the reproductive system.

Among the menstrual dysfunctions, the most common are irregular menstruation, insufficiency of the second (luteal) phase of the menstrual cycle (LF), and anovulation (no ovulation).

Why is ovulation needed?

Ovulation- this is the release of a mature egg cell capable of fertilization from the ovarian follicle.

Ovulation- the most important condition for the onset of pregnancy. In women of childbearing age, it occurs in almost every cycle. Its frequency is regulated by the hormones of the hypothalamus, pituitary gland and ovaries.

Signs of ovulation can be short-term pain in the lower abdomen, an increase in mucous discharge from the vagina in the middle of the cycle, a decrease in basal temperature on the day of ovulation, followed by an increase.

An objective diagnosis of ovulation is possible according to ultrasound, ovulation tests, and the level of progesterone in the blood plasma on the 21st-23rd day of the cycle.

Anovulation- a condition in which a woman does not ovulate. Among the causes of infertility, violation of ovulation is 27%.

Violation of ovulation processes (late ovulation, its absence) leads not only to impaired reproductive function - infertility, but also to NLF, and, consequently, menstrual irregularities - rare irregular menstruation, dysfunctional uterine bleeding.

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Menstruation

Menstruation- monthly bloody discharge from the genital tract of a woman, which is considered part of the menstrual cycle: they complete the cycle if the ripe egg has not been fertilized.

The first menstruation - spotting - menarche - appears during puberty. As a rule, this happens at 12-15, more often at 12-13 years old. The time of the onset of menstruation depends on many factors: the girl's physical development, her nutrition, past illnesses, social conditions, etc. Approximately within 1.0 - 1.5 years after the onset of the first spotting, a regular menstrual cycle is established, which ranges from 21 to 35 days (more often - 28 days), and the discharge lasts from 3 to 7 days; blood loss averages 50-70 ml.

We will tell you about what the normal menstrual cycle of a healthy woman should be in this article.

MENSTRUAL CYCLE

Traditionally, for the convenience of describing menstruation, a menstrual cycle of 28 days is taken and all calculations are made based on it. Of course, this does not mean that every woman should have a menstrual cycle like this. Everything here is individual - usually the menstrual cycle ranges from 21 to 35 days.

During the menstrual cycle, the woman's body prepares for conception and pregnancy. If conception does not occur, this process is repeated again.

During the entire menstrual cycle in a woman's body, several significant changes are observed, which are primarily associated with a cyclical change in the amount of sex hormones.

A few days after the onset of menstruation, the level of estrogen, a female hormone, rises. At the same time, the transformation of the endometrium begins - the mucous layer lining the uterus from the inside. It grows, increasing in volume and thickness. At this time, a follicle with another egg cell begins to mature in the ovary.

Approximately on the 12-14th day from the onset of menstruation, ovulation occurs - the release of a mature egg from the ovary. It is this period that is most favorable for conception. In the ovary, in the place from which the egg came out, the so-called corpus luteum is formed, which begins to produce progesterone - one of the main hormones necessary for the development of pregnancy during its first three months.

Ovulation occurs under the influence of pituitary gonadotropic hormones and estrogens.
Since during the first phase, that is, before ovulation, the follicle matures, it is called follicular. Since the growing follicles secrete a large amount of estrogen, this phase is also called estrogenic. And since under the influence of estrogens, the proliferation of the uterine mucosa occurs, the term proliferative is also used to the first phase.

Further, the reproductive cell, completely ready for fertilization, moves along the fallopian tube to the uterus. It is programmed to grow into a human baby over the next nine months after fusion with the sperm. Therefore, at the time of cell travel, under the influence of the hormone progesterone, the endometrium intensively produces nutrients for the initial nutrition of the egg with the embryo. Fertilization takes place in the fallopian tube, then the dividing cell enters the uterus and is implanted in it, that is, it sinks into its inner layer, where it begins to develop.

In the vast majority of cases, in the absence of fertilization, the menstrual cycle does not end with the onset of pregnancy. Therefore, the endometrium, the function of which has not been realized, becomes unnecessary, and somewhere by the 14th day from ovulation (this is about the 28th day of the menstrual cycle) the level of female hormones - estrogen and progesterone falls - and the rejection of the internal layer of the uterus. Menstruation occurs (endometrial detachment), which stops about 5-7 days after the drop in hormone levels. The amount of blood lost during menstruation is 50-100 ml. The circle is closed, and then the whole process is repeated.

REGULATION OF THE MENSTRUAL CYCLE

Millions of years ago, nature established and supports such a program in women. Glands and hormones work almost uninterruptedly, because the survival of all mankind depends on it. And menstruation is a necessary part of the life cycle.

During each cycle, many thousands of follicles mature, but only one of them reaches ovulation. Thus, as a rule, one egg is available for fertilization in each menstrual cycle. However, on average, in one in 200 cycles, two follicles mature at the same time, so two eggs can be fertilized, leading to the development of fraternal twins.

The biological meaning of the menstrual cycle is to prepare a good breeding ground for the further development of a fertilized egg and a comfortable stay of the fetus in the mother's womb. Genetically, a woman's body is tuned to ensure that there are long intervals between menstruation - periods of rest, that is, pregnancy, and lactation.

Meanwhile, the ruptured follicle collapses, a small blood clot remains in its void, and the rupture site closes. From the luteal cells of the granular layer of the follicle, which are yellow, a temporary endocrine gland develops - the corpus luteum. Luteal cells multiply intensively, while the corpus luteum hormone progesterone is released. The corpus luteum usually functions for 14 days, that is, the second half of the menstrual cycle.

Under the influence of an increased level of progesterone after ovulation, cryptoid glands develop in the mucous membrane of the uterus. In this state, the uterus is most prepared for pregnancy.

Progesterone acts on the centers of regulation of body temperature, causing an increase in basal temperature by about 0.5 oC. With the end of the functioning of the corpus luteum, the basal temperature decreases.

Distinguish between the corpus luteum of menstruation and the corpus luteum of pregnancy in the case of fertilization of the egg. With the onset of pregnancy, the corpus luteum continues to function throughout pregnancy (corpus luteum of pregnancy) and the entire lactation period (corpus luteum of lactation).
Thus, the second phase of the menstrual cycle, which is associated with the formation of the corpus luteum in the ovaries and glands in the uterus, is called luteal or secretory

If fertilization did not take place, the corpus luteum is in the stage of reverse development, the maturation of a new follicle begins, and the mucous membrane is rejected in the uterus and the associated bleeding (menstruation) occurs.

During the menstrual cycle, cyclical changes occur in the cervix (in the first phase, cell growth is observed and mucus secretion increases, in the second, it decreases), in the vagina (in the first phase, epithelial cells grow, in the second, they exfoliate), in the mammary glands (in the 1st phase, the development of the tubular system and the expansion of the lobules of the gland, in the II-nd the formation of lobules, an increase in the volume of the gland).

The processes that ensure the normal course of the menstrual cycle are regulated by a single functional neuroendocrine system, which includes the central sections and peripheral structures with a certain number of intermediate links. In accordance with their hierarchy (from higher regulatory structures to directly executive organs), 5 levels can be distinguished in neuroendocrine regulation, interacting according to the principle of direct and reverse positive and negative relationships.

The first (highest) level of regulation

the functioning of the reproductive system are structures that make up the acceptor of all external and internal (from subordinate departments) influences, - cerebral cortex CNS and extrahypothalamic cerebral structures (limbic system, hippocampus, amygdala).

The adequacy of the perception of the central nervous system of external influences depends on the nature of external stimuli (strength, frequency and duration of their action), as well as on the initial state of the central nervous system, which affects its resistance to stress. It is well known about the possibility of cessation of menstruation during severe stress (loss of loved ones, wartime conditions, etc.), as well as without obvious external influences with general mental imbalance ("false pregnancy" - delayed menstruation with strong desire or strong fear get pregnant).

The balance of synthesis and subsequent metabolic transformations of neurotransmitters, neuropeptides and neuromodulators in the neurons of the brain and in the supra-hypothalamic structures ensures the normal course of processes associated with ovulatory and menstrual function.

Second level

regulation of reproductive function is hypothalamus... The activity of neurosecretion in the hypothalamus is regulated both by sex hormones, which come from the bloodstream, and by neurotransmitters and neuropeptides, formed in the cerebral cortex and suprahypothalamic structures.

The third level

regulation of reproductive function is the anterior lobe of the pituitary gland, in which gonadotropic hormones are secreted - follicle-stimulating hormone, or follitropin (FSH), and luteinizing, or lutropin (LH), prolactin, adrenocorticotropic hormone (ACTH), somatotropic hormone (STH) and thyroid-stimulating hormone ... The normal functioning of the reproductive system is possible only with a balanced allocation of each of them. FSH stimulates the growth and maturation of follicles in the ovary, the proliferation of granulosa cells, the formation of FSH and LH receptors on granulosa cells, the activity of aromatases in the maturing follicle (this enhances the conversion of androgens to estrogens), the production of inhibin, activin and insulin-like growth factors.

LH promotes the formation of androgens in theca cells, ovulation (together with FSH), granulosa cell remodeling during luteinization, and progesterone synthesis in the corpus luteum.

Prolactin has a variety of effects on a woman's body. Its main biological role is to stimulate the growth of mammary glands, regulate lactation, and control the secretion of progesterone by the corpus luteum by activating the formation of LH receptors in it. During pregnancy and lactation, the inhibition of prolactin synthesis stops and, as a result, an increase in its level in the blood.

TO fourth level

regulation of reproductive function include peripheral endocrine organs (ovaries, adrenal glands, thyroid gland). The main role belongs to the ovaries, and other glands perform their own specific functions, while maintaining the normal functioning of the reproductive system.

V ovaries the growth and maturation of follicles, ovulation, the formation of the corpus luteum, the synthesis of sex steroids occur.

At birth, a girl's ovaries contain approximately 2 million primordial follicles. Most of them undergo atretic changes throughout their life, and only a very small part goes through the full cycle of development from primordial to mature, with the subsequent formation of a corpus luteum. By the time of menarche, the ovaries contain 200-400 thousand primordial follicles. During one menstrual cycle, as a rule, only one follicle with an egg inside develops. In case of maturation of a larger number, multiple pregnancies are possible.

Folliculogenesis begins under the influence of FSH in the late part of the luteal phase of the cycle and ends at the beginning of the peak of the release of gonadotropins. Approximately 1 day before the onset of menstruation, the level of FSH rises again, which ensures the entry into growth, or recruitment, of follicles (1-4 days of the cycle), selection of a follicle from a cohort of homogeneous - quasi-synchronized (5-7 days), maturation of the dominant follicle (8-12th day) and ovulation (13-15th day). This process, which constitutes the follicular phase, takes about 14 days. As a result, a preovulatory follicle is formed, and the rest of the cohort of follicles that have entered into growth undergo atresia.

The selection of a single follicle destined for ovulation is inseparable from the synthesis of estrogens in it. The stability of estrogen production depends on the interaction of theca cells and granulosa cells, the activity of which, in turn, is modulated by numerous endocrine, paracrine and autocrine mechanisms that regulate the growth and maturation of follicles.

Depending on the stage of development and morphological signs, primordial, preantral, antral and preovulatory, or dominant, follicles are distinguished.

The primordial follicle consists of an immature egg cell, which is located in the follicular and granular (granular) epithelium. Outside, the follicle is surrounded by a connective tissue membrane (theca cells). During each menstrual cycle, 3 to 30 primordial follicles begin to grow, transforming into preantral (primary) follicles.

In the preantral follicle, the oocyte grows in size and is surrounded by a membrane called the zona pellucida (zona pellucida). Cells of granulosa epithelium proliferate and round up, forming a granular follicle layer (stratum granulosum), and the theca-cell layer is formed from the surrounding stroma. This stage is characterized by the activation of the production of estrogens formed in the granulosa layer.

Preovulatory (dominant) follicle stands out among the growing follicles in the largest size (diameter at the time of ovulation reaches 20 mm). The dominant follicle has a richly vascularized layer of theca cells and granulosa cells with a large number of FSH and LH receptors. Along with the growth and development of the dominant (preovulatory) follicle in the ovaries, atresia of the remaining follicles that originally entered growth (recruited) occurs in parallel, and atresia of the primordial follicles also continues.

and the maturation time in the preovulatory follicle is a 100-fold increase in the volume of follicular fluid. In the process of maturation of the antral follicles, the composition of the follicular fluid changes.

Antral (secondary) follicle undergoes an enlargement of the cavity formed by the accumulating follicular fluid produced by the cells of the granulosa layer. The activity of the formation of sex steroids also increases. Androgens (androstenedione and testosterone) are synthesized in theca cells. Once in granulosa cells, androgens are actively aromatized, which causes their conversion to estrogens.

At all stages of follicle development, except for preovulatory, the progesterone content is at a constant and relatively low level. There are always less gonadotropins and prolactin in the follicular fluid than in the blood plasma, and the level of prolactin tends to decrease as the follicle matures. FSH is determined from the beginning of cavity formation, and LH can only be detected in a mature preovulatory follicle along with progesterone. The follicular fluid also contains oxytocin and vasopressin, and in 30 times higher concentrations than in the blood, which may indicate the local formation of these neuropeptides. Class E and F prostaglandins are detected only in the preovulatory follicle and only after the onset of the rise in LH levels, which indicates their directed involvement in the ovulation process.

Ovulation

Ovulation rupture of the preovulatory (dominant) follicle and release of the egg from it. Ovulation is accompanied by bleeding from the destroyed capillaries surrounding theca cells. It is believed that ovulation occurs 24-36 hours after the preovulatory peak of estradiol, causing a sharp rise in LH secretion. Against this background, proteolytic enzymes are activated - collagenase and plasmin, which destroy the collagen of the follicle wall and thus reduce its strength. At the same time, the observed increase in the concentration of prostaglandin F 2 a, as well as oxytocin, induces rupture of the follicle as a result of their stimulation of smooth muscle contraction and pushing the oocyte with the egg-bearing hillock out of the follicle cavity. The follicle rupture is also facilitated by an increase in the concentration of prostaglandin E 2 and relaxin, which reduce the rigidity of its walls.

After the release of the egg into the cavity of the ovulated follicle, the resulting capillaries quickly grow. Granular cells undergo luteinization, which is morphologically manifested in an increase in their volume and the formation of lipid inclusions. This process, leading to the formation of a corpus luteum, is stimulated by LH, which actively interacts with specific receptors of granulosa cells.

Corpus luteum

Corpus luteum- transient hormone-active education, functioning for 14 days, regardless of the total duration of the menstrual cycle; corpus luteum secretes not only progesterone, but also estradiol, and androgens. If pregnancy has not occurred, the corpus luteum regresses. A full corpus luteum develops only in the phase when an adequate number of granulosa cells with a high content of LH receptors are formed in the preovulatory follicle.

In the reproductive period, the ovaries are the main source of estrogens (estradiol, estriol and estrone), of which estradiol is the most active. In addition to estrogens, progesterone and a certain amount of androgens are produced in the ovaries.

In addition to steroid hormones, the ovaries also secrete other biologically active compounds: prostaglandins, oxytocin, vasopressin, relaxin, epidermal growth factor (EGF), insulin-like growth factors (IPFR-1 and IPFR-2).

It is believed that growth factors contribute to the proliferation of granulosa cells, the growth and maturation of the follicle, and the selection of the dominant follicle.

In the process of ovulation, prostaglandins F 2 a and E 2 play a certain role, as well as proteolytic enzymes, collagenase, oxytocin, relaxin contained in the follicular fluid. Ovulation is closely related to an increase (peak) in estrogen.

The cyclical secretion of sex hormones (estrogens, progesterone) leads to biphasic changes in the endometrium, aimed at the perception of a fertilized egg.

The starting material for the formation of all steroid hormones is cholesterol, from which, under the influence of LH, one of the progestins, pregnenolone, is formed. Progestins are precursors for androgens and estrogens. Estrone is the least active fraction, excreted by the ovaries mainly during aging - in postmenopausal women, and the most active fraction, estradiol, is of the greatest importance in the onset and maintenance of pregnancy.

Androgens are synthesized from cholesterol by the ovaries and adrenal glands, and are also formed by converting cholesterol in other organs (liver, skin, adipose tissue). About 90% of androgen precursors - dehydroepiandrosterone (DHEA) and its sulfate (DHEA-S) are synthesized only by the adrenal glands. The content of testosterone in the blood does not reflect the actual androgenization, since the main amount of the hormone in the blood plasma is associated with albumin and globulins. Determination of DHEA and DHEA-S in the blood is an objective criterion for adrenal function in relation to androgen expression. The transformation of androgens into estrogens is carried out under the influence of the aromatase enzyme. The gene encoding aromatase contains areas sensitive to derivatives of arachidonic acid (prostaglandin E 2), cytokines (IL-1β), growth factors, glucocorticosteroids. Accordingly, with changes in the concentration of these biological regulators, aromatase activity can increase or decrease, leading to a violation of the rhythmic formation of estrogens.

The fifth level

regulation of reproductive function are sensitive to fluctuations in the levels of sex steroids, internal and external parts of the reproductive system (uterus, fallopian tubes, vaginal mucosa), as well as mammary glands. The most pronounced cyclical changes occur in the endometrium.

Cyclic changes in the endometrium relate to its functional (surface) layer, consisting of compact epithelial cells, and the intermediate layer, which are rejected during menstruation.

The nasal layer, which is not torn away during menstruation, ensures the restoration of the desquamated layers.

According to the changes in the endometrium during the cycle, the proliferation phase, the secretion phase and the bleeding phase (menstruation) are distinguished.

The transformation of the endometrium occurs under the influence of steroid hormones: the proliferation phase - under the predominant action of estrogens, the secretion phase - under the influence of progesterone and estrogens.

Proliferation phase(follicular) lasts an average of 12-14 days starting from the 5th day of the cycle. During this period, a new surface layer is formed with elongated tubular glands lined with a cylindrical epithelium with increased mitotic activity. The thickness of the functional layer of the endometrium is 8 mm.

Secretion phase (luteal) associated with the activity of the corpus luteum, lasts 14 days (± 1 day). During this period, the epithelium of the endometrial glands begins to produce a secret containing acidic glycosaminoglycans, glycoproteins, glycogen.

The secretion activity becomes the highest on the 20-21st day. By this time, the maximum amount of proteolytic enzymes is found in the endometrium, and decidual transformations occur in the stroma (the cells of the compact layer enlarge, acquiring a rounded or polygonal shape, glycogen accumulates in their cytoplasm). There is a sharp vascularization of the stroma - the spiral arteries are sharply twisted, form "tangles" found in the entire functional layer. The veins are dilated. Such changes in the endometrium, noted on the 20-22th day (6-8th day after ovulation) of the 28-day menstrual cycle, provide the best conditions for the implantation of a fertilized egg.

By the 24-27th day, due to the onset of regression of the corpus luteum and a decrease in the concentration of hormones produced by it, the trophism of the endometrium is disrupted with a gradual increase in degenerative changes in it. Granules containing relaxin are released from the granular cells of the endometrial stroma, which prepares the menstrual rejection of the mucous membrane. In the superficial areas of the compact layer, lacunar expansion of capillaries and hemorrhages in the stroma are noted, which can be detected 1 day before the onset of menstruation.

Menstruation includes desquamation and regeneration of the functional layer of the endometrium. In connection with the regression of the corpus luteum and a sharp decrease in the content of sex steroids in the endometrium, hypoxia increases. The onset of menstruation is facilitated by prolonged spasm of the arteries, leading to blood stasis and the formation of blood clots. Tissue hypoxia (tissue acidosis) is aggravated by increased endothelial permeability, fragility of the vessel walls, numerous minor hemorrhages and massive leukocyte infiltration. Lysosomal proteolytic enzymes secreted from leukocytes enhance the melting of tissue elements. Following a prolonged vasospasm, their paretic expansion occurs with increased blood flow. At the same time, an increase in hydrostatic pressure in the microvasculature and rupture of the walls of blood vessels are noted, which by this time have largely lost their mechanical strength. Against this background, there is an active desquamation of necrotic areas of the functional layer. By the end of the 1st day of menstruation, 2/3 of the functional layer is rejected, and its complete desquamation usually ends on the 3rd day.

Endometrial regeneration begins immediately after the rejection of the necrotic functional layer. The basis for regeneration is the epithelial cells of the stroma of the basal layer. Under physiological conditions, already on the 4th day of the cycle, the entire wound surface of the mucous membrane is epithelialized. This is again followed by cyclical changes in the endometrium - the phases of proliferation and secretion.

Consecutive changes throughout the cycle in the endometrium - proliferation, secretion and menstruation depend not only on cyclical fluctuations in the levels of sex steroids in the blood, but also on the state of tissue receptors for these hormones.

The concentration of nuclear receptors for estradiol increases until the middle of the cycle, reaching a peak by the late period of the endometrial proliferation phase. After ovulation, a rapid decrease in the concentration of nuclear estradiol receptors occurs, continuing until the late secretory phase, when their expression becomes much lower than at the beginning of the cycle.

The regulation of the local concentration of estradiol and progesterone is mediated to a large extent by the appearance of various enzymes during the menstrual cycle. The content of estrogens in the endometrium depends not only on their level in the blood, but also on the formation in the tissue. A woman's endometrium is able to synthesize estrogens by converting androstenedione and testosterone with the participation of aromatase (aromatization). This local source of estrogen enhances the estrogenation of endometrial cells, which characterizes the proliferative phase. During this phase, the highest androgen aromatization capacity and the lowest estrogen metabolizing enzyme activity are noted.

Recently, it has been established that the endometrium is also capable of secreting prolactin, which is completely identical to the pituitary. The synthesis of prolactin by the endometrium begins in the second half of the luteal phase (activated by progesterone) and coincides with the decidualization of stromal cells.

The menstrual cycle is a chain of complex interconnected processes. The clarity of fertility and the days of a woman's menstrual cycle regulate the subcortical structures of the brain, which produce hormones and control the work of the endocrine glands.

If the female body for a long time without interruption and rest lives only according to one program, in it at some stage the menstrual cycle may malfunction. And because of the excessive build-up of the endometrium, the risk of cancer will significantly increase.

The well-coordinated work of organs and systems depends on many factors, which are regulated by nature itself. This means that from time to time a woman must become pregnant, carry, give birth and breastfeed. This is her biological program.

Typical Periodic Cycle

A typical menstrual cycle takes about 28 days, although the length may vary from woman to woman. The first day of menstrual bleeding is conventionally considered the first day of the cycle.

Days 1-5

A drop in the level of the hormone progesterone in the body triggers the onset of menstruation - the rejection of the membrane lining the uterine cavity. During this period, hormones produced in the pituitary gland under the influence of signals from the hypothalamus (diencephalon) stimulate the maturation of the egg in the ovaries, which in turn leads to an increase in the level of another hormone in the body, estrogen.

Days 5-14

Menstrual bleeding usually ends by day 5. Over the next few days, you may notice only a small mucous discharge from the cervix. Between 9-13 days, the level of estrogen in the body reaches a maximum and the mucus secreted from the cervix becomes light and liquid - a potential period of conception begins. On the 13th day, the level of pituitary hormones, which stimulate the maturation and release of the egg from the ovary, also reaches its maximum. The temperature rises by about 0.5 ° C and ovulation occurs on the 14th day.

Days 15-23

After ovulation, if the fertilization of the egg has not occurred, the level of estrogen is significantly reduced, and the follicle from which the egg came out turns into a gland called the corpus luteum, which secretes progesterone. On days 15-16, you may notice thick, jelly-like mucus secreted by the cervix, followed by little or no mucus for the remainder of the cycle.

Days 24-28

As the gland degenerates, the activity of the corpus luteum begins to decrease and the level of progesterone falls. Some women experience premenstrual symptoms such as breast tenderness and mood changes, especially irritability and depression. There may be slight swelling due to fluid retention in the body. The onset of menstruation is indicated by a decrease in body temperature by approximately 0.5 ° C.

From the very day the girl started menarche - the first bleeding of the menstrual cycle, she is potentially ready to become pregnant. Menstruation persists for the next 35–45 years, reminding every month that the reproductive function is active.

When does your period start?

Normally, the first bleeding of the menstrual cycle occurs between 9 and 14 years old - at the beginning or middle of puberty (adolescence). The age at which menarche appears depends on many factors. Hereditary predisposition plays a certain role. Often in maternal relatives, the menstrual cycle is activated at the same time. General health is also important: lack of nutrition, chronic diseases can delay puberty. During six months or a year, the bleeding of the menstrual cycle is irregular, with delays of several days. Anovulatory cycles also occur, those that are not accompanied by the release of the egg from the ovary into the fallopian tube. If menstruation does not appear after 14 years, there is a reason to contact a pediatric gynecologist or endocrinologist. The most favorable time for conception is from 25 to 35 years. By the beginning of this period, the growth processes completely stop, the function of the ovaries is gaining strength.

How to calculate your menstrual cycle?

The menstrual cycle is considered to be the interval from the first day of one period to the beginning of the next. Its duration is 21-32 days. 60% of women have a 28-day cycle. The first phase of the uterine cycle is called menstrual. At this time, the endometrial cells lining the uterus from the inside are rejected, and bloody discharge comes out of the woman's genital tract. The average blood loss is 20-40 ml per day and usually lasts from 2 to 5 days.

After the completion of menstruation, the cycle enters the next phase - follicular. Follicles begin to mature in the ovary. Despite the fact that in most of the fair sex several are activated at once, only one of them finally matures, which is called dominant. A follicle includes an oocyte cell surrounded by a layer of special epithelium. During maturation, the oocyte divides twice, as a result of which four cells are formed - the egg itself and three secondary cells, which then die. The epithelial cells surrounding the future ovum also split. In addition, they secrete a special liquid. As a result of changes, the follicle increases in size and turns into a kind of reservoir - the Graaf bubble, inside which the egg floats. The follicular phase ends in the middle of the menstrual cycle, on the 12-15th day.

When does ovulation occur?

The next phase of the menstrual cycle is called proliferative (from Latin proles - offspring, offspring and fero - I carry). At this moment, under the action of the hormone estradiol, changes occur in the endometrium: its layers grow, and the glands located in them work more actively. This restructuring comes to the end by the beginning of ovulation. The vesicle that has matured in the Graaf ovary begins to accumulate lipids (fats) and luteal pigment, which gives the formation a yellow color, turning it into a yellow body.

Then ovulation begins - the wall of the Graafian bubble bursts, and the egg enters the fallopian tube. Before ovulation, the funnel of the fallopian tube is at some distance from the ovary, but by the time it comes, it comes close to it and grabs its edges from all sides.

While the egg is viable, the next phase of the female menstrual cycle is triggered - the secretory phase. The glands begin to secrete thick mucus, and the endometrium grows even more, becomes loose - this is how the uterus prepares to receive a fertilized egg.

If this does not happen, the next phase of the cycle begins - luteal. It lasts about 14 days. At the end of the period, part of the newly formed uterine epithelium (also called the functional layer) is rejected, and menstruation begins. The corpus luteum ceases to function. New cells form in the ovary and the menstrual cycle repeats from start to finish.

Menstrual hormones

The entire menstrual cycle is controlled by hormones. In its different phases, the level of some hormones increases and the amount of others decreases. Before the start of the next, at the end of the previous cycle, the levels of estradiol and progesterone always fall, which leads to the rejection of the functional layer of the endometrium and the appearance of bleeding. An increase in the synthesis of follicle-stimulating hormone provokes the growth of new follicles.

Another hormone necessary for the maturation of follicles - luteinizing - is synthesized more actively as the follicle grows. At the same time, the level of estradiol increases, which causes the proliferation of the endometrium. The onset of ovulation is due to a very sharp release of luteinizing hormone (against the background of a slight decrease in the amount of estradiol). Ovulation occurs 1–1.5 days after this level has reached its maximum.

Immediately after the completion of ovulation, the level of progesterone increases, and a little later, a second wave of increase in the formation of estradiol begins. Changes lead to corresponding metamorphoses in the endometrium (secretory phase of the uterine cycle). Then the production of both hormones is inhibited, and the next bleeding begins.

Complex changes in the hormonal background during the menstrual cycle are controlled by the endocrine glands located throughout the body. Follicle-stimulating and luteinizing hormones are produced by the pituitary gland in the brain. The signal for their production comes from the hypothalamus (located there): it produces gonadoliberins - hormones that stimulate the synthesis of the sex hormones folliberin and luliberin. Estradiol is produced in the ovaries, more precisely, in the follicles and the corpus luteum, which develops at the site of the bursting Graafian vesicle. Progesterone is synthesized by the corpus luteum itself.

Temperature during ovulation

By far the most important point in the menstrual cycle is ovulation. Periodic menstrual bleeding can occur even in her absence, but pregnancy cannot occur in this case. Even in a perfectly healthy woman, ovulation does not occur in every menstrual cycle.

There are tests on the market to determine when ovulation starts and ends. There is another diagnostic method - basal temperature measurement. It is checked throughout the entire menstrual cycle: in the morning, before getting out of bed, a thermometer is placed in the rectum. On the eve of ovulation, many women record a decrease in the indicator by 0.2-0.5 ° C. But at the time of ovulation, after the release of progesterone into the blood, the basal temperature for 3-4 days is kept at around 37.1-37.3 ° C. The absence of a significant change in parameters may indicate that there was no ovulation in this cycle.

Menstrual irregularities

It happens that menstruation comes irregularly. Sometimes very often (polymenorrhea), or, conversely, rarely. Two months or more do not come (metrorrhagia), and then they start very strong and last longer than usual, they can even drag on for 10 days (menorrhagia).

These symptoms indicate various problems in the body, and there are quite a few of them. The most common cause of failure is infections of the genital tract (chlamydia, ureaplasma, mycoplasma, etc.). A smear for microflora or a blood test for sexually transmitted infections will clarify the situation. Having identified the "unexpected guest", the doctor will prescribe treatment.

The situation is more complicated when hormonal disorders occurring at different periods of the cycle are to blame for the irregularity of the cycle. To check the balance, an endocrinologist's consultation, urine and blood tests are prescribed. Menstrual irregularities are also a consequence of chronic diseases of the genital area - endometriosis, fibroids and others.

Many of these ailments begin in adolescence, are sluggish in nature and are accompanied by blurred symptoms, so the woman does not know about them. For the first time, the diagnosis is clarified when a couple is examined for infertility, when, after 1-2 years of marriage, the spouses turn to a specialist. To avoid the loss of precious time and anxiety, it is worth conducting an examination when the pregnancy is just being planned. The gynecologist will advise which of the tests will be required first.

Usually they suggest that you first take an ovulation test, a blood test for hormones, and draw up a basal temperature chart. Modern medicine is capable of eliminating many reproductive disorders.

The menstrual cycle can be disrupted due to a stressful situation: strong experiences at work or in the family, physical overload (among athletes) and even banal fasting, with which some women try to get in shape, cause a failure.

How many eggs does a woman have?

Even before the birth of a girl, a follicular supply of eggs is formed, thanks to which she can become a mother. This resource is completely dependent on genetic predisposition. And nothing else can influence him. At birth, girls' ovaries contain an average of 300,000 potential eggs. The strategic reserve is depleted every year. From 10 to 25 years old, a woman loses a few eggs - nature preserves the bulk until better times. But by the age of 35, the number of follicles is two times less. After forty, no more than a thousand remain.

Since a woman has two ovaries, the maturation of eggs in them usually occurs alternately: during one menstrual cycle - in the right, during another - in the left. If an egg appears in each ovary, and then both enter the fallopian tubes and are fertilized, then twins, or rather fraternal twins, will be born. In the treatment of some types of infertility, drugs that stimulate ovulation are used. In this case, the likelihood of becoming pregnant with twins increases. There is also a hereditary predisposition to multiple pregnancies.

The reproductive function of women is carried out primarily due to the activity of the ovaries and uterus, because in the ovaries, the egg matures, and in the uterus, under the influence of hormones secreted by the ovaries, changes occur in preparation for the perception of a fertilized ovum. The reproductive period is characterized by the ability of a woman's body to reproduce offspring; the duration of this period is from 17-18 to 45-50 years. The reproductive period is preceded by the following stages: intrauterine; newborns (up to a year); childhood (8-10 years old); prepubertal and pubertal age (17-18 years). The reproductive period turns into menopause, in which premenopause, menopause and postmenopause are distinguished.

Menstrual cycle- one of the manifestations of complex biological processes in a woman's body. The menstrual cycle is characterized by cyclical changes in all parts of the reproductive system, the external manifestation of which is menstruation. Menstruation is bloody discharge from the genital tract of a woman, periodically resulting from the rejection of the functional layer of the endometrium at the end of the biphasic menstrual cycle. The first menstrual period occurs at the age of 12-13 years, during the year after this, menstruation may be irregular, and then a regular menstrual cycle is established. The first day of your period is the first day of your period. The duration of the cycle is the time between the first two days of the next two periods. The average duration of the menstrual cycle is 21 to 35 days. The amount of blood loss on menstrual days is 40-60 ml. The duration of normal menstruation is 2 to 7 days. During the menstrual cycle, follicles grow in the ovaries and the ovum matures, which as a result becomes ready for fertilization. At the same time, sex hormones are produced in the ovaries, which provide changes in the mucous membrane of the uterus. Sex hormones (estrogens, progesterone, androgens) are steroids and affect target tissues and organs. These include the genitals, primarily the uterus, mammary glands, cancellous bone, brain, endothelium and vascular smooth muscle cells, myocardium, skin and its appendages.

Estrogens contribute to the formation of genitals, the development of secondary sexual characteristics during puberty. Androgens have an effect on the appearance of hair on the pubis and in the armpits. Progesterone controls the secretory phase of the menstrual cycle, prepares the endometrium for implantation. Cyclic changes in the ovaries involve three main processes:

Follicle growth and dominant follicle formation.

Ovulation.

Formation, development and regression of the corpus luteum.

It is customary to distinguish the following main stages of follicle development:

primordial follicle,

preantral follicle,

antral follicle,

preovulatory follicle.

Primordial the follicle consists of an immature egg, which is located in the follicular and granulosa epithelium. Outside, the follicle is surrounded by a connective membrane. During each menstrual cycle, from 3 to 30 primordial follicles begin to grow, from which preantral or primary follicles form.

Preantral follicle. With the onset of growth, the primordial follicle progresses to the preantral stage, and the oocyte grows and is surrounded by a membrane called the zona pellucida. Cells of granulomatous epithelium undergo multiplication. This growth is characterized by an increase in estrogen production.

Antral, or a secondary follicle. It is characterized by further growth: the number of cells of the granulosa layer that produce follicular fluid increases. During the period of folliculogenesis (8-9 days of the menstrual cycle), the synthesis of sex steroid hormones is noted. One dominant follicle is formed from many antral follicles (by the 8th day of the cycle). It is the largest, contains the largest number of cells of the granulosa layer. Along with the growth and development of the dominant preovulatory follicle in the ovaries, the process of atresia of the remaining growing follicles occurs in parallel.

Ovulation- rupture of the preovulatory dominant follicle and the release of an egg from it. By the time of ovulation, the process of meiosis occurs in the oocyte. Ovulation is accompanied by bleeding from the destroyed capillaries that surround the connective membrane. After the release of the egg, the resulting capillaries quickly grow into the follicle cavity. Granulosa cells undergo luteinization: the volume of the cytoplasm increases in them and lipid inclusions are formed. This process leads to the formation of a corpus luteum.

Corpus luteum- a transient endocrine gland that functions for 14 days, regardless of the duration of the menstrual cycle. In the absence of pregnancy, the corpus luteum regresses.

Regulation of the menstrual cycle

The regulation of the menstrual cycle is complex and multicomponent, it is carried out with the participation of the mediobasal (pituitary) zone of the hypothalamus, the anterior lobe of the pituitary gland and the ovaries, whose hormones (estrogens and progesterone) cause cyclic changes in the target organs of the reproductive system, primarily in the uterus. Physiological rhythmic processes in the hypothalamus and pituitary gland, accompanied by fluctuations in the secretion of gonadotropic hormones, lead to cyclical changes in the ovaries.

The first(follicular) phase in the ovaries, the growth and maturation of follicles occur, one of which (dominant, or leading) reaches the preovulatory stage.

In the middle During menstrual periods, this follicle bursts and the mature egg enters the abdominal cavity (ovulation).

After ovulation comes second (luteal) phase the menstrual cycle, during which a corpus luteum forms in place of the bursting follicle.

By the end of the menstrual cycle, if fertilization has not occurred, corpus luteum regresses... In connection with these processes, the secretion of estrogen and progesterone changes cyclically.

The secretion of hormones by the glands is controlled by the nervous system, which, in turn, is influenced by the hormonal state of the body. Thus, we can talk about a single complex - the neuroendocrine system. In this system, there is a clear vertical subordination of some glands to others. The hypothalamus is considered the central endocrine gland: it receives signals from the nervous system, according to which super-hormones are produced - releasing factors, that is, substances that stimulate the production of hormones by other glands. In relation to the reproductive system, subordination looks like this: hypothalamus - adrenal glands - ovaries, further influence on hormone-dependent organs. At the same time, there is a feedback in the system: for example, an increase in the level of estrogen produced in the ovaries leads to the release of a releasing factor by the hypothalamus, which ultimately inhibits the production of estrogen. If a woman has one ovary removed, a sharp drop in hormone levels causes the hypothalamus to stimulate the remaining ovary, which leads to its enlargement. The ovaries produce 3 types of hormones:

estrogens (estradiol, estrone, estriol),

gestagens (progesterone, 17-alpha-hydroxyprogesterone),

androgens (androstenediol, dehydroepiandrosterone).

Estrogens are produced by the cells that make up the follicle wall, inside which the egg is formed. Therefore, if at the beginning of the cycle about 200 μg of estrogens are released per day, then by the time of ovulation (maturation of the egg) their level reaches 500 μg per day. Estrogens act on target organs, whose cells retain these hormones. Cells of other organs do not seem to notice estrogens. Target organs for estrogens are the uterus, vagina, ovaries themselves, and mammary glands. The effect of estrogens on the genitals depends on the dose of hormones. Small and medium doses stimulate the development of the ovaries and the maturation of follicles, large doses inhibit the maturation of the egg, very large doses cause atrophy (shrinkage and shrinkage) of the ovaries. In the uterus, under the influence of estrogen, the formation of muscle fibers increases and muscle tone increases. Very large and long-term administered doses of estrogen can lead to the formation of uterine fibroids. Estrogens also cause overgrowth of the lining of the uterus - the endometrium. However, high doses of estrogen can lead to the formation of polyps and bleeding. The normal level of estrogen contributes to the development of the vagina, the improvement of the condition of its mucous membrane. On the ovaries, estrogens act directly and indirectly, through the pituitary gland. Thus, small doses of estrogens, produced before puberty, stimulate the development of follicles, from which eggs will subsequently appear. But the most interesting mechanism of action of estrogens on the ovaries occurs through the pituitary gland - such a developed self-regulatory system that it is very problematic to disrupt it: Small doses of estrogens stimulate the production of FSH (follicle-stimulating hormone), under the influence of which a follicle develops, in the wall of which estrogens are produced. But the entry of large doses of estrogen into the bloodstream blocks the production of FSH. In the mammary glands, estrogens stimulate the development of the entire duct system, the size and color of the nipples and areolas. Estrogens affect the entire metabolism - glucose, trace elements, high-energy compounds in muscles, fatty acids, and also lower cholesterol. In the field of mineral metabolism, estrogens most pronouncedly affect the retention of sodium, calcium and extracellular water, iron and copper in the body. All these features of metabolism lead to the formation of a feminine figure with a peculiar distribution of adipose tissue. The effect of estrogens on the genitals is manifested only in the presence of folic acid.

Gestagens produced mainly by cells of the corpus luteum, which forms at the site of a burst follicle. Progesterone acts on the same target organs as estrogens, and in most cases, only after they have been exposed to estrogens. Progesterone regulates the possibility of conception, contributing to the preservation of the viability of the egg, its movement through the tubes, causing favorable changes in the lining of the uterus, where the fertilized egg is attached. Progesterone is absolutely essential for the development and maintenance of pregnancy; under its action, the walls of the uterus thicken, its contractions are blocked, the cervix is ​​strengthened, the activity of the mammary glands is stimulated. Acting on the brain, it indirectly suppresses the secretion of LH (negative feedback). Like estrogen, it also suppresses FSH secretion. The release of progesterone is accompanied by an increase in temperature immediately after ovulation. Finally, as in the case of estrogens, progesterone levels regulate the activity of the pituitary gland in a feedback manner. The effect of progesterone on the general metabolism depends on the level of the hormone: small doses inhibit the excretion of sodium, chlorine and water, and large doses increase the excretion of urine. In addition, it enhances metabolism, especially due to amines and amino acids. The action of progesterone on thermoregulatory centers underlies the known method of controlling ovarian activity by measuring basal (rectal) temperature.

Androgens are formed in the ovaries in specific cells of the follicles, as well as in the adrenal glands. The effect of androgens on the genitals is twofold: small doses cause proliferation of the mucous membrane of the uterus (in large doses - the formation of polyps and cysts), and with a low content of estrogen they cause mucosal atrophy. In addition, prolonged use of large doses of androgens causes an increase in the clitoris and labia majora, while the labia minora, on the contrary, are sharply reduced. Small doses of androgens stimulate the activity of the ovaries, and large doses inhibit. In addition to these hormones, the activity of the ovaries, the menstrual cycle and the possibility of pregnancy are influenced by the GONADOTROPIC hormones produced in the pituitary gland. This follicle-stimulating (FSH), luteinizing (LH) and luteotropic (LTH) hormones. All of them act sequentially, as if transferring to each other control over the development of the follicle, the maturation of the egg, the formation of the corpus luteum. So, FSH in the early stages of the menstrual cycle causes the growth of the egg, but in order for it to fully mature, additional influence of LH is necessary. Under the joint influence of these hormones, the egg matures, leaves the follicle, leaving in its place the so-called corpus luteum - a temporary endocrine gland that produces progesterone, which was mentioned above. The level of LTH secretion depends on how much progesterone will be, and, consequently, how firmly the egg will hold in the uterus. In addition, LTH regulates milk production after childbirth. As already mentioned, the production of ovarian and gonadotropic hormones occurs within the framework of feedback: an increase in the level of some hormones leads to a decrease in the level of others, which automatically increases the release of the former, etc.

The flow of the MENSTRUAL CYCLE can be schematically depicted as follows. The hypothalamus produces FSH-releasing factor, which stimulates the production of FSH in the pituitary gland. FSH causes the growth and development of the follicle. The follicle produces estrogens that stimulate the secretion of LH. LH and FSH together cause the follicle to grow almost until the egg is ovulated. Estrogens, together with a small amount of progesterone, stimulate the release of LH-releasing factor, which contributes to the increased production of LH just before ovulation. After ovulation, the corpus luteum releases a lot of progesterone, but the level of estrogen decreases. Progesterone stimulates the production of LTH, which in response increases the activity of the corpus luteum and increases the release of progesterone. Progesterone suppresses the formation of LH, which leads to a deterioration in the blood supply to the uterine lining and the onset of menstruation. Left without hormonal support, the corpus luteum gradually fades away. The decrease in progesterone levels causes the pituitary gland to release FSH-releasing factor - and the cycle starts over. Thus, the dynamics of the release of ovarian hormones can be schematically depicted as follows. If the level of each hormone on the days of menstruation is taken as 100%, then they will be distributed over the cycle as follows: 16 days of the cycle), minimum - at the beginning of the folliculin phase (after menstruation). Differences in estrogen levels reach 10-fold. The level of progesterone is highest in the middle of the P phase (16-20 days of the cycle), 25 times less at the beginning of the cycle and rises before ovulation (13-15 days of the cycle). The concentration of androgens fluctuates much less, and the highest value is observed before ovulation.

Thus, the unified system of pituitary-hypothalamus-ovaries, together with the nervous system, acting on the principle of feedback, automatically provides cyclic processes specific to the female body. The endometrium is most sensitive to the action of ovarian hormones due to the presence of a large number of estrogen and progesterone receptors in the cytoplasm and nuclei of its cells. The number of estradiol receptors in the endometrium reaches a maximum by the middle of the first phase of the menstrual cycle and then decreases; the maximum content of progesterone receptors falls on the preovulatory period. During the menstrual cycle, the endometrium grows, the thickness of which at the end of the second phase of the cycle increases 10 times compared to the first phase of the cycle. According to ultrasound scanning data, the thickness of the premenstrual endometrium reaches 1 cm.Along with the growth of the endometrium, cyclical changes in the glands, stroma and blood vessels occur in it. In a histological assessment of the state of the endometrium, the proliferation phase (early, middle and late), corresponding to the follicular phase of the menstrual cycle, and the secretion phase (early, middle and late), corresponding to the luteal phase of the cycle, are distinguished.

At the end of the luteal phase of the menstrual cycle, menstruation occurs, during which the functional layer of the endometrium is rejected. Menstruation is a consequence of a decrease in the level of ovarian hormones (estrogen and progesterone) in the blood; circulatory disorders in the endometrium (dilatation and thrombosis of veins, arterial spasm, focal necrosis); increasing intravascular fibrinolysis, reducing the processes of blood coagulation in the vessels of the endometrium; increasing the content of prostaglandins in the uterus and increasing the contractile activity of the myometrium. The cessation of bloody discharge is mainly due to the regeneration of the endometrium due to the epithelium of the remnants of the glands preserved in its battle layer; regeneration begins from the second day of the menstrual cycle even before the end of the discharge. Stopping bleeding is facilitated by increased platelet aggregation in the vessels of the endometrium under the influence of prostaglandins.

Ovarian hormones cause cyclical changes in other parts of the reproductive system. In the first phase of the menstrual cycle, under the influence of estrogens, the contractile activity of the myometrium increases, in the second phase it decreases. The isthmus of the uterus, dilated in the first phase of the menstrual cycle, narrows in its second phase. In the glands of the cervical canal in the first phase of the cycle, the secretion of mucus increases - from 50 mg to 700 mg per day by the time of ovulation, while its structure changes - in the ovulatory period, mucus is liquid, easily permeable to sperm, the most viscous. In the second phase of the cycle, the secretion of the glands of the cervical canal decreases sharply, the mucus becomes viscous and opaque. During the menstrual cycle, the structure of the vaginal epithelium changes and, as a result, the cellular composition of the vaginal contents: as ovulation approaches, the number of superficial keratinizing cells increases in the vaginal contents, peristaltic movements of the fallopian tubes and vibrations of the cilia of the epithelium lining them increase.

In the mammary glands, in the first phase of the menstrual cycle, under the influence of estrogens, there is a proliferation of lactocytes - glandular cells lining the alveolar cavity; in the second phase of the cycle, secretory processes predominate in lactocytes, which is associated with the influence of progesterone. In the premenstrual period, the mammary glands are slightly swollen due to fluid retention in the connective tissue. In some women, engorgement is significant and accompanied by painful sensations (mastalgia).

In addition to changes in the organs of the reproductive system, there are cyclical changes in the functional state of other systems of the female body. It has been established that the excitability of the cerebral cortex changes during the menstrual cycle. So, in the premenstrual period, inhibition processes increase, the ability to concentrate decreases, efficiency decreases, and on the eve of menstruation, sexual activity decreases. In the first phase, the tone of the parasympathetic part of the autonomic nervous system increases, in the second phase - the sympathetic. Changes in water-salt metabolism and the function of the cardiovascular system lead to fluid retention in the body in the premenstrual period. All of these changes are mainly due to ovarian hormones (estrogens and progesterone), the action of which is realized through the cell receptors of steroid hormones and the system of neurotransmitters (transmitters of humoral and nerve impulses).

Menstrualnyj_cikl_ovuljacija_gormonalnaja_reguljacija.txt · Last modified: 2012/06/25 23:58 (external change)