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Female reproductive system:
Ovarian-menstrual cycle; age-related changes; hormonal regulation

sexual cycle

The ovarian-menstrual cycle is a successive change in the function and structure of the organs of the female reproductive system, regularly repeating in the same order. In women and female great apes, the sexual cycles are characterized by regular uterine bleeding (menstruation).

In most women who have reached puberty, menstruation is repeated regularly every other 28 days. In the ovarian-menstrual cycle, three periods or phases are distinguished: the menstrual (endometrial desquamation phase), which ends the previous menstrual cycle, the postmenstrual period (endometrial proliferation phase) and, finally, the premenstrual period (functional phase, or secretion phase), during which preparation of the endometrium for possible implantation of the embryo if fertilization has occurred.

menstrual period. It consists in desquamation, or rejection, of the functional layer. In the absence of fertilization, the intensity of secretion of progesterone by the corpus luteum decreases sharply. As a result, the spiral arteries that feed the functional layer of the endometrium spasm. In the future, non-rotic changes and rejection of the functional layer of the endometrium occur.

The basal layer of the endometrium, fed by the direct arteries, continues to be supplied with blood and is the source for the regeneration of the functional layer in the next phase of the cycle.

On the day of menstruation, there are practically no ovarian hormones in the body of a woman, since the secretion of progesterone stops, and the secretion of estrogens (which was prevented by the corpus luteum while it was in its prime) has not yet resumed.

Regression of the corpus luteum disinhibits the growth of the next follicle - estrogen production is restored. Under their influence, the regeneration of the endometrium is activated in the uterus - the proliferation of the epithelium is enhanced due to the bottoms of the uterine glands, which are preserved in the basal layer after desquamation of the functional layer. After 2-3 days of proliferation, menstrual bleeding stops and the next postmenstrual period begins. Thus, the postmenstrual phase is determined by the influence of estrogen, and the premenstrual phase by the influence of progesterone.

postmenstrual period. This period begins after the end of menstruation. At this moment, the endometrium is represented only by the basal layer, in which the distal sections of the uterine glands remain. The regeneration of the functional layer that has already begun allows us to call this period the proliferation phase. It continues from the 5th to the 14th ... 15th day of the cycle. The proliferation of the regenerating endometrium is most intense at the beginning of this phase (5...11th day of the cycle), then the rate of regeneration slows down and a period of relative rest begins (11...14th day). The uterine glands in the postmenstrual period grow rapidly, but remain narrow, straight and do not secrete.

As already mentioned, endometrial growth is stimulated by estrogens, which are produced by growing follicles. Therefore, during the postmenstrual period, another follicle grows in the ovary, which reaches the mature stage (tertiary, or vesicular) by the 14th day of the cycle.

Ovulation occurs in the ovary on the 12th ... 17th day of the menstrual cycle, i.e. approximately halfway between two consecutive periods. In connection with the participation of ovarian hormones in the regulation of uterine restructuring, the described process is usually called not the menstrual, but the ovarian-menstrual cycle.

premenstrual period. At the end of the postmenstrual period, ovulation occurs in the ovary, and in place of the bursting vesicular follicle, a corpus luteum is formed that produces progesterone, which activates the uterine glands, which begin to secrete. They increase in size, become convoluted and often branch out. Their cells swell, and the gaps of the glands are filled with secretions. Vacuoles containing glycogen and glycoproteins appear in the cytoplasm, first in the basal part, and then shifting to the apical edge. Mucus, abundantly secreted by the glands, becomes thick. In areas of the epithelium lining the uterine cavity between the mouths of the uterine glands, the cells acquire a prismatic shape, and cilia develop on the tops of many of them. The thickness of the endometrium increases compared to the previous postmenstrual period, which is due to hyperemia and the accumulation of edematous fluid in the lamina propria. Lumps of glycogen and lipid droplets are also deposited in the cells of the connective tissue stroma. Some of these cells differentiate into decidual cells.

If fertilization occurs, then the endometrium is involved in the formation of the placenta. If fertilization did not take place, then the functional layer of the endometrium is destroyed and rejected during the next menstruation.

Cyclic changes in the vagina. With the onset of endometrial proliferation (on the 4-5th day after the end of menstruation), i.e. in the postmenstrual period, epithelial cells noticeably swell in the vagina. On the 7-8th day, an intermediate layer of compacted cells differentiates in this epithelium, and by the 12-14th day of the cycle (towards the end of the postmenstrual period), the cells in the basal layer of the epithelium strongly swell and increase in volume. In the upper (functional) layer of the vaginal epithelium, the cells loosen and clumps of keratohyalin accumulate in them. However, the process of keratinization does not reach full keratinization.

In the premenstrual period, the deformed compacted cells of the functional layer of the vaginal epithelium continue to be rejected, and the cells of the basal layer become denser.

The condition of the epithelium of the vagina depends on the level of ovarian hormones in the blood, so the picture of the vaginal smear can be used to judge the phase of the menstrual cycle and its violations.

Vaginal smears contain desquamated epitheliocytes, there may be blood cells - leukocytes and erythrocytes. Among epitheliocytes, cells that are at various stages of differentiation are distinguished - basophilic, acidophilic and intermediate. The ratio of the number of the above cells varies depending on the phase of the ovarian-menstrual cycle. In the early, proliferative phase (7th day of the cycle), superficial basophilic epitheliocytes predominate; large nuclei and leukocytes; in the menstrual phase, the number of blood cells - leukocytes and erythrocytes - increases significantly.

During menstruation, erythrocytes and neutrophils predominate in the smear, epithelial cells are found in small numbers. At the beginning of the postmenstrual period (in the proliferative phase of the cycle), the vaginal epithelium is relatively thin, and the content of leukocytes in the smear decreases rapidly and epithelial cells with pycnotic nuclei appear. By the time of ovulation (in the middle of the ovarian-menstrual cycle), such cells in the smear become predominant, and the thickness of the vaginal epithelium increases. Finally, in the premenstrual phase of the cycle, the number of cells with a pyknotic nucleus decreases, but the desquamation of the underlying layers increases, the cells of which are found in the smear. Before the onset of menstruation, the content of red blood cells in the smear begins to increase.

Age-related changes in the organs of the female reproductive system

The morphofunctional state of the organs of the female reproductive system depends on the age and activity of the neuroendocrine system.

Uterus. In a newborn girl, the length of the uterus does not exceed 3 cm and, gradually increasing during the prepubertal period, reaches its final size upon reaching puberty.

By the end of the childbearing period and in connection with the approach of menopause, when the hormone-forming activity of the ovaries weakens, involutive changes begin in the uterus, primarily in the endometrium. Deficiency of luteinizing hormone in the transitional (premenopausal) period is manifested by the fact that the uterine glands, while still retaining the ability to grow, already cease to function. After the establishment of menopause, endometrial atrophy progresses rapidly, especially in the functional layer. In parallel, atrophy of muscle cells develops in the myometrium, accompanied by hyperplasia of the connective tissue. In this regard, the size and weight of the uterus, undergoing age-related involution, are significantly reduced. The onset of menopause is characterized by a decrease in the size of the organ and the number of myocytes in it, and sclerotic changes occur in the blood vessels. This is a consequence of a decrease in hormone production in the ovaries.

Ovaries. In the first years of life, the size of the ovaries in a girl increases mainly due to the growth of the brain part. Follicular atresia progressing to childhood, is accompanied by the proliferation of connective tissue, and after 30 years, the proliferation of connective tissue also captures the cortical substance of the ovary.

The attenuation of the menstrual cycle in the menopause is characterized by a decrease in the size of the ovaries and the disappearance of follicles in them, sclerotic changes in their blood vessels. Due to insufficient production of lutropin, ovulation and the formation of corpus luteum do not occur, and therefore the ovarian-menstrual cycles first become anovulatory, and then stop and occur. menopause.

Vagina. Morphogenetic and histogenetic processes leading to the formation of the main structural elements of the organ are completed by the period of puberty.

After the onset of menopause, the vagina undergoes atrophic changes, its lumen narrows, the mucosal folds smooth out, and the amount of vaginal mucus decreases. The mucous membrane is reduced to 4...5 layers of cells that do not contain glycogen. These changes create conditions for the development of infection (senile vaginitis).

Hormonal regulation of the activity of the female reproductive system

Clitoris in embryonic development and structure corresponds to the dorsal part of the male penis. It consists of two erectile cavernous bodies ending in a head, which is covered with a stratified squamous epithelium, slightly keratinized.

Innervation. The external genital organs, especially the clitoris, are richly supplied with various. In the epithelium of these organs, free nerve endings branch out. In the connective tissue papillae of the lamina propria of their mucous membrane there are tactile nerve bodies, and in the dermis - encapsulated genital bodies. Lamellar bodies are also found in the large lips and clitoris.

Milk glands

The histofunctional characteristics of the mammary glands are given earlier, in the topic.

Some terms from practical medicine:

• menopause, menopause, climacteric ( climax; Greek klimax stairs; climacterium; Greek klimakter step (stairs), turning point) - the period of life (both men and women), during which the cessation of the generative function occurs;
• menopause (menopause; Meno-Greek men month + Greek pause cessation, break) - the second phase of the menopause, which occurs after the last menstrual-like bleeding and is characterized by the cessation of cyclic changes in the endometrium and reproductive function, progressive involution of the genital organs and a decrease in the secretion of sex hormones;
• menophobia (menophobia; meno- + phobia) - obsessive fear - fear of menstruation and (or) associated discomfort;
• vaginismus (vaginismus; lat. vagina vagina; synonym: vulvism, colpospasm) - reflex spastic contraction of the muscles of the vestibule of the vagina and the pelvic floor, which makes it difficult to have sexual intercourse or gynecological examination;
• vulvovaginitis (vulvovaginitis; vulva - female external genitalia + lat. vagina vagina + -it) - inflammation of the female external genitalia and vagina;
• colpitis -- (colpitis; colp - Greek kolpos deepening, sinus, vagina + -itis, synonym: vaginitis, endocolpitis) - inflammation of the vaginal mucosa;

Natural methods for getting pregnant or avoiding pregnancy are based on the physiology of the female reproductive cycle and taking into account that the average lifespan of an egg is 12 to 24 hours…

Natural methods for getting pregnant or avoiding pregnancy are based on the physiology of the female reproductive cycle and taking into account that the average lifespan of an egg is 12 to 24 hours and a sperm up to 5 days. To determine the fertile and infertile periods, it is necessary to know the female reproductive cycle.

The sexual cycle of a woman is a period when a series of changes occur for the eventual fertilization and implantation of the embryo. It consists of two stages: pre-ovulatory or follicular, which begins on the first day of menstruation and lasts until ovulation, and post-ovulatory or luteal, which begins after ovulation until the next period. The luteal phase is the most stable phase of a woman's female menstrual cycle, but can range from 10 to 16 days depending on each woman. Thus, any change in the length of a woman's cycle is due to changes in the length of the preovulatory phase. The female reproductive cycle. The hypothalamus produces GnRH, which stimulates the secretion of FSH and LH from the pituitary gland. These two hormones are transported through the blood to reach the ovary containing the eggs. Usually one of them is fully ripe. As the egg grows, it releases estrogen. In the days leading up to ovulation, estrogen in the cervix produces a mucous secretion that causes characteristic sensations in the vulva, warning the woman that ovulation is approaching and, therefore, the days when you can become pregnant begin. Twelve hours after peak estrogen levels are reached, the pituitary gland organizes an LH surge. It takes 24 to 36 hours after ovulation for the egg to be ejected from the ovary and travel down the fallopian tube. Fertilization occurs in the outer third of the tube, where it originates new life person. The luteal egg turns yellow as estrogen production declines and progesterone production begins, reaching its peak in about eight days. If for some reason pregnancy does not occur, then in vitro fertilization can help. Here you can see the price of IVF in Moscow. All these phenomena also produce simultaneously a number of changes in the uterus to create three stages: 1) a phase of the menstrual cycle lasting about 4-5 days, in which the lining of the uterus, called the endometrium, "poured out" (corresponding to the beginning of the cycle). 2) or proliferative phase of the endometrium (thickening with variable duration). 3) secretory phase with higher rates of growth and vascularization. If there was no fertilization, the maturation of the egg begins again after the first phase of the menstrual cycle. The cervix acts as a biological valve, and its change occurs simultaneously with changes in the cervical mucus, since both respond to the same hormonal stimuli. The features that can be observed are openness, height, and tilt. Any change will mark the start of the fertile phase, which is characterized by an open, soft, high and straight cervix; the infertile phase corresponds to a closed, hard, low and tilted cervix. Body temperature in ovulatory cycles is biphasic, with a difference between the two phases of at least 0.2 degrees Celsius. In the preovulatory phase, the temperature is lower, and in the postovulatory phase it is higher, which lasts approximately 10-16 days after ovulation.

Unlike men, women are characterized only by sexual desire, sexual arousal and orgasm, which have their own specifics.

Sexual desire in women is represented by two components - the desire for affection and tenderness (erotic libido) and the desire for sexual intimacy. (sexual libido). Erotic libido, which is not inherent in the nature of men, is inherent in almost all women, because. only about 1% does not feel the need for caresses.

One of the early manifestations of sexual desire in girls is a purely platonic manifestation of interest in the opposite sex. The emergence and development of erotic libido is closely related to the increase in the level of sex hormones that occurs during puberty. This is confirmed by a direct relationship between the onset of menstruation and the occurrence of erotic libido, its delay with delayed puberty, and disappearance after severe hormonal ovarian insufficiency. At healthy women erotic libido persists throughout life, accompanying later sexual libido. Some women in their development may stop at the erotic stage of libido.

sexual libido, as a rule, it develops in women during regular sexual activity and often only after the onset of orgasm. Unlike the erotic, which depends on the hormonal saturation of the body, the development of sexual libido is determined by individual characteristics, sexual strength, social factors, and to a lesser extent, the concentration and level of sex hormones.

As a rule, sexual desire is more developed in cheerful and sociable women than in reserved women. It is believed that women's libido reaches its maximum around the age of 30, remaining at a stable level until the age of 55, and only then gradually decreases. A natural decrease in sexual desire is noted after 60 years, and therefore its increase at this age is almost always regarded as a pathological phenomenon. High level libido is retained much longer in multiparous women. However, people who have undergone pathological childbirth may experience an earlier decrease in libido. The same can be true for women who have painful periods.

Unlike men, most women have fluctuations in the strength of sexual desire. So, during the period of ovulation, i.e. the release of a mature egg from the ovary, relatively few women reach the maximum libido, although this is the time that is most favorable for conception. Before or immediately after menstruation, many women experience an increase in sexual desire. There are women who show a desire for sexual intimacy only on certain days of the menstrual cycle. A temporary decrease in libido occurs during illness, after mental and physical overwork, negative emotions.

No clear patterns in the change in the level of sexual behavior of women have been established. It is very individual and rather depends on her mental state.

certain part women may experience orgasm. During orgasm, excitement covers the internal organs and especially intensely the central nervous system. At this point, the heart rate can reach 180 beats per minute, the maximum blood pressure rises by 30-100 mm Hg. Art., respiratory rate - up to 40 breaths per minute.

At the moment of orgasm, voluntary control over the skeletal muscles largely disappears. There are involuntary, almost convulsive contractions of the abdominal, intercostal and facial muscles. General reactions of the internal organs and especially intense excitation of the central nervous system together lead to an increase in sexual sensations. At the same time, suppression of other types of sensitivity is often observed in women.

In contrast to the male peaked orgasm, the female orgasm proceeds in most cases in waves. There may be from 5 to 12 waves of orgastic sensations, and with each wave the intensity of pleasure increases. However, there are women with a single short peaked orgasm, which is still longer than that of men. In rare cases, there is a so-called protracted, undulating orgasm, lasting up to 1-3 or even 4 hours. There are also so-called multi-orgasmic women who are able to experience several orgasms during one sexual intercourse, and they experience each next one with greater intensity.

A woman's ability to orgasm to a certain extent depends on the duration of sexual life and sexual experience. While in men, orgasm is usually observed without any prior practice, then in most women it occurs after a more or less regular sexual life, and often after the first or second birth.

Not every woman and not every sexual intimacy is equally satisfying. So, some women can feel a sense of satisfaction without an orgasm. This does not cause them discomfort, because sexual intimacy is for them a symbol and physical expression of love. At the same time, there are women for whom the lack of a regular orgasm causes dissatisfaction and depression.

It is important that in a woman the psychological, conditioned reflex component of sexual desire not only affects the shades of sexual intercourse, as is most often the case with a man, but also plays a dominant role. A woman should see in a man, if not the embodiment of her ideal, then, in any case, a close, dear, respected person.

SEX CYCLE. PREGNANCY

sexual cycle

With the onset of puberty, periodic changes occur in the genital organs of the female human body and other mammals, called sex_cycle. Its regulation is carried out by the endocrine system. During each cycle, the maturation of one, and sometimes several, follicles containing maturing eggs occurs. The exit from the follicle of a mature, capable of fertilizing the egg is called ovulation. In parallel with the maturation of the follicle during the cycle, changes occur in the mucous membrane of the genital organs. Reaching a certain maximum level, these changes again undergo reverse development.

With all the diversity, the sexual cycle consists of several periods: pre-ovulation, ovulation, post-ovulation and rest period.

AT preovulatory period there is usually an increase in one of the follicles, while the epithelium of the uterus grows at the same time. Preovulatory changes occur due to an increase in the secretion of follicle-stimulating hormone by the adenohypophysis, which activates the intrasecretory function of the ovaries, resulting in increased estrogen production (Fig. 11). Under the influence of estrogens, the mucous membrane of the uterus and its glands grow, and contractions of the muscular layer of the uterus increase. Gradually increasing production of FSH accelerates the final maturation of the most mature of the follicles.

Rice. 11. Changes in the ovary and uterine mucosa during a normal menstrual cycle and a cycle that ended in pregnancy (scheme):

1 - the level of estrogen in the blood; 2 - the level of progesterone in the blood; 3 - follicle and corpus luteum during a normal menstrual cycle; 3a - exit from the follicle of the egg, which, remaining unfertilized, dies; 3b - development and then degeneration of the corpus luteum; 4 - follicle and corpus luteum during a cycle ending in pregnancy; 4a - exit from the follicle of the egg, which was then fertilized and embedded in the uterine mucosa; 4b - progressive development and preservation of the corpus luteum; 5 - changes in the mucous membrane of the uterus. The numbers below are the days of the menstrual cycle.

AT ovulation period ovulation occurs, i.e. rupture of the follicle and the exit from it of a mature, capable of fertilizing the egg. The biological reliability of the reproduction of the species in humans is provided by a huge number of eggs, reaching 300 thousand at the prepubertal age. However, in each ovulation period, out of 10-15 simultaneously growing follicles, only one fully matures and ovulates.

During ovulation, blood flow to the fallopian tubes (oviducts) increases, there is tension in their smooth muscle fibers, and

movement of cilia of epithelial cells lining the inside of the uterine rough. The ventral end of the fallopian tube opens and during ovulation can be in close contact with the ovary. This usually contributes after the rupture of the follicle to the entry of a mature egg and follicular fluid into the fallopian tube. Subsequent alternating contractions of the muscle fibers of the fallopian tube advance the mature egg towards the uterus. The passage of the egg through the tube to the uterus is about 3 days for a woman.

As the moment of ovulation approaches, and especially during the period of ovulation, the functions of the genital organs and the body as a whole are restructured. These changes occur under the influence of estrogens formed in the follicles. Changes in the hormonal function of the ovaries are reflected in basal temperature body (measured in the rectum). As a rule, before ovulation, the basal temperature fluctuates between 36.1-36.8°, and on the 1st or 2nd day after ovulation, it jumps up by 0.6-0.8°C, actually remaining at this level. before the onset of menstruation. To determine the period of ovulation, basal temperature is measured daily, in the morning after sleep at the same time, with the same medical thermometer.

The ovum released from the follicle can be fertilized. Fertilization occurs only if sexual intercourse occurs shortly before or shortly after ovulation. If fertilization does not occur, then the next period of the sexual cycle begins - post-ovulation. It occurs when a corpus luteum develops from the walls of an empty follicle in place of a burst follicle after ovulation. About 2 days after ovulation, the unfertilized egg dies.

The corpus luteum is a temporary endocrine gland that produces the hormone progesterone. Under the influence of progesterone, the release of follicle-stimulating and luteinizing hormones by the adenohypophysis decreases. A decrease in the concentration of LH in the blood leads to the fact that after a few days the corpus luteum begins to dissolve and the cavity of the former follicle is filled with connective tissue. At the same time, the production of progesterone decreases and then stops (Fig. 11). The decrease in FST leads to a decrease in the formation of estrogens in the ovaries. An unfertilized egg remains in the woman's genital tract for several days and then dies.

A decrease in the concentration of progesterone and estrogen in the blood causes change in blood circulation in the vessels of the uterine mucosa. Stagnation of blood in the vessels and slowing of blood flow leads to an increase in pressure inside the vessels, their walls are torn and bleeding begins. At the same time, tonic contractions of the uterine muscles occur,

leading to rejection of the uterine mucosa. The removal of parts of the mucous membrane from the body along with the blood is called menstruation. The average duration of menstruation is 2-3 days.

Following the post-ovulation period, the period of inter-ovulation begins. this rest. At this time, the follicles are relatively small, the uterine lining is thin and contains fewer blood capillaries. The rest period passes into the pre-ovulation period of the next sexual cycle. New follicles begin to develop in the ovaries and estrogen secretion increases again.

In women, the sexual cycle is called the menstrual cycle. It is considered to be from the first day of the onset of menstruation to the first day of the next menstruation. The duration of the menstrual cycle in women 18-45 years old, i.e. childbearing age, it also happens in the range from 21 to 35 days. The best is the menstrual cycle, lasting 28 days, because. at the same time, the most constant periodicity of cyclic changes is observed. Menstrual cycles begin at puberty, i.e. at 11-16 years old, and stop at 45-50 years old.

Changes in the concentration of gonadotropic and sex hormones in the blood plasma of a woman during the menstrual cycle can have a noticeable effect on her behavior. In some women, before menstruation, the excitability of the nervous system increases, irascibility and irritability increase.

Pregnancy

For pregnancy to occur, a mature egg, leaving the ovarian follicle and ending up in the abdominal cavity, must enter the fallopian tube, meet the sperm there, be fertilized, begin to divide and simultaneously move into the uterus, in order to then attach and penetrate into its mucous membrane. Only under these conditions is an opportunity created for the development of a new organism.

fertilization called the fusion of a sperm with an egg, leading to the formation of a zygote, which divides, grows, develops and gives rise to a new organism. During fertilization, the sperm nucleus merges with the egg nucleus, which leads to the unification of paternal and maternal genes and the restoration of the diploid set of chromosomes.

With a correct 28-day menstrual cycle, a mature egg leaves the ovary 12-14 days after the first day of the previous menstruation. Within about 3 days, the egg moves along the fallopian tube into the uterus, and along this path, it can be fertilized when it meets sperm. The best option is the one when the fertilization of the egg occurred in the upper sections of the fallopian tubes.

In some cases, spermatozoa pass the entire length of the fallopian tube and fertilize the egg immediately after ovulation, even before it enters the fallopian tube. In such cases, attachment of the embryo may occur to the ovary or abdominal wall, leading to the development of an ectopic pregnancy. An ectopic pregnancy is very dangerous for a woman, because. She definitely needs emergency surgery.

The lifespan of the ovum released from the follicle and the duration of the functioning of spermatozoa in the female genital tract are determined in the menstrual cycle period value, during which fertilization is possible. With a 28-day cycle and ovulation on the 14th day after the first day of the previous menstruation, fertilization can occur from the 12th to the 16th day. However, one should take into account possible fluctuations in the timing of ovulation, which can be caused by physical and mental stress, fluctuations in ambient temperature, moving to another climatic zone, etc. Usually, the shift in the ovulation period does not exceed 3 days closer to the beginning or to the end of the menstrual cycle. Therefore, fertilization can occur from the 9th day to the 19th day of the menstrual cycle. This period has a different duration with a different length of the menstrual cycle or with irregular menstruation.

After fertilization and formation on the second day of the embryo over the next three days, it must necessarily move through the fallopian tube into the uterus and gain a foothold in its mucous membrane. The movement of the embryo is provided by wave-like contractions of the fallopian tube and the movements of the cilia of the epithelium of its mucous membrane. If the movement of the embryo slows down due to the narrowness or poor patency of the fallopian tube, then it will remain in it. This will lead to the death of the embryo or the onset of a tubal pregnancy, in which the embryo dies at a later date. A tubal pregnancy requires urgent surgery.

If the embryo enters the uterus too quickly, as well as too late, it will not be able to penetrate and gain a foothold in the uterine mucosa and pregnancy will not occur. In some cases, even the timely entry of the embryo into the uterus does not guarantee the normal course of pregnancy. For example, if the embryo attaches to scars formed in the area of ​​the uterine mucosa after abortions or on a node that has arisen after inflammatory diseases uterus, then the conditions for its nutrition and further development will be extremely unfavorable. In such cases, there is often a threat of spontaneous miscarriage.

After the embryo has successfully penetrated into the mucous membrane of the uterine cavity, which has loosened by this time, the cells of the outer layer of the embryo begin to produce a specific hormone. This hormone

stimulates the production of other hormones that contribute to the preservation and development of pregnancy. If a woman does not have another menstruation, then we can hope that the introduction of the embryo into the uterine mucosa has occurred and the pregnancy develops. Doctors can see the fetus as early as 4 weeks of age using an ultrasound machine. Yet earlier pregnancy can be detected by biochemical research.

From the 7th week of pregnancy, the so-called baby place begins to form, or placenta. Doctors consider the period of 7 weeks to be the most critical period of pregnancy, because. it is at this time that its premature interruption most often occurs. Reason for interruption hormonal imbalance in a woman's body. The placenta secretes a complex complex of hormones and other biologically active substances into the mother's body, among which the hormone progesterone is of particular importance, which contributes to the preservation and development of pregnancy. Before the formation of the placenta, progesterone is produced only in the corpus luteum, which formed at the site of the burst follicle after the release of the egg from it. Hormonal imbalance can occur if it is by the 7th week that the function of the corpus luteum begins to fade significantly, and the formation of the placenta, which compensates for the resulting progesterone deficiency, is late. If left untreated, this hormonal imbalance can cause a miscarriage.

With normal development, a woman's pregnancy lasts an average of 280 days, counting from the first day of the last menstruation. Pregnancy is divided into three periods - trimester, each of which has its own characteristics.

First trimester(1-3 months) is the period of maximum vulnerability. At this time, in addition to the introduction of the embryo into the uterine mucosa, complex processes of laying the internal organs of the fetus occur. The first trimester is especially large danger of alcohol for the fetus. Alcohol disrupts the formation of internal organs, causing various deformities. The brain suffers the most. Brain damage manifests itself after the birth of a child in a lag in mental development up to progressive dementia. Every third child of drinking mothers has a congenital heart disease, deformities of the hands and feet, malformations of the kidneys, urinary tract of the genital organs are quite common.

Alcohol also complicates the course of pregnancy. Pregnant women who drink alcohol are much more likely to experience spontaneous miscarriages, premature births of premature and immature fetuses. They have toxicosis of pregnancy and labor is complicated.

On the Smoking is also strictly prohibited. For the fetus, not only smoking of the mother is dangerous, but also her stay in a smoky room, because. carbon monoxide, nicotine and other toxic substances contained in tobacco smoke impair the supply of oxygen to the fetus and have a toxic effect on it.

The placenta, which serves as a barrier between the organs of the mother and fetus, is unable to protect it from many chemicals, drugs and viruses. Therefore, pregnant women should not work in chemically hazardous industries. They should take medicine carefully and only as prescribed by a doctor, and should also avoid contact with patients with influenza and other viral infections.

Second trimester(4 - 6 months of pregnancy) in healthy women proceeds mostly calmly. The period of physical and psychological adaptation gradually passes, the reactions of the nervous system are balanced, salivation, nausea disappear, appetite improves. The body of a woman adapts to a new state.

In an uncomplicated pregnancy, as in the first trimester, daily morning exercises, excluding jumps, sudden movements and turns. In the second trimester, a complex of special gymnastics is recommended, which is selected by the doctor of the antenatal clinic. Walks in the fresh air are very useful, helping to improve the supply of oxygen to the fetus. You can walk up to two hours in a row and be sure to 30 minutes before bedtime. Very useful are air baths and daily showers, which improve skin respiration. The nutrition of a pregnant woman should be complete with an increase in the amount of protein, vitamins and mineral salts.

Starting from the 5th month, a pregnant woman begins to increase blood pressure, so it is important to monitor its dynamics. The second trimester is very important for women who have had previous pregnancies interrupted during this period. They need a sparing regime, and in some cases - treatment in a hospital.

third trimester pregnancy starts from the 28th week. In this trimester, the woman's body is under great stress. The intensive growth of the fetus places increasing demands on liver and kidneys mother. Work is often difficult hearts, because it begins to be crowded by the dome of the diaphragm, lifted by the fetus. It also complicates the work of the digestive system. Sometimes the contents of the stomach are thrown into the esophagus and there is a feeling of heartburn, a bitter taste in the mouth. With an increased load, the venous system functions, in which blood pressure rises.

At this time, it becomes even more important to maintain the correct regimen. First of all, it is necessary to make adjustments to

diet and completely abandon spicy, salty foods, spices and smoked foods. These products complicate the work of the kidneys, contribute to fluid retention in the body and can provoke the development of the so-called late toxicosis of pregnancy, which is extremely dangerous for the health of the mother and child.

In the third trimester, the first courses should be only vegetarian. From fats, butter and vegetable oil are recommended, vegetables - raw, boiled and stewed, bread - preferably from wholemeal flour. It is very important to follow the increase body weight, which should not exceed 500 g per week, and for persons who are inclined to be overweight - 300 g per week. The normal course of pregnancy in this period is evidenced by normal blood pressure, the absence of edema and normal urine tests. However, if it becomes difficult to remove the ring from the finger or the shoes become tight, you should consult a doctor.

In the third trimester, it is necessary to observe the correct daily routine. It is rational, at the same time to eat, be sure to walk in the fresh air. The duration of walking should be increased, but you should walk more slowly and sit down more often. Women who, on the recommendation of a doctor, were engaged in special gymnastics can continue it. However, the pace of the exercises should be slowed down and some of them, and after the 36th week - almost everything, should be performed only while sitting and lying down.

In order for a woman to rest and get stronger before childbirth, she is given prenatal leave. At this time, she can do ordinary, but not time-consuming household chores. Work with pesticides and household chemicals is strictly prohibited. A normal or even complicated pregnancy, with proper medical supervision, usually ends with the birth of a healthy, viable child.

LITERATURE

1. General course of human and animal physiology. - Ed. HELL. Nozdrachev. - M .: Higher school, 1991.

2. Human physiology. T. 4. - Ed. R. Schmidt and G. Thevs. – M.: Mir, 1986.

3. Human physiology. - Ed. G.I. Kositsky. – M.: Medicine, 1985.

4. Leont'eva N.N., Marinova K.V. Anatomy and physiology of the child's body. – M.: Enlightenment, 1986.

5. Drzhevetskaya I.A. Endocrine system of a growing organism. – M.:
High School, 1987.

6. Shepherd G. Neurobiology. T. 2. - M .: Mir, 1987.

7. Bloom F., Leyzerson L., Hofstadter L. Brain, mind and behavior. -
M.: Mir, 1988.

8. Danilova N.N. Psychophysiology. – M.: Aspect Press, 2000.

9. Shostak V.I., Lytaev S.A. Physiology of mental activity
person. - St. Petersburg: Dean, 1999.

Ministry of Education and Science of the Russian Federation

Non-state educational institution of higher

vocational education

Samara Medical Institute "ReaViZ"

In the discipline "Physiology with the basics of anatomy"

"The female sexual cycle. Fertilization. Hormonal changes and the role of placental hormones in the body

Performed:

Bokovaya Yu.V.

Specialty "Pharmacy"

Group 171

Checked:

Gerasimova O.V.

Samara - 2011

1. Introduction………………………………………………………………..…3

1. Female sexual cycle………………………………………………………..4

1. Fertilization…………………………………………………………………………………………..6

1. Hormonal changes and the role of placental hormones in the body…………………………………………………………………....9

1. Literature used………………… ……………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….

Introduction

The ability to reproduce oneself depends on both general health and the condition of the reproductive organs. Reproductive organs - the sexual sphere, neuroendocrine, vascular, immune systems - provide the possibility of conception, the development of pregnancy and the birth of offspring. In this case, the body experiences significant stress on all vital organs. During pregnancy, the nervous, immune, endocrine systems, heart, kidneys, and liver carry a double load. There is a redistribution of their activities from the body's own needs to additional costs - ensuring the vital activity of the new complex "mother - placenta - fetus". If general health, including the health of the reproductive organs, is able to withstand the “test” of pregnancy, then this new condition can be classified as physiological. But even under this condition, pregnancy should be considered as an additional burden on the body. Therefore, there is a need for timely and competent preparation for a new life stage and its implementation.

female sexual cycle

The sexual cycle of the female body lasts one lunar month (28 days) and is characterized by cyclic changes throughout the body, most pronounced in the genital organs - the ovary and uterus. A 28-day cycle is diagnosed in 60% of women, a 21-day cycle in 28%, a 30-35-day cycle in 10-12%.

The “biological clock of the sexual cycle”, located in the hypothalamic region of the diencephalon (the main part of the forebrain), determines the rhythm of the processes in the woman's body through the pituitary-ovaries-uterus.
The menstrual cycle of a woman is two-phase: in the first phase and the ovary, the growth and development of follicles producing estrogen, which cause regeneration and proliferation of the endometrial epithelium, occurs; in the second phase, the corpus luteum warms up in the ovary, producing progesterone, which causes secretory transformations of the endometrium.

The menstrual cycle is the period of time from the first day of one to the first day of the next menstruation. The length of the menstrual cycle varies from woman to woman, but the average ranges from 21 to 35 days. It is important that the duration of a woman's menstrual cycle is always approximately the same (± 3 days), that is, that the menstrual cycle is regular.

Menstruation is a blood discharge from a woman's genital tract, the first day of which marks the beginning of a new menstrual cycle. The first menstruation (menarche) usually occurs at 12-14 years of age. Normal menstruation lasts 3-7 days, and 50-150 ml of blood is lost.

Changes that occur in a woman's body during the menstrual cycle.

In the cervical canal, which connects the uterine cavity and the vagina, there are special glands that produce mucus. Most of the time, this mucus is thick and forms the so-called mucous plug. It is a physiological barrier and makes it difficult for spermatozoa to enter the uterine cavity, as well as bacteria and viruses, which often stick to their surface.

Twice during the menstrual cycle - during ovulation and menstruation - the mucus becomes more liquid and allows bacteria and viruses to enter the uterine cavity much easier, which can lead to the development of inflammatory diseases of the female genital organs. During the ovulatory menstrual cycle, anatomical and functional cyclic changes in the glands, vessels and stroma of the endometrium occur.

In the first phase - the proliferation phase - estrogen production dominates, supporting the growth of the endometrium and an increase in progesterone receptors in it. In the second phase - the phase of secretion - the production of progesterone by the corpus luteum also dominates. When the corpus luteum disappears, estrogen and progesterone levels fall, and the functional layer of the endometrium is shed in the form of menstrual bleeding.

It is known that human ovarian steroid hormones are vasoactive, that is, they are able to have an effect on blood vessels. The basal arterioles (small terminal branches of the arteries that pass into the capillaries) of the endometrium are relatively immune to steroid hormones, while the vessels of the functional layer are altered by the action of steroid hormones.

Estrogens cause a decrease in uterine vascular resistance and, as a result, an increase in uterine blood flow. In the presence of progesterone, this effect disappears.

Simultaneously with the formation of ovarian function during puberty, thyrotropic and adrenocorticotropic influences on the development of female genital organs increase. This combines the effect of hormones thyroid gland and the cortical layer of the adrenal glands, which share mechanisms of central regulation with the ovaries.

The reproductive system, like the respiratory and digestive systems, is functional. This is an integral formation, including central and peripheral links, working on the principle of feedback. The reproductive system ensures reproduction, that is, the existence of the species. By the age of 45, the reproductive system fades, and at the age of 55, the hormonal function of the reproductive system begins to fade.

Fertilization

Scientists call the ability to reproduce offspring the Latin word "fertility" (fertilis means "fertile, fruitful"). For this process to take place, certain conditions are required. If at least one link in this chain falls out, pregnancy either does not occur, or a congenital pathology of the fetus occurs. The necessary conditions for pregnancy are:

1) maturation of the follicle in the ovary, its rupture, the release of the egg (ovulation) and the formation of the corpus luteum 1 follicle in place;
2) the ability of spermatozoa to penetrate the uterus, fallopian tubes and fertilize the egg;
3) free passage of the egg and embryo through the fallopian tube into the uterine cavity;
4) the readiness of the uterus to implant (implant) an embryo into itself.
A favorable combination of the above circumstances with the full health of the spouses, with regular sexual activity in one menstrual cycle, contributes to the occurrence of pregnancy in approximately 20% of cases.

Egg. The "reserve" of eggs is already determined at the birth of a girl; it is about 400 thousand. During one menstrual cycle (from the first day of one menstruation to the first day of the next), one egg usually matures in one of the ovaries.
After the release of the egg from the ovary (ovulation), which occurs around the 14th day of the menstrual cycle, a corpus luteum forms in the ovary. It secretes hormones (progestins) that prepare the uterus to receive the fetus, and in the event of pregnancy, keep the pregnancy. The role of progestins is especially great in the first trimester of pregnancy. From the ovary, the egg enters the abdominal cavity. Next to each ovary is the oviduct - the fallopian (uterine) tube, into the funnel of which the egg must enter due to the movements of the cilia of the fallopian tube, which "capture" the egg (it itself does not have the ability to move). In 6-7 days, the egg, due to contractions of the fallopian tube, must overcome the distance from the funnel to the uterus of 30-35 cm. Under ideal conditions, fertilization occurs while the egg is in the upper third of the oviduct.
After ovulation, the egg remains viable for approximately 24 hours.

spermatozoa. Spermatozoa are formed and mature in the seminiferous tubules of the male sex gland - the testes. The process of their maturation lasts an average of 74 days. A mature normal human spermatozoon consists of a head, neck, body and tail, or flagellum, which ends in a thin terminal filament. The total length of the spermatozoon is about 50-60 microns (head - 5-6 microns, neck and body - 6-7 microns and tail - 40-50 microns). Thanks to the “beating” of the tail, the spermatozoon is able to move. Interestingly, the size of the egg is much larger than the size of the sperm: it is 0.1 mm. Ripe spermatozoa exit the seminiferous tubules into the vas deferens of the male gonads, where they can retain their fertilizing ability for a long time. At this time, they are motionless - they acquire the ability to advance only during ejaculation.
In the genital tract of a woman, spermatozoa retain the ability to move within 3-4 days, but they can only fertilize an egg during the day. There is an assumption that spermatozoa "recognize" the egg by smell - for example, receptors similar to receptors located in the nose were found on the surface of male germ cells.

Fertilization is the fusion of a male reproductive cell (sperm) with a female (ovum), leading to the formation of a zygote (a new single-celled organism). The biological meaning of fertilization is the union of paternal and maternal genes. Sex cells contain the so-called haploid (half) set of chromosomes; when they are combined, a zygote with a diploid (complete) set of chromosomes is formed.
The seminal fluid that enters the vagina usually contains 60 to 150 million spermatozoa. The speed of movement of spermatozoa is 2-3 mm per minute. Thus, already 1-2 minutes after sexual intercourse, spermatozoa reach the uterus, and in 2-3 hours in the female body they can travel 25-35 cm and reach the end sections of the fallopian tubes. After ejaculation (ejaculation), spermatozoa quickly rise through the genital tract due to contractions of the uterus and fallopian tubes; these are the so-called peristaltic movements, which are similar to bowel contractions. Intrinsic sperm motility becomes important in the later stages. Sperm, which consists of a biologically active liquid part and spermatozoa, has a slightly alkaline reaction: spermatozoa are capable of active movement only in such an environment. If the environment in the vagina is acidic, then the seminal fluid can lower its acidity to the desired level. No more than a few hundred spermatozoa reach the egg: at all stages of their movement, the least viable ones die and are removed. This happens due to the mechanisms of natural selection, that is, the goals (eggs) are most often reached by the most complete (without structural defects) spermatozoa.
During the movement of spermatozoa through the fallopian tube, capacitation occurs (a series of changes due to which spermatozoa acquire fertilizing ability). During capacitation, special substances that prevent fertilization are removed from the surface of spermatozoa. (Before the process of capitation, these substances perform a protective function.) The beating of flagella changes, becomes much faster, which causes overactive sperm motility. When capacitation is over and the spermatozoa have reached the site where fertilization is to take place, they undergo the process of acrosome activation. With the help of the acrosome, which is located on the head of the spermatozoa and contains the enzymes necessary to penetrate the female germ cell, they destroy the egg cell membrane in the area in front of the spermatozoon, due to which the male and female germ cells merge. As soon as the first sperm begins to merge with the egg, its properties immediately change: it becomes immune to other sperm.
After the embryo enters the uterine cavity on the 6-7th day of development, it "hatches" from the shell, and then the implantation process begins - the half-millimeter embryo is attached to the wall of the uterus and plunges into it entirely in less than two days.
Thus begins the long journey of "life before birth" of 9 months.

Hormonal changes and the role of placental hormones in the body

During intrauterine life, numerous signals come from the fetus, which are perceived by the mother. Therefore, the work of the mother's body is subject at this time to one main goal - to ensure the proper development of the baby.

The most important role in the regulation of metabolism, vital processes and growth of the body is played by special substances - hormones. The endocrine system is a system of glands that produce hormones and release them into the blood. These glands, called the glands of internal secretion, are located in different parts of the body, but are closely interconnected in their "type of activity".

The complexity of changes in the hormonal system of a pregnant woman is determined by the fact that the hormones of the placenta, as well as the fetus, have a great influence on the activity of the endocrine glands of the mother.

The pituitary gland increases during pregnancy by 2-3 times. This once again confirms the fact that during pregnancy, the endocrine system works to provide all body systems. The pituitary gland, as the "conductor" of the endocrine system, increases in size and begins to work more intensively. First of all, this is expressed in a sharp decrease in the production of hormones that regulate the work of the gonads (follicle-stimulating (FSH) and luteinizing (LH) hormones). This is accompanied by a natural inhibition of egg maturation in the ovaries; the process of ovulation - the release of eggs into the abdominal cavity - also stops. The production of prolactin, which is responsible for the development of lactation, during pregnancy, on the contrary, increases and by the time of delivery it increases by 5-10 times compared with the indicators characteristic of non-pregnant women. Since the increase in prolactin production begins in the first trimester of pregnancy, changes in the mammary glands appear already during this period.

In expectant mothers, there is an increase in the production of thyroid-stimulating hormone (TSH), which regulates the function of the thyroid gland.

During pregnancy, the production of adrenocorticotropic hormone (ACTH), which regulates the production of adrenal hormones, also increases.

The concentration of oxytocin formed in the pituitary gland increases at the end of pregnancy and during childbirth, which is one of the triggers of labor activity. The main property of oxytocin is the ability to cause strong contractions of the muscles of the uterus, especially in a pregnant woman. There is a synthetic analogue of this hormone, which is administered to a woman with the development of weakness in labor. Oxytocin also promotes the release of milk from the mammary glands.

The reproductive function of women is carried out primarily due to the activity of the ovaries and uterus, since the egg matures in the ovaries, and in the uterus, under the influence of hormones secreted by the ovaries, changes occur in preparation for the perception of a fertilized fetal egg. 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, or childbearing, period is preceded by the following stages of a woman's life: intrauterine; newborns (up to 1 year); childhood (up to 8-10 years); prepubertal and pubertal age (up to 17-18 years). The reproductive period passes into menopause, in which there are premenopause, menopause and postmenopause.

The menstrual cycle is one of the manifestations of complex biological processes in a woman's body. The menstrual cycle is characterized by cyclic changes in all parts of the reproductive system, the external manifestation of which is menstruation.

Menstruation is bloody discharge from the female genital tract, periodically resulting from the rejection of the functional layer of the endometrium at the end of a two-phase menstrual cycle. The first menstruation (menarhe) is observed at the age of 10-12 years, but within 1 - 1.5 years after this, menstruation may be irregular, and then a regular menstrual cycle is established.

The first day of menstruation is conventionally taken as the first day of the menstrual cycle. Therefore, the duration of the cycle is the time between the first days of the next two periods. For 60% of women, the average length of the menstrual cycle is 28 days, with fluctuations from 21 to 35 days. The amount of blood loss on menstrual days is 40-60 ml, an average of 50 ml. The duration of a normal menstruation is 2 to 7 days.

Ovaries. During the menstrual cycle, follicles grow in the ovaries and the egg 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 uterine mucosa, which can accept a fertilized egg.

Sex hormones (estrogens, progesterone, androgens) are steroids, granulosa cells of the follicle, cells of the inner and outer layers take part in their formation. Sex hormones synthesized by the ovaries affect target tissues and organs. These include the genital organs, primarily the uterus, mammary glands, spongy bone, brain, endothelium and vascular smooth muscle cells, myocardium, skin and its appendages (hair follicles and sebaceous glands), etc. Direct contact and specific binding of hormones to target cell is the result of its interaction with the appropriate receptors.

The biological effect is given by free (unbound) fractions of estradiol and testosterone (1%). The bulk of ovarian hormones (99%) is in a bound state. Transport is carried out by special proteins - steroid-binding globulins and non-specific transport systems - albumins and erythrocytes.

A - primordial follicle; b - preantral follicle; c - antral follicle; d - preovulatory follicle: 1 - oocyte, 2 - granulosa cells (granular zone), 3 - theca cells, 4 - basement membrane.

Estrogen hormones contribute to the formation of genital organs, the development of secondary sexual characteristics during puberty. Androgens affect the appearance of pubic hair and in the armpits. Progesterone controls the secretory phase of the menstrual cycle and prepares the endometrium for implantation. Sex hormones play an important role in the development of pregnancy and childbirth.

Cyclic changes in the ovaries include three main processes:

1. Growth of follicles and formation of a dominant follicle.

2. Ovulation.

3. Formation, development and regression of the corpus luteum.

At the birth of a girl, there are 2 million follicles in the ovary, 99% of which undergo atresia throughout life. The process of atresia refers to the reverse development of follicles at one of the stages of its development. By the time of menarche, the ovary contains about 200-400 thousand follicles, of which 300-400 mature to the stage of ovulation.

It is customary to distinguish the following main stages of follicle development (Fig. 2.12): primordial follicle, preantral follicle, antral follicle, preovulatory follicle.

The primordial follicle consists of an immature ovum, which is located in the follicular and granular (granular) epithelium. Outside, the follicle is surrounded by a connective sheath (theca cells). During each menstrual cycle, 3 to 30 primordial follicles begin to grow and form preantral, or primary, follicles.

preantral follicle. With the onset of growth, the primordial follicle progresses to the preantral stage, and the oocyte enlarges and is surrounded by a membrane called the zona pellucida. The granulosa epithelial cells proliferate, and the theca layer is formed from the surrounding stroma. This growth is characterized by an increase in estrogen production. The cells of the granular layer of the preantral follicle are capable of synthesizing three classes of steroids, with much more estrogen being synthesized than androgens and progesterone.

Antral, or secondary, f o l l and k u l. It is characterized by further growth: the number of cells in the granulosa layer that produces follicular fluid increases. Follicular fluid accumulates in the intercellular space of the granular layer and forms cavities. During this period of folliculogenesis (8-9th day of the menstrual cycle), the synthesis of sex steroid hormones, estrogens and androgens is noted.

According to the modern theory of the synthesis of sex hormones, androgens - androstenedione and testosterone are synthesized in the theca cells. Then the androgens enter the cells of the granulosa layer, where they aromatize into estrogens.

dominant follicle. As a rule, one such 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 and receptors for FSH, LH. The dominant follicle has a richly vascularized theca layer. Along with the growth and development of the dominant preovulatory follicle in the ovaries, the process of atresia of the remaining (90%) growing follicles occurs in parallel.

The dominant follicle in the first days of the menstrual cycle has a diameter of 2 mm, which within 14 days by the time of ovulation increases to an average of 21 mm. During this time, there is a 100-fold increase in the volume of follicular fluid. It sharply increases the content of estradiol and FSH, and growth factors are also determined.

Ovulation is the rupture of the preovular dominant (tertiary) follicle and the release of an egg from it. By the time of ovulation, the oocyte undergoes meiosis. Ovulation is accompanied by bleeding from broken capillaries surrounding the theca cells. It is believed that ovulation occurs 24-36 hours after the formation of the preovulatory peak of estradiol. The thinning and rupture of the wall of the preovulatory follicle occur under the influence of the collagenase enzyme. A certain role is also played by prostaglandins F2a and E2 contained in the follicular fluid; proteolytic enzymes produced in granulosa cells; oxytocin and relaxin.

After the release of the egg, the resulting capillaries quickly grow into the cavity of the follicle. Granulosa cells undergo luteinization: the volume of the cytoplasm increases in them and lipid inclusions are formed. LH, interacting with protein receptors of granulosa cells, stimulates the process of their luteinization. This process leads to the formation of the corpus luteum.

The corpus luteum is a transient endocrine gland that functions for 14 days, regardless of the length of the menstrual cycle. In the absence of pregnancy, the corpus luteum regresses.

Thus, the main female sex steroid hormones - estradiol and progesterone, as well as androgens are synthesized in the ovary.

In phase I of the menstrual cycle, which lasts from the first day of menstruation to the moment of ovulation, the body is under the influence of estrogen, and in phase II (from ovulation to the onset of menstruation), progesterone, secreted by the cells of the corpus luteum, joins estrogen. The first phase of the menstrual cycle is also called follicular, or follicular, the second phase of the cycle is called luteal.

During the menstrual cycle, two peaks of estradiol content are noted in the peripheral blood: the first is a pronounced preovulatory cycle, and the second, less pronounced, in the middle of the second phase of the menstrual cycle. After ovulation in the second phase of the cycle, progesterone is the main one, the maximum amount of which is synthesized on the 4-7th day after ovulation (Fig. 2.13).

The cyclic secretion of hormones in the ovary determines changes in the lining of the uterus.

Cyclic changes in the lining of the uterus (endometrium). The endometrium consists of the following layers.

1. The basal layer, which is not rejected during menstruation. From its cells during the menstrual cycle, a layer of the endometrium is formed.

2. The superficial layer, consisting of compact epithelial cells that line the uterine cavity.

3. Intermediate, or spongy, layer.

The last two layers make up the functional layer, which undergoes major cyclical changes during the menstrual cycle and is shed during menstruation.

In phase I of the menstrual cycle, the endometrium is a thin layer consisting of glands and stroma. The following main phases of endometrial changes during the cycle are distinguished:

1) proliferation phase;

2) secretion phase;

3) menstruation.

proliferation phase. As estradiol secretion increases by growing ovarian follicles, the endometrium undergoes proliferative changes. There is an active reproduction of the cells of the basal layer. A new superficial loose layer with elongated tubular glands is formed. This layer quickly thickens 4-5 times. Tubular glands, lined with columnar epithelium, elongate.

secretion phase. In the luteal phase of the ovarian cycle, under the influence of progesterone, the tortuosity of the glands increases, and their lumen gradually expands. Stroma cells, increasing in volume, approach each other. The secretion of the glands is increased. In the lumen of the glands, a copious amount of secretion is found. Depending on the intensity of secretion, the glands either remain highly convoluted or acquire a sawtooth shape. There is increased vascularization of the stroma. There are early, middle and late phases of secretion.

Menstruation. This is the rejection of the functional layer of the endometrium. The subtle mechanisms underlying the occurrence and process of menstruation are unknown. It has been established that the endocrine basis of the onset of menstruation is a pronounced decrease in the levels of progesterone and estradiol due to regression of the corpus luteum.

There are the following main local mechanisms involved in menstruation:

1) change in the tone of spiral arterioles;

2) changes in the mechanisms of hemostasis in the uterus;

3) changes in the lysosomal function of endometrial cells;

4) regeneration of the endometrium.

It has been established that the onset of menstruation is preceded by intense narrowing of the spiral arterioles, leading to ischemia and desquamation of the endometrium.

During the menstrual cycle, the content of lysosomes in endometrial cells changes. Lysosomes contain enzymes, some of which are involved in the synthesis of prostaglandins. In response to a decrease in progesterone levels, the secretion of these enzymes increases.

Regeneration of the endometrium is observed from the very beginning of menstruation. By the end of the 24th hour of menstruation, 2/3 of the functional layer of the endometrium is rejected. The basal layer contains stromal epithelial cells, which are the basis for endometrial regeneration, which is usually completed by the 5th day of the cycle. In parallel, angiogenesis is completed with the restoration of the integrity of torn arterioles, veins and capillaries.

Changes in the ovaries and uterus occur under the influence of the two-phase activity of the systems regulating menstrual function: the cerebral cortex, hypothalamus, and pituitary gland. Thus, 5 main links of the female reproductive system are distinguished: the cerebral cortex, hypothalamus, pituitary gland, ovary, uterus (Fig. 2.14). The interconnection of all parts of the reproductive system is ensured by the presence in them of receptors for both sex and gonadotropic hormones.

The role of the CNS in regulating the function of the reproductive system has long been known. This was evidenced by ovulation disorders under various acute and chronic stresses, menstrual cycle disturbances with changes in climatic and geographical zones, the rhythm of work; the cessation of menstruation in wartime conditions is well known. In mentally unbalanced women who passionately desire to have a child, menstruation can also stop.

Specific receptors for estrogens, progesterone and androgens have been identified in the cerebral cortex and extrahypothalamic cerebral structures (limbic system, hippocampus, amygdala, etc.). In these structures, the synthesis, release and metabolism of neuropeptides, neurotransmitters and their receptors take place, which in turn selectively affect the synthesis and release of the releasing hormone of the hypothalamus.

In conjunction with sex steroids, neurotransmitters function: norepinephrine, dopamine, gamma-aminobutyric acid, acetylcholine, serotonin and melatonin. Norepinephrine stimulates the release of gonadotropin-releasing hormone (GTRH) from the neurons of the anterior hypothalamus. Dopamine and serotonin decrease the frequency and amplitude of GTHR production during various phases of the menstrual cycle.

Neuropeptides (endogenous opioid peptides, neuropeptide Y, corticotropin-releasing factor and galanin) also affect the function of the reproductive system, and hence the function of the hypothalamus. Three types of endogenous opioid peptides (endorphins, enkephalins, and dynorphins) are able to bind to opiate receptors in the brain. Endogenous opioid peptides (EOPs) modulate the effect of sex hormones on the content of GTRH by a feedback mechanism, block the secretion of gonadotropic hormones by the pituitary gland, especially LH, by blocking the secretion of GTRH in the hypothalamus.

The interaction of neurotransmitters and neuropeptides provides in the body of a woman reproductive age regular ovulatory cycles, affecting the synthesis and release of GTHR by the hypothalamus.

The hypothalamus contains peptidergic neurons that secrete stimulating (liberins) and blocking (statins) neurohormones - neurosecretion. These cells have the properties of both neurons and endocrine cells, and respond both to signals (hormones) from the bloodstream and to neurotransmitters and brain neuropeptides. Neurohormones are synthesized in the ribosomes of the cytoplasm of the neuron, and then transported along the axons to the terminals.

Gonadotropin-releasing hormone (liberin) is a neurohormone that regulates the gonadotropic function of the pituitary gland, where FSH and LH are synthesized. The releasing hormone LH (Luliberin) has been isolated, synthesized and described in detail. To date, it has not been possible to isolate and synthesize releasing-follicle-stimulating hormone, or folliberin.

GnRH secretion has a pulsating character: peaks of increased secretion of the hormone lasting several minutes are replaced by 1-3-hour intervals of relatively low secretory activity. The frequency and amplitude of GnRH secretion is regulated by estrogen levels.

The neurohormone that controls the secretion of prolactin by the adenohypophysis is called the prolactin inhibitory hormone (factor), or dopamine.

An important link in the reproductive system is the anterior pituitary - adenohypophysis, which secretes gonadotropic hormones, follicle-stimulating hormone (FSH, follitropin), luteinizing hormone (LH, lutropin) and prolactin (Prl), which regulate the function of the ovaries and mammary glands. All three hormones are protein substances (polypeptides). The target gland of gonadotropic hormones is the ovary.

Thyrotropic (TSH) and adrenocorticotropic (ACTH) hormones, as well as growth hormone, are also synthesized in the anterior pituitary gland.

FSH stimulates the growth and maturation of ovarian follicles, promotes the formation of FSH and LH receptors on the surface of ovarian granulosa cells, increases the content of aromatase in the maturing follicle and, by stimulating aromatization processes, promotes the conversion of androgens into estrogens, stimulates the production of inhibin, activin and insulin-like growth factor-1, which play an inhibitory and stimulating role in the growth of follicles.

L G stimulates:

The formation of androgens in theca cells;

Ovulation together with FSH;

Remodeling of granulosa cells during luteinization;

Synthesis of progesterone in the corpus luteum.

Prolactin stimulates the growth of the mammary glands and lactation, controls the secretion of progesterone by the corpus luteum by activating the formation of LH receptors in them.

Rice. 2.14.

RGLG - releasing hormones; OK - oxytocin; Prl - prolactin; FSH - follicle-stimulating hormone; P - progesterone; E - estrogens; A - androgens; P - relaxin; I - inhibin; LH is a luteinizing hormone.

Rice. 2.15.

I - gonadotropic regulation of ovarian function: PDH - anterior pituitary gland, other designations are the same as in Fig. 2.14; II - content in the endometrium of receptors for estradiol - RE (1,2,3; solid line) and progesterone - RP (2,4,6; dotted line); III - cyclic changes in the endometrium; IV - cytology of the epithelium of the vagina; V - basal temperature; VI - cervical mucus tension.

The synthesis of prolactin by the adenohypophysis is under the tonic blocking control of dopamine, or the prolactin inhibitory factor. Inhibition of prolactin synthesis stops during pregnancy and lactation. The main stimulator of prolactin synthesis is thyroliberin, synthesized in the hypothalamus.

Cyclic changes in the hypothalamic-pituitary system and in the ovaries are interrelated and are modeled as feedback.

There are the following types of feedback:

1) "long loop" of feedback - between ovarian hormones and nuclei of the hypothalamus; between ovarian hormones and the pituitary gland;

2) "short loop" - between the anterior pituitary gland and the hypothalamus;

3) "ultrashort loop" - between GTRH and nerve cells of the hypothalamus.

The relationship of all these structures is determined by the presence of receptors for sex hormones in them.

A woman of reproductive age has both negative and positive feedback between the ovaries and the hypothalamic-pituitary system. An example of negative feedback is the increased release of LH from the anterior pituitary gland in response to low estradiol levels in the early follicular phase of the cycle. An example of positive feedback is the release of LH in response to the ovulatory maximum of estradiol in the blood.

The state of the reproductive system can be judged by the assessment of functional diagnostic tests: basal temperature, pupil symptom and karyopyknotic index (Fig. 2.15).

Basal temperature is measured in the rectum in the morning, before getting out of bed. During the ovulatory menstrual cycle, the basal temperature rises in the luteal phase of the cycle by 0.4-0.6 ° C and lasts throughout the second phase (Fig. 2.16). On the day of menstruation or the day before it, the basal temperature decreases. Increase during pregnancy basal body temperature due to the excitation of the thermoregulatory center of the hypothalamus under the influence of progesterone.