The sexual cycle is also called the menstrual cycle. These are changes that occur periodically in the body of a woman of reproductive age, which are aimed at the probable possibility of conception. In medicine, the beginning of the menstrual cycle is considered to be the first day of menstruation. In total, it includes three phases, which we will discuss in this article. These are proliferative, menstrual and secretory. While in animals females are capable of sexual behavior at any time, in humans, menopause occurs after approximately five hundred cycles. This occurs between the ages of 46 and 54 years. In this condition, the ovaries become insensitive to luteotropin and follitropin.
Duration
The duration of the sexual cycle in women can vary. The physiological processes occurring in her body play a decisive role in this. However, there are approximate deadlines within which it must be met. If this does not happen, then there is reason to suspect various violations.
The duration of a woman's sexual cycle is 28 days. Depending on various factors, it can vary, becoming a week longer or shorter.
First menstruation
To understand the concept of the sexual cycle, you should delve into the specialized terminology related to this condition. This article will talk about basic terms.
The central event in the process of sexual development of every woman is menarche. This is the first sexual cycle in her life. It indicates that the body is now ready for reproduction. Typically, women experience menarche between the ages of twelve and fourteen. The normal age range is from nine to fifteen years.
When menstruation appears at the age of nine, they speak of early menarche, and at the age of 15 - primary amenorrhea. The time at which the first menstrual bleeding occurs depends on many factors. This is nutrition, heredity, the general health of the girl.
Possible violations
Sexual cycle disorders can be caused by a wide variety of factors. These are pregnancy, hormonal imbalances in adolescence, and other natural causes. The menstrual cycle can also go wrong due to internal and external stress.
It is customary to talk about a delay in menstruation if there are no cyclic bleedings for 35 days. It should be noted that slight delays in menstruation are considered normal. However, only if their duration does not exceed ten days.
One of the most common reasons for a missed period is pregnancy. In this case, you should purchase a test to confirm. If the result is negative, you should consult a gynecologist. He will understand the reasons and, if necessary, prescribe appropriate treatment.
There can be many reasons for disturbances in the regulation of the reproductive cycle:
- neurological and mental diseases;
- mental shocks;
- obesity;
- avitaminosis;
- infectious diseases;
- liver problems;
- diseases of the hematopoietic system, blood vessels or heart;
- consequences of gynecological operations;
- puberty disorder;
- genitourinary tract injury;
- genetic diseases;
- hormonal changes that occur during menopause.
It is worth noting that late periods are common among teenagers. In the first couple of years after the start of menstruation, girls rarely experience a constant cycle. In this case, there is no need to worry, this is a common occurrence. It is due to the fact that at this age the hormonal background is still unstable, so ups and downs in mood are likely, which leads to a significant increase or decrease in the level of hormones in the blood. When the hormones stop raging, the cycle immediately stabilizes. If it does not become regular two years after the start of menstruation, you should consult a gynecologist for help.
Climax
The cessation of regular periods of the sexual cycle occurs during menopause. This is characterized by a decline in reproductive function. Irregular menstruation or complete cessation is called menopause.
When this time comes depends mainly on heredity. Medical interventions, in particular gynecological operations and certain diseases, can also have an impact. All these problems can lead to early menopause.
Phases
The processes that occur during menstruation make up the phases of the sexual cycle, they are also called stages.
They correspond to changes that occur in the ovaries and endometrium, that is, the inner mucous membrane of the uterus lining its cavity.
Follicular phase
The first stage of the sexual cycle is called menstrual or follicular. At this stage, the woman begins to bleed from the uterus. This occurs due to the rejection of the endometrial layer, which is abundantly supplied with blood vessels.
Rejection begins at the end of the ovarian cycle. It occurs necessarily only if the egg has not been fertilized. The beginning of the first stage of the sexual cycle or the follicular phase of the ovary is considered to be the very first day of menstruation. The duration of this period may vary; it is individual for each woman. During this time, the dominant follicle should finally mature. On average, it is two weeks, but the norm is a time period from seven to 22 days.
Progress of the menstrual cycle
The follicular phase and the accompanying ovarian cycle begin with the release of GnRH by the hypothalamus. It actively stimulates the pituitary gland to secrete small amounts of luteinizing and follicle-stimulating hormones. These are, respectively, lutropin and follitropin.
Due to the reduced level of estradiol secretion, the release of lutropin and follitropin is suppressed. As a result, their level of education remains low.
Under the influence of follitropin, several follicles begin to develop in the ovaries at once. Of these, a dominant follicle stands out, which has the maximum number of receptors for folliculotropin. In addition, it synthesizes estradiol most intensively. The rest undergo atresia, that is, the reverse development of follicles in the ovary.
Over time, the level of estradiol in the body begins to rise. When its concentration is low, the secretion of gonadotropins is suppressed, and when it is high, on the contrary, it is stimulated. As a result, these processes lead to a significant release of GnRH by the hypothalamus.
This effect is especially pronounced for lutropin, since a high concentration of estradiol increases the sensitivity of adenohypophysis cells. In addition, the follicles react much more intensely to lutropin due to the presence of a larger number of receptors for this hormone.
The result of this is regulation based on the principle of positive feedback. The follicle continues to increase in size until a sharp release of lutropin begins. This marks the end of the follicular phase.
Ovulatory phase
The new phase is called ovulatory or proliferative. Around the end of the first week of the cycle, a dominant follicle is released. It continues to grow steadily and also increases the amount of estradiol. At this time, the remaining follicles undergo reverse development.
A follicle that has finally matured and is ready for ovulation is scientifically called a Graafian vesicle. It is worth noting that the ovulatory phase lasts only about three days. During this time, the main release of luteinizing hormone occurs.
Hormone release
Within one and a half to two days, several waves of release of this hormone occur in a row; its concentration in the plasma at this time increases significantly. The release of luteinizing hormone is the final stage of follicle development. In addition, it stimulates the production of proteolytic enzymes and prostaglandins, which are required to rupture the follicle wall and release the egg. This is the direct process of ovulation.
At the same time, the level of estradiol in the body begins to fall. A feature of the sexual cycle is that in some cases it may be accompanied by ovulatory syndrome. It is characterized by painful and uncomfortable sensations in the abdomen and iliac regions.
As a rule, ovulation occurs within 24 hours after the maximum wave of luteinizing hormone release. The norm is considered to be a period from 16 hours to two days. This is an important part of the sexual reproduction cycle.
During ovulation, a woman's body releases 5 to 10 ml of follicular fluid, which contains the egg necessary for conception.
Secretory phase
This phase of menstruation is also called the luteal phase. This is the period of time between ovulation and the start of the next menstrual bleeding. It is also known as the corpus luteum phase. Unlike the previous follicular phase, the duration of this stage is considered more constant. It ranges from 13 to 14 days, normally it can be two days more or less.
When the Graafian vesicle ruptures, its walls immediately collapse, and luteal pigment and lipids penetrate into the cells. Due to this, it acquires its characteristic yellow color. After transformation, the follicle is already called the corpus luteum.
In total, the duration of the luteal phase depends on the period of functioning of the corpus luteum. As a rule, this is ten to twelve days. At this time, it secretes estradiol, progesterone and androgens. When there are elevated levels of progesterone and estrogen, the outer layers of the endometrium change. Its glands mature, begin to secrete and proliferate. This is a clear sign that the uterus is preparing to receive a fertilized egg.
Estrogen and progesterone reach their peak approximately in the middle of the luteal phase, and in parallel the amount of corresponding hormones decreases.
If pregnancy does not occur...
When the egg remains unfertilized, the corpus luteum stops functioning after some time. The level of progesterone and estrogen decreases. Because of this, swelling and necrotic changes in the endometrium occur.
Due to the decrease in progesterone levels, the synthesis of prostaglandins also increases. When the egg is not fertilized, after some time luteolysis begins in the corpus luteum, that is, structural destruction, since it is no longer able to synthesize estradiol and progesterone.
Because of this process, the secretion of lutropin and follitropin is no longer suppressed by anything. The secretion of these hormones increases, which leads to the stimulation of a new follicle. When the levels of progesterone and estrogen decrease, the synthesis of follicle-stimulating and luteinizing hormones is resumed. This is how a new cycle begins in a woman’s body.
Stages of excitement
An important place in the reproductive system is occupied by the stages of initiation of the sexual cycle. There are three of them in total. These are excitation, inhibition and balancing. During this period, changes occur, some of which are easy to notice, while others are subtle even to modern biological instruments.
At the stage of sexual arousal, follicle maturation and ovulation occur in the female body. During this period, he is ready to conceive.
During braking, signs of sexual arousal appear much weaker. Then comes the balancing stage, which continues again until a new stage of excitation. During this period, the woman is in the most balanced state. This is influenced by the processes that occur in the body.
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The main morphofunctional units of the ovaries are special glandular structures - follicles. A mature follicle is a sac filled with follicular fluid, inside which there is a first-order oocyte. The wall of a mature follicle consists of several layers of differentiated cells. The inner layer of epithelial cells, loosely arranged in 2-3 rows, forms a zona granulesa, on a small protrusion of which, directed into the cavity, sits the oocyte. This protrusion is called the egg stalk.
The granulosa layer is followed by a dense layer of glandular epithelial cells, which is called the inner membrane (theca interna). It is supplied with blood vessels and serves as the main follicular producer of estrogens (E2, E1), as well as a certain amount of progestins and androgens. Apparently, granulosa cells are also involved in the synthesis of female sex steroids (Savard et al., 1964; Short et al., 1964). The outer layer of the follicle wall is connective tissue, it is called the outer shell (theca externa) (see Fig. 5). The diameter of the mature follicle varies widely among different species. So, in a rat it is 900 nm, and in a horse it is 7 cm.
After the rupture of a mature follicle, accompanied by the release of an oocyte from the ovary into the body cavity - ovulation, in mammals and some viviparous reptiles (lizards, snakes), the cells of the granulosa layer undergo transformation and form the second most important glandular structure of the ovaries, consisting of special luteal cells - the corpus luteum. Thus, the corpus luteum is a product of the transformation of follicular tissue. Its main function is the synthesis of Pr and its analogues. In addition, estrogens are also synthesized in it (Savard, 1962; Hashimoto et al., 1968). In birds, corpus luteum is not formed in the ovary and Pr is secreted only by follicles (Nalbandov, 1964).
In those species in which corpora lutea are formed after ovulation, the physiological essence of the ovarian cycle is reduced to a periodic change of two phases, during which one of the types of endocrine glands of the ovary—maturing follicles or corpus luteum—alternately dominates functionally. The dominance phase of follicles producing mainly estrogens is called follicular; the phase of dominance of the corpus luteum, producing mainly progestins, is the luteal phase. The completion of the luteal phase (lysis of the corpus luteum) causes stimulation of follicular processes.
Ovulation completes the follicular processes and opens the luteal phase. The active functioning of the corpus luteum inhibits the maturation of follicles and their endocrine function. In addition, Rg is a strong anti-estrogen in the uterus and vagina.
In birds and other animal species that do not have corpora lutea, the ovarian cycle is determined only by the periodicity of follicle maturation and the intensity of their secretion of estrogens and progestins at each stage.
Follicular phase of the cycle. The development of follicles in the ovary occurs as follows. Primary oocytes, arising from germinal epithelial cells, are initially surrounded by a single layer of granulosa cells that differentiate from the interstitial ovarian stroma.
This is the original form of the follicle - the primordial follicle. Then the granulosa cells proliferate and, in parallel with this process, the internal and external thecae differentiate from the connective tissue stroma. These processes are accompanied by the growth of follicles and oocytes. At the next stage, the granulosa tissue gradually loosens, exfoliates and is pushed towards the wall of the vesicle. As a result, a cavity begins to form in the follicle, filled with follicular fluid.
Until this stage, the growth and differentiation of the follicular apparatus occurs spontaneously and does not depend on gonadotropic hormones. At this time, the theca interna and granulosa produce small amounts of estrogens, as well as progestins and androgens.
Estrogens and androgens stabilize the structure of granulosa cells (Pelluso et al., 1981). An inactive ovary usually contains many immature follicles in different stages of development.
From a certain stage of development of a follicle that has a cavity (vesicular follicle), its endocrine cells become hormone-dependent and, as it were, “enter” the ovarian cycle. Further physiological events occurring in the maturing follicles are closely related to the functions of the hypothalamic-pituitary system. As already mentioned, these events are very complex and varied. Based on many, sometimes contradictory data, they can be schematically presented as follows (Fig. 80).
Figure 80. Diagram of female reproductive cycles:
the inner circle reflects the ovarian cycle; external - astral; Fo is an unregulated follicle, F1 is a vesicular follicle entering the cycle, F2 is a growing follicle, F3 is a mature follicle that secretes estradiol (E2). F4 - ovulating follicle, PG - prostaglandins, VT1 - newly formed corpus luteum, VT2 - corpus luteum, intensively secreting progesterone (P), VT3 - involuting corpus luteum; solid arrows indicate stimulation, intermittent arrows indicate inhibition
Apparently, initially, vesicular follicles, under the influence of estrogens, begin to synthesize LTG receptors and become sensitive to this hormone. LTG in turn induces the synthesis or activation of FSH and LH receptors (Richardt, 1976). Since in the early stages of follicle maturation they synthesize small amounts of sex steroids, the secretion of both gonadotropins at this time should increase according to a positive feedback mechanism. In fact, during this period of the cycle, only FSH production increases, and LH production remains at the basal level (Ross et al., 1970).
The interpretation of such dissociation in the secretion of two gonadotropins is complicated by the fact that, according to existing data, the secretion of LH and FSH is regulated by one releasing factor - lufolliberin.
It is believed that further growth and development of follicles occurs under the influence of increased secretion of FSH and increased sensitivity to LH. Upon reaching a certain stage of development, follicular cells, under the direct control of LH, begin to intensively synthesize sex steroids and, above all, estrogens (Lipsett et al., 1975). Increased secretion of estrogen in the initial stages, apparently, through a positive feedback mechanism, activates the cyclic release of LH/FSH-RF by the hypothalamus and, possibly, inhibits the antigonadotropic function of the pineal gland. As a result, an ovulatory release of FSH and LH occurs from the pituitary gland (Eskin, 1951; Jakoti et al., 1977).
The stimulating effect of estrogens on the secretion of pituitary hormones is mediated to a certain extent by prostaglandins (PGE1, PGE2, PGE2a, and PGs can have a direct effect on both the hypothalamus and the pituitary gland (Sato et al., 1976; Warbers et al., 1976). Apparently, these histohormones reproduce their effect on the secretion of gonadotropins locally due to their enhanced formation in the hypothalamus under the influence of estrogens and in the pituitary gland under the influence of LH/FSH-RF. The cyclic release of LH and the increased sensitivity of the cells of the mature follicle to it, developing under the influence of increased at this time secretion of FSH and LTG ultimately cause the process of ovulation, which in different species occurs 8-50 hours after the LH surge.
LH is the main inducer of ovulation. Its effect on ovulation is also likely (at least in part) mediated by PGs produced by gonadotropin in the ovaries and estrogens in the uterus (Kewell et al., 1970). With the participation of prostaglandins, LH causes an increase in the synthesis of proteolytic enzymes in the follicle at the level of transcription and translation, leading to the destruction of the follicular wall and the release of the egg from the ovary into the abdominal cavity.
The cyclic preovulatory LH surge is short-lived. It is possible that its cessation is also caused by estrogens, but with their maximum secretion by ovulating follicles (Babichev, 1973; Dörner, 1974). It is believed that at the beginning of the rise in estrogen production, they stimulate the secretion of LTG, LH and FSH, and at the peak they cause its inhibition. The latter effect is enhanced by inhibin (folliculostatin).
The duration of the follicular phase and many details of changes in hormone secretion in the ovarian cycle can vary significantly among representatives of different species and even among many individuals within the same species (Bentley, 1976; Disfalusi, 1977). However, in almost all known cases, using radioimmunological and other sensitive and specific methods in the follicular phase, an increase in FSH secretion at the beginning of the phase is naturally detected; preovular increase in the secretion of estrogen and T, preceding in time a sharp increase in the concentration of LH; subsequent preovulatory peaks in the secretion of pituitary LH, as well as FSH (Fig. 81, 82).
Rice. 81. Dynamics of the content of LH, estradiol and progesterone in the blood of female rats at different stages of the reproductive cycle (according to Bentley, 1976 with modifications:
1 - LH, 2 - estradiol, 3 - progesterone
Fig. 82. Dynamics of the content of LH, FSH, estradiol and progesterone in the blood during the sexual cycle in a woman:
1 - progesterone, 2 - estradiol, 3 - LH, 4 - FSH; the abscissa axis schematically shows the state of the endometrium
The ability of gonadotropins to stimulate follicular maturation and ovulation is widely used. In clinical practice, gonadotropins are administered to women suffering from polycystic ovary syndrome, in which ovulation does not occur and reproductive function is impaired (Disfalusi, 1965). In animal husbandry, preparations of gonadotropic hormones are used to obtain multiple births in Karakul sheep (M.M. Zavadovsky, 1937-1941).
Gonadotropins are also used in fish farming to stimulate spawning and milk production (Gerbilsky, 1940, 1947).
From the moment of formation of fast-growing, hormone-dependent follicles until ovulation, the main physiological events of the ovarian cycle take place in the follicular apparatus. The activity of follicles determines the functional state of the hypothalamic-pituitary system and the reproductive tract. That is why this phase of the cycle is called follicular.
The most important role in its development is played by estrogens, which are the primary signal for the preovulatory surge of LH and subsequent ovulation, prepare the female reproductive tract for mating with a male and excite sexual behavior. At the same time, progestins, also formed in the follicles, induce the transformation of the primary oocyte into a mature egg. In some species, progestins and androgens, together with estrogens, can also stimulate preovulatory LH secretion. Thus, the biological meaning of the totality of processes occurring in the ovary during the follicular phase obviously comes down to preparing the female body for the act of mating, and the egg for fertilization.
The physiological mechanisms of the preovulatory, cyclic release of LH by the anterior pituitary gland and the ovulation induced by it may differ in nature among different species. Most often, these processes are spontaneous, entirely dependent on the internal relationships in the hypothalamus-pituitary-gonad system and, above all, on the increase in the concentration of estrogen in the blood.
However, in some species (rabbit, cat, ferret, mink, ermine, sable, etc.), the cyclic surge of LH and ovulation are reflex processes to the act of mating (see Table 15). Coitus, electrical or mechanical stimulation of the vagina or cervix causes ovulation in females of these animal species and the subsequent formation of the corpus luteum. In a rabbit, the latent period of reflex ovulation is approximately 10 hours, in a cat - 24-36 hours, in a ferret - 30 hours, in a mink - 42-50 hours.
Reflex ovulation can also occur in many species of wild birds, and the external stimulus is not only the act of mating, but also the visual perception of the appearance of an approaching male (Gilbert, 1971; Bentley, 1976). The number of ovulated follicles and eggs laid in the nest in most wild birds is strictly determined genetically. However, in domestic birds such as chickens, or wild birds such as sparrows, ovulation can occur continuously. Moreover, their ovulation and oviposition are not quantitatively determined: if after oviposition the egg is removed from the nest each time, ovulation and oviposition systematically continue (Bentley, 1976).
It is believed that the oviposition process is stimulated along with the hormones of the hypothalamic-pituitary-ovarian system by hormones of the neurohypophysis. Let us recall that in birds and other oviparous animals, follicular secretion of estrogens plays an important role in the regulation of vitellogenesis in the liver.
The luteal phase of the cycle is determined by the functioning of the corpus luteum in the ovary of mammals and some other species of vertebrates and lasts in cycling animals from the moment of formation of the corpus luteum until their lysis. The corpus luteum, which secretes mainly progestins, as well as a certain amount of estrogens, performs the following important functions in mammals: prepare the uterus for pregnancy and ensure its normal course; inhibit the late stages of follicle maturation and ovulation at the level of the hypothalamus and pituitary gland.
The duration of the ovarian cycle in this animal species is directly dependent on the functioning of the corpus luteum. The frequency of ovulation is inversely related to the lifespan of the corpus luteum. In this regard, the latter are often called the clock of the ovarian cycle. Throughout the animal's true pregnancy, when the corpus luteum is functioning and secreting Pr, ovulation does not occur in the ovary.
Surgical removal of functioning corpora lutea in the luteal phase of the cycle causes a significantly accelerated transition of the ovary to the follicular phase and premature ovulation (M.M. Zavadovsky et al., 1937, 1939). And, conversely, systematically administering large physiological doses of Pg to animals (50-2000 mcg per day) or implanting progestins in the form of tablets under their skin prevents ovulation. Stopping hormone injections or removing the implanted tablet restores the ovary's ability to ovulate (Lipschütz and Chklesias, 1961; Pincus et al., 1966).
The above experiments essentially simulate the processes occurring in cycling animals under physiological conditions. The secretion of Pg by the corpus luteum begins soon after its formation, then the production of Pg increases and, after reaching a maximum, if true pregnancy does not occur, it gradually decreases due to regression of the corpus luteum. In a number of animals, it is possible to artificially prolong the luteal phase of the cycle, causing a state of false pregnancy.
Progestins, as well as androgens, formed in high concentrations in the cyclic corpus luteum, apparently inhibit the tonic secretion of gonadotropins through a negative connection mechanism at the level of the hypothalamus and pituitary gland and, as a result, prevent the maturation of follicles and ovulation. A similar inhibitory effect on ovulation is exerted by the corpus luteum of pregnancy, as well as the placenta, which produces Pr and its derivatives even more intensively. Along with progestins, the corpus luteum of the cycle and pregnancy produces, as already noted, a certain amount of estrogens. The significance of luteal secretion of estrogen, apparently, comes down to sensitization of the hypothalamus and pituitary gland, as well as the organs of the reproductive tract to progestins.
The property of progestins to inhibit ovulation (anovulatory effect) is widely used in medical and livestock practice. In obstetrics and gynecology, progestins, in combination with or without estrogens, are used as contraceptives in women. These drugs are called contraceptives. Synthetic gestagens such as 19-nor-17a-ethynyl-testosterone, norethinodrel, chlormadinone- and megestrol-acetates, which are more effective when administered orally than natural compounds, are usually used as contraceptive progestins.
The practical use of progestins in animal husbandry is mainly aimed at synchronizing the cycles of female farm animals during artificial insemination (Nellore and Cole, 1956; Loginova et al., 1966; Prokofiev, 1977). Prostaglandins are also used for the same purposes in animal husbandry.
Returning to the characteristics of the luteal phase of the ovarian cycle, it is necessary to provide data on the endocrine mechanisms of the emergence, development and regression of the corpus luteum. Apparently, the main inducer of the formation of the corpus luteum is LH, which stimulates the differentiation of luteal cells and the biosynthesis of Pro. The effect of LH on the process of luteinization, especially in some animal species (rats, sheep), is permissible by prolactin. Hence one of the names of the latter is luteotropic hormone (LTP).
LTG enhances the formation of LH receptors and ensures high sensitivity of luteal cells to low concentrations of LH detected at this phase of the cycle. In rabbits, one of the most important factors in luteinization is estrogens. At the same time, in other species, estrogens sensitize the corpus luteum to the action of LTG and LH. Probably, having arisen under the influence of the combination of the mentioned hormones and primarily LH, the luteal cells of the corpus luteum synthesize mainly progestins, which determine the general functional state of the hypothalamus-pituitary-gonadal system and the reproductive tract in the luteal phase of the cycle.
Progestins secreted by the corpus luteum prepare the uterus for pregnancy in mammals, prevent estrus, inhibit the activity of the cyclic center of the hypothalamus and the maturation of follicles in the ovary (Nalbandov, 1964; Ross et al., 1970). The physiological meaning of this phase of the ovarian cycle obviously boils down to preparing the female body for pregnancy and inhibiting a new series of ovulations. If pregnancy does not occur in the animal, the corpus luteum involutes and the synthesis of Pro in them is inhibited. Involving corpora lutea lose lipids and become white bodies.
In the process of regression of the corpus luteum in many animal species, an important role is played not only by low levels of pituitary hormones in the blood and the sensitivity of luteal cells to them, but also by the functions of the uterus. Removal of the uterus can significantly prolong the activity of the corpus luteum, the secretion of gestagens and the state of false pregnancy (Loeb, 1927; Wunder, 1965). Conversely, inserting or sewing beads into the endometrium causes premature involution of the corpus luteum.
It has been established that at least one of the main humoral factors of the uterus that stimulate luteolysis are prostaglandins; carried retrogradely through the venous bed into the ovary, they can cause regression of the corpus luteum. It remains unclear how the standard cycle time for luteolysis is determined for a given species.
In constantly cycling rats and mice, the luteal phase of the cycle can be significantly prolonged by the act of non-productive mating or irritation of the genital tract. In this case, the reflexively prolonged luteal phase (provoked false pregnancy) lasts not 38-40 hours, as usual, but 12-14 days (Hafez, 1970). In reflexively ovulating animals, false pregnancy also occurs in response to irritation of the reproductive tract. In rabbits and cats, its duration is approximately half as long as true pregnancy (16-17 and 30-40 days instead of 30-32 and 64-67 days, respectively). The mechanisms of development of reflex false pregnancy have not yet been sufficiently studied.
V.B. Rosen
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Completed by: student 238 a group of the Faculty of Pharmacy Kaldashova Larisa Petrovna Checked by: candidate of biological sciences, associate professor Gerasimova O.V. SAMARA 2015Slide 2
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MENSTRUAL CYCLE Cyclic changes in the organs of a woman’s reproductive system, the main manifestation of which is monthly bleeding from the genital tract - menstruation. CLINICAL CHARACTERISTICS OF THE MENSTRUAL CYCLE Menstruation begins during puberty from 11-15 years and continues until menopause at the age of 45-55 years. For women, the average cycle is 28 days. The discharge lasts from 3 to 7 days. Blood loss averages 50-80 ml.
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PHASES OF THE MENSTRUAL CYCLE The menstrual cycle of women consists of four phases, which are characterized by certain changes occurring in the body. It is worth considering that the duration of each phase of the menstrual cycle in each case is as individual as the cycle itself.
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MENSTRUAL PHASE The first phase of the menstrual cycle begins on the first day of menstruation. During menstrual bleeding, under the influence of hormones, the endometrium of the uterus is shed, and the body prepares for the appearance of a new egg. In the first phase of the cycle, algomenorrhea is often observed - menstruation. Algomenorrhea is a disease that must be treated by first eliminating the causes.
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FOLLICULAR PHASE The second phase of the menstrual cycle lasts about two weeks after the end of menstruation. The brain sends impulses, under the influence of which follicle-stimulating hormone, FSH, enters the ovaries, promoting the development of follicles. A dominant follicle gradually forms, in which the egg subsequently matures. Also, the second phase of the menstrual cycle is characterized by the release of the hormone estrogen, which renews the lining of the uterus. Estrogen also affects the cervical mucus, making it resistant to sperm. Certain factors, such as stress or illness, can affect the duration of the second phase of the menstrual cycle, and delay the onset of the third phase.
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OVULATION PHASE The phase lasts about 3 days, during which luteinizing hormone (LH) is released and follicle-stimulating hormone (FSH) levels decrease. LH affects the cervical mucus, making it receptive to sperm. Also, under the influence of LH, the maturation of the egg ends and its ovulation occurs (release from the follicle). The mature egg moves into the fallopian tubes, where it waits for fertilization for about 2 days. The most suitable time for conception is before ovulation, since sperm live for about 5 days.
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LUTEAL PHASE After the release of the egg, the follicle (corpus luteum) begins to produce the hormone progesterone, which prepares the endometrium of the uterus for implantation of a fertilized egg. At the same time, LH production stops and the cervical mucus dries out. The luteal phase of the menstrual cycle lasts no more than 16 days. The body is waiting for the implantation of the egg, which occurs 6-12 days after fertilization.
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The phases of the menstrual cycle are determined by the influence of hormones that affect not only physiological processes, but also the emotional state. And although the modern rhythm of life requires women to be constantly active, observing changes in the emotional state associated with the phases of the menstrual cycle will help determine the most unfavorable days for active action or conflict resolution. This approach will allow you to avoid unnecessary stress and maintain your strength and health.
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FERTILIZATION is the process of fusion of a sperm with an egg, leading to the formation of a new single-celled organism - a zygote. About once a month, a fertile woman ovulates. This is the process of the release of an egg ready for fertilization from the follicle. In most cases, fertilization involves one sperm and one egg.
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FERTILIZATION However, in order for the fertilization process to take place, the sperm must first reach the egg. Once in the vagina, a man's seminal fluid contains from 100 to 400 million sperm. Their speed of movement is only 2-3 mm per minute. After 1-2 minutes they reach the uterus, thanks to its contractions and contractions of the tubes. 2-3 hours after sexual intercourse, sperm reach the end sections of the fallopian tubes, where they merge with the egg. The fertilized egg then moves along the fallopian tube, thanks to its peristaltic movements and the movements of the ciliated epithelium. Approximately 7-8 days after fertilization, the egg enters the uterine cavity. There it penetrates the mucous membrane, which contains nutrients for the development of the embryo. From the moment of fertilization, pregnancy begins.
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DEVELOPMENT OF THE HUMAN EMBRYO The embryonic (embryonic) development of a person is the early period of development up to 8 weeks. During this time, a body is born from a fertilized egg, which has all the basic characteristics of a person. After eight weeks of development, the intrauterine organism is called a fetus, and the development period is called fetal.
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SPERMATOZOON IN THE FALLOPIAN TUBE EGG MEETING THE SPERM WITH THE EGG. OVIDUCT
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Two sperm make contact with the egg, but only one should remain. Sperm inside an egg
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Day 8: The fertilized egg descends through the oviduct to the uterus and the embryo attaches to the wall of the uterus. Embryonic brain development begins
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On the 40th day, embryonic cells form the placenta. The placenta forms a protective barrier, provides oxygen to the fetus through the mother's circulatory system, and transports carbon dioxide in the opposite direction. Through the placenta, the fetus receives water, electrolytes, nutrients and minerals, and vitamins; The placenta also participates in the removal of metabolites (urea, creatine, creatinine).
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Week 8: The ears and face are formed, the rudiments of the gill slits atrophy. The embryo is surrounded by a water membrane. The fingers and hands are well defined and defined, the toes are clearly defined, and muscle movements begin. The embryo begins to react with feelings. The embryo reacts to irritation by fine hair on the skin of the cheeks by moving the head, moving the torso and pelvis back, stretching out the arms and hands to remove the hair (possibly the first manifestation of tactile sensitivity). Then the sensitivity spreads to other parts of the body.
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Week 10: All major body parts are in place. The eyes and ears are in their normal position. The skeleton is clearly defined. The baby's airways, which begin with the nose and continue to the lungs, are already ready for the first breathing movements. Eyes half closed. The eyelids will close over the next few days.
Slide 21
Week 16: Limbs with fingers and nails are formed. The taste buds are surrounded by pores and cells with microvilli, which complete the taste perception system and begin to function. After this, no significant changes occur in these receptors, except that their number increases, and they also develop in breadth and depth. The first manifestations of facial expressions: the ability to squint your eyes, smile mockingly. Thumb sucking begins. The development of olfactory receptors is completed. The embryo is able to distinguish several hundred odors.
Slide 22
Week 18: Fetal movement is felt and the heartbeat is heard. At this time, the fetus begins to hear. The length of the embryo is 140-190mm. Week 20: The fetal skin is covered with the finest (vellus) hairs (especially in the eyebrows and eyelashes. Week 24: Development of facial expressions: pouting lips, frowning, muscle tension around the eyes, associated with a baby’s crying.
Slide 23
6 months: There are still about 8-10 weeks until birth. At this time, the fetus turns over to emerge head first. Week 36: The fetus is fully formed, the skin is covered with vernix, and the length of the hair on the head reaches 25 mm. A hormonal signal is sent to the mother's body, requiring the end of pregnancy.
Slide 24
Slide 25
Hormonal changes and the role of placental hormones in the body In the relationship between the organisms of the mother and the fetus, the placenta plays the role of an endocrine gland. The processes of synthesis, secretion and transformation of a number of hormones of protein and steroid structure occur in it. There is a close relationship between the mother, fetus and placenta in the production of hormones. Some of them are secreted by the placenta itself and transported into the blood of the mother and (or) the fetus. Others are derivatives of precursors that enter the placenta from the mother and fetus.
Slide 26
Slide 27
The placenta is a powerful endocrine gland, in which the processes of synthesis, secretion and transformation of a number of hormones, both steroidal (gestagens and estrogens) and protein nature (CG, PL), occur intensively. Pregnancy-specific hormones. - HG. - PL. - Hormones of the hypothalamus. - Corticoliberin. Pituitary hormones. - Prolactin. - Somatotropic hormone. - ACTH. - Other peptide hormones. - Insulin-like growth factor I and II. - Parathyroid-like peptide. - Renin. - Angiotensin II. - Steroid hormones (estrogens, progesterone). - 1,25-dihydroxycholecalciferol.
Slide 28
The main hormone of the fetoplacental system is estriol, called a pregnancy protector. It makes up 85% of all estrogens during pregnancy. Its main role is the regulation of uteroplacental blood circulation, i.e. supplying the fetus with all the vital substances necessary for normal growth and development. Estriol is synthesized in the placenta from dehydroepiandrosterone sulfate, which is formed in the adrenal cortex of the fetus and, to a lesser extent, in the adrenal cortex of the pregnant woman. 90% of estriol in the blood of a pregnant woman is of fetal origin and only 10% is of maternal origin. Part of estriol is in a free state in the blood of the pregnant woman and the fetus, performing its protective function; part of it enters the pregnant woman’s liver, where, combining with glucuronic acid, it is inactivated. Inactivated estriol is excreted from the body of a pregnant woman in the urine.
Slide 29
In significantly smaller quantities than estriol, other estrogens are formed in the fetoplacental system - estrone and estradiol. They have a diverse effect on the pregnant woman’s body: they regulate water-electrolyte metabolism, cause sodium retention, an increase in circulating blood volume (CBV), vasodilation and an increase in the formation of steroid-binding plasma proteins. Estrogens cause the growth of the pregnant uterus, cervix, vagina, promote the growth of the mammary glands, change the sensitivity of the uterus to progesterone, which plays an important role in the development of labor. The content of hormones in the blood at different stages of pregnancy
Slide 30
The second important steroid hormone of pregnancy is progesterone. Progesterone causes changes in the mother's body that contribute to the occurrence and development of pregnancy. Under its influence, secretory processes occur that are necessary for implantation and development of the fertilized egg. Progesterone also promotes the growth of the genital organs of a pregnant woman, the growth and preparation of the mammary glands for lactation, is the main hormone that reduces the contractility of the myometrium, reduces the tone of the intestines and ureters, has an inhibitory effect on the central nervous system, causing drowsiness, fatigue, impaired concentration, and In addition, it helps to increase the amount of adipose tissue due to the hypertrophy of fat cells. A progesterone metabolite, pregnanediol, is excreted in the urine.
Slide 31
The main protein hormones of pregnancy are human chorionic gonadotropin (CG) and placental lactogen (PL). - HCG is a glycoprotein produced by the chorion even before the formation of the placenta. Its biological properties are similar to LH of the pituitary gland, helps preserve the function of the corpus luteum of the ovary, affects the development of the adrenal glands and gonads of the fetus, and affects the processes of steroid metabolism in the placenta. HCG is detected in the urine already on the 9th day after fertilization, reaches its peak concentration by 10-11 weeks of pregnancy (about 100,000 units) - PL is a polypeptide hormone, in its chemical and immunological properties it is close to the growth hormone of the anterior pituitary gland and prolactin . PL can be detected in the blood from 5 weeks of pregnancy. PL affects metabolic processes that are aimed at ensuring the growth and development of the fetus. PL gives an anabolic effect, retains nitrogen, potassium, phosphorus, calcium in the body; has a diabetogenic effect. PL, due to its anti-insulin effect, leads to increased gluconeogenesis in the liver, decreased body tolerance to glucose, and increased lipolysis.
Slide 32
The physiological action of hormones is aimed at: - providing humoral, i.e. carried out through the blood, regulation of biological processes; - maintaining the integrity and constancy of the internal environment, harmonious interaction between the cellular components of the body; - regulation of the processes of growth, maturation and reproduction. Hormones regulate the activity of all cells in the body. They affect mental acuity and physical mobility, physique and height, determine hair growth, tone of voice, sex drive and behavior.
Slide 33
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% do not feel the need for affection.
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 the direct relationship between the onset of menstruation and the emergence of erotic libido, its delay during delayed puberty, and its disappearance after severe hormonal insufficiency of the ovaries. In healthy women, erotic libido persists throughout life, accompanying the later emerging sexual libido. Some women may stop in their development 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 erotic libido, 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, by 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 libido in women reaches its maximum at about 30 years old, remaining at a stable level until 55 years old, and only then gradually decreases. A natural decrease in sexual desire is observed after 60 years, and therefore its increase at this age is almost always regarded as a pathological phenomenon. A high level of libido lasts much longer in multiparous women. However, people who have had a pathological birth may experience an earlier decrease in sexual desire. The same can happen in women who experience painful menstruation.
Unlike men, most women tend to fluctuations in the strength of sexual desire. So, during the period of ovulation, i.e. When a mature egg leaves the ovary, relatively few women reach maximum libido, although this is the most favorable time for conception. Before or immediately after menstruation, many women experience an increase in sexual desire. There are women who express a desire for sexual intercourse only on certain days of the menstrual cycle. A temporary decrease in libido occurs during illness, after mental and physical fatigue, and negative emotions.
No clear patterns in changes in the level of sexual behavior of women have been established. It is very individual and rather depends on her mental state.
A certain proportion of women may experience orgasm. During orgasm, excitement covers the internal organs and the central nervous system especially intensely. At this moment, the heart rate can reach 180 beats per minute, the maximum blood pressure will increase by 30-100 mmHg. Art., breathing rate – up to 40 breaths per minute.
At the moment of orgasm, voluntary control over skeletal muscles disappears to a large extent. Involuntary, almost convulsive contractions of the abdominal, intercostal and facial muscles occur. General reactions of internal organs and especially intense stimulation of the central nervous system jointly lead to increased sexual sensations. At the same time, women often experience suppression of other types of sensitivity.
Unlike the male peak-shaped orgasm, the female orgasm occurs in most cases in waves. There can be from 5 to 12 waves of orgasmic sensations, and with each wave the intensity of pleasure increases. However, there are women with a single short-term peak-shaped orgasm, which is still longer than in men. In rare cases, a so-called protracted, wave-like orgasm is observed, lasting up to 1-3 or even 4 hours. There are also so-called multi-orgasmic women who are capable of experiencing several orgasms during one sexual act, and they experience each subsequent one with greater intensity.
A woman's ability to orgasm depends to a certain extent on the length of her sexual life and sexual experience. If in men orgasm is usually observed without any preliminary practice, then in most women it occurs after more or less prolonged regular sexual activity, and often after the first or second birth.
Not every woman and not every sexual encounter is equally satisfying. So, some women can feel a sense of satisfaction without 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 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 most often happens in 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.
SEXUAL CYCLE. PREGNANCY
Sexual cycle
With the onset of puberty, periodic changes occur in the genital organs of the female body of humans and other mammals, called sexual_cycle. Its regulation is carried out by the endocrine system. During each cycle, one, and sometimes several follicles containing maturing eggs mature. The release of a mature egg capable of fertilization from the follicle is called ovulation. In parallel with the maturation of the follicle during the cycle, changes occur in the mucous membrane of the genital organs. Having reached a certain maximum level, these changes again undergo reverse development.
With all its diversity, the sexual cycle consists of several periods: redovulation, ovulation, post-ovulation and rest periods.
IN preovulation period Usually one of the follicles enlarges, and at the same time the uterine epithelium grows. Pre-ovulatory changes occur due to increased secretion of follicle-stimulating hormone by the adenohypophysis, which activates the intrasecretory function of the ovaries, resulting in increased production of estrogens (Fig. 11). Under the influence of estrogen, the mucous membrane of the uterus and its glands grow, and contractions of the muscular layer of the uterus intensify. 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 ending with pregnancy (diagram):
1 - level of estrogen in the blood; 2 - progesterone level in the blood; 3 - follicle and corpus luteum during a normal menstrual cycle; 3 a - exit from the follicle of the egg, which, remaining unfertilized, dies; 3 b - development and then degeneration of the corpus luteum; 4 - follicle and corpus luteum during a cycle ending in pregnancy; 4 a - release of an egg from the follicle, which was then fertilized and implanted into the uterine mucosa; 4 b - progressive development and preservation of the corpus luteum; 5 - changes in the uterine mucosa. The numbers below are the days of the menstrual cycle.
IN ovulation period ovulation occurs, i.e. rupture of the follicle and the release of a mature egg capable of fertilization. The biological reliability of species reproduction in humans is ensured by a huge number of eggs, reaching 300 thousand in prepubertal age. However, in each ovulation period, out of 10-15 simultaneously growing follicles, only one matures and ovulates to the end.
During ovulation, blood flow to the fallopian tubes (oviducts) increases, tension in their smooth muscle fibers occurs, and
movement of the cilia of epithelial cells lining the inside of the uterine ducts. The ventral end of the fallopian tube opens and may be in close contact with the ovary during ovulation. This usually allows the mature egg and follicular fluid to enter the fallopian tube after rupture of the follicle. Subsequent alternating contractions of the muscle fibers of the fallopian tube propel the mature egg towards the uterus. The time it takes for a woman to travel through the tube to the uterus is about 3 days.
As the moment of ovulation approaches and, especially during the period of ovulation, a restructuring of the functions of the genital organs and the body as a whole occurs. These changes occur under the influence of estrogens produced in the follicles. Changes in ovarian hormonal function affect 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 increases abruptly 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 egg 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, at the site of the burst follicle, following ovulation, a corpus luteum is formed, which develops from the walls of the empty follicle. Approximately 2 days after ovulation, the unfertilized egg dies.
The corpus luteum is a temporary endocrine gland that produces hormones progesterone. Under the influence of progesterone, the secretion 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). A decrease in FST leads to a decrease in the formation of estrogen in the ovaries. The unfertilized egg remains in the woman's genital tract for several days and then dies.
A decrease in the concentration of progesterone and estrogens 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 rupture 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 blood is called menstruation. The average duration of menstruation is 2-3 days.
Following the postovulation period comes the interovulation period. peace. At this time, the follicles are relatively small, the uterine mucosa is thin and contains fewer blood capillaries. The resting period transitions into the preovulation 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 usually called the menstrual cycle. It is usually counted from the first day 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 ranges from 21 to 35 days. The best menstrual cycle is one that lasts 28 days, because... in this case, the most constant periodicity of cyclic changes is observed. Menstrual cycles begin during 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 a woman’s blood plasma during the menstrual cycle can have a significant impact on her behavior. In some women, before menstruation, the excitability of the nervous system increases, hot temper and irritability increase.
Pregnancy
For pregnancy to occur, a mature egg, having left the ovarian follicle and ending up in the abdominal cavity, must enter the fallopian tube, meet a sperm there, be fertilized, begin to divide and simultaneously move into the uterus, in order to then attach and penetrate its mucous membrane. Only under these conditions is it possible for the development of a new organism.
Fertilization call 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 fuses 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 regular 28-day menstrual cycle, a mature egg leaves the ovary 12-14 days after the first day of the previous menstruation. Over the course of about 3 days, the egg moves through the fallopian tube into the uterus and along this path, fertilization can occur when it meets sperm. The best option is when fertilization of the egg occurred in the upper parts of the fallopian tubes.
In some cases, sperm travel 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, which leads to the development of an ectopic pregnancy. An ectopic pregnancy is very dangerous for a woman, because... it definitely requires emergency surgery.
The lifespan of the egg released from the follicle and the duration of the functioning of sperm in the female genital tract are determined in the menstrual cycle period size, 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 climate zone, etc. Typically, the shift in the timing of ovulation does not exceed 3 days closer to the beginning or end of the menstrual cycle. Therefore, fertilization can occur during the period 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 the formation of the embryo on the second day, 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 ensured by wave-like contractions of the fallopian tube and 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 tubal pregnancy, in which the embryo dies at a later date. In case of tubal pregnancy, urgent surgery is necessary.
If the embryo enters the uterus too quickly or 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 a normal pregnancy. For example, if the embryo attaches to scars formed in the area of the uterine mucosa after abortion or to a node that appears after inflammatory diseases of the 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 maintenance and development of pregnancy. If a woman does not have her next menstruation, then we can hope that the implantation of the embryo into the uterine mucosa has occurred and the pregnancy is developing. Doctors can see the embryo as early as 4 weeks of age using an ultrasound machine. Even earlier, pregnancy can be detected as a result of a biochemical study.
From the 7th week of pregnancy, the so-called baby's place, 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 releases into the mother's body a complex complex of hormones and other biologically active substances, among which the hormone progesterone, which contributes to the preservation and development of pregnancy, is of particular importance. Before the formation of the placenta, progesterone is produced only in the corpus luteum, which forms at the site of the ruptured follicle after the release of the egg. A hormonal imbalance can occur if by the 7th week the function of the corpus luteum begins to fade significantly, and the formation of the placenta, which replenishes the resulting progesterone deficiency, is delayed. If left untreated, this hormonal imbalance can cause miscarriage.
With normal development, a woman's pregnancy lasts an average of 280 days, counting from the first day of her 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 implantation of the embryo into the mucous membrane of the uterus, complex processes of the formation of the internal organs of the fetus occur. In the first trimester it is especially great danger of alcohol for the fetus. Alcohol disrupts the formation of internal organs, causing various deformities. The brain is most seriously affected. Brain damage manifests itself after the birth of a child, with mental retardation up to progressive dementia. Every third child of drinking mothers has a congenital heart defect, deformities of the arms and legs, and malformations of the kidneys and urinary tract and genital organs are quite common.
Alcohol also complicates pregnancy. Pregnant women who drink alcohol are much more likely to experience spontaneous miscarriages and premature birth of a premature and immature fetus. They experience pregnancy toxicosis and labor complications.
On Smoking is also strictly prohibited. Not only the mother’s smoking is dangerous for the fetus, but also her stay in a smoky room, because carbon monoxide, nicotine and other toxic substances contained in tobacco smoke impair the oxygen supply to the fetus and have a toxic effect on it.
The placenta, which serves as a barrier between the organs of the mother and the fetus, is not able to protect it from many chemicals, medications and viruses. Therefore, pregnant women should not work in chemically hazardous industries. They should take medications carefully and only as prescribed by a doctor, and should also avoid contact with people with influenza and other viral infections.
Second trimester(4th – 6th months of pregnancy) in healthy women proceeds mostly calmly. Gradually, a period of physical and psychological adaptation passes, the reactions of the nervous system are balanced, drooling and nausea disappear, and appetite improves. The woman's body adapts to the new state.
During an uncomplicated pregnancy, as in the first trimester, daily morning exercises are very useful, excluding jumping, sudden movements and turns. In the second trimester, a complex of special gymnastics is recommended, which is selected by the antenatal clinic doctor. Walking in the fresh air is very useful, helping to improve the oxygen supply to the fetus. You can walk for up to two hours in a row and be sure to walk 30 minutes before bed. Air baths and daily showers are very useful, improving skin respiration. A pregnant woman's diet should be complete with an increase in the amount of protein, vitamins and mineral salts.
Starting from the 5th month, a pregnant woman’s blood pressure begins to increase, so it is important to monitor its dynamics. The second trimester is very important for women who have had previous pregnancies terminated during this period. They need gentle treatment, and in some cases, hospital treatment.
Third trimester pregnancy begins from the 28th week. During this trimester, a woman’s body experiences heavy stress. The intensive growth of the fetus places increasing demands on the liver and kidneys mother. Work is often difficult hearts, because it begins to be crowded by the dome of the diaphragm, raised by the fetus. The functioning of the digestive organs is also complicated. Sometimes the contents of the stomach are thrown into the esophagus and a feeling of heartburn appears, a bitter taste in the mouth. The venous system functions under increased load, in which blood pressure increases.
At this time, maintaining the correct regimen becomes even more important. First of all, it is necessary to make adjustments to
diet and completely avoid spicy, salty foods, spices and smoking. These products complicate the functioning of the kidneys, promote fluid retention in the body and can provoke the development of so-called late toxicosis of pregnancy, which is extremely dangerous for the health of the mother and child.
In the third trimester, first courses should be vegetarian only. Recommended fats include butter and vegetable oil, vegetables - raw, boiled and stewed, bread - preferably made from wholemeal flour. It is very important to monitor the increase body weight, which should not exceed 500 g per week, and for people prone to obesity - 300 g per week. A successful pregnancy during this period is indicated by normal blood pressure, absence of edema and normal urine tests. However, if it becomes difficult to remove the ring from your finger or your shoes become tight, you should consult a doctor.
In the third trimester, you need to follow the correct daily routine. Eat rationally, at the same time, and 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, have been 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 all of them, should be performed only while sitting and lying down.
In order for a woman to rest and get stronger before giving birth, she is given prenatal leave. During this time, she can do normal, but not labor-intensive, household chores. Working with pesticides and household chemicals is strictly prohibited. A normal or even complicated pregnancy with proper medical supervision usually ends in the birth of a healthy, viable child.
LITERATURE
1. General course of human and animal physiology. – Ed. HELL. Nozdracheva. – M.: Higher School, 1991.
2. Human physiology. T. 4. – Ed. R. Schmidt and G. Teus. – M.: Mir, 1986.
3. Human physiology. – Ed. G.I.Kositsky. – M.: Medicine, 1985.
4. Leontyeva N.N., Marinova K.V. Anatomy and physiology of the child's body. – M.: Education, 1986.
5. Drzhevetskaya I.A. Endocrine system of a growing organism. – M.:
Higher school, 1987.
6. Shepherd G. Neurobiology. T. 2. – M.: Mir, 1987.
7. Bloom F., Leiserson 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.
. Menstrual cycle- this is a set of morphological and physiological changes in a woman’s body from one menstruation to the next menarche (first menstruation) manifests itself during puberty, mainly at the age of 12-14 years, sometimes much earlier (at 9-10 years) or later (15-16 years). Regardless of nationality, the average duration of the menstrual cycle (from the first day of the previous to the first day of the next menstruation) is 75% of cases 28 days, which corresponds to one month according to the lunar calendar.
After 45 years of life, the regularity of menstrual cycles is disrupted, and then they completely disappear, that is, menopause begins
The regulation of the menstrual cycle is carried out by the hypothalamus, pituitary gland and ovaries. The generator of the menstrual cycle is the ovaries, which is why they are often called the “timer” - the “biological clock” of the cycle.
During the menstrual cycle, processes occur in the ovary (ovarian cycle, has follicular and luteal phases) and in the uterus (uterine cycle, which is divided into menstrual, proliferative and secretory phases.
. Ovarian cycle(changes in the ovary)
. Follicular phase. Influenced. FSH begins to develop several (up to 15) primary follicles containing first-order oocytes. One follicle between them begins to dominate from the 7th day of the menstrual cycle, the remaining follicles degenerate (the phenomenon of atresia). In the dominant follicle, the diameter of which reaches 20-28 mm, follicular cells multiply and, thanks to the influence of luteinizing hormone, they synthesize estrogens (there are 13,000 times more of them in the follicular fluid than in the blood). A significant increase in the amount of estrogen ensures hyperplasia of the uterine mucosa, an increase in the pH of the upper part of the vagina, the spread of the cervical canal, and a thinning of its mucus.
An increase in estrogen in the blood is a prerequisite for ovulation; in addition, during days 4 to 11 of the cycle they cause a decrease in the level of follicle-stimulating hormone, but do not affect the amount of luteinizing hormone. The level of estrogen in the blood reaches its maximum value three days before ovulation, it is at this time that they stimulate the synthesis of both gonadotropic hormones of the pituitary gland. This positive relationship between the synthesis of estrogen and luteinizing hormone is characteristic only in the pre-vulation period (E Knobil, 1972-72).
luteal phase. In the mature follicle, which is also called the Graafian vesicle, the first meiotic division occurs, thanks to which the first-order oocytes arise from the second-order oocytes. After rupture of the follicle wall (nulation, which occurs mainly on the 14th day of the cycle), the oocytes, surrounded by a layer of cells, enter the fallopian tube in the abdominal cavity. At this time, it contains a haploid set of chromosomes (22 somatic and 1 Tatev, but each has 2 DNA molecules). The formation of the actual mature egg will occur only when the oocyte completes the second meiotic division, namely during the penetration of sperm into it. After this, the male and female gametes (from gamete - wife and gametes - man) merge and a zygote is formed (from zigotos - united together).
After ovulation, the level of luteinizing hormone decreases, and in place of the ruptured follicle, under the influence of prolactin, a corpus luteum is formed. It, like the dominant follicle, becomes the main structure of the ovary, inhibits the growth and development of other follicles, and produces predominantly progesterone rather than estrogens. Progesterone inhibits the synthesis of gonadotropins and maintains the state of readiness of the uterine mucosa for interruptions in pregnancy. The most favorable conditions for the uterus to receive a zygote are created on the 7th day after ovulation. If fertilization does not occur, then the second-order oocytes die in the oviduct, the corpus luteum is still preserved for 10-14 days, but it decreases and a small scar remains. A decrease in progesterone synthesis by feedback principle causes more production of follicular hormone, so a new cycle begins, and the luteal phase of menstruation ends with an end.
If the zygote has arisen and established itself in the uterus, that is, during pregnancy, the corpus luteum continues to grow, reaching a diameter of 2-3 cm. The functioning of the corpus luteum is supported by the chorionic hormone, which is ingested by the placenta and is similar in activity to luteinizing hormonal hormone.
The influence of progesterone on the thermoregulation center leads to cyclical fluctuations in the internal body temperature of women. So, during the luteal phase the temperature increases by 0.6-0.8 °. With higher than during follicular growth, growth begins 1-2 days after ovulation, when the corpus luteum is formed, the cells of which synthesize progesterone.
uterine cycle(changes in the uterus)
. Menstrual phase. Occurs due to a decrease in the level of ovarian hormones (estrogens and progesterone), so there is a narrowing of blood vessels, a deterioration in the blood supply to the uterine mucosa, its epithelial layer dies and is left without nutrients. Then the vessels dilate, more blood flows in, and dead cells are removed with it due to the increased intensity of contraction of the muscles of the uterus.
. Proliferative phase. The time coincides with the follicular phase of the ovarian cycle, as it is associated with the influence of estrogen. There is an intensive proliferation of cells of the mucous membrane, which thickens significantly, and an acidic secretion with pH = 4.5 -5 is formed.
Secretory phase. It coincides in time with the luteal phase of the ovarian cycle. Under the influence of progesterone, the tubular glands of the uterine mucosa grow and produce a lot of mucus.
Menstruation lasts 3-5 days, it actually completes the female sexual cycle, but traditionally the cycle begins from it
. Sexual behavior is a complex of complex physiological, psychological and behavioral reactions associated with sexual function. Almost all human organ systems are involved in its manifestation. Sexual intercourse is an element of the formal cycle - this is actually copulation (coitus), this is a duet of two equal people united by love. Over the course of many centuries, a far-fetched idea has been established in European and Christian civilization; in the natural cycle, this is only the insertion of the penis into the vagina and related the actions of reality are not so. For sexual lovers, there is everything that unites them, namely being together, sleeping, relaxing, reading, visiting cultural institutions, etc.
3. Freud considered sexual relations to be the main motivating factor in all aspects of human behavior. One of the most important achievements of Z. Freud is the creation of the theory of human psychosexual development. He believed that the main cause of all neuroses is a psychological disorder based on sexual relationships, so he created the method of psychoanalysis to treat them.
In human sexual life, an important role is played by erogenous zones - areas of the skin and mucous membranes, the irritation of which causes sexual arousal or enhances it. They are divided into genital, those associated with the genitals, and extragenital (oral mucosa, lips, tongue, skin of the buttocks, inner edge of the sole, inner thigh, earlobe, etc.). Men are characterized by a suppressive but genital zone, and in women both groups are common.
In men and women, the sexual cycle includes four phases, which change sequentially with each other. The first phase is an increase in sexual arousal, the second is maintaining sexual arousal at the same level (plateau), the third is orgasm, the fourth is relaxation.
These phases manifest themselves differently in different people, which is due to their individual characteristics, but the physiological manifestation of the sexual reaction is more expressive in women. Women, as a rule, are more sexual than men, since they have a larger number of erogenous zones, especially extragenital ones.
Orgasm (from o ^ is sexual intercourse, but only 30% of women regularly enjoy orgasm. In men, orgasm is achieved through ejaculation.
It is believed that as a result of sexual intercourse, the brain intensively produces endorphins and enkephalins (endogenous opioids), which have narcotic properties, like opium and morphine, so they play a vital role in human behavior and are able to influence the vegetative processes of the body.
The combination of love and pleasure makes sex an important activity in the fight against stress and its destructive power on the heart, circulation, and immune system.
Sex is often called the quintessence of all human feelings, relationships, moods, desires. This is a way of mutual enrichment of partners, when each makes the other feel what is pleasant to him and what is not.
The main biological purpose of human sexuality, in addition to self-realization, is the birth of children. The reproductive system of women significantly influences the aging process of their body
American sexologist. D. Bancroft believes that one of the most important functions of human sexuality (except reproductive) is the preservation of the family, because sexual satisfaction reinforces the desire to stay together and creates a reliable emotional background. Starting a family and maintaining it is not only great happiness, but also great art.
Libido is the mental energy of sexual desire, which is associated with love
According to dualistic theory. Freud, a person has two basic instincts - to life (eros) and to death (ta-natos). Libido, as an expression of erotic energy, resists the destructive force of the desire for death, sexual desire is an integral part of the human personality.
Phases of libido formation:
1) conceptual, when while playing gender-role games, children realize the existence of differences between people of different sexes;
2) romantic, when fantasies arise, desires to please others;
3) erotic, when interest arises in everything related to sexual relations;
4) sexual, when there is a desire for sexual relations with a partner
The main stimulator of male potency and female orgasm is infatuation or love (classical love. Aloisi do. Abelard). Love and human sexuality are integral, they belong to the highest level of human needs, as they provide the opportunity to achieve the flourishing of personality, at the height of self-realization. Students. Socrates, followers of hedonism (pleasure), believed that the goal of every person’s life is to achieve pleasure and avoid dissatisfaction, and happiness consists of the sum of the pleasures experienced. Extremely great love. Tennov called limerincia, it is influenced by the mediator serotonin (after Leibovich).
The direction of sexual desire is associated with several levels of human gender formation, which depend on such factors;
Genetic - from the presence of a pair of sex chromosomes (XX or xy);
Gonadal - from the presence of gonads that form the corresponding gametes (ovaries or testes);
Hormonal - from the formation and ratio of sex hormones (estrogens or androgens) in the blood;
Morphological - from the anatomical structure of individual organs and parts of the body (the severity of primary and secondary sexual characteristics);
Psychological - from upbringing and understanding by the person in her environment of her belonging to a certain gender
The consequence of the gradual formation of sexual desire is the conscious choice of a sexual partner and appropriate behavior in sexual relations
To the works of 3. Freud, it was believed that sexuality is inherent in children. Later, an ultrasound examination showed that an eight-month-old fetus has an erection.
3. Freud identifies three stages of pregenital sexuality in children. In each phase, one organ or function comes to the fore;
1) first phase and oral component;
2) second phase and anal component;
3) third phase and phallic component, i.e. increased interest in genitals, masturbation
Sexological manifestations of each person go through certain periods of development
1 parapubertal (from para - nearby, pubertas - puberty) - formation at the age of 1 - 7 years of self-awareness of one's gender, children's interest in the sexual sphere
2. Prepubertal (from prae - before, pubertas - puberty) - creation at the age of 7-13 years of a stereotype of future gender-role behavior
3. Puberty (from pubertas - sexual maturity) - awakening of libido at the age of 12-18 years, the desire to assert oneself, including sexually
4. Transitional - the beginning of sexual life at the age of 16-26, but not uniform relationships over time
5 mature sexuality - achievement at the age of 26-55 years of stable sexual activity characteristic of the constitution of a particular person
6. Involutional - after 50 years, gradual loss of interest in sexual relations, decreased sexual activity
Psychosexual orientation, a person’s awareness of his belonging to a certain gender, can manifest itself in the form of hetero-, bi- and homosexuality, and other forms of sexual behavior
heterosexuality(from heteros - other, sexualis - sexual) - this is a sexual desire for an individual of a different sex. The basis of heterosexuality is love
. Bisexuality(from bis - twice, sexualis - sexual) - the presence of sexual desire for individuals of both their own and the other sex
. Homosexuality(from homos - equal, identical, sexualis - sexual) - this is sexual orientation towards a partner of the same sex. According to the data. A. Kinsey, 2-3% of women and almost 4% of men are homosexuals
. Erotica(from erotikos - love) - all aspects of communication, culture and art that reflect sexual desire in a form acceptable to the majority of members of society
. Pornography(from pornos - libertine, grapho - writing) - this is a description of the genitals, sexual intercourse in literature or art with the aim of achieving sexual pleasure, but in a form that is unacceptable for the majority of members in societies.
. Monogamy(from monos - one, gamos - marriage) and polygamy (from polys - many, gamos - marriage). A large number of germ cells should incline men to polygamy in order to make it possible to pass on their genes to the maxim of the minimum number of descendants, and the maturation of only one egg in women in 28 days inclines the woman to monogamy. Therefore, in a monogamous marriage, a man cannot always satisfy his sexual needs, but a woman’s sexuality and her sexual perception does not depend on the reproductive cycle, so this discrepancy may disappear. Primates, except gibbons, are polygamous; only the female gibbon is also capable of sexual activity, regardless of the reproductive cycle.
In persons with an accentuated character, the manifestation of sexuality is also different. For example, a schizoid type is outwardly contemptuous of the sexual sphere, he is often unable to attract the attention of the opposite sex to himself by ordinary means, this causes him to have a tendency to peek or show others his genitals.
Inertia in the behavior of the epileptoid type leads to the fact that they are very afraid of infection from new partners, they are characterized by jealousy even towards flirting, they consider any reaction of their partner to attention from others to be treason, they are sadomasochistic.
The period of puberty is characterized by a pronounced change in the hierarchy of needs, the need for self-respect, approval, recognition arises, aesthetic needs, desires for self-affirmation and self-realization are formed.
Changes in sexual behavior and the onset of sexual activity require a change in the social status of a young person, her joining adults, independence from parents
Having sex too early is socially and psychologically harmful to the further development of adolescents
Erikson (1968) believes that the main task of youth is to develop the ability and skills of sexual relations. It should be noted that they depend on intelligence, character
Masters and. Johnson (doctors, scientists, spouses) - authors of the books "Human Sexual Response", "Human Sexual Inadequacy" (1966,1970), "Masters and Johnson on Love and Sex" (1982), have done a lot about what sexual relationships have become more understandable to all people. They described several types of sexual behavior and several types of sexual behavior:
- “experimenters” who strive to increase the number of sexual partners; for them the whole world is a large sexual testing ground;
- “seekers” who use any means in search of an ideal; they increase the number of sexual partners in order to find the greatest pleasure;
- “conservatives” who are very picky about sex, they willingly flirt, but do not bring the matter to sexual intercourse
In a consumer society there is a lot of sex, but little love, especially mutual love. Sexual activity without marriage is spreading too quickly these days.
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