The sexual cycle of a woman. Female reproductive cycle
Natural methods for conceiving or avoiding pregnancy are based on the physiology of the female reproductive cycle and taking into account that the average lifespan of an egg cell is 12 to 24 hours, and that of a sperm cell is up to 5 days. To determine the fertile and infertile periods, it is necessary to know the female reproductive cycle.
A woman's sexual cycle is a period when a number of changes occur for the possible fertilization and implantation of an embryo. It consists of two stages: preovulatory or follicular, which begins on the first day of menstruation and lasts until ovulation, and postovulatory or luteal, which begins after ovulation until the next menstruation. The luteal phase is the most stable phase of a woman's menstrual cycle, but can range from 10 to 16 days depending on each woman. Thus, any change in a woman's cycle length is due to changes in the length of the pre-ovulatory phase. The female reproductive cycle. The hypothalamus produces gonadoliberin, which stimulates the secretion of FSH and LH from the pituitary gland. These two hormones are transported through the bloodstream to the ovary, which contains the eggs. Usually one of them is fully ripe. As the egg grows, it secretes estrogen. In the days leading up to ovulation, estrogen in the cervix produces a mucous secretion, which causes characteristic sensations in the external genital area, warning the woman that ovulation is approaching and, therefore, the days when it is possible to become pregnant begin. Twelve hours after reaching the maximum estrogen level, the pituitary gland organizes an LH surge. It takes 24 to 36 hours after ovulation for the egg to be pushed out of the ovary and down the fallopian tube. Fertilization takes place in the outer third of the tube, where a new human life is born. The luteal egg turns yellow as estrogen production decreases and progesterone production begins, which will 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 simultaneously produce a series of changes in the uterus to create three stages: 1) the phase of the menstrual cycle lasting about 4-5 days, in which the uterine lining, called the endometrium, "spills out" (corresponds to the beginning of the cycle). 2) or the proliferative phase of the endometrium (thickening with variable duration). 3) secretory phase with higher growth rates and vascularization. If fertilization has not occurred, 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 cervical mucus, since both respond to the same hormonal stimuli. The functions that can be observed are openness, height and tilt. Any change will mean the beginning of the fertile phase, which is characterized by an open, soft, high and straight neck; the infertile phase corresponds to a closed, rigid, low and tilted cervix. The 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 about 10-16 days after ovulation.
Slide 1
Completed by: student of the 238 a group of the pharmaceutical faculty Kaldashova Larisa Petrovna Checked by: candidate of biological sciences, associate professor Gerasimova O.V. SAMARA 2015Slide 2
Slide 3
Slide 4
Slide 5
MENSTRUAL CYCLE Cyclic changes in the organs of a woman's reproductive system, the main manifestation of which is monthly bloody discharge from the genital tract - menstruation. CLINICAL CHARACTERISTICS OF THE MENSTRUAL CYCLE Menstruation begins at puberty at the age of 11-15 and continues until menopause at the age of 45-55. For women, the average cycle is 28 days. Discharge lasts from 3 to 7 days. Blood loss averages 50-80 ml.
Slide 6
PHASES OF THE MENSTRUAL CYCLE The menstrual cycle of women consists of four phases, which are characterized by certain changes in the body. It should be borne in mind that the duration of each phase of the menstrual cycle in each case is as individual as the cycle itself.
Slide 7
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 rejected, 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.
Slide 8
FOLLICULAR PHASE The second phase of the menstrual cycle lasts about two weeks after your period ends. The brain sends impulses, under the influence of which the follicle-stimulating hormone, FSH, enters the ovaries, which promotes the development of follicles. A dominant follicle is gradually formed, in which the ovum 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 cervical mucus, making it immune to semen. Some 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.
Slide 9
OVULATION PHASE The phase lasts about 3 days, during which there is a release of luteinizing hormone (LH) and a decrease in the level of follicle stimulating hormone (FSH). LH affects the cervical mucus, making it susceptible to semen. Also, under the influence of LH, the maturation of the egg ends and its ovulation occurs (release from the follicle). A mature egg moves into the fallopian tubes, where it is waiting for fertilization for about 2 days. The most suitable time for conception is just before ovulation, since sperm cells live for about 5 days.
Slide 10
LUTEINE 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, the production of LH stops, the cervical mucus dries up. 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.
Slide 11
The phases of the menstrual cycle are caused by the influence of hormones that affect not only physiological processes, but also the emotional state. And although the modern rhythm of life requires constant activity from women, observing the changes in the emotional state associated with the phases of the menstrual cycle will help determine the most unfavorable days for active actions or conflict resolution. This approach will allow you to avoid unnecessary stress and maintain your strength and health.
Slide 12
FERTILIZATION is the process of fusion of a sperm with an egg, leading to the formation of a new unicellular organism - a zygote. A woman capable of bearing children ovulates about once a month. This is the process of release of an egg ready for fertilization from the follicle. In most cases, one sperm and one egg are involved in fertilization.
Slide 13
FERTILIZATION However, in order for the fertilization process to take place, the sperm must first reach the egg. Once inside the vagina, a man's seminal fluid contains between 100 and 400 million sperm. Their movement speed 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 intercourse, the sperm reach the end sections of the fallopian tubes, in which they merge with the egg. Then the fertilized egg moves along the fallopian tube, thanks to its peristaltic movements and movements of the ciliated epithelium. Approximately 7-8 days after fertilization, the egg enters the uterine cavity. There it is embedded in the mucous membrane, which contains nutrients for the development of the embryo. From the moment of fertilization, pregnancy begins.
Slide 14
DEVELOPMENT OF THE HUMAN GERM 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 period of development is called fetal.
Slide 15
SPERMATOZOID IN THE UTERINE TUBE OF THE EGG CELL MEETING OF THE SPERMATAZOID WITH THE EGG. OVIDUCT
Slide 16
Two sperm come into contact with the egg, but only one should remain. Sperm inside the egg
Slide 17
Day 8: The fertilized egg goes down the oviduct to the uterus and the embryo attaches to the wall of the uterus. The development of the brain of the embryo begins
Slide 18
On the 40th day, the embryonic cells form the placenta. The placenta forms a protective barrier, provides oxygen to the fetus through the mother's circulatory system, and carbon dioxide is transported in the opposite direction. Through the placenta, the fetus receives water, electrolytes, nutrients and minerals, vitamins; the placenta is also involved in the removal of metabolites (urea, creatine, creatinine).
Slide 19
Week 8: The auricles and face are formed, the rudiments of the gill slits atrophy. The embryo is surrounded by an aqueous membrane. The fingers and hands are well defined and delineated, the toes are well defined, and muscle movement begins. The embryo begins to react with feelings. The embryo reacts to irritation of thin cheek hair by moving the head, moving the torso and pelvis back, stretching the arms and hands to remove the hair (possibly the first manifestation of tactile sensitivity). Then the sensitivity spreads to the rest of the body.
Slide 20
Week 10: All major body parts are in place. The eyes and ears are in a normal position. The skeleton is well defined. The baby's airway, which starts from the nose and continues to the lungs, is ready for the first breaths. The eyes are half closed. The eyelids will close over the next few days.
Slide 21
Week 16: Formation of the limbs with fingers and nails. The papillae are surrounded by pores and cells with microvilli, which complete the taste perception system and begin to function. After this, significant changes in these receptors do not occur, except that their number increases, and they also develop in breadth and depth. The first manifestations of facial expressions: the ability to skew eyes, smile mockingly. Thumb sucking begins. The development of olfactory receptors ends. The embryo is capable of distinguishing several hundred odors.
Slide 22
Week 18: Fetal movement is felt, heartbeat is heard. At this time, the fetus begins to hear. The embryo length is 140-190mm. Week 20: The skin of the fetus becomes covered with the finest (vellus) hairs (especially in the area of \u200b\u200beyebrows and eyelashes. Week 24: Development of facial expressions: pouting lips, frowning, muscle tension around the eyes associated with crying of the child.
Slide 23
6 months: About 8-10 weeks before birth. The fruit at this time turns over to come out head first. Week 36: The fetus is fully formed, the skin is covered with original lubricant, the hair on the head reaches 25 mm. A hormonal signal is sent to the mother's body, requiring the end of the pregnancy.
Slide 24
Slide 25
Hormonal changes and the role of placenta hormones in the body In the relationship between the mother and the fetus, the placenta plays the role of an endocrine gland. In it, the processes of synthesis, secretion and transformation of a number of hormones of the protein and steroid structure take place. There is a close relationship between the mother's body, the fetus and the 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 steroid (gestagens and estrogens) and protein (CG, PL), are intensively occurring. Pregnancy-specific hormones. - HG. - PL. - Hormones of the hypothalamus. - Corticoliberin. Pituitary hormones. - Prolactin. - Growth 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 accounts for 85% of all estrogen during pregnancy. Its main role is the regulation of the uteroplacental blood circulation, i.e. supplying the fetus with all 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 enters the liver of the pregnant woman, where, combining with glucuronic acid, it is inactivated. Inactivated estriol is excreted in the urine of a pregnant woman.
Slide 29
In a much smaller amount than estriol, other estrogens are formed in the fetoplacental system - estrone and estradiol. They have a diverse effect on the body of a pregnant woman: they regulate water-electrolyte metabolism, cause sodium retention, an increase in the volume of circulating blood (BCC), 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 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 for pregnancy is progesterone. Progesterone causes changes in the mother's body that contribute to the onset and development of pregnancy. Under its influence, secretory processes occur that are necessary for the implantation and development of the ovum. Progesterone also promotes the growth of the genitals of the 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 hypertrophy of fat cells. A metabolite of progesterone, pregnandiol, is excreted in the urine.
Slide 31
The main protein hormones of pregnancy are chorionic gonadotropin (CG) and placental lactogen (PL). - HCG is a glycoprotein produced by the chorion even before the formation of the placenta. In terms of its biological properties, it is similar to the LH of the pituitary gland, contributes to the preservation of the function of the corpus luteum of the ovary, affects the development of the adrenal glands and fetal gonads, and affects the exchange of steroids in the placenta. CG is found in 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 approaches the growth hormone of the anterior pituitary gland and prolactin ... PL can be detected in blood from 5 weeks of gestation. 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. Due to its anti-insulin action, PL leads to an increase in glyconeogenesis in the liver, a decrease in the body's tolerance to glucose, and an increase in 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 growth, maturation and reproduction processes. 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, libido and behavior.
Slide 33
Atlas: Human Anatomy and Physiology. Complete practical guide Elena Yurievna Zigalova
Human sexual cycle
Human sexual cycle
The human sexual cycleconnection with the characteristics of human sexuality is closely related to the psyche and depends on many psychological, personal and interpersonal factors. And at men and women, the sexual cycle consists of four phases, successively replacing each other: increasing sexual arousal, maintaining sexual arousal at the same level (plateau), orgasm and relaxation (resolution)(fig. 56). These phases do not always have clear time boundaries, they are different in intensity and duration, not only for different people, but even for the same person. Both men and women with sexual arousal, two main physiological reactions necessarily occur: a sharp rush of blood to the genitals (and in women, to the mammary glands) and muscle (or rather, neuromuscular) tension.
Excitement in a man is manifested by an erection. Penile erection is the main condition for the male sexual cycle.The mechanism of erection is described above (see section "Penis", p. XX). Erection is associated with arousal of the parasympathetic nervous system.Sexual arousal in a woman after 10-40 seconds. leads to changes in the female genital organs, and primarily to lubrication,moisturizing the vagina. Initially, separate drops appear on the vaginal mucosa, which then merge, moisturizing the entire mucous membrane. Lubrication indicates the readiness of the female genital tract for sexual intercourse, it continues throughout the entire sexual cycle, the volume of the clitoris and its head (erection) increases. As a rule, at the height of an erection, provided the woman is ready, the penis is inserted into the vagina (introitus) and begins itself copulative,or frictional,stage (from Lat. copulation - "connection"; frictio - "friction"). From the point of view of physiology, at this time there is plateau,during which the excitement remains at approximately the same level.
Figure: 56. Sexual cycle (A, B - according to W. Masters and V. Johnson; C - according to GS Vasilchenko).A - three variants of the female sexual cycle: 1 - multiple orgasm; 2 - excitement, turning into a plateau phase without reaching orgasm, in this case the resolution phase proceeds very slowly; 3 - a sharp, intermittent increase in arousal, orgasm achievement with a fast resolution phase. B - the most typical variants of the male sexual cycle, the dashed line shows one of the possible variants of repeated orgasm with ejaculation after the end of the refractory period, other variants of the development of the male sexual cycle are also possible, which in many cases coincide in shape with curves 2 and 3 characterizing the female genital cycle. B - a typical curve of the male sexual cycle
The introduction of the penis into the vagina and subsequent frictions increase the woman's sexual arousal to a certain level, after which it begins plateau phase,during which the sexual tension does not increase or decrease for a certain time. The duration of this phase varies widely. If the frictions continue, sexual arousal increases and the next phase develops. orgasm(from the Greek. orgao - "I burn with passion"). Orgasm is the culmination of sexual intercourse in which the entire human body participates. Orgasm is the highest pleasure that a person can experience. A man achieves an orgasm thanks to emissions(from lat. emissio - "release, emission") and ejaculation(from Lat. ejaculatio - "eruption").
Due to the rhythmic contractions of the penis (pulsation), muscles of the perineum, prostate with an interval of 0.7-0.8 s, the seminal fluid moves to the anterior part of the urethra and ejaculation begins. As a rule, in men, orgasm and ejaculation occur simultaneously, but these are different processes. Ejaculation is the release of semen. Moreover, in some cases it is not accompanied by an orgasm.
The anatomical and physiological basis of the female orgasm is the rhythmic contractions of the genitals.Orgasm in women is characterized by simultaneous rhythmic contractions of the muscles of the uterus, the lower third of the vagina ("orgasm cuff") and the rectal sphincter. At the beginning of orgasm, the muscles contract with great intensity and speed (the interval between contractions is approximately 0.8 seconds). Then the strength, duration and frequency of contractions are reduced. A "soft" orgasm can be accompanied by only three to five contractions, while a strong one is 10-15. However, in different women and even in the same woman, some orgasms occur gently, with a feeling of faint trembling or warmth, while others can be compared to the "explosion of an aerial bomb." Changes during orgasm affect not only the genitals, but all organs and systems. During orgasm, the heart rate rises sharply, which can reach 160-180 per minute; arterial pressure rises (systolic - by 30–90 mm Hg, diastolic - by 20–40 mm Hg); respiratory rate increases to 36–42 per minute; skeletal muscles contract, especially facial, intercostal and abdominal muscles.
There are many differences between male and female orgasms, but there are also important anatomical and physiological similarities: orgasm is accompanied by rhythmic contractions of the muscles of the genitals, perineum, rectal sphincter; the same nerves cause muscle contraction in men and women.
The female orgasm is one of the important distinctive features of Homo sapiens. Modern researchers are unanimous in the opinion that a woman is the only female creature that is capable of experiencing an orgasm.
Resolution phase.After ejaculation, sexual arousal subsides. The refractory period is comingthe duration of which is different not only for different men, but also for the same man. For most men in adulthood, after ejaculation occurs absolute refractoriness, that is, absolute sexual non-excitability, when it is practically impossible to cause an erection. As a rule, the man falls asleep. A woman should know about this and not be offended. The absolute is replaced by relative refractoriness, during which a second erection and subsequent intercourse may occur.
Regardless of whether the woman has experienced one or more orgasms, the resolution phase follows the orgasm. If after a sharp excitement in the plateau phase, orgasm does not come, the resolution phase may be delayed; many women develop frustration- a painful psycho-emotional state caused by an acute feeling of dissatisfaction.
From the book Life Safety the author Victor Sergeevich Alekseev the author author unknown From the book Children's Infectious Diseases. Complete reference the author author unknown From the book Children's Infectious Diseases. Complete reference the author author unknown From the book Normal Physiology the author Nikolay Alexandrovich Aghajanyan From the book Atlas: Human Anatomy and Physiology. Complete practical guide the author Elena Yurievna Zigalova From the book The Complete Encyclopedia of Wellness the author Gennady Petrovich Malakhovauthor Gleb Pogozhev From the book A Healthy Man in Your Home the author Elena Yurievna Zigalova
author Yu.M. Ivanov
From the book MAN AND HIS SOUL. Life in the physical body and the astral world author Yu.M. Ivanov
Luliberin of the hypothalamus affects the adenohypophysis, stimulating the production of FSH by its cells. This hormone controls oogenesis, stimulating the transformation of oogonium into an ooblast, and then into an oocyte and egg cell. The development of the oocyte occurs inside the follicle, which under the influence of FSH also undergoes a number of changes, turning through a number of stages into a graaf bubble. The follicle membrane is formed by epithelial cells, lying in several layers. The inner layer is formed by secretory cells that produce estrogens, the main of which is estradiol. Follicle maturation is accompanied by increased secretion estradiol. By the time the Graafian vesicle is formed, the concentration of estradiol in the blood reaches a level that, through a positive feedback mechanism, increases the release of FSH and LH.
A surge in LH concentration is a signal for the onset of ovulation, in addition, LH triggers the formation of a temporary endocrine gland - the corpus luteum - at the site of the bursting Graafian bubble. The corpus luteum is formed by the remaining cells of the epithelial wall, which immediately after ovulation begin to secrete progesterone - another female sex hormone. Progesterone prepares the female body for pregnancy. It stops the secretion of FSH and LH, inhibiting the maturation of the next follicle, and also causes the growth of the inner layer of the uterus, preparing it for the attachment of a fertilized egg (for implantation). If fertilization did not occur, then the corpus luteum degenerates after about two weeks, progesterone stops flowing, and the overgrown uterine wall against the background of a sharp decrease in the concentration of PG and estrogen is partially rejected and excreted from the body (Fig.3.6).
Figure: 3.6.
This process is called menstruation and during the reproductive period of a woman's life occurs regularly - with a frequency of about once every 28 days. Normally, the menstrual cycle is disturbed only by the fertilization of the egg and subsequent pregnancy. In this case, the corpus luteum does not collapse in days, but participates, due to the production of its hormones, in the formation of the placenta and secretes the peptide hormone relaxin, which relaxes the cervix and pelvic ligaments during childbirth.
In addition to hormonal control of the female reproductive cycle, hormonal support for pregnancy and childbirth, female sex hormones are responsible for the formation of secondary sexual characteristics, for the development of the female skeleton, for the “female” metabolism. Estrogens are anabolic (weaker than androgens); they lower blood cholesterol. In addition, they accelerate the maturation of bones, which explains the cessation of skeletal growth during puberty, and accelerate blood clotting, which is extremely important during menstruation. The cessation of estrogen secretion, leading to menopause, is also accompanied by a number of cardinal physiological changes in the female body.
The structure and function of the female reproductive system is much more complex than that of the male. Its endocrine regulation, as well as a variety of diseases associated with a violation of this regulation, are equally more complicated. A common external manifestation of such disorders is amenorrhea - the cessation of menstruation. Amenorrhea can be caused by a variety of genetic disorders, excessive secretion of androgens, trauma and tumors affecting the hypothalamic-pituitary system. Amenorrhea can develop as a result of shock, depression, excessive physical exertion (amenorrhea of \u200b\u200bathletes and travelers).
Less common than amenorrhea, there are cases of hypersecretion of female sex hormones. They are usually caused by overgrowth of follicular tissue. These tumors - folliculomas - develop in adult women. Excessive production of estrogen causes numerous disorders in the female body, including symptoms of increased sex drive. In childhood, the development of such a tumor leads to too early puberty and early cessation of growth.
Even from a runaway review of cyclical changes different parts of the female reproductive apparatus clearly shows that all periodic phenomena must be coordinated to a certain extent with each other. Each organ plays a role in reproduction. It is not enough for him to periodically perform this role with maximum efficiency; the period of readiness of each organ or its part should come when the entire complex mechanism of reproduction is ready for functioning.
For a long time with certainty establishedthat hormones control and coordinate in time the various stages of the reproductive cycle. The interaction of these hormones is very complex. It took a long and persistent experimental work to refine the results obtained under the influence of any one hormone. A much more difficult task is interpreting the effects of multiple hormones acting together or sequentially.
Currently in biology there is no field where research has been as intense as in endocrinology. Almost every biological or medical journal replenishes our information about the methods of formation, chemical properties or physiological action of hormones. Nevertheless, it is still impossible to give even a brief approximate outline of some of the most important hormones that regulate the sexual cycle, without the proviso that most of the data obtained recently have not yet been thoroughly verified and therefore a clear idea of \u200b\u200bthe subject will only develop in the future.
Paradoxically, the primary reproductive activator - the pituitary gland is not located near the reproductive organs, but is located deep in the skull, in close connection with the brain. The pituitary gland, slightly larger than a cherry stone, is a little noticeable mass of tissue, but its action has long piqued human curiosity. In the Middle Ages, scientists argued about whether the pituitary gland is the permanent seat of the soul or a special organ that secretes mucus from the brain.
It has now been found that pituitary at different times produces from 5 to 15 hormones, most of which are known under several names.
Long before the onset of sexual activity maturity the anterior lobe of the pituitary gland, through one of the hormones it produces, begins to influence the development of the genitals. In young hypophysectomized animals, the reproductive organs remain underdeveloped, the characteristic sexual cycle is not established and the individual turns out to be sterile. Although it has long been known that with early removal of the ovaries, the menstrual cycle is not observed at all and that their removal at puberty leads to the cessation of menstruation, but only now have we begun to understand that the reasons for these changes are much deeper. Even before the ovary begins to activate the uterus, it must first come into a state of functional activity under the influence of stimulating influences exerted on it during the period of its growth by the hormone of the anterior pituitary gland.
We recommend watching the training video:
This action pituitary gland is just the beginning of a whole series of processes. After reaching puberty, the pituitary gland begins to produce hormones that have a profound effect on the gonads and are therefore called gonadotropic hormones, in contrast to other hormones of pituitary origin that act on other organs, such as thyroid-stimulating and adrenocorticotropic hormones. Currently, it is believed that there are two gonadotropic hormones, one of which stimulates the development of the follicle, and the second - the development of the corpus luteum.
Hormone, stimulating follicular development, activates their consistent growth and maturation. Here another link in the chain of hormonal action arises: when the follicles enlarge, they begin to produce a hormone that can be obtained from the follicular fluid. This hormone is estradiol. The injection of the required amount of estradiol in experimental animals that did not have estrous changes due to complete oophorectomy led to the restoration of typical symptoms of estrus.
On this basis estradiol often referred to as estrogen hormone. The value of estradiol, the amount of which increases significantly by the time of ovulation, is quite obvious. The maximum amount of this hormone that stimulates sexual activity is observed in the period preceding the release of the egg from the follicle into the abdominal cavity.
Following ovulation, another group is activated hormones... The hormone from the anterior pituitary gland, which stimulates the development of the corpus luteum, causes rapid proliferation of the epithelial cells of the burst follicle. In this case, the chemical properties of these cells change, which is associated with the formation of a yellow body. In turn, the corpus luteum, under the influence of additional stimulation from the lactogenic hormone, produces a hormone that acts on the uterus. This hormone, called progesterone, stimulates the lining of the uterus to make changes to prepare it for pregnancy.
Here again with obviousness advocates clear consistency in time, because the chain of processes that leads to the preparation of the uterus for the perception of the embryo begins even during the first stages of egg development.
With such sequences phenomena, the relationship between ovulation and menstruation is of particular importance. If ovulation takes place, say, on the 13th day of the menstrual cycle, and sexual intercourse occurs at about the same time, this allows the embryo to develop within 7 days, which contributes to its successful implantation into the already prepared uterine lining. During these 7 days, under the influence of the corpus luteum hormone, the mucous membrane of the uterus thickens, its glands become active, the amount of blood in it increases. When the uterus is in this premenstrual phase, it is already ideally prepared to receive and strengthen the embryo.
It turned out that corpus luteum hormone in addition to its action on the uterus, it has another, no less important physiological action. It has been repeatedly shown that injection of corpus luteum extract delays ovulation. This action is determined by the relationship in time between the maximum development of the corpus luteum of ovulation and other phenomena of the cycle. The corpus luteum reaches a noticeable degree of development and acquires histological signs of active secretion a few days after the rupture of the follicle from which it was formed.
Microscopic examination it can be seen that the regressive changes in the corpus luteum appear when the next menstrual period should begin, and a noticeable decrease in the size of the corpus luteum reaches the time of the maturation of the new follicle. These data showed that ovulation corpus luteum is a source of a hormone that acts as an antagonist of pituitary follicle-stimulating hormone, causing a delay in the development of the following follicles.
Sexual cycle phenomena were presented in the simplest form, without undue detailing, a number of facts that make these phenomena one of the most fascinating areas of modern biological science. However, even this brief essay demonstrates how amazingly coordinated the entire reproduction mechanism is. So far, we've only seen a series of changes that are repeated in preparation for pregnancy. Ovulation is a critical phenomenon that all other cyclical changes are confined to. The egg released by the rupture of the follicle is ready for fertilization and all other organs are also ready to play their role if the egg is fertilized.
It has now been found that pituitary at different times produces from 5 to 15 hormones, most of which are known under several names.