Endocrinology / / August 12, 2017
Implementation of cyclic changes in the ovaries is the result of a complex neurohormonal regulation.
Although sexual cycle, ovulation and corpus luteum development of the cerebral cortex may have a great influence, until the complete cessation of them, but for the rhythmic cyclical changes in the ovaries of participation is not mandatory.It is now well established that the necessary links for the occurrence of these processes are the hypothalamus, pituitary, ovaries.The involvement of other parts of the nervous system (the reticular formation, amygdaloidal area) is very likely, since their injury disrupted cyclical, but more accurate information about their role in the course of the cycle yet.
apparently decisive in the occurrence of cyclic processes of maturation of follicles in the ovaries and ovulation is the effect of hypothalamic centers that define the whole rhythm of the sexual cycle.This is confirmed by experiments showing recovery of a normal cycle in female hypophysectomized rats, which in t
In animal studies, found that the centers of regulating the allocation and possibly production of gonadotropins by the pituitary gland located at the optic chiasm, and in the ventromedial paraventricular nuclei of the hypothalamus in gray mound.Regulation of allocation of luteinizing hormone (LH) from the pituitary gland in two ways: centers in eminentia mediana, maintain a constant release of LH small enough to stimulate estrogen production in the ovaries.Therefore, when they are damaged due to genital atrophy develops termination of estrogen production.Cyclic same selection LH is responsible for ovulation, the suprachiasmatic regulated centers.Therefore, when standing estrus fault develops in rats, guinea pigs, to the lack of ovulation, ovarian cystic change.
has now been found that the regulation of gonadotropin release from the hypothalamus is carried out by neurohumoral - entering the blood of the portal system pituitary-specific factors (probably of polypeptide nature), regulating output of luteinizing hormone and pituitary gland into the blood.They call them gipofizotropnymi factors.
Previously, it was believed that follicle stimulating hormone (FSH) causes the development of follicles in the ovaries and the secretion of estrogen and luteinizing hormone - ovulation.However, recent data show that all the processes in the ovary are the result of the combined action of FSH and LH, since the action of pure FSH, without the slightest trace of LH occurs not only development, but even the growth of follicles.This has been shown in experiments with the introduction of FSH together with antisera to LH than achieved a complete neutralization of endogenous LH and its impurities in preparations of FSH.With a lack of LH during the follicular maturation even reached the large size of the follicles are not able to ovulate when giving ovulatory dose of LH.At the same time capable of normally developed follicle to ovulate even with increasing doses of FSH and not LH.In the intact organism at the time of ovulation is an increase in separation of both hormones - FSH and LH, but nevertheless with a predominance of LH in the mixture.ovarian estrogen production is also the result of the combined effect of FSH and LH.
Besides FSH and LH anterior pituitary produces also luteotrophic hormone.Previously it was thought that its function is to maintain the corpus luteum and the resulting stimulation in conjunction with LH progesterone production by the corpus luteum.These conclusions drawn from experiments on rats, which is the situation really is true, however, not be applicable to other animals (cows, rabbits, pigs), who luteotrophic hormone does not stimulate the release of progesterone, and the stimulation of progesterone carried out under the influence of only onePH.The man luteotrophic hormone also increases the secretion of progesterone.The proposition that lyuteotropin not needed to maintain the corpus luteum activity, confirmed by clinical observations of hypophysectomized on the pituitary adenoma in women who as a result of ovulation induced by administration of FSH and human chorionic gonadotropin, became pregnant, which ended in a normal birth.Applicable products do not contain luteotrophic hormone therefore luteotrophic hormone is not necessary to preserve the structure and activity of the yellow loop body and the corpus luteum of pregnancy.
ovarian hormones, in turn, influence the hypothalamic, thereby changing the output drivers of the allocation of pituitary gonadotropins.When this physiological estrogen quantities do not affect the selection of LH and FSH, reduced only selection.Small doses of the estrogen, on the contrary, stimulate the secretion of FSH from the pituitary gland.The regulation of production of LH in the body, apparently carried progesterone: small doses of progesterone stimulate the secretion of LH, large - suppressed.Thus, the flow of the menstrual cycle in the body based on the principle of self-regulation, according to the principle of feedback, but is decisive in this disk appears, hypothalamic centers.
The beginning of the cycle is detected in the urine increased amounts of gonadotrophins when tested mouse uterine weight, which represents the amount of FSH and LH.It is not yet established which of the hormones - FSH or LH is dominant in this period.The role of this initial peak of gonadotropins is not yet elucidated;perhaps it gives rise to the development of the follicle, which will continue to ovulate under favorable conditions.Then gonadotropin production is reduced, but continues to be allocated a certain number of them, stimulating the development of the follicle and the production of estrogen in it.Isolation of estrogen, which has been low at the beginning of the cycle, starts to increase gradually.In addition to estrogen, in the maturing follicle is also carried out and production of progesterone.Before ovulation occurs a slight increase in release of progesterone into the blood, and at this time there is a small peak in the urine excretion pregnanediol.Possibly, this increase in progesterone production causes an increase of LH release from the pituitary gland that causes ovulation.With this agreement is evidence that in the middle of the cycle is an increase in urinary excretion of gonadotropins, mainly, which coincides with the moment of ovulation.
During ovulation in the urine stands out as the maximum amount of estrogen - the so-called ovulation peak of their excretion.
After ovulation products like gonadotropins and estrogen is reduced, and then after 3-4 days increased production of progesterone and estrogen-formed yellow body & lt; 0.Lifting gonadotropin release during luteal phase is not observed.Some authors believe that to maintain the secretory activity of the corpus luteum in the nonpregnant enough of the gonadotropic stimulation, which he received during follicle rupture.After the regression of the corpus luteum and progesterone reduce the production of estrogen and observed a new upsurge release of gonadotropins, resulting in the onset of a new cycle.
Currently, there are more or less complete picture of the regulation of sexual cycle, covering all involved in the process units.It is unclear how the production of androgens during the menstrual cycle.Some authors found cyclical fluctuations highlight 17-ke-tosteroidov over the cycle, others - did not show them.To clarify this question is necessary to determine a more accurate indicator - the amount of testosterone, as 17-keto steroids contain metabolites not only ovarian androgens, but also to a large extent the metabolites of adrenal hormones.It is also unclear what role androgens in the regulation of cyclic production of gonadotropins, although androgen excess in pathological conditions, with an unchanged number of common cyclical release of gonadotropins FSH and LH disappears.
for regulation of follicular development and corpus luteum in the ovary in the whole organism may be significant not only changes in the quantity and quality of gonadotropins, but the sensitivity of the ovaries to change gonadotrophic stimulation.This may be due to the presence of gonadotropin-invariant-factors allocated simultaneously with gonadotropins.There is evidence, for example, that in the middle of the cycle, when the maximum output of gonadotropins antigonadotropiny amount, on the contrary, reduced.Furthermore, ovarian sensitivity to gonadotropic stimulation of nerve impulses can be adjusted up to the complete development of refractoriness to gonadotropins.
What is the role of these mechanisms in the system of the rhythmic flow of follicular maturation, ovulation and hormonal activity of the ovaries.
Cyclic changes of estrogen and progesterone production in the ovaries related to the production of cyclic gonadotropin hormones cause cyclic transformation of the endometrium.These cyclic endometrial transformation are biphasic and menstruation ends.
I phase - the phase of proliferation - lasts 12 to 14 days.Endometrial transformations occur in the functional layer.Basal layer does not change and serves for the regeneration of the functional layer.
beginning of the proliferative phase is considered to be the first day of menstruation, although taking place at this time of the processes in the endometrium are the result of hormonal influences of the previous cycle.During the month, continuing 3-5 days there is rejection of the functional layer.Following the processes of desquamation begins regeneration and epithelialization in the basal layer.The regeneration process involves all components endometrium - prostate stroma and blood vessels.In the early proliferative phase (first week after a month) from the basal layer toward the surface of the marked growth of direct tubular glands with narrow openings.The glands are lined with first cube, and then columnar epithelium.Strom new functional layer is loose, with the presence of a network of fibers argyrophil.Blood vessels are more narrow lumens.In the second week of the cycle (late stage of proliferation) glands increase in size and take a meandering (serpentine) shape.At the end of the proliferation phase, which coincides in time with the end of the egg maturation, functional layer is greater than the thickness of the basal layer of 4-5.Stroma is loosened.After ovulation, in the glands of the functional layer are beginning to show signs of secretion.Increased twist glands, glands gaps widen.Gradually glands become sawtooth appearance, the gaps are filled with their secret.At the same time it changed the structure of the stroma cells.They swell, increasing in size, they lose their spindly character, getting kind of decidual tissue.Consequently, the mucosa of the functional layer is divided into two layers: an upper compact, in which there are narrow gaps and detsiduopodobnye gland epithelial stroma and spongy or cancellous consisting of dilated glands sawtooth filled secret.This entire process takes mucous adjustment of the 14th to 28th day of the cycle (at 28-day menstrual cycle).The endometrium is prepared for implantation of a fertilized egg.If this does not happen, then the beginning of the corpus luteum regression coincides beginning of the collapse of the endometrium - menstruation.By the early onset of menstruation under the influence of progesterone relaxes the muscle tone of the uterus;after regression of the corpus luteum due to the influence of estrogen, originating from a new follicular ripening, increases tone of the uterus, which is one of the factors cessation of menstrual bleeding.
rejection mucosa during menstruation is now seen as a complex process in which the primary role played by the influence of hormonal factors on the cardiovascular system of the endometrium.
blood supply and functional basal layer of the endometrium is not the same.Depart from the muscle layer shorter arteries supplying the basal layer, and a long, elastic fibers surrounded by a helically coiled supplying the functional layer.During maturation of the follicle exposed to estrogen number of spiral arteries supplying the functional layer increases.During the heyday of the corpus luteum number of spiral arteries even more increases.They acquire a serpentine shape, twists, giving a branching network of capillaries on the surface of the functional layer.The number of diverters veins and their width is also significantly increased.In general, the total volume in the vessels of the corpus luteum phase in relation to the proliferation phase is increased by three times.These vascular changes in the endometrium are specific to the uterus, they can be artificially created by the introduction of certain doses of hormones.Of the numerous clinical observation it is known that under the influence of estrogen can achieve significant endometrial proliferation in castrated women with its original atrophy.Cancel hormonal stimulation results in 4-5 days to uterine bleeding.Maturity of the bleeding after cessation of estrogen action (withdrawal bleeding) depends on the dose administered estrogen.The more they are, the later comes krovootdelenie.This can cause bleeding and other steroid hormones, as it comes as a result of vascular reaction of the endometrium to a drop in hormone levels in the blood.According Caffier, it has the character of diapedesis due to increased permeability of the vessel walls.In the normal menstrual cycle, as shown by Markee study, Kaiser, under the influence of progesterone spiral vessels of the functional layer, highly proliferating and twisting, are suitable for the endometrial surface, giving arteriovenous anastomoses.Falling levels of progesterone during the corpus luteum atresia causes a disturbance of blood supply to the vessels of the endometrium - spiral vessels are sharply reduced, they disrupted the blood supply, slowing blood flow and stasis occurs.Stagnation of blood and a slowing of the blood flow in the capillaries of the numerous leads to increased intravascular pressure, increased permeability of their walls and their rupture - begins menstruation.Circulatory disturbance of the endometrium in a functional layer (together with lytic enzymes exposure) leads to the disintegration of menstrual functional layer.Anastomoses with the basal layer of the arteries of the muscular layer providing him normal blood circulation, resulting in the basal layer dissolves.
- ovarian hormones.Estrogens
- ovarian anatomy
- ovarian hormones.Androgens
- Treatment syndrome Cushing's
- androgen-producing tumors of the adrenal cortex
- Biological effects of catecholamines
- diagnosis and treatment of pheochromocytomas
- Diseases of the adrenal medulla
- Treatment of chronic adrenal insufficiency
- Diseases of the thymus (thymus) gland
- relationship thymus gland with endocrine glands
- thymus gland and its physiology
- sTATUS THYMICO-LYMPHATICUS (lymphoidotoxemia)
On the other hand, it is possible to artificially pushstart bleeding, increasing the hormone levels in the blood.Markee managed to arrest bleeding in castrated monkeys, whose administration of estrogen and progesterone causes endometrial changes premenstrual type.