The hypothalamus secretes a small peptide from which gonadotropin-releasing hormone (GnRH, also known as luteinizing hormone-releasing hormone known).
The hormonal interaction between the hypothalamus, pituitary and ovaries controls the reproductive system of women. The hypothalamus secretes a small peptide from which gonadotropin-releasing hormone (GnRH, also known as luteinizing hormone-releasing hormone known). GnRH controls the release of the gonadotropins luteinizing hormone (LH) and follicle stimulating hormone (FSH) from specialized (gonadotropic) cells in the anterior pituitary (the axis CNS hypothalamic-pituitary-gonadal-target organ.). These hormones are released every 1-4 hours in short bursts (pulses). LH and FSH promote ovulation and stimulate the release of sex hormones estradiol (an estrogen) and progesterone by the ovaries. Estrogens and progesterone in the circulating blood are bound almost exclusively to plasma proteins. Apparently, only the free estrogens and progesterone are biologically active. They stimulate the target organs of the reproductive system (z. B. mammary gland, uterus, vagina). They usually have an inhibiting effect, under certain circumstances (eg. As around the time of ovulation) but they can trigger the release of gonadotropins. The CNS-hypothalamic-pituitary-gonadal axis target organ. Ovarian hormones act directly and indirectly to other tissues (eg., Bone, skin, muscle). FSH = follicle stimulating hormone, GnRH = gonadotropin-releasing hormone, LH = luteinizing hormone. Puberty as puberty, the sequence of events is referred to as the developed the physical characteristics of an adult and the ability to reproduce a child. The LH and FSH concentrations in the circulating blood are elevated at birth, then fall within a few months to a low level and remain there until puberty. Until then, only a few qualitative changes in the reproductive target organs are held. Age at onset of puberty Various factors influence the onset of puberty and the duration of the stages of development. Over the past 150 years, the age at menarche has declined steadily, mainly due to improved health and nutrition; now this trend has stabilized. Often puberty starts earlier at moderately obese girls and for heavily underweight and malnourished girl later than an average of one (1). suggest such observations that a critical body weight or body fat content of puberty is necessary. Other factors can influence the onset of puberty and the duration of the stages of development. For example, there is evidence that intrauterine growth retardation, especially if it is combined with postnatal overfeeding, may cause an earlier onset and more rapid development of puberty result. Puberty starts earlier in girls whose mothers were precocious, and (for unknown reasons) in girls who live in cities or are blind. Even the onset of puberty depends on ethnicity from (z. B. it sets tends to be earlier in dark-skinned people and Latin Americans than with Asians and non-Hispanic skinned ). Physical changes of puberty, the physical changes of puberty were raised in the course of adolescence (puberty – development of female sexual characteristics.). The buds of the breasts (Schematic representation of the maturation of human breast (stages I-V according to Tanner) )) and the beginning of the growth spurt are usually the first visible changes. After that, the Pubes- and underarm hair appears (Schematic representation of the stages I-V Tanner for the development of pubic hair in girls.), And the growth spurt reached its peak. Menarche (the first menstrual period) occurs about 2-3 years after breast buds. The menstrual cycles after menarche are often irregular, and it can take up to 5 years before a regularity is established. The growth rate slowed sharply after menarche. The physical appearance changed; the pelvis and hips are wider. The body fat is increasing, especially in hips and Oberschenkeln.Die mechanisms that trigger puberty The mechanisms that trigger puberty, are still unclear. One of the key factors that regulate the release of GnRH, including neurotransmitters and peptides (eg., Gamma-aminobutyric acid [GABA] Kisspeptin). Perhaps these factors inhibit GnRH release during childhood, they then set in motion to induce puberty in early adolescence. In the early puberty, the release of hypothalamic GnRH to inhibition by estrogens and progesterone becomes less sensitive. The resulting increase in GnRH secretion promotes the release of LH and FSH, which in turn stimulates the production of sex hormones, primarily estrogen. Estrogens stimulate the development of secondary sexual characteristics. The growth of Pubes- and underarm hair can be by the adrenal androgens dehydroepiandrosterone (DHEA) and DHEA sulfate encouraged; the production of such androgens takes too a few years before puberty; this process is called Adrenarche. Puberty – development of female sexual characteristics. The bars indicate the normal distributions. Schematic representation of the maturation of the human breast (stages I-V Tanner) from Marshall WA, Tanner JM: Variations in patterns of pubertal changes in girls. Archives of Disease in Childhood 44: 291-303, 1969; approved imprint. Schematic representation of the stages I-V Tanner for the development of pubic hair in girls. From Marshall WA, Tanner JM: Variations in patterns of pubertal changes in girls. Archives of Disease in Childhood 44: 291-303, 1969; approved imprint. Notes puberty first Rosenfield RL, Lipton RB, Drum ML: thelarche, pubarche, and menarche attainment in children with normal and elevated body mass index. Pediatrics 123 (1): 84-8, 2009. doi: 10.1542 / peds.2008-0146. 2. Herman-Giddens ME, Slora EJ, Wasserman RC, et al: Secondary sexual characteristics and menses in young girls seen in office practice: A study from the Pediatric Research in Office Settings Network. Pediatrics 99: 505-512, 1997. 3. Marshall WA, Tanner JM: Variations in patterns of pubertal changes in girls. Arch Dis Child 44: 291-303, 1969. development of follicles in the ovary A girl is born with a limited number of Eizellvorläufern (germ cells). The germ cells begin as primordial oogonia that share to the 4th Gestationsmonat actively by mitosis. During the third Gestationsmonats sets in some oogonia a meiotic division, which the chromosome number is reduced by half. By 7 months of all viable germ cells a shell of granulosa cells, thus forming a primordial follicle, develops and they remain in prophase of meiosis; these cells are the primary oocytes. After the 4th Gestationsmonat many oogonia go (and later oocytes) spontaneous basis; This process is known as atresia. Finally, the loss is 99%. For older mothers, the long period could, during which remain the surviving oocytes in meiotic prophase, explain the rising incidence of genetically abnormal pregnancies. FSH induces follicular growth in the ovaries. With each monthly cycle 3-30 follicles are recruited for the Accelerated Growth. Mostly it comes in each cycle to ovulation of a single follicle. This so-called. Dominant follicle continues its oocyte released at ovulation and promotes atresia of the other recruited follicles. Menstrual cycle sub menstruation refers to the periodic outflow of blood and endometrium abgeschilfertem (collectively referred to as menses or menstrual) through the vagina. It is a result of the rapid decrease of progesterone and estrogen produced in the ovaries that every cycle except during pregnancy accompanies. find the menses, when pregnancy is not achieved throughout the reproductive period of life of the woman instead. As menopause refers to the final cessation of menses. The menses take an average of 5 (± 2) days. Blood loss is on average 30 ml per cycle (normal range 13-80 ml); mostly he is strongest on the second day. A napkin or a tampon can accommodate 5-15 ml liquid. Menstrual blood clots usually not (unless the bleeding is very strong), probably because fibrinolysin and other factors inhibit clotting. The median length of the menstrual cycle is 28 days (normal range about 25 to 36 days). The variation reaches a maximum with the longest intervals in the years immediately after menarche and before menopause when ovulation occurs less frequently. The menstrual cycle begins and ends with the first day of bleeding (day 1). On the basis of the ovarian status, it can be divided into phases. The ovary proceeds through the following phases: follicular (prävulatorisch) ovulatory Luteal (. Postovulatory- Simplified representation of the cyclic changes of Hypophysengonadotropinen, estradiol (E2), progesterone (P) and the endometrium during a normal menstrual cycle) Also, the endometrium undergoes phases. Follicular The duration of this phase varies faster than the other phases. in the early follicular phase (first half of the follicular phase), the primary event The growth of recruited follicles At this time the gonadotropic cells of the anterior pituitary contain little LH and FSH, and the production of estrogens and progesterone is low. This leads to a slight increase in FSH release, whereby the growth of recruited follicles is stimulated. The LH levels rise in the blood, from 1-2 days after the increase of FSH, slowly. In the recruited follicles production of estradiol increases soon; Estradiol stimulates the synthesis of LH and FSH, but inhibits its release. During the lspäten half of the follicular phase (second half of the follicular phase) of certain ovulation follicle matures and is surrounded by granulosa cells that release hormones. The antrum swells with follicular fluid before ovulation and reaches a size of 18-20 mm. drop the FSH concentrations, the LH levels are against less affected. FSH and LH levels diverge, z. Partly because estradiol inhibits the release of FSH stronger than that of LH. Also produce follicles that are in the development stage, the hormone inhibin, which does not, however, inhibits the release of FSH, LH. There may be other factors such as the different half-lives (20-30 minutes for LH; 2-3 hours for FSH) and unknown factors a role. The levels of estrogen, particularly estradiol rise exponentially an.Ovulationsphase It comes to ovulation (ovulation). The estradiol culminate with the onset of ovulation; the progesterone levels begin to rise. Stored LH is in massive amounts released (LH peak), usually over a period of 36-48 hours, the increase of FSH will be lower. The LH peak comes about because the high estradiol levels at this time a LH release by the gonadotropic cells trigger (positive feedback). the LH peak is also supported by GnRH and progesterone. estradiol concentrations fall off during the LH peak, however, the rise of progesterone to continue. The LH peak stimulates enzymes that put the resolution of the follicle in motion and cause the release of the now mature ovum within about 16 to 32 hours. Also, the end of the first meiotic division of the egg within 36 hours is ausgelöst.Lutealphase by the LH peak, the dominant follicle is transformed into the corpus luteum (the corpus luteum) after release from the ovary to. The length of the luteal phase is fairly constant with an average of 14 days; then the corpus luteum is, unless pregnancy is quoted. He is primarily progesterone in increasing amounts from; the maximum quantities are 6-8 days after ovulation about 25 mg / day. Progesterone stimulates required for implantation of an embryo development of the secretory endometrium. Since progesterone acts heat generating, the basal body temperature increases the duration of the luteal phase at about 0.5 ° C. Due to the high concentrations of estradiol, progesterone – and inhibin in the blood during the luteal phase LH and FSH concentrations decrease. If no pregnancy occurs, the estradiol and progesterone decrease mirror at the end of this phase, and the corpus luteum degenerates into corpus albicans. If implantation occurs, the corpus luteum does not perish but remains functional in early pregnancy, receive, supported by the human chorionic gonadotropin, which is produced by the developing embryo. Simplified representation of the cyclic changes of Hypophysengonadotropinen, estradiol (E2), progesterone (P) and the endometrium during a normal menstrual cycle. Days of the menstrual discharge are characterized by M. FSH = follicle-stimulating hormone, LH = luteinizing hormone. (. Based on Rebar RW: Normal physiology of the reproductive system in: Endocrinology and Metabolism Continuing Education Program, American Association of Clinical Chemistry, November 1982. Copyright 1982 by the American Association for Clinical Chemistry, approved imprint.) Cyclic changes in other reproductive organs endometrium the endometrium is composed of glandular and stromal tissue, and is built up of 3 layers, a basal layer (Zona basalis), an intermediate layer (Zona spongiosa) and a layer of compact epithelial cells lining the uterine cavity (zona compacta). Together, the cancellous bone and the epithelial layers form the functionalis, a temporary layer that is sloughed during menses. During the menstrual cycle, the endometrium undergoes its own phases: menstrual proliferative secretory After menstruation the endometrium is usually thin and constructed from a dense stroma with narrow, straight, lined with low columnar epithelium glands. With the increase in estradiol levels, the endometrium is regenerated from the intact basal layer from on its maximum thickness in the late follicular ovarian (proliferative phase of the endometrial cycle). The mucosa is higher, and the glands are wound spirally and longer. Ovulation takes place at the beginning of the secretory phase of the endometrial cycle. In the ovarian luteal progesterone stimulation caused by a dilation of the endometrial glands, which fill with glycogen and secretory be active while the vessel density of the stroma increases. With the decrease of estradiol and progesterone mirror in the late luteal / secretory phase, the stroma is edematous, and the endometrium and its blood vessels become necrotic; this leads to the menstrual bleeding (menstrual phase in the endometrial cycle). The fibrinolytic activity of the endometrium reduces blood clots in the menstrual blood. Since the histological changes in each phase of the menstrual cycle characteristic, one can cycle the respective phase or tissue response to sex hormones by endometrial biopsy accurately bestimmen.Zervix The cervix serves as a barrier which limits the access to the uterine cavity. During the follicular phase, the vessel density and the fluid content of the cervical tissue and the amount of spinnability and salt concentration (sodium chloride or potassium chloride) take the Zervikalschleimhaut due to increasing estradiol. At the time of ovulation, the external os opens slightly and fill with mucus. In the luteal phase of rising progesterone mirror effect that the cervical mucus thickened and the spinnability decreases; the favorable properties of a sperm transport decrease. The respective cycle phase can be microscopically sometimes based on an air dried specimen slide design determine stroke; the so-called. Farnkrautphänomen is a sign of increased salt concentrations in the cervical mucus. Particularly pronounced, it is just before ovulation, when estrogen levels are very high; in the luteal phase there is minimal or non-detectable. Spinnability, d. H. the elongation (elasticity) of the mucus increases with increasing levels of estrogen to (for example, just before ovulation.); This change can be used to the periovulatorische (fertile) phase of the menstrual cycle to identifizieren.Vagina In the early follicular phase, in which the estradiol concentrations are low, the vaginal epithelium appears thin and pale. Later in the follicular phase, with increasing estradiol concentration, mature squamous and become horny, leading to thickening of the epithelium. During the luteal phase, the number of präkornifizierten intermediate cells increases; the number of leukocytes and the amount of cell detritus increase with the exfoliation of mature squamous cells.