How does puberty in girls

Formation endocrine functions of the female reproductive system.

Puberty lasts about ten years.Generally accepted standards is considered to be age from 7-8 to 17-18 years.During this time, there is not only the maturation of the reproductive system, but also ends the physical development of the body: body is formed, completed body growth and ossification of long bones, fat is distributed on the female type.

are three stages in the maturation of the female reproductive system.

first (prepubertal) period

It is between the ages of 7-9 years and is characterized by increased secretion of gonadotropin-releasing hormone by the hypothalamus, have reached a certain maturity.At this age, sex hormones selection occurs episodically, every 5-7 days.Estrogen secretion is minimal at this point.

Physiologically, this period is growth spurt, the first signs of feminization figures, redistributed adipose tissue, as well as changes vaginal epithelial structure.

second period - the first phase of puberty

It is between the ages of 10-13 years and is characterized by the formation of the cyclic release of gonadotropins daily, under the influence of which increases the secretion of ovarian hormones.The end of this period is marked by menarche - first menstruation.

During this period, the final maturation of the central brain structures are responsible for the activity of the reproductive system.The main hormone, which is subject to the action of the reproductive system is a gonadotropin-releasing hormone (GnRH, GnRH).In this period it becomes rhythmic secretion, daily, closely associated with the time of day (circadian).Under the influence of this hormone secretion of gonadotropins (FSH and luteinizing hormone) is also becoming a regular.And under their influence, the ovaries begin to produce estrogen.

Simultaneously with these processes increases the amount of estrogen receptors in all organs and tissues of the body.At the time when the concentration of estradiol in the blood reaches a desired level, it emits large amounts of gonadotropins which causes follicle maturation and release of an egg.Following the first ovulation and first menstruation occurs, which completes a second puberty, as well as the period of active growth of the body length.

In this phase of puberty is an increase in breast - thelarche changes the vaginal flora, lactobacilli appear in it, and at the age of 11-12 years begins body hair pubis - pubarhe.

third period - the second phase of puberty

In 14-17 years completed the maturation of the hypothalamic structures responsible for the regulation of the reproductive system.The secretion of gonadotropin-releasing hormone becomes stable, emissions occur every 70-100 minutes.In response to the rhythmical selection amplified GnRH secretion of LH and FSH and consequently oestradiol by the ovaries.Moreover, not only monotonous is set, the background secretion of these hormones and their peak emission in response to a threshold concentration of estradiol that provide ovulation and menstruation.

Physiologically, the second phase of the menstrual cycle is the establishment of regular ovulatory menstrual cycle, halt and the final formation of the pelvic bone.

Factors puberty

At the onset and duration of puberty affects a huge number of factors.They can be subdivided into internal and external.External relate climate and food.Domestic - heredity, body, health and body weight.

known that menarche occurs when the body weight 47.8 ± 0.5 kg when adipose tissue is about 22% of total body weight.

Adipose tissue plays a very important role in the formation and development of the reproductive function.It occurs metabolism and synthesis of large number of hormones and bioactive substances, including estrogens and androgens.Under the influence of these hormones is a growth and maturation of the body: androgens have anabolic effect and are responsible for the growth of the body processes estrogen and ensure the correct ossification and bone mineralization.

since menarche before puberty the amount of adipose tissue in healthy women increases by 4.5 kg.At the time of puberty and throughout the reproductive period, the number of adipose tissue should be about 30% by weight.

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