TEXTBOOK OF PEDIATRIC GYNECOLOGY - 2013

Chapter 3. ANATOMICAL AND PHYSIOLOGICAL ASPECTS OF GIRLS' SEXUAL DEVELOPMENT

GIRLS' SEXUAL DEVELOPMENT

The sexual development of girls is conventionally divided into three main periods: the neutral or asexual period (the first 5–6 years of life), the prepubertal period (from 7 to 9–10 years), and the pubertal period (from 9–10 years until the onset of full sexual maturity).

During the neutral period, Sex Hormones have a negligible impact on the child's GROWTH AND DEVELOPMENT. Hormonal Regulation of sexual development remains at a low level, and the hypothalamic-pituitary structures are highly sensitive to the inhibitory action of sex hormones.

The prepubertal period is characterized by increased adrenal androgen secretion, a phase known as physiological adrenarche. During this time, linear growth accelerates, and bone mass develops more intensively.

The pubertal period involves a systemic reorganization driven primarily by the estrogen-producing activity of the Ovaries. Under the progressive and heightened influence of gonadotropic hormones, follicular growth accelerates. Follicles of varying degrees of maturity secrete increasing amounts of estrogens. These hormones alter body habitus, promote The Development of the Mammary Glands, external and internal genitalia, and modify The Structure of the endometrium and vaginal mucosa. When estrogen levels become sufficiently high, menarche—the first menstruation—occurs. The timing of menarche is highly individualized; for girls living in temperate climates, it typically occurs between 12.5 and 13 years of age (Table 8).

Table 8. Stages of Differentiation of the endocrine and Reproductive System Organs during the antenatal period (Yu. A. Gurkin, P. A. Krotina, N. Yu. Solomkina, 1992)

The external genitalia form between the 12th and 20th weeks of intrauterine life. The foundation for the development of external genitalia in fetuses of both sexes consists of the genital tubercle, labioscrotal swellings, and urogenital sinus. In female fetuses, the differentiation of the external genitalia occurs independently of the functional state of the Gonads.

The female external genitalia develop from a shared genital Swelling. The genital tubercle transforms into the Clitoris, and the genital folds become the Labia minora. The Labia Majora develop from the labioscrotal swellings. The greater vestibular glands originate from the urogenital sinus. A person's biological sex is determined not by their external genitalia, but by their gonads.

In terms of structure, the ovaries of a newborn girl resemble those of an adult woman, but they are situated significantly higher above the pelvic inlet. I. I. Bondarev (1966) noted Asymmetry in the ovaries of newborn girls. Between the ages of two and five years, they descend into the lesser pelvis and assume their physiological position. According to M. P. Gundobin, the length of the ovaries in a newborn girl ranges from 0 to 3 cm; by the age of 16, the ovaries increase in length by only 0.6 cm, but undergo significant thickening.

The ovaries of infant girls contain A large number of primordial follicles. As growth proceeds, primary follicles undergo atresia. In children, follicular growth is acyclic and occurs in the absence of ovulation. In girls aged 8–10 years, the ovaries produce sufficient quantities of estrogens to begin influencing the growth of reproductive organs and contributing to the development of secondary sexual characteristics.

During the first two years following menarche, cycles may be anovulatory, meaning that the vesicular follicle undergoes rapid atresia without ovulation or corpus luteum formation. Endometrial desquamation (menstruation) results from a sharp drop in estrogen levels at the time of follicular atresia.

Female Sex Hormones. The ovaries synthesize specific hormones—estrogens—along with other Steroid compounds (androgens and progesterone). Estradiol is synthesized through the hydroxylation and aromatization of the androgenic compound androsterone.

As a result of estrogen Biosynthesis in the body, estradiol, estrone, and estriol are produced. This synthesis takes place in the granulosa layer or interstitial Cells of the ovarian stroma. Estradiol, the more potent estrogen, is readily converted into the less active compound estrone. Estriol is considered a metabolite of both estradiol and estrone.

Estrogens are rapidly degraded in The Liver and excreted in the urine as estriol, exhibiting potent biological activity. In addition to regulating the growth and development of FEMALE REPRODUCTIVE ORGANS and secondary sexual characteristics, estrogens activate proenzymes necessary for Protein Synthesis AND stimulate metabolic processes.

A girl is born with reproductive organs that are clearly differentiated along the female pattern. The clitoris is relatively large; at birth, the labia are frequently edematous, hyperemic, and prone to agglutination, with the labia minora only partially covered by the labia majora. The Skin is thin, lightly pigmented, and often covered with vernix caseosa. The vestibular glands are non-functional. The hymen is located somewhat deeper within the Vagina than in subsequent years. The vagina lies parallel to the vertical axis, measuring 25–35 mm in length, and the vaginal fornices are poorly defined.

The Uterus in a newborn girl is located in the Abdominal cavity, measuring 30 mm in length; its body is lenticular in shape, and the fundus is "saddle-shaped." The cervix-to-uterus body ratio is 3:1. The uterine position is anteversio. The myometrium is well developed, and the endometrium is folded. The internal os is not yet formed, while the external os is slit-like. The cervical canal is filled with thick mucus. Secretory changes are most frequently detected in the endometrium, and a desquamation phase is occasionally observed. The uterine tubes are long (up to 35 mm), tortuous, and possess well-developed muscular wall layers. The uterine tubes are patent throughout their entire length.

The ovaries of a newborn girl are located in the ABDOMINAL CAVITY AND are cylindrical or prismatic in shape. Ovarian length ranges from 15 to 22 mm. Follicular cysts are absent. The histological STRUCTURE OF THE ovaries resembles that of an adult woman; however, certain differences exist: the presence of primordial follicles, a pronounced atresia process, the absence of ovulation, immaturity of the ovarian structure, and well-developed interstitial cells with high endocrine activity.

During the "neutral" period, the external genitalia develop slowly: the labia majora do not completely conceal the labia minora, the vestibular glands appear during the 3rd to 4th year of life and mature by age 6. By the age of 3, a descent of the internal reproductive organs and certain adjacent structures into the lesser pelvis is observed. Vaginal length remains unchanged, the epithelial layer thins to 4–5 Cell layers, the vaginal pH is alkaline or neutral, and the vaginal flora is unstable, potentially showing diplococci, streptococci, and staphylococci. Vaginal smears are characterized by high eosinophilic and karyopyknotic indices, with microflora represented by cocci. These specific features play a certain role in the development of vulvovaginitis.

During the first years of a girl's life, the uterus decreases in size. The ratio of the cervix to the body of the uterus shifts dynamically: at 1 year—2:1; at 4 years—1.7:1; and at 7–8 years—1.4:1.

By the age of three, the uterine fundus descends to the level of the pelvic inlet. The uterine tubes undergo minor changes and lack peristalsis. The ovaries begin descending into the lesser pelvic cavity earlier than any other Internal Organs, yet their high anatomical position can still be observed at 5 years of age. The size and shape of the ovaries remain unchanged; however, a limited number of maturing and atretic follicles are always present. Follicular maturation is non-cyclic in nature.

The neutral period is marked by low sex hormone levels, indicating the absence of rapid reproductive organ development.

Key Features of the reproductive organs during this period include their enlargement due to the accumulation of adipose tissue. This period marks the onset of greater vestibular gland function. Vaginal length reaches 63 mm, and its rugae become pronounced. The folding of the endometrium gradually disappears, and endometrial glands hypertrophy and branch. The cervix-to-uterus body length ratio changes to 1:3. The ovaries increase noticeably in size (mass: 4–5 g, length: 3–3.5 cm). Follicular maturation becomes more intensive yet chaotic, occasionally resulting in ovulation.

The prepubertal period in girls is characterized by the onset of rapid growth and the maturation of all sections of the reproductive tract, which are ready for function by the end of this term.

During Puberty, the reproductive organs correspond to those of an adult woman. By the end of this period, the length of the vagina reaches 80–100 mm, and the fornices are well-defined. Colpocytological findings reflect the characteristic cyclical Changes in the vaginal contents. The uterus increases rapidly in size, the asymmetry of the ovaries and fallopian tubes persists with age, and tubal peristalsis appears. Changes in the ovaries and endometrium are cyclical in nature. By the end of the period, complete Integration of the reproductive System and Its regular function are established. Sexual maturity typically occurs after the age of 18.