Neonatal period
During this time, the girl's reproductive system is actively influenced by maternal hormones.
- Vagina is positioned vertically, its introitus is often blocked by thick mucus. The mucosa consists of 3–4 layers of squamous epithelium (mostly intermediate cells). The environment is acidic, with lactobacilli present. However, in the first 10 days of life, maternal hormone levels drop sharply: the epithelium thins, lactobacilli disappear, and pH shifts toward neutral values.
- Uterus is located high in the abdominal cavity. Its length is about 3 cm, and its mass is 4 g. The cervix predominates over the body (ratio of 3:1), while the angle between them is not pronounced. Secretory and proliferative changes are noticeable in the endometrium, and the myometrium is well developed. The external os is slit-like, and pseudo-erosion is frequently observed. The cervical canal is filled with thick mucus.
- Fallopian tubes are long (about 35 mm), tortuous due to short broad ligaments, but fully patent.
- Ovaries are elongated and cylindrical in shape with a smooth surface, located in the abdominal cavity. They contain 500,000 to 700,000 primordial follicles. The presence of mature follicles indicates that the newborn's ovaries are already capable of synthesizing estrogens, although many follicles undergo atresia.
Neutral period (up to 8 years)
This is a time of hormonal dormancy. The hypothalamus and pituitary gland secrete hormones in small quantities, and the level of endogenous sex hormones remains low. Secondary sexual characteristics are completely absent.
External genitalia are located deep, the pudendal cleft is closed. The labia majora cover the labia minora and clitoris. The vulvar mucosa is thin and pale pink, and the Bartholin glands are not functioning. The hymen (hymen) appears as a thin annular or crescentic membrane.
Vagina changes its direction, forming an angle with the pelvic axis. Its walls are thin, the fornices are barely pronounced, and rugosity is weak. Secretions are extremely sparse, with a neutral or weakly alkaline reaction, containing mixed flora and a small number of leukocytes. Parabasal cells predominate in the smear.
Internal organs undergo topographic and dimensional changes:
- Uterus decreases slightly in the first three years and then begins to grow slowly. By age 6, its mass returns to the newborn values. By 3–4 years of age, the organ descends into the lesser pelvis.
- Ovaries gradually increase in mass (from 0.53 g to 1.5 g by age 8). This growth occurs due to the chaotic maturation of follicles, none of which reach full maturity. Concurrently, intense oocyte death takes place.
By age 8, all five levels of the reproductive system are formed, but their activity is regulated exclusively by a negative feedback mechanism.
Prepubertal period
Begins at 8 years of age and ends with the first menstruation (menarche). During this time, the hypothalamic-pituitary system, ovaries, and adrenal glands become activated.
- Hormonal restructuring: The hypothalamus episodically releases releasing hormones, and the pituitary gland produces acyclic surges of follicle-stimulating and luteinizing hormones. The level of estradiol in the ovaries is still low. The adrenal glands play an important role: exclusively during sleep, wave-like surges of luteinizing hormone occur, which stimulate the adrenal cortex, causing its hyperfunction.
- Physical development: Under the influence of androgens, a rapid growth spurt occurs (at 11–12 years of age, girls surpass boys). Estrogens are responsible for the first body shape changes: pelvic bones begin to grow, and hips round out due to the increase and redistribution of adipose tissue. Puberty proceeds in parallel with intensive bone growth, and physically developed girls reach it earlier.
To easily remember the dynamics of uterine proportions, use a countdown: in the newborn, the ratio of the cervix to the body is 3:1, by the end of the first year — 2:1, and by age 8 it approaches 1:1 (more precisely, 1.4:1). The cervix gradually "gives way" to the growing uterine body.
Class and exam questions
Why do newborn girls have an acidic vaginal environment?
This is the result of the action of maternal sex hormones. In the first 10 days of life, their concentration drops sharply, lactobacilli disappear, and the pH shifts toward the neutral side.
Where is the uterus located in young girls?
In newborns, the uterus is located high in the abdominal cavity, above the pelvic inlet. Its final descent into the pelvic cavity occurs only by 3–4 years of age.
What causes the increase in ovarian mass in the neutral period?
Ovarian mass grows due to the continuous, albeit chaotic, maturation of follicles. At the same time, the total number of oocytes steadily decreases due to their mass death and atresia.
What else to study on this topic
- Cytological picture of vaginal smears in different age periods
- Negative feedback mechanisms in the regulation of the reproductive system up to 8 years
- The role of the adrenal glands and nocturnal luteinizing hormone surges in prepuberty
- Follicular atresia processes in the ovaries from intrauterine development to menarche
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