Puberty and Adolescence
Biological Sequential Events Observed during Puberty
Adolescence is the age between 10 and 19 years. Puberty is the period of transition from childhood to adult sexual maturation. It is the process of biological, psychological and physical development through which sexual reproduction becomes possible. Progression occurs through sequential changes described as thelarche → adrenarche → peak growth spurt → menarche →ovulation.
Endocrinal influences, genetic, nutritional and other environmental factors play an important role during this transitional period of life.
Age of onset of puberty:
The age of onset is influenced by nutritional status, genetic and environmental influences including racial and cultural background, climate and residence. Hence a great deal of variations is observed in the evolution of puberty changes. Normal age of puberty varies between 9 and 13 years, and the duration lasts 2–3 year.
Factors Affecting Time of Onset of Puberty
- The African-American girls enter puberty about 1–1.5 years earlier than the White American girls
- Nutritional status. Puberty sets in earlier in moderately obese girls and is delayed in malnourished girl. Leptin (peptide) secreted by the fat cells stimulate GnRh secretion and induce early puberty. Minimum of a 45 kg body weight is required to induce pubertal changes.
- Macrosomic babies tend to grow obese and have early menarche thereby.
- General health status
- Delayed in Eskimo girls as compared to girls living in the tropics
- Psychological state. Exposure to education, media
- Exposure to light (blind individuals enter puberty earlier than sighted individuals
Thelarche The first sign of puberty is the development of the breasts. Breast budding usually appears between the ages of 9–11 years; it is indicative of the competency of the hypothalamic– pituitary–ovarian axis.
Adrenarche The adrenals are the main source of androgens, which are responsible for the growth of pubic and axillary hair.
Vulva—vulval skin under the influence of oestrogen becomes keratinized and resistant to infection.
Fat is deposited in the labia majora.
Vaginal mucosa becomes multilayered with the formation of superficial layer containing glycogen and PH is maintained at 4.5 by Döderlein’s bacillus acting on glycogen.
The uterus grows rapidly, and prepubertal ratio of uterus/ cervix of 1:1 changes to 2:1 or 3:1.
The ovaries start developing primordial follicles into Graafian follicles. However, a dominant follicle with ovulation occurs in 50% cases
Menarche The first menstrual period generally follows thelarche by about 2 years, when growth development is almost complete and breast development reaches the adult mature stage. The initial menstrual cycles are generally anovulatory for about 12–18 months after menarche