Describe the physical changes occurring in boys and girls.

During adolescence, both boys and girls undergo significant physical changes as they mature sexually. These changes are primarily driven by hormonal fluctuations and contribute to the development of secondary sexual characteristics.

Boys:

1. Growth Spurt: Boys typically experience a rapid growth spurt during adolescence, with increases in height and weight. This growth is often most noticeable between the ages of 12 and 16, although it can vary among individuals.

2. Muscle Development: As testosterone levels increase, boys experience an increase in muscle mass and strength. They may notice changes in body shape as their muscles become more defined, particularly in the arms, chest, and shoulders.

3. Facial and Body Hair: Another prominent physical change in boys is the growth of facial and body hair. This typically begins with the appearance of sparse facial hair around the upper lip and chin and gradually extends to the cheeks and jawline. Body hair, including chest, armpit, and pubic hair, also becomes more abundant.

4. Voice Changes: Boys' voices deepen as the larynx (voice box) grows and the vocal cords lengthen and thicken. This results in a deeper, more resonant voice. Voice changes usually occur during the later stages of puberty and can continue into late adolescence.

5. Genital Development: Boys experience genital development, including the growth of the penis and testes. The scrotum may also undergo changes in size and texture as it matures.

Girls:

1. Growth Spurt: Girls also experience a growth spurt during adolescence, typically beginning around ages 10-11 and continuing until ages 14-15. This results in increases in height and weight, although girls generally reach their full height earlier than boys.

2. Breast Development: One of the earliest signs of puberty in girls is the development of breast buds, which are small, firm lumps beneath the nipples. Breast development continues over several years, with the breasts gradually increasing in size and shape.

3. Body Fat Redistribution: Girls experience changes in body composition, with an increase in body fat, particularly in the hips, thighs, and buttocks. This contributes to the development of a more rounded body shape characteristic of adult females.

4. Menstruation: Menstruation, or the onset of the menstrual cycle, is a significant milestone in girls' physical development. It typically occurs around ages 12-13, although the timing can vary widely. Menstruation involves the shedding of the uterine lining and occurs approximately every 28 days in a regular menstrual cycle.

5. Pubic and Axillary Hair: Girls also develop pubic and axillary (underarm) hair during adolescence. Pubic hair typically appears first, followed by the growth of axillary hair. The hair may start out sparse and fine but becomes thicker and coarser over time.

These physical changes mark the transition from childhood to adulthood and are part of the natural process of sexual maturation during adolescence.