By this time, the vagina has already begun to lengthen and the uterus is slowly enlarging. On the onset of menstruation, breast growth nears completion and almost invariably comes after the peak growth spurt. Menstruation is influenced by socio economic factors, climate, heredity, family size and nutrition. The age at menarche varies from 8-16 years. Physical changes due to puberty start occurring by the age of 14 years.
Earliest change is the growth of the testes.
Then growth of the penis. Genitai development occurs from 11-15 years. Sperm production which begins in childhood becomes fully established during puberty. Ejaculation starts, which results in nocturnal emissions and Masturbation. Pubic hair growth begins around this time followed a year or two later by the facial and axillary hair.