Changes occurring in boys
• The chest and shoulders develop.
• Facial hair starts to grow, and possibly chest hair.
• The penis and testicles grow.
• The testicles descend into the scrotum and begin to produce sperm.
• It is possible that the boy suddenly and unexpectedly has an erection.
• The boy begins to experience ejaculation, meaning that liquid called semen comes out of the penis (something which can occur during sleep – wet dream).
Girls are born with thousands of eggs in each of their two ovaries. In adolescence, one of these eggs is released every month by the ovary. This process is called ovulation and occurs around 14 days before the next "period". After the egg leaves the ovary, it passes through the fallopian tube where it remains for around 24 hours, waiting for potential fertilization by male sperm. At the same time the walls of the uterus become softer and thicker as they prepare for the possibility to accept and nourish a fertilized egg. If there is no fertilization, the walls of the uterus wither and are expelled with the egg from the body, as "period" blood. The menstrual cycle is calculated from the first day that period starts until the day that the next one starts. The cycle is usually around 28 days. The duration of the menstrual cycle can however vary from 21 to 40 days. It is important to know when we are expecting the next period, although many women have irregular cycles.
The changes in the hormone levels during this cycle affect our mood. It is normal for girls to feel:
• Full of energy or in a bad mood when ovulation takes place.
• Emotional and angry just before the period starts.
• Slight pain in the breasts and to get spots on the face just before the period.
The release of an egg from the ovaries as described above, stops at a period of time in a woman's life known as menopause, usually just before or just after the age of 50. After this point, menstruation no longer occurs and the woman can not become pregnant.
Changes occurring in boys and girls during puberty
• The muscles develop, weight and height increases.
• The genital organs develop.
• The person is biologically capable to have children.
• The voice deepens.
• The skin glands work in a more intense pace and spots may occur.
• The sweat glands develop.
• Hair begins to grow in the armpits and the genital area.
• The person experiences sudden and intense mood swings.
• Attraction to persons of the opposite sex begins.
Changes occurring girls
• The breasts grow and may cause some slight pain while it happens.
• The nipples begin to stand out.
• The body changes.
• The genital organs develop; the ovaries begin to produce eggs.
• Menstruation (period) begins.