REVISION NOTES
Chapter: Reaching the Age of Adolescence
1. Adolescence
Adolescence is the period of life when the body undergoes changes leading to reproductive maturity.
It usually begins around 11 years and lasts up to 18–19 years.
Adolescents are also called teenagers.
2. Puberty
Puberty is the stage when the body becomes capable of reproduction.
It causes many physical and hormonal changes in boys and girls.
3. Changes at Puberty
1. Increase in Height
Sudden increase in height occurs.
Long bones of arms and legs grow longer.
Initially girls grow faster, but by about 18 years both reach maximum height.
2. Change in Body Shape
Boys
Shoulders become broader
Muscles develop
Girls
Hips become wider
Body shape becomes rounded
3. Voice Change
Voice box (larynx) grows during puberty.
In boys it becomes larger and forms Adam’s apple.
Boys develop deep voice.
Girls generally have high-pitched voice.
4. Increased Activity of Sweat and Oil Glands
Sweat glands become more active.
Skin becomes oily.
Pimples may appear on the face.
5. Development of Sex Organs
Boys
Testes and penis develop fully.
Testes begin to produce sperms.
Girls
Ovaries enlarge.
Eggs start maturing and releasing.
4. Secondary Sexual Characters
Features that distinguish males and females during puberty.
Boys
Growth of moustache and beard
Hair on chest and underarms
Deep voice
Girls
Breast development
Hair in armpits and pubic region
Widening of hips
These changes are caused by sex hormones.
5. Hormones
Hormones are chemical substances secreted by endocrine glands.
They control growth and changes during puberty.
Important Endocrine Glands and Hormones
| Gland | Hormone | Function |
|---|---|---|
| Pituitary gland | Growth hormone | Controls growth |
| Testes | Testosterone | Male characters |
| Ovaries | Estrogen | Female characters |
| Thyroid | Thyroxine | Body metabolism |
| Pancreas | Insulin | Controls blood sugar |
| Adrenal gland | Adrenalin | Stress response |
6. Role of Hormones in Reproduction
Pituitary gland releases hormones that control other glands.
Testes release testosterone.
Ovaries release estrogen.
These hormones cause changes during puberty and enable reproduction.
7. Reproductive Phase of Life
In Females
Begins at puberty (10–12 years).
Ends around 45–50 years.
Menstruation
Monthly shedding of uterine lining with blood.
Occurs every 28–30 days.
Terms
| Term | Meaning |
|---|---|
| Menarche | First menstruation |
| Menopause | End of menstruation |
8. Sex Determination in Humans
Humans have 23 pairs of chromosomes.
Two chromosomes determine sex: X and Y.
| Parent | Chromosomes |
|---|---|
| Female | XX |
| Male | XY |
Egg always carries X chromosome.
Sperm carries X or Y.
| Combination | Result |
|---|---|
| XX | Girl |
| XY | Boy |
Thus father determines the sex of the baby, not the mother.
9. Hormones in Insects and Frogs
Hormones also control metamorphosis in animals.
Example:
Frog: Thyroxine controls transformation of tadpole into frog.
10. Reproductive Health
Reproductive health means physical and mental well-being.
Important for Adolescents
Balanced diet
Personal hygiene
Regular exercise
Avoid junk food and drugs
Balanced diet includes:
Rice / chapati
Pulses
Vegetables
Fruits
Milk
Iron-rich foods like leafy vegetables and jaggery.
11. Personal Hygiene
Daily bath and cleanliness are necessary.
Girls should maintain hygiene during menstruation.
Use sanitary napkins or clean pads and change regularly.
12. Say NO to Drugs
Drugs are addictive and harmful.
Sharing injection needles may spread HIV/AIDS.