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Definition

The period of life between childhood and adulthood, roughly ages 11 to 18. Also called the “teenage” period.

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Puberty

The phase when reproductive organs start to mature and secondary sexual characteristics appear. It marks the onset of adolescence.

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Changes during this phase

Physical, emotional, mental, and reproductive changes occur. These are all controlled by chemical messengers called hormones.

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When does it end?

Adolescence ends when growth in height stops, usually around 18–19 years. The person is then considered an adult.

1. Growth spurt in height

Bones grow faster. Girls start earlier (~10–11 yrs); boys later (~13–14 yrs). Growth in height stops when the sex hormones cause the growing ends of long bones (epiphyses) to fuse.

2. Change in body shape

Boys develop broader shoulders and more muscular bodies. Girls develop wider hips due to growth of the pelvic bones to facilitate future childbirth.

3. Growth of body hair

Hair grows in the armpits and pubic area in both boys and girls. Boys also develop facial hair — beard and moustache.

4. Skin changes and acne

Sebaceous (oil) glands secrete more sebum, causing pimples/acne on the face, chest, and back. Sweat glands also become more active.

5. Voice change

Boys develop a deeper voice as the larynx (voice box) grows larger — the protruding larynx is called the Adam’s apple. Girls’ voices become slightly high-pitched.

6. Reproductive organs mature

Testes (in boys) and ovaries (in girls) become functional and begin producing sex hormones and gametes (sperm and eggs).

7. Emotional and mental changes

Adolescents become more self-conscious, curious, and emotionally sensitive. The brain becomes highly active; analytical thinking and creativity increase.

♂ Boys

✔ Broader shoulders and chest
✔ Deeper voice (Adam’s apple visible)
✔ Facial hair — beard and moustache
✔ Growth of the penis and testes
✔ Underarm and pubic hair
✔ More muscular body
✔ Production of sperm begins

♀ Girls

✔ Wider hips
✔ Breast development
✔ Onset of menstruation (menarche)
✔ Ovaries become active
✔ Underarm and pubic hair
✔ Slightly high-pitched voice
✔ Release of mature eggs (ovulation)

🧠 Pituitary Gland

Location: Base of the brain
Hormone: Growth hormone
Role: Master gland; controls all other endocrine glands.

🔵 Testes

Location: Male reproductive system
Hormone: Testosterone
Role: Secondary sexual characteristics in boys; sperm production.

🔴 Ovaries

Location: Female reproductive system
Hormone: Oestrogen
Role: Secondary sexual characteristics in girls; menstrual cycle.

🟡 Pancreas

Location: Abdomen
Hormone: Insulin
Role: Regulates blood sugar. Deficiency → diabetes mellitus.

🟠 Thyroid Gland

Location: Neck
Hormone: Thyroxine (needs iodine)
Role: Regulates metabolism and growth. Deficiency → goitre.

🔶 Adrenal Glands

Location: Above the kidneys
Hormone: Adrenaline
Role: The fight-or-flight response increases heart rate and breathing.

🔵 Menarche

The first occurrence of menstruation in girls. Marks the start of the reproductive phase, usually at 10–12 years.

📆 Menstrual Cycle

A ~28-day cycle. The uterus lining thickens each month. If no fertilisation occurs, the lining sheds — this is menstruation.

🔴 Menopause

The end of menstruation and the reproductive phase in women, usually around 45–50 years of age.