The Bio Brief

During puberty, many changes take place in the body. These changes prepare a child to become an adult. Let’s understand them in a simple way.

 1. Increase in Height

The most noticeable change during puberty is a sudden increase in height (growth spurt).

 Why does height increase?

• The long bones of arms and legs grow longer.
• This makes the body taller.

 Important facts

• Girls usually grow faster earlier than boys.
• By about 18 years, most people reach their full height.
• Growth rate is different for each person.

 How to Calculate Full Height

Formula:

Full height (cm) = Present height × 100
                  % of full height at that age

Example:

• Age = 9 years
• Present height = 120 cm
• % of full height at age 9 (boy) = 75%

Full height = 120 × 100 / 75
            = 160 cm

 So the boy may grow to about 160 cm.

Flow Chart: Growth in Height

Puberty begins
      ↓
Long bones grow longer
      ↓
Sudden increase in height
      ↓
Body reaches maximum height (~18 years)

 Uneven Growth (Don’t Worry!)

Sometimes during adolescence:

• Arms and legs look too long
• Hands and feet look big
• Face looks smaller

 This is normal because body parts grow at different speeds.
Soon the body becomes properly proportioned.

 What Affects Height?

Main factors:

• Genes (parents’ height)
• Proper nutrition
• Good health

 Eating healthy food helps bones and muscles grow well.

 2. Change in Body Shape

Body shape changes differently in boys and girls.

 In Boys

• Shoulders broaden
• Chest becomes wider
• Muscles grow more prominently

 In Girls

• Region below waist becomes wider
• Body becomes more rounded

 Flow Chart: Body Shape Changes

Puberty hormones released
        ↓
Different growth patterns
        ↓
Boys → broader shoulders & muscles
Girls → wider hips

 3. Voice Change

During puberty, the voice box (larynx) grows.

 In Boys

• Larynx becomes larger
• Throat shows Adam’s apple
• Voice becomes deep
• Voice may crack or become hoarse for some time

 In Girls

• Larynx grows slightly
• Voice remains high-pitched

 Hoarse voice in boys is temporary and normal.

 4. Increased Activity of Sweat and Oil Glands

During puberty:

• Sweat glands become more active
• Oil (sebaceous) glands produce more oil

Effects

• More sweating
• Body odour
• Acne and pimples

This is normal during adolescence.

 Types of Glands (Quick Note)

Glands with ducts:

• Sweat glands
• Oil glands
• Salivary glands

Endocrine glands (ductless):

• Release hormones directly into blood

 5. Development of Sex Organs

At puberty, reproductive organs mature.

 In Boys

• Testes and penis grow fully
• Testes start producing sperms

 In Girls

• Ovaries enlarge
• Eggs begin to mature
• Ovaries start releasing eggs

 This marks the ability to reproduce.

 6. Mental, Intellectual and Emotional Changes

Adolescence is not only physical — the mind also changes.

 Mental changes

• Thinking ability improves
• Brain learns faster
• More independent behavior

 Emotional changes

• Self-consciousness increases
• Mood swings may occur
• Sometimes feel insecure

 Remember: These feelings are normal parts of growing up.

 Quick Revision Box

 Sudden height increase is the most visible change
 Body shape changes differently in boys and girls
 Boys’ voice becomes deeper
 Sweat and oil glands become more active
 Reproductive organs mature
 Mental and emotional development occurs
All changes are natural and normal