The Bio Brief

What are Secondary Sexual Characters?

You already know:

• Testes and ovaries are reproductive organs
• They produce gametes (sperms and ova)

During puberty, some new physical features appear that help distinguish males from females. These are called secondary sexual characters.

 They do not directly produce gametes, but show that puberty has begun.

 Examples of Secondary Sexual Characters

 In Boys

• Growth of moustache and beard
• Hair on chest
• Hair under arms
• Hair in pubic region
• Broader shoulders
• Deep voice

 In Girls

• Development of breasts
• Hair under arms
• Hair in pubic region
• Wider hips

 Hair under arms and in pubic region occurs in both boys and girls.

 Flow Chart: Secondary Sexual Characters

Puberty begins
      ↓
Hormones are released
      ↓
Physical changes appear
      ↓
Secondary sexual characters develop
      ↓
Male and female bodies look different

 What Controls Changes at Puberty?

All changes at puberty are controlled by hormones.

 What are hormones?

• Chemical substances
• Secreted by endocrine glands
• Travel through bloodstream
• Control body changes

 Endocrine glands together form the endocrine system.

 Role of Testosterone (Male Hormone)

• Released by testes at puberty
• Responsible for changes in boys

 Effects in boys

• Facial hair grows
• Voice becomes deep
• Muscles develop
• Shoulders broaden

 Role of Estrogen (Female Hormone)

• Released by ovaries at puberty
• Responsible for changes in girls

 Effects in girls

• Breasts develop
• Mammary (milk-secreting) glands form
• Body shape changes

Who Controls These Hormones?

The release of testosterone and estrogen is controlled by another gland:

 Pituitary gland (called the master gland)

 Hormonal Control Flow Chart

Pituitary gland releases hormones
            ↓
Testes / Ovaries are activated
            ↓
Testosterone (boys) / Estrogen (girls) released
            ↓
Puberty changes occur
            ↓
Secondary sexual characters develop

 Key Terms to Remember

• Secondary sexual characters → features that distinguish males and females
• Hormones → chemical messengers
• Endocrine glands → ductless glands releasing hormones
• Testosterone → male hormone
• Estrogen → female hormone
• Pituitary gland → master gland controlling others

 Quick Revision Box

 Secondary sexual characters appear at puberty
They help distinguish boys and girls
 Hormones control all puberty changes
 Testes release testosterone in boys
 Ovaries release estrogen in girls
 Pituitary gland controls hormone release