The Bio Brief

What Do Endocrine Glands Do?

Endocrine glands are ductless glands that release hormones directly into the bloodstream.

 These hormones travel through blood to a specific body part called the target site.

Important idea:
 Hormone = messenger
 Target site = body part that responds

Basic Hormone Action (Flow Chart)

Endocrine gland releases hormone
            ↓
Hormone enters bloodstream
            ↓
Hormone reaches target site
            ↓
Target organ responds
            ↓
Body changes occur

 Sex Hormones and Reproduction

The reproductive organs also act as endocrine glands.

In Boys

• Testes release male hormone (testosterone)
• Helps in:
  • Development of male secondary sexual characters
  • Formation of sperms

 In Girls

• Ovaries release female hormone (estrogen)
• Helps in:
  • Development of female secondary sexual characters
  • Maturation of ova (eggs)

 Role of Pituitary Gland (Master Gland)

The pituitary gland controls the testes and ovaries.

 It releases hormones that:

• Make ovaries mature eggs
• Make testes produce sperms
• Start puberty changes

 Hormonal Control of Reproduction (Important Flow Chart)

Pituitary gland releases hormones
                ↓
Testes and ovaries get stimulated
                ↓
Sex hormones are released
                ↓
Secondary sexual characters develop
                ↓
Sperms and ova begin to form
                ↓
Person becomes capable of reproduction

 What Does Puberty Mark?

Puberty marks the beginning of reproductive life.

That means:

• Boys start producing sperms
• Girls start producing mature ova
• Body becomes capable of reproduction

 Does Reproductive Life Continue Forever?

No.

• In girls/women, reproductive life ends at menopause (around 45–50 years).
• In boys/men, sperm production may continue for a much longer time, though it may slow with age.

 Key Points to Remember

 Endocrine glands release hormones into blood
 Hormones act on specific target sites
 Testes and ovaries produce sex hormones
 Pituitary gland controls reproductive hormones
 Puberty begins reproductive capability
 Reproductive life does not continue forever

 In Simple Words

Hormones released by endocrine glands travel through the blood and control body changes. The pituitary gland starts puberty by activating the testes and ovaries. These organs then produce sex hormones, which lead to sperm and egg formation and make the body capable of reproduction.