6.2.6 Gonads

Gonads are special type of endocrine glands which beside hormone secretions also produce gametes. Female gonads are ovaries while male gonads are testes. They secrete sex hormones that are responsible for sexual development and reproduction.

Definition

Gonads: Gonads are special type of endocrine glands which beside hormone secretions also produce gametes. Female gonads are ovaries while male gonads are testes.

Main Idea

• Gonads are special endocrine glands.
• They produce gametes (sperm and eggs).
• They secrete sex hormones.
• Female gonads are ovaries.
• Male gonads are testes.
• Ovaries secrete estrogen and progesterone.
• Testes secrete testosterone.
• These hormones are responsible for sexual development and reproduction.

Core Concept

• Gonads = endocrine glands that also produce gametes
• Ovaries = female gonads
• Testes = male gonads
• Estrogen = female sex hormone; secondary sex characteristics
• Progesterone = female sex hormone; pregnancy
• Testosterone = male sex hormone; secondary sex characteristics
• FSH = stimulates follicle development
• LH (ICSH) = stimulates ovulation and testosterone secretion

Detailed Explanation

Gonads

• Gonads are special type of endocrine glands which beside hormone secretions also produce gametes.
• Female gonads are ovaries while male gonads are testes.

Ovaries

• The ovaries secrete female sex hormones estrogen and progesterone.
• Estrogen is secreted by Graffian follicle under the stimulation of FSH but estrogen has negative feedback upon FSH.
• Estrogen is secreted at the time of puberty and is responsible for secondary sex characteristics in females.
• It aids in healing and repair of uterine wall after menstruation.
• Due to its under secretion in the young females, they fail to mature sexually.
• Deficiency of this hormone in adults leads to sterility.
• Its oversecretion may leads to the development of fibroids (abnormal growth) in uterus and polycystic ovaries.
• Progesterone is produced by corpus luteum in response to LH during normal menstrual cycle but it is produced and released from placenta during pregnancy.
• It inhibits further FSH secretion from pituitary, thus preventing any more follicles from ripening.
• It causes further thickening and vascularisation of the uterus wall for maintaining state of pregnancy.
• Progesterone suppresses ovulation.
• Under secretion of progesterone during menstrual cycle, decreases the chance of pregnancy and may cause early menstruation.
• Under secretion during pregnancy may leads to the miscarriage.

Testes

• The male gonads are testes.
• Testes produce sperm and male sex hormones called testosterone which is secreted from interstitial cells among seminiferous tubules under the influence of ICSH.
• During puberty, testosterone initiates the maturation of the male reproductive organs and the appearance of secondary sex characteristics and sex drive.
• In addition, testosterone is necessary for normal sperm production and maintains the reproductive organs in their mature functional state in adult males.
• Under secretion of this hormone causes the development of feminine characteristics and male sterility.

Skills: Interpreting and Communication

Explain on what grounds some companies claim that growth is possible in people having short heights.

• If growth hormone is administered to young people before growth of their long bones is completed, it causes long bones to grow and they will grow taller.
• To accomplish this however, GH would have to be administered over a considerable period of time.

Summary Table of Gonadal Hormones

Disorders of Gonads

Intermediate Level

Gonadal Hormones

Effects of Estrogen

Effects of Progesterone

Effects of Testosterone

Formula / Mathematical Form

Not applicable to this topic.

Solved Example

Not applicable to this topic (descriptive topic).

Important Points

• 1. Gonads are special endocrine glands.
• 2. They produce gametes.
• 3. Female gonads are ovaries.
• 4. Male gonads are testes.
• 5. Ovaries secrete estrogen and progesterone.
• 6. Testes secrete testosterone.
• 7. Estrogen is secreted by Graffian follicle.
• 8. Estrogen is under stimulation of FSH.
• 9. Estrogen has negative feedback on FSH.
• 10. Estrogen is responsible for secondary sex characteristics.
• 11. Estrogen aids in healing and repair of uterine wall.
• 12. Under secretion of estrogen causes failure to mature sexually and sterility.
• 13. Oversecretion of estrogen causes fibroids and polycystic ovaries.
• 14. Progesterone is produced by corpus luteum.
• 15. Progesterone inhibits FSH secretion.
• 16. Progesterone causes thickening and vascularisation of uterus.
• 17. Progesterone suppresses ovulation.
• 18. Under secretion of progesterone causes early menstruation and miscarriage.
• 19. Testosterone is secreted by interstitial cells.
• 20. Testosterone is under influence of ICSH.

Remember

• - Gonads = endocrine glands that also produce gametes
• - Ovaries = female gonads
• - Testes = male gonads
• - Estrogen = female sex hormone; secondary sex characteristics
• - Progesterone = female sex hormone; pregnancy
• - Testosterone = male sex hormone; secondary sex characteristics
• - FSH = stimulates follicle development
• - LH (ICSH) = stimulates ovulation and testosterone secretion
• - Sterility = deficiency of estrogen
• - Fibroids = oversecretion of estrogen
• - Polycystic ovaries = oversecretion of estrogen
• - Miscarriage = under secretion of progesterone
• - Male sterility = under secretion of testosterone

Common Mistakes

• 1. Confusing ovaries and testes — Ovaries = female; testes = male.
• 2. Mixing up the hormones — Ovaries: estrogen, progesterone; testes: testosterone.
• 3. Forgetting the role of FSH and LH — FSH stimulates follicle; LH stimulates corpus luteum and testosterone.
• 4. Confusing estrogen and progesterone — Estrogen = secondary sex characteristics; progesterone = pregnancy.
• 5. Mixing up the disorders — Under secretion of estrogen: sterility; oversecretion: fibroids.
• 6. Forgetting the role of testosterone — Male sexual characteristics and sperm production.
• 7. Thinking progesterone is only for pregnancy — Progesterone also suppresses ovulation.
• 8. Believing estrogen is only produced in females — Estrogen is also produced in small amounts in males.
• 9. Mixing up the sources — Estrogen: Graffian follicle; progesterone: corpus luteum.
• 10. Forgetting the role of ICSH — ICSH stimulates testosterone secretion.

Quick Revision

Gonads are special type of endocrine glands which beside hormone secretions also produce gametes. Female gonads are ovaries while male gonads are testes. The ovaries secrete female sex hormones estrogen and progesterone. Estrogen is secreted by Graffian follicle under the stimulation of FSH but estrogen has negative feedback upon FSH. Estrogen is secreted at the time of puberty and is responsible for secondary sex characteristics in females. It aids in healing and repair of uterine wall after menstruation. Due to its under secretion in the young females, they fail to mature sexually. Deficiency of this hormone in adults leads to sterility. Its oversecretion may leads to the development of fibroids (abnormal growth) in uterus and polycystic ovaries. Progesterone is produced by corpus luteum in response to LH during normal menstrual cycle but it is produced and released from placenta during pregnancy. It inhibits further FSH secretion from pituitary, thus preventing any more follicles from ripening. It causes further thickening and vascularisation of the uterus wall for maintaining state of pregnancy. Progesterone suppresses ovulation. Under secretion of progesterone during menstrual cycle, decreases the chance of pregnancy and may cause early menstruation. Under secretion during pregnancy may leads to the miscarriage. The male gonads are testes. Testes produce sperm and male sex hormones called testosterone which is secreted from interstitial cells among seminiferous tubules under the influence of ICSH. During puberty, testosterone initiates the maturation of the male reproductive organs and the appearance of secondary sex characteristics and sex drive. In addition, testosterone is necessary for normal sperm production and maintains the reproductive organs in their mature functional state in adult males. Under secretion of this hormone causes the development of feminine characteristics and male sterility.

60-Second Revision

• Gonads = endocrine glands that also produce gametes
• Ovaries = female gonads
• Testes = male gonads
• Estrogen = female sex hormone; secondary sex characteristics
• Progesterone = female sex hormone; pregnancy
• Testosterone = male sex hormone; secondary sex characteristics
• FSH = stimulates follicle development
• LH (ICSH) = stimulates ovulation and testosterone secretion
• Sterility = deficiency of estrogen
• Fibroids = oversecretion of estrogen
• Polycystic ovaries = oversecretion of estrogen
• Miscarriage = under secretion of progesterone
• Male sterility = under secretion of testosterone
• Warning: Under secretion of testosterone causes feminine characteristics and male sterility

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• 6.3 NEUROSECRETORY ROLE OF HYPOTHALAMUS

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