In this presentation you will: investigate the role of hormones in human reproduction

1. Hormonal Control of Human Reproduction • In this presentation you will: • investigate the role of hormones in human reproduction Next >

2. Introduction Male and female sex hormones control sexual development, taking children through puberty to become fully developed adults capable of reproduction. Hormones also have a very important role to play in pregnancy, birth, and breast feeding. Next >

3. Testosterone – Where it is Made Male sex hormones are known as androgens. The most important of these is testosterone. Testosterone is a steroid hormone that is produced by the testes. Seminiferous tubule Epididymis The cells that make testosterone are found in between the seminiferous tubules (where sperm production begins to occur at puberty) and are called interstitial or Leydigcells. Vas deferens Next >

4. Placenta Fetus Amnion Amniotic fluid Plug of mucus in cervix Vagina Testosterone – When it is Made Testosterone starts to be made by the Leydig cells while the male fetus is developing in the uterus. The presence of testosterone causes the male embryo to develop male sex organs and other characteristics. Next >

5. Placenta Fetus Amnion Amniotic fluid Plug of mucus in cervix Vagina Testosterone – When it is Made In the female fetus, very small amounts of testosterone are secreted by the ovaries. This results in the absence of male characteristics and in the development of female sex organs. Next >

6. Testosterone – Its Role During childhood, almost all the Leydig cells in the testes disappear, so only very small amounts of testosterone are produced. At puberty, Leydig cells reappear and testosterone secretion begins again, causing the development of secondary sexual characteristics, such as body hair growth and the enlargement of the larynx (or Adam’s Apple), which makes the voice deeper. Next >

7. Luteinizing Hormone The secretion of testosterone by the Leydig cells is controlled by another hormone known as luteinizing hormone, or LH. Hypothalamus Cerebrum This hormone is secreted from the anterior pituitary gland that is located near the base of the brain. Cerebellum Pituitary Brain stem Next >

8. Question 1 Which of the following is a secondary sexual characteristic in men? A) Increased body hair growth B) Enlargement of the larynx C) Deepening of the voice D) All of the above Next >

9. Question 1 Which of the following is a secondary sexual characteristic in men? A) Increased body hair growth B) Enlargement of the larynx C) Deepening of the voice D) All of the above Next >

10. 30 25 20 15 Rate of testosterone secretion in milligrams 10 5 0 10 15 20 30 40 50 60 70 80 Age (years) = Men = Women Testosterone Production The secretion of LH (luteinizing hormone) is inhibited by high levels of testosterone. Therefore, testosterone release is dependent upon the levels of LH. Testosterone production, therefore, continues at a steady rate on a day-to-day basis. However, testosterone production does not remain constant throughout the male lifespan, as it peaks around age 20 then slowly declines. Next >

11. Egg released Estrogen Progesterone Menstruation Lining maintained Lining breaks down Lining of uterus builds up Day 1 Day 4 Day 14 Day 28 The Menstrual Cycle The secretion of hormones in women follows a cycle which is repeated approximately once a month. This is known as the menstrual cycle. The average menstrual cycle lasts for 28 days. However, quite commonly they are as short as 20 days or as long as 34 days. Next >

12. Uterus Zygote Oviduct Ovary Cervix Vagina The Control of the Female Hormones The ovaries secrete two female sex hormones: estrogen and progesterone. Like testosterone, estrogen and progesterone are both steroid hormones. Blastocyst The secretion of these hormones is, in turn, controlled by two hormones secreted by the anterior pituitary gland: luteinizing hormone (LH) and follicle stimulating hormone (FSH). Next >

13. Uterus Zygote Oviduct Ovary Cervix Vagina The Roles of Estrogen and Progesterone Estrogen is first secreted by a girl’s ovaries when she reaches puberty. It causes an increase in the size of the reproductive organs and results in the development of secondary sexual characteristics, such as the growth of breasts. The chief role of progesterone is to prepare the lining of the uterus for pregnancy. Next >

14. Question 2 When does estrogen production begin in girls? A) Before birth B) At birth C) At puberty D) After puberty Next >

15. Question 2 When does estrogen production begin in girls? A) Before birth B) At birth C) At puberty D) After puberty Next >

16. Healthy bone structure Estrogen and Bone Growth Estrogen has an important role in stimulating bone growth in women, the same as testosterone does in men. However, the effect of estrogen is less pronounced and drops off earlier in life. Next >

17. Healthy bone structure Bone affected by osteoporosis Estrogen and Bone Growth By the time women reach age 50, their estrogen production drops. In some women, this can cause bones to become weak, by a condition known as osteoporosis. This can be treated with oral doses of estrogen and testosterone. Next >

18. The Menstrual Cycle – Days 1-12 When discussing the days of the menstrual cycle, day 1 is taken as the first day of menstruation. 2. Secondary follicle 3. Ovarian follicle 1. Primary follicle During the first few days of the cycle, the secretion of FSH and LH from the anterior pituitary gland increases slightly. This stimulates the growth of a few primary follicles in the ovaries. 5. Corpus luteum 4. Ovulation Primary oocyte Granulosa cells Area filled by thecal cells Next >

19. The Menstrual Cycle – Days 1-12 Only one of these follicles becomes completely developed. The granulosacells in the developing follicle secrete estrogen, and the level of estrogen in the blood rises sharply. 2. Secondary follicle 3. Ovarian follicle 1. Primary follicle 5. Corpus luteum 4. Ovulation Primary oocyte Granulosa cells Area filled by thecal cells Next >

20. Question 3 Osteoporosis in women is caused by a drop in the levels of a particular hormone. What is this hormone? A) LH B) FSH C) Estrogen D) Progesterone Next >

21. Question 3 Osteoporosis in women is caused by a drop in the levels of a particular hormone. What is this hormone? A) LH B) FSH C) Estrogen D) Progesterone Next >

22. FSH Egg released LH Day 1 Day 4 Day 14 Day 28 The Menstrual Cycle – Days 12-14 The rise in estrogen secretion inhibits the secretion of LH and FSH and their levels begin to drop. The estrogen causes the endometrium (lining) of the uterus to grow, so that it becomes about 3 to 4 mm thick by day 12. Next >

23. FSH Egg released LH Day 1 Day 4 Day 14 Day 28 The Menstrual Cycle – Days 12-14 At about day 12 of the cycle, the secretion of LH suddenly rises. This causes the granulosa cells to slow down their estrogen secretion, and from this point they begin to secrete progesterone instead. LH also induces ovulation (release of an oocyte from the follicle), typically, on day 14 of the cycle. Next >

24. Question 4 Ovulation test sticks detect the surge of a particular hormone just before ovulation (on day 12 in a 28-day cycle). What is the hormone that the test sticks will detect? A) FSH B) LH C) estrogen D) progesterone Next >

25. Question 4 Ovulation test sticks detect the surge of a particular hormone just before ovulation (on day 12 in a 28-day cycle). What is the hormone that the test sticks will detect? A) FSH B) LH C) estrogen D) progesterone Next >

26. The Corpus Luteum When the oocyte leaves the follicle, the remaining granulosa cells (stimulated by the high levels of LH) rapidly enlarge and fill with a yellow substance. 2. Secondary follicle 3. Ovarian follicle 1. Primary follicle This mass of cells is called a corpus luteum, or yellow body. The cells of the corpus luteum secrete large quantities of progesterone and smaller amounts of estrogen. 5. Corpus luteum 4. Ovulation Ovarian follicle Secondary oocyte Thecal cells Nucleus Fluid Granulosa cells Next >

27. Question 5 If ovulation typically occurs 14 days before the onset of menstruation, on what day will it occur in a 26-day cycle? Enter your answer as a number. Next >

28. Question 5 If ovulation typically occurs 14 days before the onset of menstruation, on what day will it occur in a 26-day cycle? Enter your answer as a number. 12 Next >

29. Egg released Oestrogen Progesterone Menstruation Lining maintained Lining breaks down Lining of uterus builds up Day 1 Day 4 Day 14 Day 28 The Role of Progesterone The progesterone causes the endometrium to continue developing, including an increase in its blood supply and the amount of nutrients it receives. Its thickness grows to about 5 or 6 mm. If the ovum that is released from the ovary is fertilized, the endometrium will be ready to receive and nourish it. Next >

30. FSH Egg released LH Day 1 Day 4 Day 14 Day 28 When Fertilization Does Not Occur If fertilization does not occur, the estrogen and progesterone (secreted by the corpus luteum) inhibit the secretion of FSH and LH from the anterior pituitary. Next >

31. Egg released Oestrogen Progesterone Menstruation Lining maintained Lining breaks down Lining of uterus builds up Day 1 Day 4 Day 14 Day 28 When Fertilization Does Not Occur As the levels of FSH and LH in the body fall, the corpus luteum begins to degenerate. The corpus luteum is responsible for estrogen and progesterone secretion. Therefore, with its degeneration, all four hormones drop to low concentrations at this last stage of the cycle. Next >

32. FSH Egg released LH Day 1 Day 4 Day 14 Day 28 The Fate Of The Endometrium When estrogen and progesterone levels drop below a certain level, their inhibitory effect on the anterior pituitary gland ends. FSH and LH begin to be secreted again from this point. Next >

33. Egg released Oestrogen Progesterone Menstruation Lining maintained Lining breaks down Lining of uterus builds up Day 1 Day 4 Day 14 Day 28 The Fate Of The Endometrium As estrogen and progesterone are responsible for the development and maintenance of the endometrium, its structure begins to break down. It is lost during the first 4-7 days of the next menstrual cycle. Next >

34. Question 6 Which hormone directly acts to maintain the thickness of the endometrium? A) LH B) FSH C) Estrogen D) Progesterone Next >

35. Question 6 Which hormone directly acts to maintain the thickness of the endometrium? A) LH B) FSH C) Estrogen D) Progesterone Next >

36. When Fertilization Does Occur If a mature ovum is successfully fertilized, a different sequence of events takes place. On its journey to the uterus, the zygote divides several times by mitosis to form a fluid filled ball of cells called a blastocyst, which implants into the wall of the uterus. Tissue of endometrium Epithelium of the uterus Blastocyst Cells that form the embryo Next >

37. Tissue of endometrium Epithelium of the uterus Cells that form the embryo When Fertilization Does Occur Some of these cells, the trophoblasts, secrete a hormone called human chorionic gonadotrophin (HCG). HCG stimulates the corpus luteum in the ovary to increase its output of estrogen and progesterone, which further stimulates the development of the endometrium. Trophoblast cells that form the placenta Next >

38. Question 7 Which hormone is needed to stimulate the production of estrogen and progesterone in early pregnancy? A) LH B) FSH C) HCG D) All of the above Next >

39. Question 7 Which hormone is needed to stimulate the production of estrogen and progesterone in early pregnancy? A) LH B) FSH C) HCG D) All of the above Next >

40. Sinus Fetal vein Villus Fetal arteries Umbilical cord After Implantation Over the next few weeks, the placenta develops. This provides oxygenated blood and nutrition to the developing embryo, and it secretes estrogen and progesterone. Next >

41. Sinus Fetal vein Villus Fetal arteries Umbilical cord After Implantation About 5-6 weeks after fertilization, the placenta secretes enough of these hormones to maintain the endometrium. The corpus luteum is no longer required and eventually disintegrates. Next >

42. Placenta Fetus Amnion Amniotic fluid Plug of mucus in cervix Vagina Hormones During Pregnancy The placenta produces increasing amounts of these two hormones, especially progesterone, throughout pregnancy. These hormones cause enlargement of the uterus and breasts and maintain the endometrium. Next >

43. Placenta Fetus Amnion Amniotic fluid Plug of mucus in cervix Vagina Hormones During Pregnancy Progesterone also inhibits the ability of the muscles in the uterus to contract, which helps to minimize the chance that labor might begin before the baby is fully developed. Next >

44. The Role of Hormones During Birth Towards the end of the pregnancy, the level of estrogen rises. It is believed that this may help to increase the ability of the uterine muscles to contract. Another hormone called oxytocin is also secreted at this time from both the mother’s posterior pituitary gland and the fetus. This hormone causes contraction of the muscles in the uterus. This part of the birth process is called labor. Next >

45. The Role of Hormones During Birth Stretching of the cervix by the baby’s head increases the secretion of oxytocin. As a result of these events, natural birth may take place. Next >

46. Mammary gland Lactiferous sinus which stores milk Nipple Tissue which synthesizes colostrum and breast milk The Role of Hormones During Lactation Another hormone, prolactin, is secreted from the mother’s anterior pituitary gland during the later stages of pregnancy. This hormone promotes the production of milk, but its effects are inhibited when estrogen and progesterone levels are high. Next >

47. Mammary gland Lactiferous sinus which stores milk Nipple Tissue which synthesizes colostrum and breast milk The Role of Hormones During Lactation Prolactin only has any effect when the baby has been born and the placenta delivered. The base level of prolactin rises each time the baby suckles, ensuring supply on demand. Next >

48. Question 8 Which hormone is responsible for the stimulation of milk production? A) HCG B) FSH C) Oxytocin D) Prolactin Next >

49. Question 8 Which hormone is responsible for the stimulation of milk production? A) HCG B) FSH C) Oxytocin D) Prolactin Next >

50. Summary In this presentation you have seen: • the role of hormones in sexual development • the role of hormones in the menstrual cycle • the role of hormones in pregnancy • the role of hormones in the process of birth • the role of hormones in lactation End >