Chapter 12 R eproductive P hysiology

1. Chapter 12Reproductive Physiology Wang Guoqing Department of Physiology, Medical School, Soochow University, Suzhou 215123, China E-mail:wangguoqing@suda.edu.cn Tel:0512-62096158; 13506212030

2. I. Sexual differentiation and formation of genitalia II. Male reproductive system: function and regulation III. Female reproductive system: function and regulation IV. Pregnancy and parturition V. Mechanism of milk secretion VI. Sex Physiology What will we discuss in this chapter? (Outline)

3. I. Sexual differentiation and formation of genitalia 1. Sexual Differentiation 性别的分化 • Sexual differentiation is determined at three levels: chromosomes, gonads, and phenotype. • Males have XY and females have XX chromosomes. • Female characteristics develop spontaneously in the absence of the Y chromosome. • Y chromosome contains the gene－sex-determining region (SRY)－that is necessary for the development of male characteristics. • Gonads are composed of three cell types in both males and females: supporting cells (Sertoli or granulosa cells); stomal cells (Leydig or theca cells); and germ cells (spermatogonia or oocytes). • Fetal testes secrete two hormones－antimullerian hormone and testosterone－that are essential for development of the male gonads and internal genitalia; in their absence female gonads and internal genitalia develop. • Dihydrotestosterone is responsible for development of male external genitalia.

4. Human chromosomes人类染色体

5. Chromosomes may decide sex染色体决定性别

6. 2. Formation of internal genitalia内生殖器的形成

7. 3. Formation of external genitalia外生殖器的形成

8. Origin of mammalian life

9. Puberty 青春期 • Onset of puberty is marked by pulsatile secretion of GnRH, FSH, and LH (female, age of 6-8 years and male, age of 9-10 years). • In the male, FSH stimulates sperm and Sertoli cell development while LH stimulates Leydig cell proliferation and testosterone secretion. • In the female, FSH stimulates follicle development and, along with LH, the synthesis of estradiol. • Testosterone and estradiol stimulate the development of secondary sex characteristics and a growth spurt in the male and female, respectively.

10. Male reproductive system: function and regulation • Testes are composed of seminiferous tubules that produce sperm and Leydig cells, which produce testosterone. • Spermatogenesis results from conversion of spermatogonia to mature sperm through mitosis, meiosis, and differentiation. • Sertoli cells of the seminiferous tubules support sperm development as well as surround and isolate developing sperm from the blood supply. • Leydig cells, under the influence of LH, secrete testosterone. • FSH and testosterone acting through Sertoli cells enable spermatogenesis. • Blood levels of testosterone and inhibin feed back to regulate pituitary release of FSH and LH.

11. Spermatogonia Spermatozoa Sertoli Cell Basement Membrane Leydig Cell Maturing sperm come from the testes.成熟的精子源自睾丸 The testes are composed of maturing sperm (spermatogonia, spermatozoa), Sertoli cells, and Leydig cells that interact to ensure a continuous production of sperm.

12. Histology of testes 睾丸的组织学

13. Histology of testes

14. Testicle tissue under the microscope

15. Structure of sperm 精子的结构

16. Male formation

17. Male main sexual gland —Testis男性主性腺-睾丸

18. Anatomy of male genitalia

19. Anatomy of male external genitalia

20. sperm Endocrine regulation of male reproduction

21. III. Female reproductive system: function and regulation • Ovary has three regions: cortex composed of follicles; medulla composed of stromal and hormone-producing cells; and hilum, the point of entry of blood vessels and nerves. • Follicles are composed of three cell types: oocytes, granulosa, thecal. • Initial development of oocytes beings in fetal life, but maturation is delayed until puberty when single oocytes mature and are released monthly for the next 4 decades. • Progesterone and estradiol are main steroid hormones produced by the ovaries –estradiol from granulosa cells and progesterone from many cell types. • Estradiol is released prior to ovulation, progesterone after ovulation; both prepare the uterus for egg implantation. • FSH stimulates monthly development of follicles, LH stimulates monthly ovulation, and both stimulate synthesis and secretion of progesterone and estradiol. • Corpus luteum, the postovulation follicle, secretes estradiol and progesterone to sustain the egg and uterus if fertilization and implantation occur.

22. Anatomy of female genitalia

23. Anatomy of female genitalia

24. Female internal genitalia女性内生殖器

25. Female main sexual gland —Ovary女性的主性腺-卵巢

26. Cavity Structure of uterine wall子宫壁的结构

27. Synthesis of testosterone, progesterone and estradiol

28. Endocrine regulation of sexual hormone 性激素的内分泌调节

29. Various sexual hormones changes in early to mid-follicular phase卵泡期

30. Various sexual hormones changes in early to mid-luteal phase黄体期

31. Various sexual hormones changes in late follicular phase and ovulation

32. Various sexual hormones changes in late luteal phase

33. Mechanism of menstrual cycle induced by the changes in various sexual hormone * Endometrium

34. Pregnancy and parturition1. Pregnancy • Fertilization of the oocyte occurs within 24 hours of ovulation in the distal end of the oviduct. • Fertilized egg completes second meiosis and divides repeatedly to form multicelled blastocyst. • Blastocyst implants in uterine wall within 5 days of ovulation. • After implantation, blastocyst secretes human chorionic gonadotropin (hCG, within 9 days of ovulation), which signals the corpus luteum to continue secreting progesterone and estradiol and is basis of the pregnancy test. • Progesterone is produced from cholesterol by the placenta and estriol through the interaction of the placenta and fetal adrenal cortex and liver. • Progesterone and estriol support development of the fetus as well as maternal breast development. • The mechanism by which parturition is initiated is unclear but involves an interplay between progesterone, prostaglandins, and oxytocin that increase the frequency of uterine contraction.

35. Theca Cells Granulosa Cells Cholesterol Cholesterol Pregnenolone Pregnenolone - - - - 17-Hydroxypregnenolone Dehydroepiandrosterone Androstenedione Androstenedione Testosterone Testosterone Estradiol Estradiol Androstenedione & Testosterone Effect of the theca and granulose cells of the ovary The theca and granulose cells of the ovary interact to ensure adequate production of androgens (androstenedione, testosterone) and estradiol.

36. Precondition of pregnancy is ovum must combine with sperm

37. Precondition of pregnancy is ovum must combine with sperm to be zygote

38. The process of zygote Formation受精卵的形成过程

39. Ovulation and fecundation排卵与受精

40. Growth of fetus (10 weeks)

41. Structure of placenta 胎盘的结构

42. Fetal Adrenal Placenta DHEA-Sulfate From the maternal blood Cholesterol Pregnenolone Fetal Liver Estriol 16-OH-DHEA-Sulfaye Synthesis of the major form of estrogen—estriol during pregnancy Ensuring an adequate production of estriol during pregnancy requires exchange of substances between the maternal blood, the placenta, the fetal adrenal gland, and the fetal liver.

43. 2. Parturition 分娩

44. Parturition

45. Parturition

46. Expulsion of the placenta after Parturition

47. Endocrine mechanism of Parturition分娩的内分泌机制

48. V. Mechanism of milk secretion1.Anatomy of breast 乳房的解剖 Progesterone and estrogen stimulate the development and growth of the mother’s breasts. Estrogen also stimulates prolactin secretion by the anterior pituitary, which participates in breast development. At parturition, the breasts are ready for milk production and release induced by increased prolactin and oxytocin levels brought on by suckling.

49. 2. Histology of breast 乳房的组织学

50. 3. Mechanism of milk secretion泌乳的机制