The document summarizes key aspects of human reproduction, including: 1) Sexual reproduction involves the combination of genes from two individuals through sexual intercourse, increasing genetic variation and the chances of species survival. 2) Sex determination is based on whether a zygote inherits an X or Y chromosome from the sperm. Males have XY and females have XX. 3) The development of testes or ovaries in early development depends on the presence or absence of testis-determining factor on the Y chromosome. 4) Sex hormones direct the development of external and internal reproductive structures during development.

1. Reproduction www.freelivedoctor.com

2. Reproduction Reproductive System Not needed for the survival of the individual Species survival Sexual reproduction Genes from two individual Combine at random Creates new combinations Increases chances of species survival www.freelivedoctor.com

3. Sexual Reproduction Each individual produces gametes Formed in gonads by meiosis Male: testes produce: Sperm Testosterone Female: ovaries produce: Ova Estrogens, Progesterone Gametes unite in process of fertilization Restores diploid number Forms zygote www.freelivedoctor.com

4. Sexual Determination Each zygote inherits 23 chromosomes from mother 23 chromosomes from father. 23 pairs of homologous chromosomes. alleles Kinds of chromosomes 1-22 pairs of chromosomes: autosomal 23 rd pair are sex chromosomes. Male: XY Female: XX Chromosomal gender of zygote determined by fertilizing sperm. www.freelivedoctor.com

5. Formation of Testes First 40 days after conception the gonads of males and females are similar in appearance. During this time: Spermatogonia and oogonia migrate from yolk sac to developing embryonic gonads Gonads could become either. TDF (testis-determining factor): hypothetical promotes the conversion to testes: gene located on short arm of Y, called SRY (sex determining region of Y chromosome) Found in all mammals www.freelivedoctor.com

6. Formation of Testes Structures in the testes: Seminiferous tubules: 43 to 50 days post conception Germinal cells: sperm. Nongerminal cells: Sertoli cells (sustentacular cells). Leydig cells (interstitial cells): Appear about day 65. Endocrine function: secrete androgens Main: Testosterone www.freelivedoctor.com

7. Formation of Testes Leydig cells secrete testosterone. Begins 8 th week and peaks at 12-14 th week. Masculinizes embryonic structures. Testosterone then declines to very low levels until puberty. Decline occurs by end of second trimester Testes descend into scrotum shortly before birth. Temp about 3 degrees below internal temp 35 degrees C www.freelivedoctor.com

8. Formation of Ovaries Absence of Y chromosome and TDF, female develop ovaries. Ovarian follicles do not appear until 2 nd trimester. www.freelivedoctor.com

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10. Development of Accessory Sex Organs and Genitalia Presence or absence of testes determines the accessory sex organs and external genitalia. Male accessory organs derived from wolffian ducts.( mesonephric ) Sertoli cells secrete MIF(mullerian inhibition factor). Female accessory organs derived from mullerian ducts. ( paramesonephritic ) www.freelivedoctor.com

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12. Development of Accessory Sex Organs and Genitalia Both duct systems in both sexes between days 25 and 50 Regression of mullarian ducts begins about day 60 Testosterone responsible for development of male accessory sex organs External genitalia identical first 6 weeks, then testosterone stimulates development of penis Not the active agent in all cells converted to dihydrotestosterone (DHT) in some target cells Needed for penis, spongy urethra, scrotum, prostrate Testosterone directly needed for wolfian derivatives: Epididymis, ductus deferens, ejaculatory duct, SV www.freelivedoctor.com

13. Development of Accessory Sex Organs and Genitalia www.freelivedoctor.com

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15. Endocrine Regulation of Reproduction First trimester Embryonic testes are active endocrine glands Secrete large amounts of testosterone Embryonic ovaries not mature until third trimester Time of birth: Gonads in both sexes relatively inactive Before puberty: Low levels of sex steroids in both Due to lack of stimulation Puberty: Increased stimulation from gonadotropic hormones Induce increase in sex steroids www.freelivedoctor.com

16. Endocrine Regulation of Reproduction Hypothalamus releases LHRH (GnRH) into hypothalamo-hypophyseal portal vessels. Anterior pituitary secretes: LH: luteinizing hormone. In male: interstitial-cell stimulating hormone (ICSH) FSH: follicle-stimulating hormone. Secreted in pulsatile fashion to prevent desensitization and down regulation of receptors. www.freelivedoctor.com

17. Endocrine Interactions Primary effects of LH and FSH on gonads: Stimulation of spermatogenesis and oogenesis. Stimulation of gonadal hormone secretion. Maintenance of gonadal structure. www.freelivedoctor.com

18. Endocrine Regulation Negative Feedback: Inhibit GnRH from hypothalamus. Inhibit anterior pituitary response to GnRH. Inhibin secretion inhibit anterior pituitary release of FSH. By sertoli cells Female: estrogen and progesterone. Male: testosterone. www.freelivedoctor.com

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20. Onset of Puberty FSH and LH high in newborn, falls to low levels in few weeks. Puberty: driven by increased secretion of FSH and LH www.freelivedoctor.com

21. Onset of Puberty FSH and LH Brain maturation increases GnRH secretion. Decreased sensitivity of GnRH to negative feedback. LH: Increased secretion triggers puberty Late puberty, pulsatile secretion of LH and FSH increase during sleep. Stimulate a rise in sex steroid secretion. www.freelivedoctor.com

22. Onset of Puberty Stimulate rise in testosterone and estradiol-17  . Produce secondary sexual characteristics. Age of onset related to the amount of body fat and physical activity in the female Leptin secretion from adipocytes may be required for puberty. www.freelivedoctor.com

23. Pineal Gland Secretes melatonin. Secretion influenced by light-dark cycles. Inhibit gonadotropin secretion. Role in humans not established. www.freelivedoctor.com

24. 4 Phases of Human Sexual Response Excitation phase (arousal): Myotonia and vasocongestion. Engorgement of a sexual organ with blood. Erection of the nipples. Plateau phase: Clitoris becomes partially hidden. Erected nipples become partially hidden by swelling of areolae. Orgasm: Uterus and orgasmic platform of vagina contract. Contractions accompanying ejaculation. Resolution phase: Body return to preexcitation conditions. Refractory period In males Erection possible, but not ejaculation www.freelivedoctor.com

25. Male Reproduction System Testes: Seminiferous tubules: Where spermatogenesis occurs. Contain receptor proteins for FSH in Sertoli cells. Leydig cells: Secrete testosterone. Contain receptor proteins for LH. www.freelivedoctor.com

26. Control of LH and FSH Secretion Negative feedback: Testosterone inhibits LH and GnRH production. Inhibin inhibits FSH secretion. Aromatization reaction producing estadiol in the brain is required for the negative feedback effects of testosterone on LH. Brain is a target organ for testosterone Converted to derivatives www.freelivedoctor.com

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28. Testosterone Secretion Responsible for initiation and maintenance of body changes in puberty. Stimulate growth of muscles, larynx, and bone growth until sealing of the epiphyseal discs. Promote hemoglobin synthesis. Acts in paracrine fashion and is responsible for spermatogenesis. www.freelivedoctor.com

29. Testosterone Secretion Negative feedback of testosterone and inhibin Keep relatively constant levels of gonadotropins Results in relatively constant levels Different in female At menopause: no more sex steroids In males, gradual decrease www.freelivedoctor.com

30. Endocrine function: testes Testosterone: main androgen Sertoli and Leydig cells secrete small amounts of estradiol. Have receptors for estradiol (as do other male structures) May be needed for spermatogenesis Estradiol may be responsible for: Negative feedback in brain. Sealing of epiphyseal plates. Regulatory function in fertility. www.freelivedoctor.com

31. Spermatogenesis Spermatogonia: Replicate initially by mitosis. Produce two cells One becomes a primary spermatocytes undergoes meiosis: 2 nuclear divisions. 2 nd meiotic division produce 4 spermatids. www.freelivedoctor.com

32. Spermiogenesis Maturation of spermatozoa. Cytoplasm is pinched off and ingested by the Sertoli cell cytoplasm. www.freelivedoctor.com

33. Sertoli Cells Blood-testes barrier: Prevents autoimmune destruction of sperm. Produce FAS ligand which binds to the FAS receptor on surface to T lymphocytes, triggering apoptosis. Secretes inhibin. Phagocytize residual bodies: Transmit information molecules from germ cells to Sertoli cells. Secrete ABP (androgen-binding protein): Binds to testosterone and concentrates testosterone in the tubules. www.freelivedoctor.com

34. Hormonal Control of Spermatogenesis Testosterone required for completion of meiosis and spermatid maturation. Testes secrete paracrine regulators: IGF-1. Inhibin. FSH necessary in the later stages of spermatid maturation. www.freelivedoctor.com

35. Male Accessory Organs Epididymis: Maturational changes. Resistance to pH changes and temperature. Storage. Prostate secretes: Alkaline fluid. Citric acid. Ca ++ . Coagulation proteins. Seminal vesicles secrete: Fructose. www.freelivedoctor.com

36. Erection, Emission, and Ejaculation Erection: Increased vasodilation of arterioles. NO is the NT. Blood flow into the erectile tissues of the penis. Parasympathetic Emission: Movement of semen into the urethra. Sympathetic Ejaculation: Forcible expulsion of semen from the urethra out of the penis. Sympathetic www.freelivedoctor.com

37. Female Reproductive System Ovaries: Contain large number of follicles which enclose ova. Extensions called fimbriae partially cover each ovary. At ovulation, secondary oocyte is extruded. www.freelivedoctor.com

38. Female Reproductive System Fallopian (uterine) tubes: Ova drawn into the tube by cilia. Uterus: Womb. Endometrium shed during menstruation. Vagina: Cervical mucus plug. www.freelivedoctor.com

39. Ovarian Cycle 5 mo. gestation ovaries contain 6-7 million oogonia. Oogenesis arrested in prophase of 1 st meiotic division (primary oocyte). Apoptosis occurs: 2 million primary oocytes at birth. 400,000 primary oocytes at puberty. 400 oocytes ovulated during the reproductive years. www.freelivedoctor.com

40. Ovarian Cycle Primary oocytes contained in primary follicles. FSH stimulates cell growth. Develop into secondary follicles. Fusion of its vesicles into the antrum. Mature graafian follicle: 1 st meiotic division completed (secondary oocyte). www.freelivedoctor.com

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42. Ovarian Cycle Secondary oocyte: Under FSH stimulation: Theca cells secrete testosterone. Granulosa cells: contain the enzyme aromatase to convert testosterone into estrogen. www.freelivedoctor.com

43. Ovulation Graafian follicle forms bulge on surface of ovary. Extrudes secondary oocyte into the uterine tube. Empty follicle becomes corpus luteum and secretes: Progesterone. Estrogen. If not fertilized becomes corpus albicans. www.freelivedoctor.com

44. Menstrual Cycle 3 phases: Ovarian Follicular Phase Ovulation Luteal Phase Duration approximately 28 days. Day 1 is the first day of menstruation. www.freelivedoctor.com

45. Follicular Phase FSH: Stimulates production of FSH receptors on granulosa cells. Follicles grow and become secondary follicle. Granulosa cells secrete estradiol. Increases sensitivity of FSH receptors. FSH and estradiol stimulate production of LH receptors in graafian follicle. www.freelivedoctor.com

46. Follicular Phase Rapid rise in estradiol: Negative feedback on LH and FSH. Hypothalamus increase frequency of GnRH pulses. Augments the ability of anterior pituitary to respond to GnRH to increase LH secretion. www.freelivedoctor.com

47. Follicular Phase Positive feedback: LH surge begins 24 hours before ovulation. Triggers ovulation. FSH increase stimulates development of new follicles. www.freelivedoctor.com

48. Ovulation Under FSH, graafian follicle grows large and thin-walled. Triggers LH surge. Wall of graafian follicle ruptures. Day 14. Ist meiotic division is completed. www.freelivedoctor.com

49. Luteal Phase LH stimulates formation of the empty follicle into corpus luteum. Corpus luteum secretes: Progesterone: Plasma concentration rapidly rises. Estradiol. Negative feedback on LH and FSH. Inhibin: suppress FSH. www.freelivedoctor.com

50. Luteal Phase Corpus luteum regresses unless fertilization occurs: Estradiol decreases. Progesterone decreases. Withdrawal of estradiol and progesterone cause menstruation to occur. www.freelivedoctor.com

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53. Endometrial Changes 3 phases of endometrium changes: Proliferative phase. Secretory phase. Menstrual phase. www.freelivedoctor.com

54. Proliferative Phase Ovary is in follicular phase. Estradiol stimulate growth of endometrium. Spiral arteries develop. Stimulate production of receptor proteins for progesterone. Cornification of vaginal epithelium occurs. www.freelivedoctor.com

55. Secretory Phase Ovary is in luteal phase. Progesterone stimulates development of uterine glands, which become engorged with glycogen. Endometrium becomes thick, vascular and spongy. Cervical mucus thickens and becomes sticky. www.freelivedoctor.com

56. Menstrual Phase Progesterone cause constriction of spiral arteries. Necrosis and sloughing of endometrium occurs. Lasts 1-5 days. www.freelivedoctor.com

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58. Menopause Cessation of ovarian activity. Age ~ 50 years. Ovaries depleted of follicles. Estradiol and inhibin withdrawl causes hot flashes, and atrophy of the vaginal wall. LH and FSH increase. www.freelivedoctor.com

59. Fertilization Ejaculation 300 million sperm, 100 reach (uterine) fallopian tube. Fertilization occurs in the uterine tubes Acrosomal reaction: Acrosome of sperm contains hyaluronidase, an enzyme that digests a channel through zona pellucida. Sperm fuses with ovum cell membrane. www.freelivedoctor.com

60. Fertilization As fertilization occurs, secondary oocyte completes 2 nd meiotic division. Sperm enters ovum cytoplasm. Ovum nuclear membrane disappears, zygote formed. www.freelivedoctor.com

61. Blastocyct Formation Cleavage: 30-36 hrs. after fertilization the zygote divides by mitosis. Blastocyst develops: Inner cell mass: fetus. Surrounding chorion: trophoblasts form placenta. www.freelivedoctor.com

62. Implantation 6 th day after fertilization, blastocyst attaches to uterine wall. Blastocyst secretes enzymes that allow blastocyst to burrow into endometrium. Trophoblast cells secrete hCG. www.freelivedoctor.com

63. hCG Human chorionic gonadotropin. Trophoblast cells secrete hCG. Signals corpus luteum not to degenerate until placenta secretes adequate [hormone]. Effects similar to LH. Basis of pregnancy test. www.freelivedoctor.com

64. Placenta Syncytiotrophoblast secretes enzymes that create blood filled cavities in the maternal tissue. Cytotrophoblast then from projections (villi) that grow into the venous blood. Producing chorion frondosum on the side that faces the uterine wall. Other side of chorion bulges into the uterine cavity. www.freelivedoctor.com

65. Placental Changes Decidual reaction: Endometrial growth. Accumulation of glycogen. Decidua basalis: maternal tissue in contact with the chorion frondosum. Maternal and fetal blood do not mix. www.freelivedoctor.com

66. Amnion Envelop the embryo. Amnionic fluid contains sloughed cells of the fetus. www.freelivedoctor.com

67. Placenta Function Gas exchange: 0 2 and C0 2 . Nutrient exchange. Waste exchange. Synthesis of proteins and enzymes. www.freelivedoctor.com

68. Placental Hormones hCS: Chorionic somatomammotropin. GH effects. Diabetic-like effect: Glucose sparing effect. Polyuria. Lipolysis. www.freelivedoctor.com

69. Placental Hormones Fetal-placental unit: Placenta must cooperate with the adrenal cortex in the fetus to produce estrogen. Estrogen stimulates: Endometrial growth. Inhibit prolactin secretion. Growth of mammary ducts. Enlargement of mother’s uterus. www.freelivedoctor.com

70. Placental Hormones Progesterone: Suppresses uterine contractions. Stimulates uterine growth . Suppresses LH and FSH. Stimulate development of alveolar tissue of the mammary gland. www.freelivedoctor.com

71. Parturition Estrogen in late pregnancy: Increases amount of oxytocin stored. Stimulate production of oxytocin receptors in myometrium. Stimulate prostaglandin production. Uterine contractions: Oxytocin. Prostaglandins. www.freelivedoctor.com

72. Lactation Hypothalamus releases PRH. Anterior pituitary releases prolactin: Stimulate milk production. Oxytocin needed for “milk letdown”. www.freelivedoctor.com

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