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Female Reproductive Endocrinology

Female Reproductive Endocrinology. Chapter 18. Anatomy. Vulva – external genitalia Vagina Functions: Sperm, menstrual flow passage Receptacle for penis Birth canal Rugae Acidic environment. Uterus Functions: Sperm transport Implantation fert’d ovum Fetal dev’t Labor Menstruation

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Female Reproductive Endocrinology

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  1. Female Reproductive Endocrinology Chapter 18

  2. Anatomy • Vulva – external genitalia • Vagina • Functions: • Sperm, menstrual flow passage • Receptacle for penis • Birth canal • Rugae • Acidic environment

  3. Uterus • Functions: • Sperm transport • Implantation fert’d ovum • Fetal dev’t • Labor • Menstruation • Cervix secretes mucus

  4. Uterus – cont’d • Three histological layers • Perimetrium – outside • Myometrium – sev muscle layers + connective tissue • Forms bulk of uterine wall • Endometrium – closest to uterine cavity • Covered w/ epithelium • Vascular w/ tubular glands • Further divided  3 layers • Innermost shed w/ menstruation • Outermost  new inner layer during cycle

  5. Oviducts • Transport • Peristalsis • Cilia • Isthmus, ampulla, infundibulum • Not static tube • Ovaries = gonads • Inner medulla, outer cortex • Gametogenesis, hormonogenesis

  6. Ovaries • Prepubertal • Anatomy • Smooth outer germinal epithelium • Connective tissue • Cortex w/ ovarian follicles in stroma • Low quantities of sex steroid • Feedback inhibition of gonadotropins • Puberty  gonadotropins  sex steroids • LH  PKA  StAR  P450scc in partic cells • FSH  E2 secr’n in partic cells

  7. Ovarian Cycle • Controls, controlled by hormones • Coupled to uterine cycle • Related to maturation ovarian follicles • Gonadotropin dependent • Two phases • Follicular • Luteal

  8. Follicular Phase • Variable length • Maturing follicles secrete • 17b-estradiol • Inhibin • Absence functional CL • Plasma progesterone low • FSH elevated @ beginning, diminishes • High FSH impt to follicle selection, early maturation

  9. As follicle dev’s, more E2, inhibin  • Decr’d FSH (neg feedback) • Decr’d LH • Upregulation ant pit GnRH receptors • E2 peaks @ midcycle  FSH/LH surge • Now new ability some ovarian cells to produce sex steroids (progesterone) • Now ovum released from mature follicle

  10. Luteal Phase • Invariant 14+2 d length • CL begins, develops, dies • CL secretes progesterone (also E2, inhibin) as matures • Progesterone  postov decr LH, FSH (neg feedback) • Midluteal peak over week • E2 minimally elevated

  11. Hormone secretion diminishes as CL declines • If no fertilization • Get sharp decline in plasma progesterone • Now less neg feedback due to progesterone •  FSH/LH again secreted • FSH influences new follicle selection, early maturation

  12. Gametogenesis • Ovarian follicles named by maturation stage • Primordial • Primary oocyte • Squamous epithelium; single layer • Dev’s  granulosa cells • Growth & remodeling • 40 m; oocyte 15-25 m • Quiescent

  13. Primary follicle • Oocyte enlarges (80-100 m) • Follicle epithelium • Simple cuboidal • “Granulosa cells” • Express FSH receptors • FSH response  organize, stratify granulosa cell layers • Zona pellucida (glycoprotein layer) deposits • Stroma begins to organize as theca

  14. Secondary=preantral follicle • Granulosa proliferates, stratifies • Signaled by oocyte growth factors • Growth Differentiation Factor 9 (GDF-9) • Bone Morphological Protein 15 (BMP-15) • Mitosis and/or pattern of arrangement stim’d • Simple cuboidal  stratified, pseudostratified columnar • Diff layers have diff morphology, function • Granulosa cells produce activin • Stim’s FSH receptor synth • Granulosa cells become sensitive to FSH • Impt to selection • Impt to differentiation • Impt to maturation

  15. Figure 9. The early differentiation of the granulosa cells during preantral folliculogenesis involves the expression of FSH receptors. Animal studies support the concept that this process involves an activin autocrine/paracrine mechanism. (Erickson GF: Dissociation of Endocrine and Gametogenic Ovarian Function. In Lobo, R. (ed.): Perimenopause. Serono Symposia, Springer-Verlaag, 1997. Reproduced with permission from Springer-Verlag, New York.)

  16. Secondary follicle – cont’d • Granulosa cells connected by gap junctions • Synchronization • Nutrient transfer • Basement membr dev’s • When 6 layers granulosa • Definitive theca layer • Angiogenesis  blood supply to theca

  17. Secondary follicle (cont’d) • Final 2o follicle 100-200 m • Fully grown oocyte w/ zp • Approx 9 layers granulosa • Basal lamina • Theca interna w/ capillary net • Theca externa

  18. Granulosa cells

  19. Thecal cells

  20. Tertiary=antral follicle • Chamber • Follicular fluid contains hormones • Blood-derived • From oocyte • From granulosa cells • Cavitation signalled by follicle cells • Corona radiata = granulosa cells anchored to zp • Theca fully developed

  21. Tertiary follicle – cont’d • Theca interna = steroid producing (androstenedione) • Extensive sER, cytoplasmic lipid droplets, tubular mitoch cristae • Receptors for LH, insulin • Richly vascularized • Theca externa • Smooth muscle cells • Autonomic neurons

  22. Figure 12. Photomicrograph of an early tertiary follicle 0.4 mm in diameter at the cavitation or early antrum stage. zona pellucida (ZP); granulosa cells (GC); basal lamina (BL); theca interna (TI); theca externa (TE); granulosa mitosis (arrowheads). (Bloom W, Fawcett DW In A Textbook of Histology. Philadelphia, WB Saunders Company, Philadelphia 1975. With permission from Arnold.)

  23. Preovulatory=Graafian follicle • Now single, dominant follicle • Overall size varies; deter’d by amt follicular fluid • Cumulus oophorus = oocyte + corona radiata • Will be expelled @ ovulation • Hyaluronic acid accumulates • Break attachment corona radiata and granulosa • LH surge induces completion 1st meiotic division  2o oocyte • 2nd meiotic division @ fert’n

  24. Ovulation • Induced by LH surge • Rupture • Follicle wall • Follicle cell layers •  Corona radiata w/ oocyte expelled into peritoneal cavity

  25. Luteinization • Initiated by LH surge • CL forms from • Graunulosa lutein • Theca lutein • Assoc’d microvasculature • Defined life span • If no fertilization, involution & apoptosis 14 d after form’n

  26. Contributes to next developing cohort of follicles • CL degeneration  decr’d E2, inhibin A •  incr’d FSH •  incr’d FSH in follic fluid of Graafian follicle •  dominant follicle selection, maturation

  27. Atresia • Remaining 99.9% follicles • Apoptosis of oocyte, granulosa cells • Ligand signalling pathways  cell death • FSH=survival factor • Prevents apoptosis

  28. Ovarian Steroidogenesis • Maturing follicles and CL • Maturing follicles – 2 adjacent impt pop’ns • Granulosa cells • Theca interna cells • CL – impt cells der’d from follicle after ov’n • Granulosa lutein • Theca lutein

  29. Sex steroids • Prior to ov’n (from maturing follicle): E2 • After ov’n (from CL): progesterone + E2 • Book notes progesterone=distinctive female hormone • CL and placenta only • Cell pop’ns coordinate in prod’n sex steroids

  30. Theca (interna & externa) express P450scc • Cholesterol  pregnenolone • Sensitive to LH •  cAMP  PKA  StAR  PBR  P450scc activity in inner mitoch membr • Pregnenolone  androgen pathway • Uses P450c17 • Preovulatory LH surge  • Ovulation • Luteinization theca interna, granulosa • Development CL

  31. Theca interna express aromatase (androgens  estrogens) • BUT once ovulation occurs, expression ceases • So decr’d secr’n estrogens from CL

  32. Granulosa cells lack P450scc, P450c17 • No cholesterol  pregnenolone • No further androgen synth • Rely on theca cell androgens • Insensitive to LH signal for androgen prod’n • EXCEPT when advanced follicle dev’d • Just prior to ov’n • Small numbers LH receptors expressed • LH stim’s steroidogenesis in these cells • Impt to luteinization

  33. Granulosa cells – cont’d • BUT sensitive to FSH • FSH stim’n  • Proliferation granulosa cells • Secretion inhibin B • Expression aromatase through cAMP, PKA act’n • Granulosa cells express aromatase • Androgens  estrogens • Most impt source of E2

  34. Granulosa lutein cells express P450scc • So can produce pregnenolone • BUT granulosa lutein cells lack P450c17 • No androgen synth from pregnenolone • Rely on theca lutein cells for androgens • BUT progesterone synth from pregnenolone • Insensitive to LH signal to produce androgens • BUT small numbers LH receptors expressed in advanced follicle • LH  secr’n progesterone, secr’n inhibin A

  35. Granulosa lutein cells express aromatase • Androgens  estrogens • Activated with LH • If pregnancy, interrelationships balanced also with placental cells

  36. Endometrial (Uterine) Cycle • Coupled to ovarian cycle • Gametogenesis • Hormonogenesis • Three phases

  37. Menstruation – during follicular phase • With demise of CL • Plasma progesterone decr’d • Uterine endometrium shed • Leaves basal portion of endometrial glands • 2-7 d (4 d avg) • 30 mL blood loss avg

  38. Proliferative – during follicular phase • E2 dependent regeneration, growth of endometrium • E2 receptor binding @ remaining basal stratum  stromal, epithelial cell growth • Secretory – during luteal phase • Progesterone-dependent maturation of endometrium • Requires E2 prep’n endometrium • Now suitable for blastocyst implantation

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