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Animal Science 434 Reproductive Physiology

Animal Science 434 Reproductive Physiology. Lec 5: Embryogenesis of the Pituitary and Sexual Development. Development of the Pituitary Gland. Infundibulum. Brain. Rathke’s Pouch. Stomodeum. Germ Cell Migration. Migration begins by the 4 week of gestation in cow and human.

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Animal Science 434 Reproductive Physiology

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  1. Animal Science 434Reproductive Physiology Lec 5: Embryogenesis of the Pituitary and Sexual Development

  2. Development of the Pituitary Gland Infundibulum Brain Rathke’s Pouch Stomodeum

  3. Germ Cell Migration Migration begins by the 4 week of gestation in cow and human.

  4. Migration from endoderm through mesoderm.

  5. In birds the migration is via the blood stream.

  6. Fetal Kidneys • Pronephros • regresses • Mesonephros • portions of reproductive tract • Metenephros • Adult kindney and urinary ducts

  7. Development of Mesenephros and Metenephros

  8. Jost Experiments Mesonephric Ducts (Wolffian Ducts) Paramesonephric Ducts (Mullerian Ducts) Testis Ovary Epididymis Epididymis Oviduct Vas Deferens Seminal Vesicles Uterus

  9. Chromosomal Sex Gonadal Sex Phenotypic Sex Chromosomal Sex Gonadal Sex Phenotypic Sex Hormonal Sex Brain and/or Behavioral Sex Sex Determination: The Jost Paradigm

  10. Chromosomal Sex • Single Pair of sex chromosomes • mammals, some but not all vertebrates • Sex is environmentally determined • sea worms, fish, reptiles • Multiple sex chromosomes • invertebrates, insects, reptiles • Haplodiploidy • bees, spiders

  11. Chromosomal Sex • A. Drosophila • Sex depends on the number of X chromosomes • X or XY or XO = Male • XX or XXX or XXY = Female • B. Human (mammals) • XY or XXY or XXYY or XXXY = Male (testis) • XX or XXX = Female (ovary) • XO = Female with incomplete ovarian development • XXY or XXYY or XXXY or XXXXY = testis but impaired sperm production • C. Conclusion • The gene that controls testicular differentiation is on the Y chromosome in mammals.

  12. Human X and Y Chromosomes

  13. The Y Chromosome A. Region coding for testicular development • Short arm of Y chromosome • H-Y Antigen • no longer believed to be involved • SRY • Codes for a DNA binding protein • acts as a transcription factor • Causes • primary sex chord (seminiferous tubule) development • Anti-Mullerian Hormone production • Testosterone production • absence of SRY • 2nd sex chords (egg nests) develop

  14. The Y Chromosome Cont. B. Other genes on the Y chromosome • Spermatogenesis • androgen production • long bone growth

  15. SRY and Birds • Birds • females ZW, males ZZ • W chromosome determines sex • SRY is found on the Z chromosome ! • SRY is not the only sex determining gene in animals

  16. Gonadal Sex

  17. Testes develop Testis Determining Factor (SRY gene product) XY Male

  18. Testicular Development Mesonephric Tubules Mesonephric Duct (Wolffian Duct) Rete Tubules Mullerian Duct Tunica Albuginea Undifferentiated Sex Chords

  19. Mesonephric Tubules Rete Tubules Wolffian Duct • Primary, Epithelial or • Medullary Sex Chords • Primordial germ cells (gonocytes) • Pre-Sertoli Cells Mullerian Duct Tunica Albuginea

  20. Primary Sex Chords in Fetal Testis Pre-Sertoli Gonocyte

  21. Hormonal Sex

  22. Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate Testosterone Development of male duct system Testis Determining Factor (SRY gene product) XY Male Testes develop

  23. Wolffian Duct Cells Nucleus T Testis T TR

  24. Rete Tubules Efferent Ducts (Vas Efferentia) Epididymis Seminiferous Tubules Vas Deferens Tunica Albuginea

  25. Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate Degeneration of Mullerian duct Testosterone Development of male duct system Testis Determining Factor (SRY gene product) XY Male Testes develop

  26. Vas efferentia

  27. Ovaries Develop Wolffian Ducts Regress No AMH No Testosterone Mullerian ducts become the oviducts, uterus, cervix and part of the vagina Female Development No TDF Testes Determining Factor XX Female

  28. Ovarian Development Regressing Tubules Mullerian Duct Primary or Epithelial Sex Chords Future Ovarian Cortex Wolffian Duct

  29. Regressing Tubules Mullerian Duct Regressing Epithelial Sex Chords Future Ovarian Cortex Regressing Wolffian Duct

  30. Regressing Tubules Primordial Follicles Mullerian Duct Regressing Epithelial Sex Chords Future Ovarian Cortex Regressing Wolffian Duct Secondary or Cortical Sex Chords (egg nests)

  31. Primordial Follicles Mullerian Duct Ovarian Medulla Ovarian Cortex Regressing Wolffian Duct

  32. 2nd Sex Chords in Fetal Ovary

  33. Development of the Uterus, Cervix and Vagina Mullerian Duct

  34. Fused Mullerian Duct Hymen

  35. Reproductive tract develops outside the peritoneum! Broad Ligament Development (transverse anterior section) Ovary Regressing Wolffian Duct Mullerian Duct

  36. Ovary Regressing Wolffian Duct Mullerian Duct

  37. (Posterior Transverse Section) Genital Fold (Future Broad Ligament) Regressing Wolffian Duct Mullerian Duct

  38. Testis Determining Factor (SRY gene product) No TDF XX Female XY Male Testes develop Ovaries Develop No Testosterone No AMH Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate Degeneration of Mullerian duct Degeneration of Wolffian duct Mullerian ducts become the oviducts, uterus, cervix and part of the vagina Testosterone Development of male duct system

  39. Phenotypic Sex

  40. Dihydrotestosterone Development of penis scrotum and accessory sex glands Testis Determining Factor (SRY gene product) XY Male Testes develop Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate Degeneration of Mullerian Duct Testosterone Development of male duct system

  41. Wolffian Duct Cells Nucleus T Testis T TR

  42. Accessory Sex Glands* and External Genitalia Cells Nucleus T Testis D T DR 5- Reductase *Prostate, Cowper’s Gland

  43. Significance of DHT • Androgen receptor has a higher affinity for DHT • Can get effects with low levels of circulating testosterone • Secondary sex characteristic tissue in the male expresses 5a-reductase

  44. External Genitalia Differentiation

  45. Dihydrotestosterone Development of penis scrotum and accessory sex glands Testis Determining Factor (SRY gene product) No TDF XX Female XY Male Testes develop Ovaries Develop No Testosterone No AMH Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate Degeneration of Mullerian duct Degeneration of Wolffian duct Mullerian ducts become the oviducts, uterus, cervix and part of the vagina Testosterone Development of male duct system

  46. Brain or Behavioral Sex

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