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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. Germ Cell Migration. Migration begins by the 4 week of gestation in cow and human. Migration from endoderm through mesoderm.

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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

  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

  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 • Sex is environmentally determined • sea worms, fish • Single Pair of sex chromosomes • mammals, some but not all vertebrates • 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 or XXXXY  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 primary gene that controls testicular differentiation is on the Y chromosome in mammals.

  12. 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 or assists other transcription factors • the gene products which are transcribed regulate primary sex chord differentiation (formation of seminiferous tubules), androgen production and Anti-Mullerian Hormone (AMH) production • in the absence of the SRY protein, primary sex chord regress and secondary sex chords (egg nests) develop

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

  14. 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

  15. Gonadal Sex

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

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

  18. Mesonephric Tubules Rete Tubules Wolffian Duct • Primary, Epithelial or • Medullary Sex Chords • Primordial germ cells • Sertoli Cells Mullerian Duct Tunica Albuginea

  19. Hormonal Sex

  20. 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

  21. Wolffian Duct Cells Nucleus T Testis T TR

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

  23. 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

  24. Vas efferentia

  25. 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

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

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

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

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

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

  31. Fused Mullerian Duct Hymen

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

  33. Ovary Regressing Wolffian Duct Mullerian Duct

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

  35. 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

  36. Phenotypic Sex

  37. 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

  38. Wolffian Duct Cells Nucleus T Testis T TR

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

  40. 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

  41. External Genitalia Differentiation

  42. 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

  43. Brain or Behavioral Sex

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