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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 the Metenephros and Regression of the Mesonephros (Wolffian - Male) (Mullerian - female)

  8. The Sexually Indifferent Stage (Wolffian - Male) (Mullerian - female)

  9. Chromosomal Sex Gonadal Sex Hormonal Sex Phenotypic Sex Brain and/or Behavioral Sex Chromosomal Sex Gonadal Sex Phenotypic 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 developement • 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 Mullerian duct inhibiting substance (MIS) 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. Problems With SRY as the Male Determining Gene • Transgenic mice studies • SRY a testis and male tract • No Spermatogenesis! • Birds • females ZW, males ZZ • W chromosome determines sex • SRY is found on the Z chromosome !

  15. Gonadal Sex

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

  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. Testis Determining Factor (SRY gene product) XY Male Testes develop Sertoli cells secrete anti-mullerian hormone (AMH)

  21. Testis Determining Factor (SRY gene product) XY Male Testes develop Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate

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

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

  24. Wolffian Duct Cells Nucleus T Testis T TR

  25. 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

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

  27. Vas efferentia

  28. Female Development No TDF XX Female Ovaries Develop

  29. Female Development No TDF XX Female Ovaries Develop No Antimullerian Hormone

  30. Female Development No TDF XX Female Ovaries Develop No AMH Mullerian ducts become the oviducts, uterus, cervix and part of the vagina

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

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

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

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

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

  36. Fused Mullerian Duct Hymen

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

  38. Ovary Regressing Wolffian Duct Mullerian Duct

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

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

  41. Phenotypic Sex

  42. 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 paramesonephric duct Dihydrotestosterone Testosterone Development of penis scrotum and accessory sex glands Development of male duct system

  43. Wolffian Duct Cells Nucleus T Testis T TR

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