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

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

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

8. Migration from endoderm
through mesoderm.

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

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

11. Development of Mesenephros and Metenephros

12. Development of Mesenephros and Metenephros
Early Development Flash Movie
Early Development Flash Movie
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13. Paramesonephric Ducts
Jost Experiments
Mesonephric Ducts
(Wolffian Ducts)
Paramesonephric Ducts
(Mullerian Ducts)
Testis
Ovary
Epididymis
Oviduct
Epididymis
Vas Deferens
Seminal Vesicles
Uterus

14. Sex Determination: The Jost Paradigm
Chromosomal Sex
Gonadal Sex
Phenotypic Sex

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

16. 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

17. Chromosomal Sex A. Drosophila
Sex depends on the number of X chromosomes
X or XY or XO = Male
XX or XXX or XXY = Female

18. 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

19. 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.

20. Human X and Y Chromosomes

21. 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
Development of Sertoli Cells
Anti-Mullerian Hormone production by Sertoli Cells
absence of SRY
2nd sex chords (egg nests) develop

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

23. 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

24. Gonadal Sex

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

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

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

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

29. Hormonal Sex

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

31. Wolffian Duct Cells
Nucleus T
Testis T TR

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

33. Testis Determining Factor
XY Male
Testis Determining Factor
(SRY gene product)
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

34. Vas efferentia

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

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

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

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

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

40. 2nd Sex Chords in Fetal Ovary

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

42. Fused Mullerian
Duct
Hymen

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

45. Ovary
Regressing
Wolffian
Duct
Mullerian
Duct

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

47. XX Female XY Male No TDF Ovaries Develop No No AMH Testosterone
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

48. Phenotypic Sex

49. XY Male Testis Determining Factor (SRY gene product) 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

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

51. Wolffian Duct Cells
Nucleus T
Testis T TR

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

53. 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

54. External Genitalia Differentiation

57. XX Female XY Male No TDF Ovaries Develop No No AMH Testosterone
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
Dihydrotestosterone
Development of penis
scrotum and accessory
sex glands
Development of male
duct system