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Animal Science 434 Reproductive Physiology

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Animal Science 434 Reproductive Physiology Lec 5: Embryogenesis of the Pituitary and Sexual Development – PowerPoint PPT presentation

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Title: Animal Science 434 Reproductive Physiology


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

2
Development of the Pituitary Gland
3
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5
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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
  • regresses
  • Mesonephros
  • portions of reproductive tract
  • Metenephros
  • Adult kindney and urinary ducts

11
Development of the Metenephros and Regression of
the Mesonephros
(Wolffian - Male)
(Mullerian - female)
12
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14
The Sexually Indifferent Stage
(Wolffian - Male)
(Mullerian - female)
15
Sex Determination The Jost Paradigm
16
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

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
  • 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.

18
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

19
The Y Chromosome Cont.
  • B. Other genes on the Y chromosome
  • Spermatogenesis
  • androgen production
  • long bone growth

20
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 !

21
Gonadal Sex
22
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
23
Testicular Development
Mesonephric Tubules
Mesonephric Duct (Wolffian Duct)
Rete Tubules
Mullerian Duct
Tunica Albuginea
Undifferentiated Sex Chords
24
Mesonephric Tubules
Rete Tubules
Wolffian Duct
  • Primary, Epithelial or
  • Medullary Sex Chords
  • Primordial germ cells
  • Sertoli Cells

Mullerian Duct
Tunica Albuginea
25
Hormonal Sex
26
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
Sertoli cells secrete anti-mullerian hormone (AMH)
27
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
Sertoli cells secrete anti-mullerian hormone (AMH)
AMH causes leydig cells to differentiate
28
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
Sertoli cells secrete anti-mullerian hormone (AMH)
AMH causes leydig cells to differentiate
Testosterone
29
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
30
Wolffian Duct Cells
Nucleus
T
Testis
T
TR
31
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
32
Rete Tubules
Efferent Ducts (Vas Efferentia)
Epididymis
Seminiferous Tubules
Ductus Deferens
Tunica Albuginea
33
Vas efferentia
34
Female Development
No TDF
XX Female
Ovaries Develop
35
Female Development
No TDF
XX Female
Ovaries Develop
No Antimullerian Hormone
36
Female Development
No TDF
XX Female
Ovaries Develop
No AMH
Mullerian ducts become the oviducts, uterus,
cervix and part of the vagina
37
Ovarian Development
Regressing Tubules
Mullerian Duct
Epithelial Sex Chords
Future Ovarian Cortex
Wolffian Duct
38
Regressing Tubules
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
39
Regressing Tubules
Primordial Follicles
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
Secondary or Cortical Sex Chords (egg nests)
40
Primordial Follicles
Mullerian Duct
Ovarian Medulla
Ovarian Cortex
Regressing Wolffian Duct
41
Development of the Uterus, Cervix and Vagina
Mullerian Duct
42
Fused Mullerian Duct
Hymen
43
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44
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)
Genital Fold (Future Broad Ligament)
Regressing Wolffian Duct
Mullerian Duct
47
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
48
Phenotypic Sex
49
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
50
Wolffian Duct Cells
Nucleus
T
Testis
T
TR
51
Accessory Sex Glands and External Genitalia Cells
Nucleus
T
Testis
D
T
DR
5??- Reductase
Prostate, Cowpers Gland
52
Significance of DHT
  • Androgen receptor has a higher affinity for DHT
  • Can get effects with low levels of circulating
    testosterone

53
External Genitalia Differentiation
54
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56
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 paramesonephric duct
Parameonephric ducts become the oviducts, uterus,
cervix and part of the vagina
Dihydrotestosterone
Testosterone
Complete Female Tract
Development of penis scrotum and accessory sex
glands
Development of male duct system
57
Brain or Behavioral Sex
58
Brain and Behavioral Sex Differentiation
Genetics
Gonadal Steroid Hormones
Sexual Behavior
Brain Structure
Experience
59
Brain Sexual Differentiation
  • Rat female
  • Give testosterone shortly after birth and fail to
    copulate or cycle like female
  • Sexually dimorphic nucleus
  • Human male and female differences in behaviors
  • aggression
  • childhood play
  • 3D visual rotation

60
Decent of the Testis into the Scrotum
61
Testicular Descent
Growth of testis
Fusion of the tunica albuginea and peritoneum to
form the visceral tunica vaginalis
62
Front View
63
Rapid growth of gubernaculum
Testis is pulled down to the inguinal ring.
64
Gubernaculum regresses
Testis pulled into scrotum
65
Continued regression of Gubernaculum
Testis pulled deeper into Sscrotum
Vaginal Process attaches to Scrotum
Space between Visceral and Parietal T.V. is
continuous with Peritoneum
66
Failure or Problems With Testicular Descent
  • Cryptorchid
  • unilateral
  • bilateral
  • Inguinal Hernia

67
Abnormalities in Development
68
5 ? Reductase Deficiency in an XY Individual
  • testis
  • AMH present so Mullerian ducts regress
  • some Wolffian ducts
  • psuedovagina and female external genitalia
  • at puberty may differentiate into phenotypic male

69
Testicular Feminization in an XY Individual
  • No androgen receptor
  • Testis
  • No testosterone response so no Wolffian duct
    development
  • AMH present so mullerian ducts regress
  • External genitalia is female due to lack of
    androgen

70
The Freemartin in Cattle
  • Female born twin to a bull
  • Extra embryonic membranes fuse to form a common
    chorion
  • Comon blood supply
  • Both fetuses share a common hormone milieu
  • testoterone
  • anti-mullerian hormone
  • Animals are chimeric
  • both express TDF

71
Describe the development of the reproductive
tract and/or gonad in an undifferentiated
  • embryo that is castrated.
  • female embryo (XX) that has a testis transplated
    next to the right gonad.
  • female embryo (XX) that has a testosterone
    implant placed next to each gonad.
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