Animal Science 434 Reproductive Physiology

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Animal Science 434Reproductive Physiology

• Lec 5 Embryogenesis of the Pituitary and Sexual
  Development

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Development of the Pituitary Gland
Infundibulum
Brain
Rathkes Pouch
Stomodeum
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Germ Cell Migration
Migration begins by the 4 week of gestation in
cow and human.
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Migration from endoderm through mesoderm.
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In birds the migration is via the blood stream.
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Fetal Kidneys

• Pronephros
• regresses
• Mesonephros
• portions of reproductive tract
• Metenephros
• Adult kindney and urinary ducts

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Development of Mesenephros and Metenephros
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Development of Mesenephros and Metenephros
Early Development Flash Movie
http//www.ansci.wisc.edu/jjp1/as434/powerpoint/fa
07/early_dev.swf
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downloaded from www.adobe.com
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Jost Experiments
Mesonephric Ducts (Wolffian Ducts)
Paramesonephric Ducts (Mullerian Ducts)
Testis
Ovary
Epididymis
Epididymis
Oviduct
Vas Deferens
Seminal Vesicles
Uterus
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Sex Determination The Jost Paradigm
Chromosomal Sex Gonadal Sex Phenotypic Sex
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Sex Determination The Jost Paradigm
Chromosomal Sex Gonadal Sex Phenotypic Sex
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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

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Chromosomal Sex

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

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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

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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.

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Human X and Y Chromosomes
X
Y
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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

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The Y Chromosome Cont.

• B. Other genes on the Y chromosome
• Spermatogenesis
• androgen production
• long bone growth

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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

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Gonadal Sex
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Testis Determining Factor (SRY gene product)
XY Male
Testes develop
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Testicular Development
Mesonephric Tubules
Mesonephric Duct (Wolffian Duct)
Rete Tubules
Mullerian Duct
Tunica Albuginea
Undifferentiated Sex Chords
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Mesonephric Tubules
Rete Tubules
Wolffian Duct

• Primary, Epithelial or
• Medullary Sex Chords
• Primordial germ cells (gonocytes)
• Pre-Sertoli Cells

Mullerian Duct
Tunica Albuginea
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Primary Sex Chords in Fetal Testis
Pre-Sertoli
Gonocyte
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Hormonal Sex
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Testis Determining Factor (SRY gene product)
XY Male
Testes develop
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Wolffian Duct Cells
Nucleus
T
Testis
T
TR
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Rete Tubules
Efferent Ducts (Vas Efferentia)
Epididymis
Seminiferous Tubules
Vas Deferens
Tunica Albuginea
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Testis Determining Factor (SRY gene product)
XY Male
Testes develop
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Vas efferentia
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Female Development
No TDF
Testes Determining Factor
XX Female
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Ovarian Development
Regressing Tubules
Mullerian Duct
Primary or Epithelial Sex Chords
Future Ovarian Cortex
Wolffian Duct
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Regressing Tubules
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
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Regressing Tubules
Primordial Follicles
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
Secondary or Cortical Sex Chords (egg nests)
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Primordial Follicles
Mullerian Duct
Ovarian Medulla
Ovarian Cortex
Regressing Wolffian Duct
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2nd Sex Chords in Fetal Ovary
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Development of the Uterus, Cervix and Vagina
Mullerian Duct
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Fused Mullerian Duct
Hymen
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Reproductive tract develops outside
the peritoneum!
Broad Ligament Development (transverse anterior
section)
Ovary
Regressing Wolffian Duct
Mullerian Duct
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Ovary
Regressing Wolffian Duct
Mullerian Duct
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(Posterior Transverse Section)
Genital Fold (Future Broad Ligament)
Regressing Wolffian Duct
Mullerian Duct
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Testis Determining Factor (SRY gene product)
No TDF
XX Female
XY Male
Testes develop
Ovaries Develop
No AMH
No Testosterone
Sertoli cells secrete anti-mullerian hormone (AMH)
AMH causes leydig cells to differentiate
Degeneration of Mullerian duct
Mullerian ducts become the oviducts, uterus,
cervix and part of the vagina
Degeneration of Wolffian duct
Testosterone
Development of male duct system
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Phenotypic Sex
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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
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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
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Wolffian Duct Cells
Nucleus
T
Testis
T
TR
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Accessory Sex Glands and External Genitalia Cells
Nucleus
T
Testis
D
T
DR
5??- Reductase
Prostate, Cowpers Gland
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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

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