Animal Science 434
Reproductive Physiology
Development of the Pituitary Gland
Infundibulum
Brain
Lec 5: Embryogenesis of the Pituitary and
Sexual Development
Stomodeum
Rathke’s Pouch
Germ Cell Migration
Migration from endoderm
through mesoderm.
Migration begins by the 4 week of gestation in cow and human.
Fetal Kidneys
• Pronephros
» regresses
• Mesonephros
» portions
of reproductive tract
• Metenephros
» Adult
kindney and urinary ducts
In birds the migration is via the blood stream.
Development of Mesenephros and Metenephros
Development of Mesenephros and Metenephros
Early Development Flash Movie
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Sex Determination: The Jost Paradigm
Jost Experiments
Mesonephric Ducts
Chromosomal Sex
(Wolffian Ducts)
Paramesonephric Ducts
(Mullerian Ducts)
Gonadal Sex
Testis
Ovary
Epididymis
Oviduct
Phenotypic Sex
Epidi
Vas
Deferens
dymi
Seminal
s
Vesicles
Uterus
Sex Determination: The Jost Paradigm
Chromosomal Sex
Chromosomal Sex
Chromosomal Sex
•
Single Pair of sex chromosomes
•
Sex is environmentally determined
•
Multiple sex chromosomes
•
Haplodiploidy
Gonadal Sex
Gonadal Sex
Hormonal Sex
Phenotypic Sex
Phenotypic Sex
Brain and/or Behavioral Sex
»
mammals, some but not all vertebrates
»
sea worms, fish, reptiles
»
invertebrates, insects, reptiles
»
bees, spiders
Chromosomal Sex
A. Drosophila
• Sex depends on the number of X chromosomes
– X or XY or XO = Male
– XX or XXX or XXY = Female
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
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 X and Y Chromosomes
X
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
Y
C. Conclusion
• The gene that controls testicular differentiation is
on the Y chromosome in mammals.
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
The Y Chromosome Cont.
B. Other genes on the Y chromosome
»
»
»
Spermatogenesis
androgen production
long bone growth
• 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
SRY and Birds
Gonadal Sex
• 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
XY Male
Testicular Development
Testis Determining Factor
(SRY gene product)
Mesonephric Tubules
Mesonephric Duct
(Wolffian Duct)
Testes develop
Rete Tubules
Mullerian Duct
Tunica
Albuginea
Mesonephric
Tubules
Undifferentiated
Sex Chords
Primary Sex Chords in Fetal Testis
Rete Tubules
Pre-Sertoli
Wolffian
Duct
Mullerian Duct
Primary, Epithelial or
Medullary Sex Chords
Tunica
• Primordial germ cells
Albuginea (gonocytes)
Gonocyte
• Pre-Sertoli Cells
Hormonal Sex
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
Wolffian Duct Cells
Efferent Ducts
Rete Tubules
(Vas Efferentia)
Nucleus
Epididymis
T
Testis
TR
T
Vas
Deferens
XY Male
Tunica
Albuginea
Seminiferous
Tubules
Testis Determining Factor
(SRY gene product)
Vas efferentia
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
Female Development
XX Female
No TDF
Testes Determining Factor
Wolffian Ducts
Regress
Regressing
Tubules
Mullerian
Duct
Ovaries Develop
No
Testosterone
Ovarian
Development
Primary or
Epithelial
Sex Chords
No AMH
Mullerian ducts become
the oviducts, uterus, cervix
and part of the vagina
Future Ovarian
Cortex
Wolffian
Duct
Regressing
Tubules
Regressing
Tubules
Mullerian
Duct
Regressing
Epithelial
Sex Chords
Regressing
Epithelial
Sex Chords
Future Ovarian
Cortex
Future Ovarian
Cortex
Regressing
Wolffian
Duct
Primordial
Follicles
Primordial
Follicles
Mullerian
Duct
Regressing
Wolffian
Duct
2nd Sex Chords in Fetal Ovary
Mullerian
Duct
Ovarian
Medulla
Regressing
Wolffian
Duct
Secondary or
Cortical Sex
Chords
(egg nests)
Ovarian
Cortex
Development
of the Uterus, Cervix
and Vagina
Fused Mullerian
Duct
Mullerian Duct
Hymen
Reproductive tract develops outside the
peritoneum!
Broad Ligament Development
(transverse anterior section)
Ovary
Regressing
Wolffian Duct
Mullerian
Duct
(Posterior Transverse Section)
Ovary
Genital Fold
(Future Broad Ligament)
Regressing
Wolffian
Duct
Mullerian
Duct
Regressing
Wolffian
Duct
Mullerian
Duct
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
Degeneration of
Mullerian duct
No TDF
Phenotypic Sex
XX Female
Ovaries Develop
No
Testosterone
Degeneration of
Wolffian duct
No AMH
Mullerian ducts
become
the oviducts,
uterus, cervix
and part of the
vagina
XY Male
XY Male
Testis Determining Factor
(SRY gene product)
Testis Determining Factor
(SRY gene product)
Testes develop
Testes develop
Sertoli cells secrete
anti-mullerian hormone (AMH)
Sertoli cells secrete
anti-mullerian hormone (AMH)
AMH causes leydig
cells to differentiate
Degeneration of
Mullerian Duct
AMH causes leydig
cells to differentiate
Degeneration of
Mullerian Duct
Testosterone
Testosterone
Dihydrotestosterone
Development of male
duct system
Development of male
duct system
Development of penis
scrotum and accessory
sex glands
Wolffian Duct Cells
Accessory Sex Glands* and External
Genitalia Cells
Nucleus
Testis
T
T
TR
Nucleus
Testis
T
D
5α Reductase
T
DR
*Prostate, Cowper’s Gland
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 5α-reductase
External Genitalia Differentiation
Testis Determining Factor
(SRY gene product)
XY Male
No TDF
XX Female
Testes develop
Ovaries Develop
No
Testosterone
Sertoli cells secrete
anti-mullerian hormone (AMH)
AMH causes leydig
cells to differentiate
Degeneration of
Mullerian duct
Degeneration of
Wolffian duct
Testosterone
Dihydrotestosterone
Development of male
duct system
Development of penis
scrotum and accessory
sex glands
No AMH
Mullerian ducts
become
the oviducts,
uterus, cervix
and part of the
vagina