Animal Science 434 Reproductive Physiology - PowerPoint PPT Presentation

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Animal Science 434 Reproductive Physiology

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Testes develop. Rete Tubules. Undifferentiated. Sex Chords. Mullerian ... Testes develop. Sertoli cells secrete. anti-mullerian hormone (AMH) AMH causes leydig ... – 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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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 Mesenephros and Metenephros
12
Jost Experiments
13
Sex Determination The Jost Paradigm
14
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

15
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.

16
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 or assists other
    transcription factors
  • the gene products which are transcribed regulate
    primary sex chord differentiation (formation of
    seminiferous tubules), androgen production and
    Anti-Mullerian Hormone (AMH) production
  • in the absence of the SRY protein, primary sex
    chord regress and secondary sex chords (egg
    nests) develop

17
The Y Chromosome Cont.
  • B. Other genes on the Y chromosome
  • Spermatogenesis
  • androgen production
  • long bone growth

18
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

19
Gonadal Sex
20
Testis Determining Factor (SRY gene product)
XY Male
21
Testicular Development
Mesonephric Tubules
Mesonephric Duct (Wolffian Duct)
Rete Tubules
Mullerian Duct
Tunica Albuginea
Undifferentiated Sex Chords
22
Mesonephric Tubules
Rete Tubules
Wolffian Duct
  • Primary, Epithelial or
  • Medullary Sex Chords
  • Primordial germ cells
  • Sertoli Cells

Mullerian Duct
Tunica Albuginea
23
Hormonal Sex
24
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
25
Wolffian Duct Cells
Nucleus
T
Testis
T
TR
26
Rete Tubules
Efferent Ducts (Vas Efferentia)
Epididymis
Seminiferous Tubules
Ductus Deferens
Tunica Albuginea
27
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
28
Vas efferentia
29
Female Development
No TDF
Testes Determining Factor
XX Female
30
Ovarian Development
Regressing Tubules
Mullerian Duct
Epithelial Sex Chords
Future Ovarian Cortex
Wolffian Duct
31
Regressing Tubules
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
32
Regressing Tubules
Primordial Follicles
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
Secondary or Cortical Sex Chords (egg nests)
33
Primordial Follicles
Mullerian Duct
Ovarian Medulla
Ovarian Cortex
Regressing Wolffian Duct
34
Development of the Uterus, Cervix and Vagina
Mullerian Duct
35
Fused Mullerian Duct
Hymen
36
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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
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
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 Mullerian Duct
Testosterone
Development of male duct system
43
Wolffian Duct Cells
Nucleus
T
Testis
T
TR
44
Accessory Sex Glands and External Genitalia Cells
Nucleus
T
Testis
D
T
DR
5??- Reductase
Prostate, Cowpers Gland
45
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

46
External Genitalia Differentiation
47
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48
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49
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
50
Brain or Behavioral Sex
51
Brain and Behavioral Sex Differentiation
Genetics
Gonadal Steroid Hormones
Sexual Behavior
Brain Structure
Experience
52
Brain Sexual Differentiation
  • Rat female
  • Give testosterone shortly after birth
  • fail to copulate or cycle like female as adult
  • Sexually dimorphic nucleus
  • Human male and female differences in behaviors
  • aggression
  • childhood play
  • 3D visual rotation

53
Decent of the Testis into the Scrotum
54
Testicular Descent
Growth of testis
Fusion of the tunica albuginea and peritoneum to
form the visceral tunica vaginalis
55
Front View
56
Rapid growth of gubernaculum
Testis is pulled down to the inguinal ring.
57
Gubernaculum regresses
Testis pulled into scrotum
58
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
59
Failure or Problems With Testicular Descent
  • Cryptorchid
  • unilateral
  • bilateral
  • Inguinal Hernia

60
Inguinal Hernia
Loop of Intestine
61
Abnormalities in Development
62
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
  • testosterone
  • anti-mullerian hormone
  • Animals are chimeric
  • both express TDF

63
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

64
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

65
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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