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Animal Science 434 Reproductive Physiology

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Title: Animal Science 434 Reproductive Physiology Author: John Parrish Last modified by: John Parrish Created Date: 2/5/1998 8:36:34 AM Document presentation format – 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
Infundibulum
Brain
Rathkes Pouch
Stomodeum
3
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4
Germ Cell Migration
Migration begins by the 4 week of gestation in
cow and human.
5
Migration from endoderm through mesoderm.
6
In birds the migration is via the blood stream.
7
Fetal Kidneys
  • Pronephros
  • regresses
  • Mesonephros
  • portions of reproductive tract
  • Metenephros
  • Adult kindney and urinary ducts

8
Development of Mesenephros and Metenephros
9
Jost Experiments
Mesonephric Ducts (Wolffian Ducts)
Paramesonephric Ducts (Mullerian Ducts)
Testis
Ovary
Epididymis
Epididymis
Oviduct
Vas Deferens
Seminal Vesicles
Uterus
10
Sex Determination The Jost Paradigm
11
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

12
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.

13
Human X and Y Chromosomes
14
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
  • Anti-Mullerian Hormone production
  • Testosterone production
  • absence of SRY
  • 2nd sex chords (egg nests) develop

15
The Y Chromosome Cont.
  • B. Other genes on the Y chromosome
  • Spermatogenesis
  • androgen production
  • long bone growth

16
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

17
Gonadal Sex
18
Testis Determining Factor (SRY gene product)
XY Male
19
Testicular Development
Mesonephric Tubules
Mesonephric Duct (Wolffian Duct)
Rete Tubules
Mullerian Duct
Tunica Albuginea
Undifferentiated Sex Chords
20
Mesonephric Tubules
Rete Tubules
Wolffian Duct
  • Primary, Epithelial or
  • Medullary Sex Chords
  • Primordial germ cells (gonocytes)
  • Pre-Sertoli Cells

Mullerian Duct
Tunica Albuginea
21
Primary Sex Chords in Fetal Testis
Pre-Sertoli
Gonocyte
22
Hormonal Sex
23
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
24
Wolffian Duct Cells
Nucleus
T
Testis
T
TR
25
Rete Tubules
Efferent Ducts (Vas Efferentia)
Epididymis
Seminiferous Tubules
Vas Deferens
Tunica Albuginea
26
Testis Determining Factor (SRY gene product)
XY Male
Testes develop
27
Vas efferentia
28
Female Development
No TDF
Testes Determining Factor
XX Female
29
Ovarian Development
Regressing Tubules
Mullerian Duct
Primary or Epithelial Sex Chords
Future Ovarian Cortex
Wolffian Duct
30
Regressing Tubules
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
31
Regressing Tubules
Primordial Follicles
Mullerian Duct
Regressing Epithelial Sex Chords
Future Ovarian Cortex
Regressing Wolffian Duct
Secondary or Cortical Sex Chords (egg nests)
32
Primordial Follicles
Mullerian Duct
Ovarian Medulla
Ovarian Cortex
Regressing Wolffian Duct
33
2nd Sex Chords in Fetal Ovary
34
Development of the Uterus, Cervix and Vagina
Mullerian Duct
35
Fused Mullerian Duct
Hymen
36
(No Transcript)
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
(No Transcript)
48
(No Transcript)
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
Descent of the Testis into the Scrotum
54
Testicular Descent
Fusion of the tunica albuginea and peritoneum to
form the visceral tunica vaginalis
55
Spermatic Artery
Front View
Fusion of Peritoneum and Gubernaculum
Testis
Gubernaculum
Peritoneum
Inguinal Ring
56
Rapid growth of gubernaculum
Spermatic Artery
Peritoneum
Visceral Growth
Visceral Growth
Inguinal Ring
Testis
Peritoneum
Gubernaculum (rapid growth)
Parietal Tunica Vaginalis
Testis is pulled down to the inguinal ring.
Visceral Tunica Vaginalis
57
Gubernaculum regresses
Testis pulled into scrotum
58
Continued regression of Gubernaculum
Testis pulled deeper into Scrotum
Vaginal Process attaches to Scrotum
Space between Visceral and Parietal T.V. is
continuous with Peritoneum
59
Failure or Problems With Testicular Descent
  • Cryptorchid - highly heritable
  • Unilateral or bilateral
  • Germ cells fail to multiply and then die, sertoli
    cells only in seminferous tubules
  • High percentage develop testicular cancer
  • Surgical correction possible but does not reduce
    cancer risk

60
Normal Dog Seminiferous Tubule
61
Cryptorchid Dog Seminiferous Tubule
Sertoli Cells
62
Failure or Problems With Testicular Descent
  • Cryptorchid - highly heritable
  • Unilateral or bilateral
  • Germ cells fail to multiply and then die, sertoli
    cells only in seminferous tubules
  • High percentage develop testicular cancer
  • Surgical correction possible but does not reduce
    cancer risk
  • Inguinal Hernia

63
Inguinal Hernia
Loop of Intestine
64
Abnormalities in Development
65
The Freemartin in Cattle
  • Female born twin to a bull
  • Placenta membranes of the 2 fetuses fuse
  • Common blood supply
  • At time of testis formation
  • Before ovarian formation
  • Both fetuses share a common hormone milieu
  • testosterone
  • anti-mullerian hormone
  • Animals are chimeric (WBC from other twin)
  • TDF (SRY) expressed in both individuals

66
Normal
67
Freemartin
68
Normal Vs. Freemartin
69
Freemartin
  • AMH from bull - blocks Mullerian ducts
  • Posterior vagina, no anterior vagina
  • Testosterone from bull
  • clitoral enlargment
  • Brain changes like that of male
  • Ovaries do not grow but are chimeric
  • Ovotestis
  • SRY and therefore AMH and Testosterone
  • Further changes and adult male behavior
  • Use as estrus detector
  • Abnormalities exist as a continuum

70
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

71
Testicular Feminization
72
5? Reductase Deficiency in an XY Individual
  • Guevedoces (penis at 12)
  • testis
  • AMH present so Mullerian ducts regress
  • Wolffian ducts
  • psuedovagina and female external genitalia
  • at puberty may differentiate into more of a
    phenotypic male

73
Guevedoces Development
Normal tissue dependent upon testosterone is
shown in black.
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