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Animal Science 434 Reproductive Physiology. Lec 5: Embryogenesis of the Pituitary and Sexual Development. Development of the Pituitary Gland. Germ Cell Migration. Migration begins by the 4 week of gestation in cow and human. Migration from endoderm through mesoderm.

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animal science 434 reproductive physiology

Animal Science 434Reproductive Physiology

Lec 5: Embryogenesis of the Pituitary and Sexual Development

slide7

Germ Cell Migration

Migration begins by the 4 week of gestation in cow and human.

slide8

Migration from endoderm

through mesoderm.

fetal kidneys
Fetal Kidneys
  • Pronephros
    • regresses
  • Mesonephros
    • portions of reproductive tract
  • Metenephros
    • Adult kindney and urinary ducts
slide11

Development of the Metenephros and

Regression of the Mesonephros

(Wolffian - Male)

(Mullerian - female)

slide14

The Sexually Indifferent Stage

(Wolffian - Male)

(Mullerian - female)

slide15

Chromosomal Sex

Gonadal Sex

Phenotypic Sex

Chromosomal Sex

Gonadal Sex

Phenotypic Sex

Hormonal Sex

Brain and/or Behavioral Sex

Sex Determination: The Jost Paradigm

chromosomal sex
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
slide17

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.
slide18

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 Anti-Mullerian Hormone (AMH) production
    • in the absence of the SRY protein, primary sex chord regress and secondary sex chords (egg nests) develop
the y chromosome cont
The Y Chromosome Cont.

B. Other genes on the Y chromosome

  • Spermatogenesis
  • androgen production
  • long bone growth
slide20

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 !
slide22

Testis Determining Factor

(SRY gene product)

XY Male

Testes develop

slide23

Testicular Development

Mesonephric Tubules

Mesonephric Duct

(Wolffian Duct)

Rete Tubules

Mullerian Duct

Tunica

Albuginea

Undifferentiated

Sex Chords

slide24

Mesonephric

Tubules

Rete Tubules

Wolffian

Duct

  • Primary, Epithelial or
  • Medullary Sex Chords
  • Primordial germ cells
  • Sertoli Cells

Mullerian Duct

Tunica

Albuginea

slide26

Testis Determining Factor

(SRY gene product)

XY Male

Testes develop

Sertoli cells secrete

anti-mullerian hormone (AMH)

slide27

Testis Determining Factor

(SRY gene product)

XY Male

Testes develop

Sertoli cells secrete

anti-mullerian hormone (AMH)

AMH causes leydig

cells to differentiate

slide28

Testis Determining Factor

(SRY gene product)

XY Male

Testes develop

Sertoli cells secrete

anti-mullerian hormone (AMH)

AMH causes leydig

cells to differentiate

Testosterone

slide29

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

slide30

Wolffian Duct Cells

Nucleus

T

Testis

T

TR

slide31

Rete Tubules

Efferent Ducts

(Vas Efferentia)

Epididymis

Seminiferous

Tubules

Ductus

Deferens

Tunica

Albuginea

slide32

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

female development
Female Development

No TDF

Testes Determining Factor

XX Female

Ovaries Develop

female development1
Female Development

No TDF

XX Female

Ovaries Develop

No Antimullerian Hormone

female development2
Female Development

No TDF

XX Female

Ovaries Develop

No AMH

Mullerian ducts become

the oviducts, uterus, cervix

and part of the vagina

slide37

Ovarian Development

Regressing

Tubules

Mullerian

Duct

Epithelial

Sex Chords

Future Ovarian

Cortex

Wolffian

Duct

slide38

Regressing

Tubules

Mullerian

Duct

Regressing

Epithelial

Sex Chords

Future Ovarian

Cortex

Regressing

Wolffian

Duct

slide39

Regressing

Tubules

Primordial

Follicles

Mullerian

Duct

Regressing

Epithelial

Sex Chords

Future Ovarian

Cortex

Regressing

Wolffian

Duct

Secondary or Cortical Sex Chords

(egg nests)

slide40

Primordial

Follicles

Mullerian

Duct

Ovarian

Medulla

Ovarian

Cortex

Regressing

Wolffian

Duct

slide41

Development

of the Uterus, Cervix

and Vagina

Mullerian Duct

slide44

Reproductive tract develops outside the

peritoneum!

Broad Ligament Development

(transverse anterior section)

Ovary

Regressing

Wolffian Duct

Mullerian

Duct

slide45

Ovary

Regressing

Wolffian

Duct

Mullerian

Duct

slide46

(Posterior Transverse Section)

Genital Fold

(Future Broad Ligament)

Regressing

Wolffian

Duct

Mullerian

Duct

slide47

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

slide49

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

slide50

Wolffian Duct Cells

Nucleus

T

Testis

T

TR

slide51

Accessory Sex Glands* and External Genitalia Cells

Nucleus

T

Testis

D

T

DR

5-

Reductase

*Prostate, Cowper’s Gland

significance of dht
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
slide56

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

brain and behavioral sex differentiation
Brain and Behavioral Sex Differentiation

Genetics

Gonadal Steroid Hormones

Sexual Behavior

Brain Structure

Experience

brain sexual differentiation
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
slide61

Testicular Descent

Growth of testis

Fusion of the tunica

albuginea and peritoneum

to form the visceral tunica vaginalis

slide63

Rapid growth of gubernaculum

Testis is pulled down to the inguinal ring.

slide64

Gubernaculum regresses

Testis pulled into scrotum

slide65

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

failure or problems with testicular descent
Failure or Problems With Testicular Descent
  • Cryptorchid
    • unilateral
    • bilateral
  • Inguinal Hernia
inguinal hernia
Inguinal Hernia

Loop of Intestine

the freemartin in cattle
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
testicular feminization in an xy individual
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
5 reductase deficiency in an xy individual
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
describe the development of the reproductive tract and or gonad in an undifferentiated
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.