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Animal Science 434 Reproductive Physiology. Lec 5: Embryogenesis of the Pituitary and Sexual Development. Development of the Pituitary Gland. Infundibulum. Brain. Rathke’s Pouch. Stomodeum. Germ Cell Migration. Migration begins by the 4 week of gestation in cow and human.

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animal science 434 reproductive physiology

Animal Science 434Reproductive Physiology

Lec 5: Embryogenesis of the Pituitary and Sexual Development

development of the pituitary gland
Development of the Pituitary Gland

Infundibulum

Brain

Rathke’s Pouch

Stomodeum

slide4

Germ Cell Migration

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

slide5

Migration from endoderm

through mesoderm.

fetal kidneys
Fetal Kidneys
  • Pronephros
    • regresses
  • Mesonephros
    • portions of reproductive tract
  • Metenephros
    • Adult kindney and urinary ducts
jost experiments
Jost Experiments

Mesonephric Ducts

(Wolffian Ducts)

Paramesonephric Ducts

(Mullerian Ducts)

Testis

Ovary

Epididymis

Epididymis

Oviduct

Vas Deferens

Seminal Vesicles

Uterus

slide10

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
  • 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
slide12

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.
slide14

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
the y chromosome cont
The Y Chromosome Cont.

B. Other genes on the Y chromosome

  • Spermatogenesis
  • androgen production
  • long bone growth
sry and birds
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
slide18

Testes develop

Testis Determining Factor

(SRY gene product)

XY Male

slide19

Testicular Development

Mesonephric Tubules

Mesonephric Duct

(Wolffian Duct)

Rete Tubules

Mullerian Duct

Tunica

Albuginea

Undifferentiated

Sex Chords

slide20

Mesonephric

Tubules

Rete Tubules

Wolffian

Duct

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

Mullerian Duct

Tunica

Albuginea

slide23

Sertoli cells secrete

anti-mullerian hormone (AMH)

AMH causes leydig

cells to differentiate

Testosterone

Development of male

duct system

Testis Determining Factor

(SRY gene product)

XY Male

Testes develop

slide24

Wolffian Duct Cells

Nucleus

T

Testis

T

TR

slide25

Rete Tubules

Efferent Ducts

(Vas Efferentia)

Epididymis

Seminiferous

Tubules

Vas

Deferens

Tunica

Albuginea

slide26

Sertoli cells secrete

anti-mullerian hormone (AMH)

AMH causes leydig

cells to differentiate

Degeneration of

Mullerian duct

Testosterone

Development of male

duct system

Testis Determining Factor

(SRY gene product)

XY Male

Testes develop

female development

Ovaries Develop

Wolffian Ducts

Regress

No AMH

No

Testosterone

Mullerian ducts become

the oviducts, uterus, cervix

and part of the vagina

Female Development

No TDF

Testes Determining Factor

XX Female

slide29

Ovarian Development

Regressing

Tubules

Mullerian

Duct

Primary or

Epithelial

Sex Chords

Future Ovarian

Cortex

Wolffian

Duct

slide30

Regressing

Tubules

Mullerian

Duct

Regressing

Epithelial

Sex Chords

Future Ovarian

Cortex

Regressing

Wolffian

Duct

slide31

Regressing

Tubules

Primordial

Follicles

Mullerian

Duct

Regressing

Epithelial

Sex Chords

Future Ovarian

Cortex

Regressing

Wolffian

Duct

Secondary or Cortical Sex Chords

(egg nests)

slide32

Primordial

Follicles

Mullerian

Duct

Ovarian

Medulla

Ovarian

Cortex

Regressing

Wolffian

Duct

slide34

Development

of the Uterus, Cervix

and Vagina

Mullerian Duct

slide37

Reproductive tract develops outside the

peritoneum!

Broad Ligament Development

(transverse anterior section)

Ovary

Regressing

Wolffian Duct

Mullerian

Duct

slide38

Ovary

Regressing

Wolffian

Duct

Mullerian

Duct

slide39

(Posterior Transverse Section)

Genital Fold

(Future Broad Ligament)

Regressing

Wolffian

Duct

Mullerian

Duct

slide40

Testis Determining Factor

(SRY gene product)

No TDF

XX Female

XY Male

Testes develop

Ovaries Develop

No

Testosterone

No AMH

Sertoli cells secrete

anti-mullerian hormone (AMH)

AMH causes leydig

cells to differentiate

Degeneration of

Mullerian duct

Degeneration of

Wolffian duct

Mullerian ducts become

the oviducts, uterus, cervix

and part of the vagina

Testosterone

Development of male

duct system

slide42

Dihydrotestosterone

Development of penis

scrotum and accessory

sex glands

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

slide43

Wolffian Duct Cells

Nucleus

T

Testis

T

TR

slide44

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
slide49

Dihydrotestosterone

Development of penis

scrotum and accessory

sex glands

Testis Determining Factor

(SRY gene product)

No TDF

XX Female

XY Male

Testes develop

Ovaries Develop

No

Testosterone

No AMH

Sertoli cells secrete

anti-mullerian hormone (AMH)

AMH causes leydig

cells to differentiate

Degeneration of

Mullerian duct

Degeneration of

Wolffian duct

Mullerian ducts become

the oviducts, uterus, cervix

and part of the vagina

Testosterone

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
testicular descent
Testicular Descent

Fusion of the tunica

albuginea and peritoneum

to form the visceral tunica vaginalis

slide55

Spermatic Artery

Front View

Fusion of Peritoneum and Gubernaculum

Testis

Gubernaculum

Peritoneum

Inguinal Ring

slide56

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

slide57

Gubernaculum regresses

Testis pulled into scrotum

slide58

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

failure or problems with testicular descent
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
failure or problems with testicular descent62
Failure or Problems With Testicular Descent
  • Inguinal Hernia
  • 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
Inguinal Hernia

Loop of Intestine

the freemartin in cattle
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
freemartin69
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
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
  • 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
guevedoces development
Guevedoces Development

Normal tissue dependent upon testosterone is shown in black.