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.

Migration from endoderm through mesoderm.

In birds the migration is via the blood stream.

Fetal Kidneys Pronephros Mesonephros Metenephros regresses portions of reproductive tract Metenephros Adult kindney and urinary ducts

Development of Mesenephros and Metenephros

Development of Mesenephros and Metenephros Early Development Flash Movie http://www.ansci.wisc.edu/jjp1/as434/powerpoint/fa07/early_dev.swf http://www.ansci.wisc.edu/jjp1/as434/powerpoint/fa07/early_dev.swf Early Development Flash Movie Requires the free flash player which can be downloaded from: www.adobe.com

Paramesonephric Ducts Jost Experiments Mesonephric Ducts (Wolffian Ducts) Paramesonephric Ducts (Mullerian Ducts) Testis Ovary Epididymis Oviduct Epididymis Vas Deferens Seminal Vesicles Uterus

Sex Determination: The Jost Paradigm Chromosomal Sex Gonadal Sex Phenotypic Sex

Sex Determination: The Jost Paradigm Chromosomal Sex Gonadal Sex Phenotypic Sex Chromosomal Sex Gonadal Sex Phenotypic Sex Hormonal Sex Brain and/or Behavioral 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

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 (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.

Human X and Y Chromosomes

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 Development of Sertoli Cells Anti-Mullerian Hormone production by Sertoli Cells absence of SRY 2nd sex chords (egg nests) develop

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

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

Gonadal Sex

Testis Determining Factor XY Male Testis Determining Factor (SRY gene product) Testes develop

Testicular Development Mesonephric Duct (Wolffian Duct) Mesonephric Tubules Rete Tubules Mullerian Duct Tunica Albuginea Undifferentiated Sex Chords

Mesonephric Tubules Wolffian Duct Tunica Albuginea Rete Tubules Wolffian Duct Primary, Epithelial or Medullary Sex Chords Primordial germ cells (gonocytes) Pre-Sertoli Cells Mullerian Duct Tunica Albuginea

Primary Sex Chords in Fetal Testis Pre-Sertoli Gonocyte

Hormonal Sex

Testis Determining Factor 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 Nucleus T Testis T TR

Efferent Ducts Seminiferous Tubules Vas Deferens Tunica Albuginea (Vas Efferentia) Rete Tubules Epididymis Seminiferous Tubules Vas Deferens Tunica Albuginea

Testis Determining Factor XY Male Testis Determining Factor (SRY gene product) 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

Vas efferentia

Testes Determining Factor Female Development No TDF Testes Determining Factor XX Female Ovaries Develop No Testosterone No AMH Mullerian ducts become the oviducts, uterus, cervix and part of the vagina Wolffian Ducts Regress

Ovarian Development Regressing Tubules Mullerian Duct Primary or Epithelial Sex Chords Future Ovarian Cortex Wolffian Duct

Regressing Tubules Mullerian Duct Regressing Epithelial Sex Chords Future Ovarian Cortex Regressing Wolffian Duct

Secondary or Cortical Sex Chords Regressing Tubules Primordial Follicles Mullerian Duct Regressing Epithelial Sex Chords Future Ovarian Cortex Regressing Wolffian Duct Secondary or Cortical Sex Chords (egg nests)

Primordial Follicles Mullerian Duct Ovarian Medulla Ovarian Cortex Regressing Wolffian Duct

2nd Sex Chords in Fetal Ovary

Development of the Uterus, Cervix and Vagina Mullerian Duct

Fused Mullerian Duct Hymen

Broad Ligament Development (transverse anterior section) Reproductive tract develops outside the peritoneum! Broad Ligament Development (transverse anterior section) Ovary Regressing Wolffian Duct Mullerian Duct

Ovary Regressing Wolffian Duct Mullerian Duct

(Posterior Transverse Section) (Future Broad Ligament) Genital Fold (Future Broad Ligament) Regressing Wolffian Duct Mullerian Duct

XX Female XY Male No TDF Ovaries Develop No No AMH Testosterone 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

Phenotypic Sex

XY Male Testis Determining Factor (SRY gene product) 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

XY Male Testis Determining Factor (SRY gene product) Testes develop Sertoli cells secrete anti-mullerian hormone (AMH) AMH causes leydig cells to differentiate Degeneration of Mullerian Duct Testosterone Dihydrotestosterone Development of penis scrotum and accessory sex glands Development of male duct system

Wolffian Duct Cells Nucleus T Testis T TR

Accessory Sex Glands* and External Genitalia Cells Nucleus T Testis T D DR 5- Reductase *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 5a-reductase

External Genitalia Differentiation

XX Female XY Male No TDF Ovaries Develop No No AMH Testosterone 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 Dihydrotestosterone Development of penis scrotum and accessory sex glands Development of male duct system