Download presentation
Presentation is loading. Please wait.
1
Animal Science 434 Reproductive Physiology
Lec 5: Embryogenesis of the Pituitary and Sexual Development
2
Development of the Pituitary Gland
Infundibulum Brain Rathke’s Pouch Stomodeum
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 Mesonephros Metenephros regresses
portions of reproductive tract Metenephros Adult kindney and urinary ducts
11
Development of Mesenephros and Metenephros
12
Paramesonephric Ducts
Jost Experiments Mesonephric Ducts (Wolffian Ducts) Paramesonephric Ducts (Mullerian Ducts)
13
Paramesonephric Ducts
Jost Experiments Mesonephric Ducts (Wolffian Ducts) Paramesonephric Ducts (Mullerian Ducts) Testis Ovary Epididymis Oviduct Epididymis Vas Deferens Seminal Vesicles Uterus
14
Sex Determination: The Jost Paradigm
Chromosomal Sex Gonadal Sex Phenotypic Sex Chromosomal Sex Gonadal Sex Phenotypic Sex Hormonal Sex Brain and/or Behavioral Sex
15
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
16
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.
17
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
18
The Y Chromosome Cont. B. Other genes on the Y chromosome
Spermatogenesis androgen production long bone growth
19
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
20
Gonadal Sex
21
Testis Determining Factor
XY Male Testis Determining Factor (SRY gene product) Testes develop
22
Testicular Development
Mesonephric Duct (Wolffian Duct) Mesonephric Tubules Rete Tubules Mullerian Duct Tunica Albuginea Undifferentiated Sex Chords
23
Mesonephric Tubules Wolffian Duct Tunica Albuginea
Rete Tubules Wolffian Duct Primary, Epithelial or Medullary Sex Chords Primordial germ cells Sertoli Cells Mullerian Duct Tunica Albuginea
24
Hormonal Sex
25
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
26
Wolffian Duct Cells Nucleus T Testis T TR
27
Efferent Ducts Seminiferous Tubules Vas Deferens Tunica Albuginea
(Vas Efferentia) Rete Tubules Epididymis Seminiferous Tubules Vas Deferens Tunica Albuginea
28
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
29
Vas efferentia
30
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
31
Ovarian Development Regressing Tubules Mullerian Duct Epithelial
Sex Chords Future Ovarian Cortex Wolffian Duct
32
Regressing Tubules Mullerian Duct Regressing Epithelial Sex Chords Future Ovarian Cortex Regressing Wolffian Duct
33
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)
34
Primordial Follicles Mullerian Duct Ovarian Medulla Ovarian Cortex Regressing Wolffian Duct
35
Development of the Uterus, Cervix and Vagina
Mullerian Duct
36
Fused Mullerian Duct Hymen
38
Broad Ligament Development (transverse anterior section)
Reproductive tract develops outside the peritoneum! Broad Ligament Development (transverse anterior section) Ovary Regressing Wolffian Duct Mullerian Duct
39
Ovary Regressing Wolffian Duct Mullerian Duct
40
(Posterior Transverse Section) (Future Broad Ligament)
Genital Fold (Future Broad Ligament) Regressing Wolffian Duct Mullerian Duct
41
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
42
Phenotypic Sex
43
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
44
Wolffian Duct Cells Nucleus T Testis T TR
45
Accessory Sex Glands* and External Genitalia Cells
Nucleus T Testis T D DR 5- Reductase *Prostate, Cowper’s Gland
46
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
47
External Genitalia Differentiation
50
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
51
Brain or Behavioral Sex
52
Brain and Behavioral Sex Differentiation
Genetics Gonadal Steroid Hormones Sexual Behavior Brain Structure Experience
53
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
54
Descent of the Testis into the Scrotum
55
albuginea and peritoneum to form the visceral tunica vaginalis
Testicular Descent Fusion of the tunica albuginea and peritoneum to form the visceral tunica vaginalis
56
Fusion of Peritoneum and Gubernaculum
Front View Spermatic Artery Fusion of Peritoneum and Gubernaculum Testis Gubernaculum Peritoneum Inguinal Ring
57
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
58
Gubernaculum regresses Testis pulled into scrotum
59
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
60
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
61
Normal Dog Seminiferous Tubule
62
Cryptochid Dog Seminiferous Tubule
63
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
64
Inguinal Hernia Loop of Intestine
65
Abnormalities in Development
66
The Freemartin in Cattle
Female born twin to a bull Extra embryonic membranes fuse to form a common chorion 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
67
Freemartin AMH - blocks Mullerian ducts Ovaries do not grow
Posterior vagina, no anterior vagina Ovaries do not grow SRY expressed from chimeric cells (Ovotestis) Testosterone produced Clitoral enlargement Bullish behavior - masculinization Use as estrus detector Abnormalities exist as a continuum
68
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
69
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
Similar presentations
© 2025 SlidePlayer.com. Inc.
All rights reserved.