Embryological Development of Sex Flashcards
When does the ‘genital ridge’ develop?
3.5-4 weeks
From what are the gonads developed from?
A common, bipotential genital primordium together with 3 invading/migratory cell types: 1) PGCs; 2) germinal epithelial cells and; 3) mesonephric cells
From what is the common, bipotential genital primordium formed?
Mesenchymal cells/tissue
Where is the gonadal ridge found?
The posterior abdominal wall
When are PGCs first identifiable?
3 weeks
Where are the PGCs found pre-migration?
The yolk sac, near the base of the developing allantois
From what are PGCs derived?
The epiblast
When is migration of the PGCs complete?
6 weeks
When are PGCs arrested in males?
Mitosis
When are PGCs arrested in females?
Prophase I of meiosis
From where do the germinal epithelial cell originate?
They originally overly the mesenchymal cells of the genital ridges
What do the germinal epithelial cells form?
The primitive sex cords
Do the germinal epithelial cells/primitive sex cords express sry?
Yes
Do the PGCs express sry?
No
Do the mesonephric cells express sry?
No
Which cell types expresses sry?
The germinal epithelial cells/primitive sex cords
Where is sry located?
Near the end of the short arm of the Y chromosome
What is the function of sry?
Sry is the ‘controller’ gene - it determines whether or not testis develop (by determining whether or not Sertoli cells develop)
What do the primitive sex cords become in males?
The testis cords
What do the germinal epithelial cell of the primitive sex cords ultimately form in males?
Sertoli cells
What is the action of sry mediated by?
Sox9
What does Sox9 stimulate the production of?
1) AMH; 2) PGD2; 3) Fgf9
What is the function of Fgf9?
= a chemoattractant for the mesonephric cells to the gonadal ridges
What is the function of AMH?
AMH ensures the formation of the male internal genital tract from the Wolffian ducts
From where do the mesonephric cells originate?
Lateral to the gonadal ridges
What do the mesonephric cells form in males?
1) Vasculature; 2) Leydig cells; 3) Myoid cells
What do the mesonephric cells form in females?
1) Vasculatrue; 2) Theca cells
What does the clustering of the primitive sex cords result in in females?
Primordial ovarian follicles
What do the germinal epithelial cells of the primitive sex cords ultimately form in females?
Granulosa cells
What genes maintain ovarian development?
Wnt4 and Foxl2
What inhibits Wnt4 and Foxl2?
Sox9
From what do the male internal genitalia develop?
Wolffian ducts
From what do the female internal genitalia develop?
Mullerian ducts
Which cell type produces AMH?
Sertoli cells
Which cell type produces androgens?
Leydig cells
What is the action of AMH on the Mullerian ducts in males?
The PRESENCE of AMH in males results in the regression of the Mullerian ducts
What is the action of the absence of AMH on the Mullerian ducts females?
The ABSENCE of AMH in females allows the Mullerian ducts to persist
What do the Wolffian ducts form in males?
1) Epididymis; 2) vas deferens; 3) prostate
What do Mullerian ducts from in females?
1) Oviducts; 2) uterus; 2) upper 2/3rds of the vagina; 4) cervix
What do the urethral folds form in males?
The penile shaft
What des the genital swellings/labioscrotal swellings form in males?
The scrotum
What does the genital tubercle form in males?
The glans penis
What doe the urethral folds and genital swellings/labioscrotal swellings form in females?
The labia majora and minora
What doe she genital tubercle form in females?
The clitoris
