UG Development 3 Flashcards
Identify the common male/female primordia at the 8-week "indifferent stage" and the adult UG structures they become.
What is the sexually indifferent stage?
At 8 weeks, all embryos have a single, common set of UG structures.
What are the common structures at the indifferent stage?
- metanephros
- mesonephros
- gonads attached medially to the mesonephros (from the genital ridges)
- mesonephric (wolffian) ducts
- paramesonephric (mullerian) ducts
- UG sinus
- genital tubercle (phallus)
- labioscrotal folds
What do the following develop into?
Medulla of primitive gonads?
Primary sex cords?
Cortex of primitive gonads?
Secondary sex cords?
- Medulla - testis, diminishes in females
- Primary sex cords - seminiferous tubules, disappear or retained as rete ovarii
- Cortex of primitive gonads - ovary
- Secondary sex cords - epithelial ovarian follicles surrounding the oocytes
What happens to the mesonephric duct and paramesonephric duct in males?
- Mesonephric duct - retained as ductus deferens and epididymus
- Paramesonephric duct - disappears
What happens fo the following structures in the female?
Paramesonephric ducts?
Mesonephric ducts?
-
Paramesonephric ducts
- uterine tubes
- uterus
- upper part of vagina
- lower part derived from extension of endoderm of the UG sinus - sinovaginal bulbs form a solid vaginal plate
-
Mesonephric ducts
- ducts and tubules disappear
What happens when the paired paramesonephric ducts fail to use in a female?
vertical septae in the uterus/vagina or double uterus (bicornuate or Didelphys if complete)
What happens in a female when there is agenesis of one or both paramesonephric ducts?
unicornate uterus or complete absence of the uterus/vagina
In the male, what is the role of the fibrous gubernaculum?
- Guides descent of the testis through the deep body wall via the inguinal canal
- Descends behind the processus vaginalis (pouch of parietal peritoneum)
- Pinches off as the tunica vaginalis testis - coelomic sac that envelops the testis with visceral and parietal layers