Development of the Genital System Flashcards
What does the genital ridge develop from?
Intermediate mesoderm
Primordial germ cells are where and form what?
Go to genital ridges, form the primitive sex cords
Primitive sex chords in males go on to form
Testis cords
These comprise of sertoli cells (epithelial origin) and germ cells
What do Leydig cells do
Found between the cords, produce testosterone from week 8
What happens to the sex cords in females?
The primitive sex cords regress
The cortical cords develop. These cords divide into groups of cells that surround the germ cells
What is the primordial follicle (females) comprised of?
Germ cells and surrounding cells (derived from cortical cords)
The gonad is identical in both males and females until week…
7
When they are still undifferentiated, there are two pairs of ducts - mesonephric (Mullerian) and paramesonephric ducts (Wollfian).
What gene drives male development
SRY (Sex-determining Region on Y chromosome)
Causes development of testes
Produces testosterone, which also contributes to driving development
What does anti-Mullerian hormone do in males?
Actively suppresses development of paramesonephric ducts. (stops development of uterus and uterine tubes)
What factors contribute to female development?
Absence of SRY
WNT4 gene required for ovarian development (not well understood)
Oestrogen causes female differentiation.
Paramesonephric ducts develop.
What do the mesonephric ducts form?
Under influence of testosterone, forms the vas deferens.
Distal end opens into urogenital sinus, is absorbed by bladder wall. Ureter and duct enter separately.
Duct opens into part which is prostatic urethra - forms ejaculatory duct.
Prostate develops around ejaculatory ducts.
Seminal vesicle develops from vas deferens
What hormone is released by the sertoli cells?
anti-Mullerian hormone (causes regression of paramesonephric ducts).
Produced in males
What does the upper part of the paramesonephric duct form?
Uterine tubes
What is formed when the caudal ends of the paramesonephric ducts fuse together?
Uterus, cervix, upper vagina
In females, which ducts regress?
Mesonephric ducts
What happens to the lower part of the paramesonephric ducts in females?
contact the urogenital sinus, grow into the sinovaginal bulbs and allow lumen to develop.
Atresia (absence) of the lower part of vagina happens if
the sinovaginal bulbs don’t develop
What happens if the paramesonephric ducts don’t fuse together? (rare)
Didelphys (duplication)
What happens if there is only partial fusion of the paramesonephric ducts?
Bicornuate
What happens if only one paramesonephric duct develops?
Unicornuate
What happens if the uterine septum doesn’t regress?
Septate
What does oestrogen cause in female development of external genitalia?
Genital tubercle -> clitoris
urethral folds -> labia minora
urethral groove -> vestibule
genital swellings -> labia majora
What does testosterone cause in male development of external genitalia?
genital tubercle -> elongates into penis
urethral folds -> fuse into penile urethra
genital swellings -> scrotum
What is hypospadias?
The urethral folds don’t fuse properly
Urethral opening is on the ventral surface of the penis
What is ambiguous genitalia
External genitalia aren’t clearly or typically male or female.
Arise due to conditions called Disorders of Sex Development
