Development Of Reproductive Tracts Flashcards
Where do the primordial germ cells develop from?
Yolk sac + migrate to urogenital ridge
Outline the formation of the primitive sex cords
Epithelium of genital ridges proliferate + penetrate the intermediate mesoderm
What forms the indifferent gonad?
Combination of germ cell + primitive sex cords
What is the testis determining factor?
SRY protein on short arm of Y chromosome
What happens in the presence and absence of SRY protein?
- SRY present: male development occurs
- SRY absent: female development occurs
Development of ovaries
- SRY absent
- primitive sex cords degenerate
- epithelium of gonad proliferates > cortical cords
- cords surround germ cells to form > primordial follicle
Development of testes
- SRY present
- primitive sex cords develop into testicles
- medullary cord is formed > develops into seminiferous tubule after puberty
- between the cords there are leydig cells which produce testosterone at week 8
What is the male internal genital duct?
Mesonephric duct (Wolffian duct)
What is the female internal genital duct?
Paramesonephric duct (Mullerian duct)
Which type of duct develop depends on…
Whether there is functioning testes
What happens to internal genital ducts if testis are produced?
- anti-mullerian hormone by Sertoli cells: suppresses paramesonephric duct > regresses
- testosterone produced by leydig cells : supports mesonephric duct > develops into vas deferens + epididymis
- male internal genitalia develops
What happens to internal genital ducts if no testis are produced?
- NO anti-mullerian hormone: no suppresion of paramesonephric duct > develops into uterus, fallopian tubes + upper vagina
- NO testosterone produced: no support of mesonephric duct > regresses
- female internal genitalia develops
What are the basic components of the undifferentiated external genitalia?
Genital tubercle
Genital folds
Genital swellings
When do the external genitalia start to develop?
9th week
Development of male external genitalia
- under influence of testis-derived androgen hormones dihydrotestosterone
- genital tubercle: elongates to forms glans penis
- genital folds: fuse to form spongy urethra/shaft of penis
- genital swelling: scrotum
Development of female external genitalia
- absence of testes
- no fusion occurs
- genital tubercle: clitoris
- genital folds: labia minora
- genital swellings: enlarge to become labia majora
Where does the Gubernaculum attach?
The gonad inferiorly to labio-scrotal folds (genital swellings)
What are the remnants of the Gubernaculum in women?
Round ligament
Ovarian ligament
What condition results in a genetically male baby being born with female external genitalia?
Androgen insensitivity syndrome
What external and internal genitalia does someone with androgen insensitivity syndrome have and why?
- external female
- genetically male > XY genotype
. - mesonephric duct fails to persist due to insensitivity to testosterone
- testicles function normally due to SRY protein on Y chromosome > anti-mullerian hormone released > paramesonephric duct degenerates > no uterus
- insensitivity to DHT > female external genitalia
- no ducts present
What hormone is produced by Sertoli cells of testicle?
Anti Mullerian hormone
What gene on the Y chromosome is responsible for the specialisation of the genitalia as a male?
SRY
What does the mesonephric duct form?
Vas deferens
Epididymis
What does the paramesonephric duct form?
Uterus
Fallopian tubes
Upper vagina
What forms the vagina?
- Paramesonephric duct > upper vagina
- Urogenital sinus > lower vagina
- Both parts fuse to complete vagina
What do the genital tubercle become in men + women?
men: glans penis
women: clitoris
What do the genital folds become in men and women?
men: spongy urethra/shaft of penis
women: labia minora
What do the genital swellings become in men and women?
men: scrotum
women: labia majora
What is the Gubernaculum?
- A fibrous structure that pulls the gonads from the posterior wall to their correct position
- Testicles in scrotum
- Ovaries in pelvis
Where is anti-mullerian hormone produced?
Sertoli cells
What is development of male external genital under the influence of?
Dihydrotestosterone
Which tissues do the gonads develop from?
Intermediate mesoderm in abdomen
