3 Development of Reproductive Tracts Flashcards
Which part of the gut tube gives rise to the cloaca?
Hindgut
(Gut tube= foregut, midgut and hindgut)
What does the cloaca become?
Urogenital sinus
(Common opening ofr reproductive and urinary systems)
What is the urogenital ridge?
Area of intermediate mesoderm
Gives rise to embryonic kidney and gonad
What are the primordial germ cells and what do they do?
- Specialied cells- arise from yolk sac
- Develop soon after gastrulation
- Produce sperm and ova once sexual maturation has occured
What determines the differentiation of the gonad?
Karyotype of fertilised oocyte (XX or XY)
The Y chromosome contains genes in a region that cause differentiation fo the gonad into a testis. What is the name of that region?
SRY gene
–> leads to formation of seminiferous tubules
If the SRY region is absent (ie no Y chromosome), what will the gonad differentiate into?
Ovary- no tubules develop
The testes in the embryo produce androgens (testosterone). What do these androgens drive the development of?
Duct system in men:
- Epididymis
- Vas deferens
(maintain mesonephric duct- fuses with testes)
What is another name for the mesonephric duct?
Wolffian duct
What happens to the mesonephric duct in the absence of male androgens?
It degenerates
In females the mesonephric duct degenerates and the formation of the internal female genitalia occurs (uterus, fallopian tubes, parts of vagina). Which duct remains?
Paramesonephric duct
(Mullerian duct)
(doesn’t require stimulation)
Why is there no Mullerian duct (paramesonephric duct) in males?
Mullerian Inhibitory Substance (MIH) produced by testes- prevent duct developing
Why is there a gap between the fallopian tubes and the ovaries which persists in adulthood?
Mullerian duct (paramesonephric duct) doesnt fuse with gonad
What are the 3 undifferentiated elements of external genitalia?
- Genital tubercle
- Genital folds
- Genital swellings
How are the penis and scrotum formed from the undifferentiated external genitalia?
Penis: Elongation and fusion of genital folds
Scrotum: Fusion of genital swellings
How do the vulva, labia minor and labia majora form from the undifferentiated external genitalia?
Absence of testes- no fusion of genital folds or swellings
Describe the descent of the testes.
Will be connected to the scrotum by gubernaculum
Area of peritoneum (processes vaginalis) pinches off (eventually closes)
Describe the descent of the ovaries.
Area of peritoneum picnhes off pinches off
Gubernaculum guides ovaries down
Remains as round ligament in women
Stays in pelvis due to barrier of developing uterus
What can happen as a consequence of the processus vaginalis remaining patent?
Connection to peritoneal cavity
Route for hernias to occur
What is it important to remember to examine on new born babies in relation to the descent of the testes?
Check that they are loacted in the scrotum and haven’t decended along an ectopic path- may require surgical correction
Along which structure do the primordial germ cells migrate?
Along dorsal mesentery into retroperitoneum
What happens to the mesonephric and paramesonephric ducts in Androgen Insensitivity Syndrome?
Receptors for testosterone don’t work
Wolffian ducts don’t survive
Mullerian ducts degenerate as MIH present
What happens if a female embryo receives exogenous testosterone?
What problems can present due to maldescent of the testes?
- Infertility (too hot for spermatogenesis)
- Increased risk- testicular torsion
- Increased risk- testicular cancer
If a baby has an XY genotype but their fetal genitalia is insensitive to testosterone, what would you expect their internal and external genitalia to be like?
Internal: Testes present BUT no ducts
External: Female (as default) BUT blind ended, short vagina
What embryological orgins do the upper and lower vagina have?
- Upper: paramesonephric ducts
- Lower: external genitalia
A baby is born with XX genotype but has excessive secretion of androgens from the adrenal glands. What would you expect to see from their external and internal genitalia?
