3 - SEXUAL DEVELOPMENT Flashcards
what is the early stage of sexual development?
undifferentiated gonads develop in the first few months
the chemicals from undifferentiated gonads flood surrounding tissue
can switch on TDF gene if present
sequence:
the initial male development (in normal XY males)
TDF gene is present in all cells (on Y chromosome)
1 - gonadal signals trigger TDF protein production
2 - immature gonads respond to TDF and turn into testes
3 - sertoli cells secrete MIH
4 - müllerian duct degenerates
5 - leydig cells secrete androgens (testosterone)
do gonads produce testosterone?
no, only once developed into testes
don’t need testosterone for the initial development (TDF is needed)
sequence:
subsequent male development following hormonal instructions
- androgens masculinise all body tissue (except brain)
- müllerian duct = already gone
- wolffian duct = male internal sex organs
- urogenital groove = male external genitals but needs 5-alpha-reductase
- androgens make body ‘male shaped’
what is 5-alpha-reductase?
an enzyme in urogenital tissue that converts testosterone into DHT (dihydrotestosterone)
what does the urogenital groove (cloaca) need to develop in males?
DHT - dihydrotestosterone
a type of testosterone
sequence:
initial female development starts by default
- gonads develop into ovaries
(granulosa cells=supporting cells)
(thecal cells=hormone producing)
what are granulosa cells?
supporting cells in the ovaries
what are thecal cells?
hormone producing cells in the ovaries
when are hormones produced by the ovaries?
only in puberty (if gametes are present)
what is the purpose of sertoli cells?
secretion of MIH (müllerian inhibiting hormone) in males
to cause the müllerian duct to degenerate
what is the purpose of leydig cells?
to secrete androgens in the testes
statement:
gamete-producing cells originate somewhere else (in the yolk sac) and migrate to the gonads (through the gut)
-
what does the cloaca separate into?
the rectum and urogenital structures (external genitals)
it is an all purpose output (unitary tract and intestines)
sequence:
subsequent female development
- müllerian duct = female internal sexual organs
- wolffian duct = degenerates
- urogenital groove = female external genitalia
- female body = happens in the absence of chemical shaping (some required, but in broad terms not needed like in males)
