What does SRY transcription factor gene code for? When would it switch on..week.?
male pathway -> testes that make AMH & testosterone
week 7
The bipotential gonads are derived from what?
At week..?
Common somatic mesenchymal tissue “the genital ridge primordia” around week 3/week 4
What is the duct called that forms the: epididymus, vas deferans, prostate gland and seminal vesicles?
Wolffian/mesonephric
What duct forms the uterus, fallopian tubes, cervix and upper 1/3rd of vagina?
Mullerian/paramesonephric duct
What are the 3 waves of cells that invade the genital ridge?
- primordial germ cells (PGCs)
- primitive sex chords
- mesonephric cells
PGCs begin as cell cluster in yolk sac epithelium than expand by mitosis (wk 3) then migrate to….
..CT of the hind gut -> genital ridge (colonised at wk 6)
PGCs form..
- oocytes
- spermatoza
The primitive sex chords are from the germinal epithelium that overlies the genital ridge then migrates.. and in men/women..
inwards as columns
- men: they penetrate the medulary mesenchyme, and surround PGCs forming testis cordis. Become sertoli cells.
- women: ill defined, dont penetrate, condense in cx as clusters around PGCs. Become granulosa cells.
What do sertoli cells express?
AMH (Anti Mullerian Hormone)
Where do mesonephric cells originate?
Mesonephric primordium (lat to genital ridge)
Mesonephric cells in men vs women (make vascular tissue in both)?
Men: pre-sertoli cells and SRY…leydig cells make testosterone, the basement membrane helps to make semineferous tubules and rete testes
Women: Theca cells make adrostenedione, a substrate for E2 production from granulosa.
If men..what about women:
PCG -> spermatoza
P. sex chords -> sertoli cells (AMH, SRY)
mesonephric cells -> Leydig cells (testosterone)
PCG -> oocytes
P. sex chords -> granulosa cells (E2)
mesonephric cells -> Theca cells (androstenedione)
Where is testosterone converted to DHT (dihydrotestosterone) by enzyme…
in the genital skin, by 5a reductase
DHT on the testosterone receptor causes differentiation of ext. male genitalia how?
- genital tubercle and urethral fold enlarges into penis
- genital swellings fuse and become ruggated into scrotum
In females (with no DHT) what does the genital tubercle, swellings and urethral fold form?
- tubercle forms clitoris
- swellings form labia majora and minora
- urethral fold forms opening of vagina
What is testosterone’s function?
-differentiation and growth of Wolffian duct structures (seminal vesicles, vas deferens…)
What leads to the female external genitalia development?
Lack of androgens
What is gonadal dysgenesis? Cause in male/female?
- incomplete sexual differentiation
- missing SRY in males, partial/full deletion of 2nd X in females
what is sex reversal?
When phenotype doesnt match genotype
What is intersex?
When components of both tracts are present or ambiguous genitalia
Androgen Insensitivity Syndrome (AIS) 1/20,000 is due to androgen receptor issue. What happens is..
an XY individual appears female at birth
- they have SRY (make testis, make AMH)
- make testosterone & DHT but no receptors so Wolffian duct cant grow/no ext. male genitalia
How may AIS present?
Primary Amenorrhoea, no body hair, undescended testes..NB they may feel female as brain has been exposed to only female signals
Partial AIS has varying degrees of srotal/penile development, may be large clitoris..ambiguous..ajd at puberty..
..the large androgen surge can cause the appearence of male genitalia on the “female”
5a reductase deficiency is normally A.Recessive condition when testosterone is made but no/little DHT so..
at puberty..
- XY, testis form, AMH, Wolffian ducts grow (int=male)
- no DHT (no ext male so ext=female/ambiguous)
- adrenarche testosterone may induce virilisation so “female” gets male ext genitalia
