M1 - Reproductive Physio Flashcards
at what week does a fetus reach full sexual differentiation?
week 12
where do germ cells migrate to?
genital ridge
SRY gene encodes
TDF/SRY protein
causes male sexual differentiation
TDF makes
SOX 9 protein –> turns indeterminate gonad into testes
what is needed to turn indeterminate gonads into male?
TDF makes SOX9 (forms testes).
Testosterone develops Wolffian ducts.
AMH makes Mullerian ducts disappear.
Testosterone–>DHT (by 5-a-reductase) : formation of external genetalia
5-a-reductase
converts testosterone to DHT
where is TDF expressed?
somatic cells of testes
SOX9
Transcription initiated by TDF.
Initially works with TDF, then takes over to complete the differentiation of testes when TDF expression ceases.
Acts as a transcription factor.
hormones directing male sexual differentiation
TESTOSTERONE
Maintencance of Wolffian duct structures.
Critical for normal male external genitalia.
AMH
Regression of Mullerian duct structures.
Testosterone is secreted from?? AMH?
Testosterone secreted from Leydig cells.
AMH secreted from Sertolic cells.
DAX-1 actions
Expression of proteins that cause female sexual differentiation.
Supression of expression of proteins leading to male sexual differentiation.
[DAX-1 : Dosage sensitive sex reversal // on x chromosome]
which structures persist in female sexual development?
Mullerian duct.
Wolffian duct degenerates w/o testosterone
effect of lack of testosterone in female development
No testosterone –> no DHT –> female pathway
are genes from both X chromosomes expressed in human cells?
Yes and no. One of the X chromosomes is partially deactivated in each cell of a woman.
what happens if a person has XX genotype, but due to a mistake in crossing over, has an SRY gene?
Klinefelter-like (XXY).
Male gonads/genetalia.
Wolffian ducts.
androgen insensitivity syndrome (XY)
[gonads, mullerian/wolffian ducts, external genitalia.
Androgen receptor is not functional.
No axillary/pubic hair.
Testes bc SRY present.
Testes secrete AMH, so no Mullerian duct.
No Wolffian duct bc no testosterone action.
Vagina bc no DHT.
No periods bc no uterus (blind vaginal pouch bc no mullerian ducts)
what causes ambiguous external genitalia?
Male fetus exposed to too little androgen effect.
Female is exposed to too much androgen effect.
partial androgen insensitivity
ambiguous genitalia.
Perineal hypospadias/bifid scrotum.
describe body transitions that occur in pubertal development
- external genital development (T, E)
- growth spurt (E)
- increased musculature, beard, deep voice in boys (T)
- breast development, increased fat deposits in girls (E)
age of pubertal onset: US males
9-10 years old
age of pubertal onset: US females (caucasian, Afr.-Am.)
Caucasian: 8-9 years old
African-American: 7-8 years old
delayed puberty
Age 13 in females (lack of onset of menses)
Age 14 in males (absent testicular development)
tanner stages of male puberty
1) pre-pubertal
2) testes/scrotal enlargement, early pubic hair growth
3) growth of glans penis
4) completion of appearance of adult genitalia
adrenarche/pubcarche
appearance of pubic/axillary hair
thelarche
breast development
menarche/gonadarche
Period onset.
Activation of GnRH secretion.
tanner stages of female puberty
1) pre-pubertal
2) early thelarche, early pubarche
3) further development of breast tissue
4) continued development of breast tissue
5) adult female breast and pubic escutcheon (shape)
kisspeptin
Secreted from hypothalamus.
Potent stimulator of GnRH secretion.