The gonads are both ______ at seven weeks of gestation.
*This means that they have both XX and XY genotypes.
NOTE: In males, testicular differentiation begins after the seventh week of gestation
Regression of the Mullerian ducts occurs response to secretion of _________. Differentiation of the Wolfian (mesonephric) ducts occurs in response to ________.
AMH (Anti-Müllerian hormone); testoterone
What cells secrete AMH?
Primitive sertoli-like cells
REMEMBER: AMH triggers the regression of Mullerian ducts (paramesonephric duct).
Mullerian ducts (paramesonephric duct) gives rise to which structures?
Uterine tubes, uterus, cervix, and the upper two third of the vagina
NOTE: They are lost in males, due to release of AMH from Sertoli cells
Mesonephric duct (Wolfian) gives rise to which structures?
Epididymis, vas deferens, and seminal vesicles
NOTE: In females this structure regresses
Differentiation of the male external genitalia occurs during the 9-13 weeks of gestation in response to ________.
What down stream affect does the SRY gene have differentiation?
SRY stimulates the differentation of the bipotential gonadal cells into sertoli and leydig cells.
Sertoli cells secrete anti-mullerian hormone, leading to the regression of mullerian duct
- REMEMBER: In females, the mullerian duct (paramesonephric duct) develops into uterine tubes, uterus, cervix, and the upper one-third of the vagina.
Leydig cells secrete testosterone, which causes differentiation of the Wolffian ducts (mesonephric duct) and is catalyzes into DHT by 5-alpha DHT reductase
- Wolffian duct differentiates into the epididymis, vas deferens, and seminal vesicles
- DHT stimulates the formation of the penis and scrotum
NOTE: The SRY genes is found on the Y chromosome
What would be the effect of a deficiency or block of 5-alpha DHT reductase?
The baby will look femal externally, as there will be no fusion of the urehtral folds. There will be no scrotum and the testes will remail in the labial fold
After week ______, the system cannot differentiate.
What is the genital tubercle?
A body of tissue that eventually develops into a primordial phallus, which develops into the penis or clitoris.
Fetal testosterone reaches peak plasma levels at ____ weeks of gestation.
NOTE: hCG and fetal LH are important for continued growth of the penis and testis during the second and third trimesters. If there isn't enough activity during the second and third trimesters this is when you can get the micropenis.
The 1st premordial follicle appears near the _______ month of gestation.
The last oogonia enter meiosis at ____ months of gestation.
NOTE: The folliculogenesis doesn't finish until about 6 months post partum but all of the oogonia are made
In the absence of ________, gonadal cells have an inherent tendency to form ovarian-like structures.
TDF (Testis-differentiation factor)
The maximum follicle formation period occurs during the peak plasma levels of fetal ___.
NOTE: We have follicles that go into atresia, others continue to grow, and the ovary keeps getting larger.
______ stimulates the Leydig cells to secrete testosterone.