Sexual Differentation

Question 1

The gonads are both ______ at seven weeks of gestation.

Answer 1

Bipotential

*This means that they have both XX and XY genotypes.

NOTE: In males, testicular differentiation begins after the seventh week of gestation

Question 2

Regression of the Mullerian ducts occurs response to secretion of _________. Differentiation of the Wolfian (mesonephric) ducts occurs in response to ________.

Answer 2

AMH (Anti-Müllerian hormone); testoterone

Question 3

What cells secrete AMH?

Answer 3

Primitive sertoli-like cells

REMEMBER: AMH triggers the regression of Mullerian ducts (paramesonephric duct).

Question 4

Mullerian ducts (paramesonephric duct) gives rise to which structures?

Answer 4

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

Question 5

Mesonephric duct (Wolfian) gives rise to which structures?

Answer 5

Epididymis, vas deferens, and seminal vesicles

NOTE: In females this structure regresses

Question 6

Differentiation of the male external genitalia occurs during the 9-13 weeks of gestation in response to ________.

Answer 6

DHT

Question 7

What down stream affect does the SRY gene have differentiation?

Answer 7

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

Question 8

What would be the effect of a deficiency or block of 5-alpha DHT reductase?

Answer 8

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

Question 9

After week ______, the system cannot differentiate.

Answer 9

13

Question 10

What is the genital tubercle?

Answer 10

A body of tissue that eventually develops into a primordial phallus, which develops into the penis or clitoris.

Question 11

Fetal testosterone reaches peak plasma levels at ____ weeks of gestation.

Answer 11

16

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.

Question 12

The 1st premordial follicle appears near the _______ month of gestation.

Answer 12

.4th

Question 13

The last oogonia enter meiosis at ____ months of gestation.

Answer 13

Seven

NOTE: The folliculogenesis doesn’t finish until about 6 months post partum but all of the oogonia are made

Question 14

In the absence of ________, gonadal cells have an inherent tendency to form ovarian-like structures.

Answer 14

TDF (Testis-differentiation factor)

Question 15

The maximum follicle formation period occurs during the peak plasma levels of fetal ___.

Answer 15

FSH

NOTE: We have follicles that go into atresia, others continue to grow, and the ovary keeps getting larger.

Question 16

______ stimulates the Leydig cells to secrete testosterone.

Answer 16

hCG