Embryology of Reproductive System

Question 1

Where is the testis-determining factor?

Answer 1

on the short arm of the Y chromosome

Question 2

What makes the genital ridges?

Answer 2

germ cells migrate to the posterior wall via dorsal mesentery and induce coelomic epithelium to form sex cords that proliferate creating the genital ridges

Question 3

What 2 parts make up the sex cords?

Answer 3

1. Medullary region

2. cortical region

Question 4

What do sex cords become in males vs females?

Answer 4

males=sertoli cells of germinal epithelium in seminiferous tubules
females=ovarian follicles

Question 5

Can sex cords develop without germ cells?

Answer 5

NO! and without sex cords there will be no germ cell maturation

Question 6

What is present at the end of the indifferent stage?

Answer 6

paramesonephric ducts, mesonephric ducts, primary UG sinus, and gonads

Question 7

What genes are involved in sertoli cell production?

Answer 7

On the Y chromosome is the SRY gene that up regulates SF1 which acts through SOX9 in the sex cords causing them to differentiate into sertoli cells

Question 8

What do sertoli cells produce?

Answer 8

anti-mullerian hormone

Question 9

what happens if SRY is not present?

Answer 9

then we get differentiation into oogonia and follicle cells leading to a lack of sertoli cells and no anti-Mullerian hormone

Question 10

What genes are involved in early ovary development?

Answer 10

WNT4, DAX1 and FoxL2.
- WNT4 is produced by the mesonephric mesenchyme and coelomic epithelium and up regulates Dax1 which causes the cortical sex cords to differentiate into oogonia and follicle cells. FoxL2 is expressed in pregranulosa and granulosa cells

Question 11

What does AMH cause?

Answer 11

degeneration of paramesonephric ducts and cells in the gonadal ridge to become leydig cells which produce testosterone dihydrostestosterone.

Question 12

What causes production of sex determination (ducts) in males?

Answer 12

AMH and testosterone (mainly T)

Question 13

What gives rise to the male genital duct system?

Answer 13

mesonephric duct. If AMH is present, paramesonephric duct degenerates. AMH also causes development of leydig cells which make testosterone that binds to receptors in the mesonephric duct and initiates its development into male genital duct system

Question 14

In the male, what is the role of DHT?

Answer 14

prostate development and external genitalia into a penis and scrotum

Question 15

What gives rise to the female genital duct system?

Answer 15

paramesonephric duct. In absence of AMH, mesonephric duct degenerates because of lack of testosterone. Paramesonephric develops into the uterine tubes, uterus, cervix, and upper 1/3rd of the vagina with the help of estrogen from maternal adrenal and placenta

Question 16

What does the uterovaginal canal give rise to in the female?

Answer 16

uterine tubes and upper 1/3 of the vagina

Question 17

What does the UG sinus give rise to in the female?

Answer 17

pelvic urethra

Question 18

What does the pelvic urethra give rise to in the female?

Answer 18

sinovaginal bulbs that develop into lower 2/3 of the vagina

Question 19

What does the genital tubercle give rise to?

Answer 19

Male: glans and shaft of penis
Female: glans and shaft of clitoris

Question 20

What does the def. UG sinus give rise to?

Answer 20

Male: penile urethra
Female: vestibule of vagina

Question 21

What do the urethral folds become?

Answer 21

Male: penis
Female: labia minora

Question 22

What do the labioscrotal folds become?

Answer 22

Male: scrotum
Female: labia majora

Question 23

What is hypospadias?

Answer 23

When the urethral folds fail to fuse in the midline so the urethra exits the penis midshaft.

Question 24

What is the time difference in phenotypic sexual differentiation vs brain sexual differentiation?

Answer 24

Phenotypic: first 2 months of pregnancy
Brain: 2nd half of pregnancy