Development of the Genital System

Question 1

What does the genital ridge develop from?

Answer 1

Intermediate mesoderm

Question 2

Primordial germ cells are where and form what?

Answer 2

Go to genital ridges, form the primitive sex cords

Question 3

Primitive sex chords in males go on to form

Answer 3

Testis cords

These comprise of sertoli cells (epithelial origin) and germ cells

Question 4

What do Leydig cells do

Answer 4

Found between the cords, produce testosterone from week 8

Question 5

What happens to the sex cords in females?

Answer 5

The primitive sex cords regress

The cortical cords develop. These cords divide into groups of cells that surround the germ cells

Question 6

What is the primordial follicle (females) comprised of?

Answer 6

Germ cells and surrounding cells (derived from cortical cords)

Question 7

The gonad is identical in both males and females until week…

Answer 7

7

When they are still undifferentiated, there are two pairs of ducts - mesonephric (Mullerian) and paramesonephric ducts (Wollfian).

Question 8

What gene drives male development

Answer 8

SRY (Sex-determining Region on Y chromosome)

Causes development of testes
Produces testosterone, which also contributes to driving development

Question 9

What does anti-Mullerian hormone do in males?

Answer 9

Actively suppresses development of paramesonephric ducts. (stops development of uterus and uterine tubes)

Question 10

What factors contribute to female development?

Answer 10

Absence of SRY

WNT4 gene required for ovarian development (not well understood)

Oestrogen causes female differentiation.
Paramesonephric ducts develop.

Question 11

What do the mesonephric ducts form?

Answer 11

Under influence of testosterone, forms the vas deferens.
Distal end opens into urogenital sinus, is absorbed by bladder wall. Ureter and duct enter separately.

Duct opens into part which is prostatic urethra - forms ejaculatory duct.

Prostate develops around ejaculatory ducts.

Seminal vesicle develops from vas deferens

Question 12

What hormone is released by the sertoli cells?

Answer 12

anti-Mullerian hormone (causes regression of paramesonephric ducts).

Produced in males

Question 13

What does the upper part of the paramesonephric duct form?

Answer 13

Uterine tubes

Question 14

What is formed when the caudal ends of the paramesonephric ducts fuse together?

Answer 14

Uterus, cervix, upper vagina

Question 15

In females, which ducts regress?

Answer 15

Mesonephric ducts

Question 16

What happens to the lower part of the paramesonephric ducts in females?

Answer 16

contact the urogenital sinus, grow into the sinovaginal bulbs and allow lumen to develop.

Question 17

Atresia (absence) of the lower part of vagina happens if

Answer 17

the sinovaginal bulbs don’t develop

Question 18

What happens if the paramesonephric ducts don’t fuse together? (rare)

Answer 18

Didelphys (duplication)

Question 19

What happens if there is only partial fusion of the paramesonephric ducts?

Answer 19

Bicornuate

Question 20

What happens if only one paramesonephric duct develops?

Answer 20

Unicornuate

Question 21

What happens if the uterine septum doesn’t regress?

Answer 21

Septate

Question 22

What does oestrogen cause in female development of external genitalia?

Answer 22

Genital tubercle -> clitoris

urethral folds -> labia minora

urethral groove -> vestibule

genital swellings -> labia majora

Question 23

What does testosterone cause in male development of external genitalia?

Answer 23

genital tubercle -> elongates into penis

urethral folds -> fuse into penile urethra

genital swellings -> scrotum

Question 24

What is hypospadias?

Answer 24

The urethral folds don’t fuse properly

Urethral opening is on the ventral surface of the penis

Question 25

What is ambiguous genitalia

Answer 25

External genitalia aren’t clearly or typically male or female.

Arise due to conditions called Disorders of Sex Development