1.1 Development of the Reproductive Tracts

Question 1

What is sexual dimorphism?

Answer 1

A fetus has two potential outcomes- male or female

Question 2

Which germ layer are the gonads derived from?

Answer 2

Intermediate mesoderm and primordial germ cells

Question 3

What are primordial germ cells?

Answer 3

A special cell population

They arise in the yolk sac wall and migrate into the retroperitoneum along the dorsal mesentry

Question 4

What happens in a fetus with XY chromosomes?

Answer 4

SRY genes on the Y chromosome are expressed and drive development of testis and external male genitalia

Question 5

What happens in a fetus with XX chromosomes?

Answer 5

Primordial germ cells develop into ovaries and internal and external female genitalia

Question 6

Name the 2 duct systems present in an early fetus

Answer 6

Paramesonephric (Mullerian) ducts

Mesonephric (Wolffian) ducts

Question 7

What non-repro function does the mesonephric duct have?

Answer 7

Formation of the embryonic kidney

Question 8

What happens to the 2 duct systems in males?

Answer 8

Testis develop and release androgens
Testosterone supports the mesonephric duct
Testis secrete Mullerian Inhibiting Substance (MIS) which makes the paramesonephric ducts regress

Question 9

What happens to the 2 duct systems in females?

Answer 9

Ovary develops so no androgens are released
Mesonephric duct not supported so regresses
No MIS so paramesonephric duct remains

Question 10

What 3 things make up the indifferent external genitalia at week 7?

Answer 10

Genital tubercle
Genital folds
Genital swellings

Question 11

How does the external genitalia develop in the male?

Answer 11

Dihydrotestosterone causes the genital tubercle to elongate and the genital folds to fuse forming the spongy urethra and the glans penis
The genital swellings grow to become the scrotum

Question 12

How does the external genitalia develop in the female?

Answer 12

Genital tubercle becomes the clitoris
Genital fold becomes the labia minora
The genital swelling becomes the labia majora

Question 13

Describe the pathway of the descent of the testis

Answer 13

Retroperitoneal testis move down the abdominal wall and through the inguinal canal to rest in the scrotum

Question 14

Describe the pathway of the descent of the ovaries

Answer 14

Ovary descends down the abdominal wall retroperitoneally and rests in the pelvis
DOES NOT enter the inguinal canal