Sex Determination & Differentiation

Question 1

• Where in the embryo is the reproductive system formed from?

Answer 1

Mesoderm

Question 2

• What are the three levels of sexual dimorphism?

Answer 2

Genetic sex -> gonadal sex -> phenotypic sex

Question 3

• What chromosome must be present for the male gender?

Answer 3

Y chromosome

Question 4

• What hormone causes the external appearance of the penis and scrotum?

Answer 4

Dihydrotestosterone

Question 5

• What are the four phases of sexual development?

Answer 5

The pregonadal phase, the bipotential gonad, primary sexual differentiation, secondary sexual differentiation

Question 6

• How do primordial germ cells migrate from inner lining of the yolk sac to the gonadal ridge?

Answer 6

Amoeboid movement

Question 7

• What are the three embryonic renal systems?

Answer 7

Pronephros -> mesonephros -> metanephros

Question 8

• Which gut is important in the formation of components of the female reproductive system?

Answer 8

Paramesonephric duct

Question 9

• Which gut develops in the male and female, in order to determine the sex?

Answer 9

Male – Wolffian duct, Female – Mullerian duct

Question 10

• What is the function of anti-mullerian hormone (AMH)?

Answer 10

Causes leydig cells to differentiate

Question 11

• What is the fate of the mesonephric duct?

Answer 11

Becomes the epididymis and ductus deferens

Question 12

• What is important for masculinisation?

Answer 12

A peak of testosterone in early pregnancy

Question 13

• In ovary development, what forms the future infundibulum?

Answer 13

Paramesonephric duct, mesonephric duct regresses

Question 14

• In the female when is the number of germ cells determined?

Answer 14

Before birth

Question 15

• How does the gubernaculum aid in testicular descent?

Answer 15

Goes through a process of rapid expansion pulling the testis down through the inguinal ring, before regressing, pulling the testis further down towards the base of the scrotum

Question 16

• What hormone causes de-feminisation of the male brain?

Answer 16

Estradiol, in females alpha fetoprotein binds to estradiol and prevents it crossing BBB

Question 17

• What happens in freemartinism?

Answer 17

Female fetus exposed to AMH and testosterone from male fetus

Question 18

• What problems can occur with testicular descent?

Answer 18

Cryptorchidism, inguinal herniation and hypospadias (urethral opening at base of penis)