Development Of Reproductive Tracts

Question 1

What happens 30 hours after fertilisation?

Answer 1

Fertilised egg splits into two blastomeres

Question 2

How many divisions until the oocyte becomes the morula?

Answer 2

4 (16 cells)

Question 3

What structure originating from the hindgut becomes the common opening of the reproductive and urinary tracts?

Answer 3

Cloaca - Urogenital sinus

Question 4

How does the SRY region of the Y chromosome determine sex?

Answer 4

Producing a transcription factor initiating a cascade of downstream genes (testis determining factor TDF)

Question 5

What is the first step of the development of the reproductive system?

Answer 5

Primordial germ cells migrate along retro peritoneum to the gonad at the urogenital ridge

Question 6

What three sources make up the gonad?

Answer 6

Mesothelium
Underlying mesenchyme
Primordial germ cells

Question 7

Which cords develop in males?

Which cords develop in females?

Answer 7

Medullary cords

Cortical cords

Question 8

Which duct persists in males?

Which duct persists in females?

Answer 8

Mesonephric (Wolffian) duct

Paramesonephric (Mullerian) duct

Question 9

What structures does the mesonephric duct become if stimulated by androgens?

Answer 9

Rete testis and vas deferens

Question 10

What dictates the prescence of each duct?

Answer 10

Mesonephric - prescence of androgens from testes

Paramesonephric- abscence of androgens and MIH secreted by testes

Question 11

How do the male external genitalia form?

Answer 11

Genital tubercle elongates
Genital folds fuse to form spongy urethra
Genital tubercle develops into glans penis

Question 12

How do the external genitalia of the female form?

Answer 12

No fusion of genital folds gives rise to labia majors and minora
Genital tubercle develops into clitoris

Question 13

What drives the descent of the gonads in males and females? Why can the female genitalia not descend?

Answer 13

Gubernaculum (caudal genital ligament)

Uterus prevents descent of the ovary in females, and the gubernaculum degenerates forming the round ligament

Question 14

What does a person of 45X0 makeup suffer from?

What are the clinical signs?

Answer 14

Turners syndrome

Short stature, high arched palate, webbed neck, shield like chest, cardiac and renal abnormalities, inverted nipples

Question 15

What is Klinefelter syndrome?

What are some clinical signs?

Answer 15

Karyoptype 47 XXY or XXXY etc
Decreased fertility
Small testes
Low testosterone levels
Gynecomastia (enlarged breasts) in 33%

Question 16

What is the most common cause of ambiguous genitalia?

Answer 16

Congenital adrenal hyperplasia - genetically female but exposed to androstenedione by the adrenal glands causing external masculisation of genitalia

Question 17

What’s the most common cause of sexual ambiguity in males?

Answer 17

Androgen insensitivity syndrome - lack of androgen receptors in tissue
Note: testes still produce MIH so paramesonephric system is still supressed