3 Development of Reproductive Tracts

Question 1

Which part of the gut tube gives rise to the cloaca?

Answer 1

Hindgut

(Gut tube= foregut, midgut and hindgut)

Question 2

What does the cloaca become?

Answer 2

Urogenital sinus

(Common opening ofr reproductive and urinary systems)

Question 3

What is the urogenital ridge?

Answer 3

Area of intermediate mesoderm

Gives rise to embryonic kidney and gonad

Question 4

What are the primordial germ cells and what do they do?

Answer 4

• Specialied cells- arise from yolk sac
• Develop soon after gastrulation
• Produce sperm and ova once sexual maturation has occured

Question 5

What determines the differentiation of the gonad?

Answer 5

Karyotype of fertilised oocyte (XX or XY)

Question 6

The Y chromosome contains genes in a region that cause differentiation fo the gonad into a testis. What is the name of that region?

Answer 6

SRY gene

–> leads to formation of seminiferous tubules

Question 7

If the SRY region is absent (ie no Y chromosome), what will the gonad differentiate into?

Answer 7

Ovary- no tubules develop

Question 8

The testes in the embryo produce androgens (testosterone). What do these androgens drive the development of?

Answer 8

Duct system in men:

• Epididymis
• Vas deferens

(maintain mesonephric duct- fuses with testes)

Question 9

What is another name for the mesonephric duct?

Answer 9

Wolffian duct

Question 10

What happens to the mesonephric duct in the absence of male androgens?

Answer 10

It degenerates

Question 11

In females the mesonephric duct degenerates and the formation of the internal female genitalia occurs (uterus, fallopian tubes, parts of vagina). Which duct remains?

Answer 11

Paramesonephric duct

(Mullerian duct)

(doesn’t require stimulation)

Question 12

Why is there no Mullerian duct (paramesonephric duct) in males?

Answer 12

Mullerian Inhibitory Substance (MIH) produced by testes- prevent duct developing

Question 13

Why is there a gap between the fallopian tubes and the ovaries which persists in adulthood?

Answer 13

Mullerian duct (paramesonephric duct) doesnt fuse with gonad

Question 14

What are the 3 undifferentiated elements of external genitalia?

Answer 14

1. Genital tubercle
2. Genital folds
3. Genital swellings

Question 15

How are the penis and scrotum formed from the undifferentiated external genitalia?

Answer 15

Penis: Elongation and fusion of genital folds

Scrotum: Fusion of genital swellings

Question 16

How do the vulva, labia minor and labia majora form from the undifferentiated external genitalia?

Answer 16

Absence of testes- no fusion of genital folds or swellings

Question 17

Describe the descent of the testes.

Answer 17

Will be connected to the scrotum by gubernaculum

Area of peritoneum (processes vaginalis) pinches off (eventually closes)

Question 18

Describe the descent of the ovaries.

Answer 18

Area of peritoneum picnhes off pinches off

Gubernaculum guides ovaries down

Remains as round ligament in women

Stays in pelvis due to barrier of developing uterus

Question 19

What can happen as a consequence of the processus vaginalis remaining patent?

Answer 19

Connection to peritoneal cavity

Route for hernias to occur

Question 20

What is it important to remember to examine on new born babies in relation to the descent of the testes?

Answer 20

Check that they are loacted in the scrotum and haven’t decended along an ectopic path- may require surgical correction

Question 21

Along which structure do the primordial germ cells migrate?

Answer 21

Along dorsal mesentery into retroperitoneum

Question 22

What happens to the mesonephric and paramesonephric ducts in Androgen Insensitivity Syndrome?

Answer 22

Receptors for testosterone don’t work

Wolffian ducts don’t survive

Mullerian ducts degenerate as MIH present

Question 23

What happens if a female embryo receives exogenous testosterone?

Answer 23

Question 24

What problems can present due to maldescent of the testes?

Answer 24

• Infertility (too hot for spermatogenesis)
• Increased risk- testicular torsion
• Increased risk- testicular cancer

Question 25

If a baby has an XY genotype but their fetal genitalia is insensitive to testosterone, what would you expect their internal and external genitalia to be like?

Answer 25

Internal: Testes present BUT no ducts

External: Female (as default) BUT blind ended, short vagina

Question 26

What embryological orgins do the upper and lower vagina have?

Answer 26

• Upper: paramesonephric ducts
• Lower: external genitalia

Question 27

A baby is born with XX genotype but has excessive secretion of androgens from the adrenal glands. What would you expect to see from their external and internal genitalia?

Answer 27