Reproductive tract embryology

Question 1

What is the default developmental status for the reproductive system?

Answer 1

Female (germ cells influence development of indifferent gonad)

Question 2

What tissue sources do the gonads develop from?

Answer 2

Gonadal ridge
Mesodermal epithelium
Primordial germ cells

Question 3

What is required in order for an indifferent gonad to develop into male testicles?

Answer 3

Expression of genes on the Y chromosome (e.g. Testis Determining Factor, TDF)
Testosterone

Question 4

What is androgen insensitivity syndrome?

Answer 4

Condition in which a genetically male individual (XY chromosomes) is resistant to androgens resulting in a genetic male with a normal female appearance - testicles are present but vagina ends as a blind pouch

Question 5

Are gonads intra- or retroperitoneal?

Answer 5

Retroperitoneal

Question 6

How does the location of the testes change throughout development?

Answer 6

Descend from the posterior abdominal wall, through the inguinal canal and into the scrotum - accompanied by the gubernaculum

Question 7

What can be the result of the testes failing to descend?

Answer 7

Cryptorchidism - generally get stuck in the inguinal canal region [most common]

Ectopic testicle - testes descends through inguinal canal but fails to end up in scrotum (instead can end up in the abdominal wall, thigh or peritoneum)

Question 8

How would undescended testes be managed?

Answer 8

Majority appear naturally within 3 months of birth but if not then must be corrected surgically

Question 9

What are the two genital ducts that go on to form male or female reproductive systems?

Answer 9

Mesonephric/ Wolffian (male)

Paramesonephric/ Mullerian (female)

Question 10

Where are the kidneys embyrologically derived from?

Answer 10

Metanephros

Question 11

What is the fate of the mesonephric duct in males and females?

Answer 11

Males: testosterone drives development of the mesonephric duct (at approx. 8 weeks) to become the epidydymis, ductus deferens, ejaculatory duct and seminal vesicle

Females: absence of testosterone causes spontaneous degeneration

Question 12

What is the fate of the paramesonephric duct in males and females?

Answer 12

Males: antimullerian hormone production by Sertoli cells in the testicles causes duct regression at approx. week 6/7

Females: persists and develops into uterine tubes which join to become the uterus and upper vagina

Question 13

What is an Appendix of testicle?

Answer 13

Embryological remnant of the paramesonephric duct if this fails to fully degenerate - generally asymptomatic but can cause cysts

[Nb. can be mistaken for tumour on testicle]

Question 14

What can remnants of the mesonephric duct in females result in?

Answer 14

Epoophoron (remnants around the ovary) 
Gartner duct (lateral to uterus and vaginal wall)

Both can result in cysts

Question 15

How does the female reproductive system form from the paramesonephric duct and what is the consequence of this going wrong?

Answer 15

Ducts move to the midline and fuse to form uterus, pulling with them a covering fold of peritoneum

Failure to do so can lead to uterine and vaginal malformations which can lead to amenorrhoea (failure to menstrate), subfertility or problematic pregnancies

Question 16

What is the perineal body?

Answer 16

Point of union between the pelvic floor and the perineal membrane, important for integrity of the pelvic floor and to provide support to the posterior vaginal wall.
Also an attachment point for the anal sphincter

Question 17

What is the result of maldevelopment of the anorectal region?

Answer 17

Imperforate anus (different forms including complete closure or opening into various parts of the urinary/ reproductive system)

Question 18

Where does the vagina develop from?

Answer 18

Uterovaginal primordium and the sinovaginal bulb or the urogenital sinus meet to form the vaginal plate which then canalises (opens) to form the vaginal lumen

Question 19

What is the consequence of failure of canalisation of the vaginal plate?

Answer 19

Vaginal atresia (no external opening) or transverse vaginal septa

Question 20

What is the fate of the hymen through development and what is the consequence of this failing?

Answer 20

Normally thin so ruptures in early life - failure requires surgical correction

Question 21

What does the urogenital/ urethral fold go on to develop in males and females?

Answer 21

Males: spongy urethra
Females: labia minora

Question 22

What does the labioscrotal swelling go on to develop in males and females?

Answer 22

Males: testosterone causes labioscrotal swelling to increase in size and fuse at the midline raphe to form the scrotum
Females: labia majora

Question 23

What does the genital tubercle go on to develop in males and females?

Answer 23

Males: penile glans and erectile tissue
Females: clitoris

Question 24

What is the result of malformation of the male urethra?

Answer 24

Can be open on dorsal or ventral penis

Hypospadias or epispadias (urethral opening on dorsal aspect; associated with other congenital abnormalities)