6. Development of the Genital System (Brauer)

Question 1

When is the earliest that ultrasound-based sex determination can occur?

Answer 1

Week 12.

Question 2

Where do the genital ducts form?

Answer 2

Within the intermediate mesoderm of the urogenital ridge.

Question 3

What reproductive organs form from the mesonephric duct?

Answer 3

Epididymis.

Vas deferens.

Seminal vesicles.

Ejaculatory duct.

Question 4

What reproductive organs form from the paramesonephric duct?

Answer 4

Oviduct.

Uterus.

Upper vagina.

Question 5

What gene drives male phenotype?

Answer 5

SRY

Question 6

What forms from the somatic support cells in males and females respectively?

Answer 6

Male: Sertoli cells.

Female: follicle cells.

Question 7

When is SRY/testis determining factor active?

Answer 7

Days 41-52

Question 8

Where is SRY (TDF) expressed?

Answer 8

In the somatic support cells of the male.

Question 9

What are the functions of the early Sertoli cells in the development of the testis?

Answer 9

The early Sertoli cells surround the primordial germ cells and organize seminiferus tubule.

The early Sertoli cells also recruit a subset of intratubular cells to differentiate into fetal Leydig cells.

Question 10

How is the paramesonephric duct inhibited in males?

Answer 10

SRY -> SOX9 -> anti-müllerian hormone.

Question 11

When does the paramesonephric duct regress in males?

Answer 11

Between weeks 8 and 10

Question 12

What are the remnants of the paramesonephric duct in males?

Answer 12

Appendix testis.

Prostatic utricle.

Question 13

Testosterone drives mesonephric ducts to form what structures in males?

Answer 13

Efferent ductules.

Epididymis.

Vas deferens.

Seminal vesicles.

Question 14

What cell type secretes anti-müllerian hormone?

Answer 14

Sertoli cells.

Question 15

What two hormones are secreted by Sertoli cells?

Answer 15

Anti-müllerian hormone.

Androgen binding factor (initiates spermatogenesis).

Question 16

What is the function of 5 α-reductase?

Answer 16

Conversion of testosterone to dihydrotestosterone.

Question 17

Dihydrotestosterone is responsible for which three structural conversions in males?

Answer 17

Genital tubercle -> penis.

Genital swellings -> scrotum.

Urethral epithelium -> prostate.

Question 18

From which germ layer are the seminal vesicles and vas deferens derived?

Answer 18

Intermediate mesoderm.

Question 19

From which germ layer is the prostate gland derived?

Answer 19

Endoderm.

Question 20

During what week is the prostate gland formed?

Answer 20

Week 10.

Question 21

From which germ layer are the bulbourethral glands derived?

Answer 21

Endoderm.

Question 22

At what vertebral level do the male and female gonads first develop?

Answer 22

T10

Question 23

What pro-female gene is expressed in the absence of SRY?

Answer 23

WNT-4

Question 24

What is the function of FOXL2?

Answer 24

Suppression of SOX9, and thereby maintaining the female gonad by suppressing Sertoli and Leydig cell differentiation.

Question 25

What embryological layers form the vagina?

Answer 25

The upper vagina (from the paramesonephric/müllerian duct) comes from mesoderm.

The lower vagina (from the sinuvaginal bulb) comes from endoderm.

Question 26

What structure results from the superior gubernaculum?

What structure results from the inferior gubernaculum?

Answer 26

The round ligament of the ovary.

The round ligament of the uterus.

Question 27

Describe androgen insensitivity syndrome.

Answer 27

The patient is a male genetically, and has testes.

Testosterone is metabolized to estradiol at puberty, initiating female secondary characteristics.

The paramesonephric system is suppressed due to the presence of anti-müllerian hormone, therefore the patient has no uterus or uterine tube – but does have a short blind ended vagina.

Question 28

Describe 5 α-reductase deficiency.

Answer 28

Genetically male with a normal testis and duct system due to normal presentation of anti-müllerian hormone and testosterone.

However the patient has underdeveloped mail external genitalia or possibly even an external female phenotype.

This is due to the inability to convert testosterone -> dihydrotestosterone.

Question 29

What is the most common cause of female sexual ambiguity?

Answer 29

Congenital adrenal hyperplasia.

Question 30

Describe ovotesticular disorders.

Answer 30

A patient with an ovotesticular disorder has both testicular and ovarian tissue. This could be due to translocation of a piece of a Y chromosome onto the X chromosome, or an inactivation mutation in some Y chromosomes.

For these patients, the “true facts” of these individuals is the one they can best adapt into society.

Question 31

What embryological layer gives rise to the somatic support cells of the indifferent gonad?

Answer 31

The somatic layer of the lateral plate mesoderm.

Question 32

Where do the primordial germ cells originally come from?

Answer 32

The epiblast.

Question 33

Proliferation of the primordial germ cells causes delamination and formation of somatic support cells from what previous cell type?

Answer 33

Coelomic epithelium.

Question 34

During what week do the primitive germ cells enter the genital ridge?

Answer 34

6th week.

Question 35

What is a Gartner’s cyst?

Answer 35

A cyst on the lateral wall of the vagina, which is a remnant of the mesonephric duct.

Question 36

What is the navicular fossa?

Answer 36

An invagination of the surface ectoderm of the penis which allows the urethra to open into the outside environment.