Development of the Reproductive System

Question 1

What is the indifferent stage of gonadal development?

Answer 1

Initial stage

Undifferentiated gonads - cannot distinguish male and female

Question 2

Where do the gonads begin development?

Answer 2

Genital ridges = pair of longitudinal ridge derived from intermediate mesoderm and overlying epithelium

Question 3

From where do germ cells migrate into the gonads?

Answer 3

Endoderm lining of yolk sac

Question 4

When do the germ cells migrate to the gonads?

Answer 4

Weeks 4-6

Question 5

How are the primitive sex cords formed?

Answer 5

Proliferation of epithelium of genital ridge

Penetrates intermediate mesoderm

Question 6

Which gene on the Y chromosome stimulates the formation of the testis cords?

Answer 6

SRY gene

Question 7

What is the tunica albuginea?

Answer 7

Fibrous connective tissue layer that forms over testis cords

Question 8

What do the testis cords form?

Answer 8

Rete testis
Germ cells
Sertoli cells

Question 9

When do the seminiferous tubules form?

Answer 9

During puberty

Question 10

How do the seminiferous tubules form?

Answer 10

Testis cords acquire lumen

Question 11

What do the seminiferous tubules do?

Answer 11

Site of sperm production

Question 12

Where are the Leydig cells in the developing embryo?

Answer 12

Between testis cords

Question 13

What do the Leydig cells do?

Answer 13

Produce testosterone

Question 14

What happens to the primitive sex cords in the female embryo?

Answer 14

Degenerate

Question 15

What forms the cortical cords in the female embryo?

Answer 15

Proliferation of epithelium of gonads

Question 16

How do the primordial follicles of the ovaries form?

Answer 16

Cortical cords break into clusters, surrounding each oogonium with layer of epithelial follicular cells

Question 17

What is an oogonium?

Answer 17

Germ cell

Question 18

When do the primordial follicles form?

Answer 18

Month 3

Question 19

What are the two pairs of ducts, ending at the cloaca, that all embryos have at the initial stage of urogenital development?

Answer 19

Mesonephric/Wolffian ducts

Paramesonephric/Mullerian ducts

Question 20

What happens to the mesonephric ducts in male embryos?

Answer 20

Mesonephric ducts develop into primary male genital ducts in presence of testosterone
Give rise to
- Efferent ductules
- Epididymis
- Vas deferens
- Seminal vesicles

Question 21

What happens to the paramesonephric ducts in male embryos?

Answer 21

Degenerate in presence of anti-Mullerian hormone

Question 22

Which cells in the male embryo produce anti-Mullerian hormone?

Answer 22

Sertoli cells

Question 23

What is the remnant of the paramesonephric ducts in males?

Answer 23

Appendix testis

Question 24

What happens to the mesonephric ducts in female embryos?

Answer 24

Degenerate in the absence of testosterone

Question 25

What is the remnant of mesonephric ducts in female embryos?

Answer 25

Gartner's duct

Question 26

What happens to the paramesonephric ducts in female embryos?

Answer 26

``` Develop in absence of anti-Mullerian hormone Form - Uterine/Fallopian tubes - Uterus - Cervix - Upper 1/3 of vagina ```

Question 27

What forms the lower 2/3 of the vagina?

Answer 27

Sinovaginal bulbs, derived from pelvic part of urogenital sinus

Question 28

How do the external genitalia form during the indifferent stage of reproductive embryological development?

Answer 28

Mesenchymal cells from primitive streak migrate to cloacal membrane > form pair of cloacal folds Cranially, cloacal folds fuse > genital tubercle Caudally, cloacal folds divide into - Urethral folds, anteriorly - Anal folds, posteriorly Genital swellings develop either side of urethral folds

Question 29

What drives the formation of indifferent genitalia into male external genitalia?

Answer 29

Androgens from testes, mainly dihydrotestosterone (DHT)

Question 30

What forms the phallus in male embryos?

Answer 30

Genital tubercle

Question 31

What forms the urethral groove in male embryos?

Answer 31

Urethral folds

Question 32

What is derived from the urethral groove in male foetuses?

Answer 32

Penile urethra

Question 33

From what is the scrotum derived?

Answer 33

Genital swellings > scrotal swellings

Question 34

What drives formation of indifferent genitalia into female external genitalia?

Answer 34

Oestrogens

Question 35

What forms the clitoris in female embryos?

Answer 35

Genital tubercle

Question 36

What forms the labia minora in female foetuses?

Answer 36

Urethral folds

Question 37

What forms the labia majora in female foetuses?

Answer 37

Labia majora

Question 38

What forms the vestibule into which the urethra and vagina open?

Answer 38

Urogenital groove

Question 39

What is the gubernaculum?

Answer 39

Ligamentous structure tethering gonads to scrotum/labia

Question 40

When do the testes pass through the inguinal canal?

Answer 40

During week 28

Question 41

By when do the testes reach the scrotum?

Answer 41

Week 33

Question 42

What is the adult remnant of the gubernaculum in males?

Answer 42

Scrotal ligament

Question 43

What is the adult remnant of the gubernaculum in females?

Answer 43

Ovarian ligament | Round ligament of uterus