Embryology

Question 1

what sets up the body axis during development?

Answer 1

the formation of the primitive streak

Question 2

what occurs during gastrulation?

Answer 2

formation of the three primary germ layers

Question 3

where do the urogenital systems arise from in an embryo?

Answer 3

the intermediate mesoderm

Question 4

where do the excretory ducts of the urogenital system enter during development?

Answer 4

the cloaca

Question 5

what goes on to form the reproductive system in the embryo?

Answer 5

the genital ridge

medial part of the urogenital ridge

Question 6

what is the first stage of genital development called and why?

Answer 6

the indifferent stage

no anatomical indications of sex until week 7

Question 7

when does the indifferent stage occur?

Answer 7

weeks 4-6

Question 8

what are PGC’s?

Answer 8

primordial germ cells

Question 9

what happens at the beginning of the indifferent stage?

Answer 9

PGC’s from the yolk sac migrate to the intermediate mesoderm

via the dorsal mesentery

Question 10

how are the genital ridges formed during the indifferent stage?

Answer 10

coelomic epithelium proliferates and thickens

Question 11

what does proliferation of epithelium in the genital ridges form?

Answer 11

the primitive sex cords

Question 12

what enters the primitive sex cords once they have developed?

Answer 12

PGC’s

Question 13

what do the PGC’s in the sex cords give rise to?

Answer 13

the ova and sperm

Question 14

what is the second phase in genital development?

Answer 14

ambisexual/bipotential phase

Question 15

what happens during the ambisexual phase?

Answer 15

the genital ducts develop

Question 16

what are the two sets of genital ducts present in all embryos?

Answer 16

mesonephric ducts

paramesonephric ducts

Question 17

what is another name for the mesonephric dust?

Answer 17

Wollfian ducts

Question 18

what is another name for the paramesonephric ducts?

Answer 18

Mullerian ducts

Question 19

what genitals do the mesonephric ducts give rise to?

Answer 19

male genitalia

Question 20

what genitals do the paramesonephric ducts give rise to?

Answer 20

female genitals

Question 21

what mark the ambisexual phase of development?

Answer 21

genital ducts

indifferent gonads

Question 22

when does sexual differentiation occur in a foetus?

Answer 22

week 7 onwards

Question 23

in female development, what do the germ cells differentiate into?

Answer 23

oogonia

then into primary oocytes

Question 24

in female development, what do somatic support cells differentiate into?

Answer 24

granulose cells

these surround primary oocytes

Question 25

what is formed when granulosa cells surround the primary oocytes?

Answer 25

primordial follicles

Question 26

what causes female development to begin in an foetus?

Answer 26

absence of the SRY transcription factor

Question 27

what does the surface epithelium surrounding a developing ovary give rise to?

Answer 27

the cortical cords

Question 28

what is another name for the cortical cords?

Answer 28

the secondary sex cords

Question 29

what happens as the cortical cords grow?

Answer 29

PGC's are incorporated into them proliferate and arrest in prophase I

Question 30

alongside the primordial follicles, what else is produced by the female gonad during development?

Answer 30

theca cells

Question 31

what are thecal cells?

Answer 31

essentially endocrine cells associated with the follicles

Question 32

do the thecal cells produce?

Answer 32

androgen required to build oestrogen in the ovaries

Question 33

what effect does presence of oestrogen have during female development?

Answer 33

stimulates formation of female external genitalia and the development of the paramesonephric ducts

Question 34

what do the paramesonephric ducts give rise to in female development?

Answer 34

uterine tubes uterus superior vagina

Question 35

what are the three parts of the paramesonephric ducts?

Answer 35

cranial portion horizontal portion caudal portion

Question 36

what happens to the cranial portion of the paramesonephric ducts?

Answer 36

opens into the coelomic cavity

Question 37

what happens to the horizontal portion of the paramesonephric ducts?

Answer 37

crosses the mesonephric duct

Question 38

what happens to the caudal portion of the paramesonephric ducts?

Answer 38

fuses with the opposite paramesonephric duct

Question 39

what happens to the mesonephric ducts in females?

Answer 39

eventually regress

Question 40

what is the fused portion of the caudal mesonephric ducts called?

Answer 40

uterovaginal canal

Question 41

what does the uterovaginal canal give rise to?

Answer 41

uterus | superior vagina

Question 42

what creates the vaginal lumen?

Answer 42

vacuolisation of the paramesonephric portion of the vagina

Question 43

what are some possible congenital abnormalities that can arise during female development?

Answer 43

double uterus double vagina cervical atresia

Question 44

in male development, what do the somatic support cells develop into?

Answer 44

Sertoli cells

Question 45

what do the primary sex cords form during male development?

Answer 45

testis medullary cords these engulf the PGC's

Question 46

what connects the mesonephric tubules to the testis cords during male development?

Answer 46

rete testis

Question 47

what forms between the coelomic epithelium and testis cords during male development?

Answer 47

tunica albuginea a thickened layer of connective tissue

Question 48

what do Sertoli cells secrete during development?

Answer 48

anti-mullerian hormone (AMH)

Question 49

what does AMH do?

Answer 49

causes degeneration of the paramesonephric duct

Question 50

what effect do Sertoli cells have on the gonadal ridge cells during development?

Answer 50

stimulate them to form leydig cells

Question 51

what do Leydig cells do during development?

Answer 51

secrete testosterone

Question 52

what effects does testosterone have during development?

Answer 52

induces formation fo the epididymis, vas deferent and seminal vesicles

Question 53

what effect does dihydrotestosterone have during development?

Answer 53

induces male specific external genitalia development and development of the prostate

Question 54

what happens in persistent mullerian duct syndrome?

Answer 54

the paramesonephric ducts fail to regress

Question 55

how does persistent mullerian duct syndrome present?

Answer 55

have a uterus, vagina and uterine tubes testes where ovaries would be male external genitalia

Question 56

what moves the testes caudally during development?

Answer 56

the gubernaculum

Question 57

what is it called if the testes fail to descend/

Answer 57

cryptorchidism

Question 58

what develops near the junction of the mesonephric duct and urethra during week ten of male development?

Answer 58

three accessory glands

Question 59

what three accessory glands are produced at week 10 in males?

Answer 59

prostate and bulbourethral glands | seminal vesicle

Question 60

what forms the prostate and bulbourethral glands?

Answer 60

endodermal invaginations from the urethra

Question 61

what does the seminal vesicle develop from?

Answer 61

mesonephric duct