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Flashcards in embryology Deck (22):
1

what does the urogenital tract originate from?

intermediate mesoderm

2

what are the three sets of kidney structures during development

Pronephros -cervical region
mesonephros - abdo region
Metanephros - pelvic region

3

features of pronephros

rudimentary and non functional
7-10 solid cells in the cervical region
regresses by week 4

4

features of mesonephros

derived from intermediate mesoderm from the upper thoracic and upper lumbar segments
week 4 after regression of the pronephros the first excretory tubules appear
contributes supporting cells to genital ridge

5

metanephros

appears in week 5 and is functional by week 11
excretory units develop from the metanephric mesoderm
formed from 2 parts - uteric bud and metanephric cap

6

what does the definitive kidney develop from

metanephric mesoderm- excretory units
uteric duct - collecting system

7

what divides the cloaca

the urorectal septum divides the cloaca by fusion with colaca membrane to form the
- anterior urogenital sinus
posterior rectal /anal canal

8

bladder forms from the ...

urogenital sinus and caudal parts of the mesonephric duct

9

what is the cloaca

posterior orifice that serves a the only opening for the intestinal , reproductive and urinary tracts at early stages

10

define uteric bud

protrusion of the mesonephric duct
allows urine drainage from the developing kidney

11

allantois is what?

sac like structure involved in nutrition and excretion
evagination of hind gut

12

urachus?

duct between bladder and yolk sac , forms from the allantois at 5-7 weeks

13

male female indifferent stage

2 genital ducts
- mesonephric (wolffian)-male duct system (regresses in the female due to absence of testosterone
- paramesonephric (mullerian ) female duct system ( regress in male due to antimullerian hormone

14

where do primordial germ cells originate from

yolk sac and move to the genital ridge via dorsal mesentery

15

development of the testes

due to the sex determining region of Y chromosome which acts on the bipotential gonad
- AMH produced by sertoli cells causes regression of mullerian duct
- testosterone from leydig cells acts on mesonphric duct to progress into the ejaculatory duct and internal genitalia
-dihydrotestosterone is the active form of testosterone (converted by 5 alpha reductase ) causes development of external

16

what is the ovary determining gene

WNT4

17

what do primordial germ cells arrange into

primitive sex cords

18

variations with female development reproductive tract

double uterus - failure of fusion
bicornuate uterus

vaginal atresia - failed canalisation

absence of vagina and uterus - failure of sinovaginal bulbs

19

klinefelters

1 in 400 mlaes
infertility , gynaecomastia , impaired sexual maturation
leydig cells do not produce enough steriods. low sperm count

20

testicular feminising hormone

genetic males - 46 XY
Female external phenotype , internal testes
testes produce testosterone but a mutation on the X chromosome causes a deficiency in androgen receptors
testosterone cannot act on target tissues . uterus and upper vagina are absent cause AMH is present

21

turners syndrome

Sex chromosome XO
primordial germ cells degenerate shortly after arrival at the ridge
failure of gonadal development - infantile genitalia , mesenephric duct regression

22

dihydrotestosterone

small community of dominican republic - high incidence of inhabitants lacked the gene for 5 alpha reductase . XY children looked like girls - blind vaginal pouch , enlarged clitoris , internal testes