7. ectopic pregnancy (lecture) Flashcards
what causes ectopic pregnancy?
failure of transport of morula into uterus
implantation in fallopian tube, ovary or peritoneal cavity
what is the major risk of ectopic pregnancy?
risk of maternal haemorrhage
what happens to the embryo in ectopic pregnancy?
embryo is non-viable
unable to survive independently after birth
when does the blastocyst stage appear?
5 days after fertilisation
blastocyst cavity
what is the blastocyst cavity?
fluid-filled cavity develops in morula (blastocoele)
what does the blastocyst stage mark?
loss of totipotency
what is the inner cell mass known as? what does it go onto become?
embryoblast –> embryo
what is the outer cell mass known as? goes onto become?
trophoblast
contributes to formation of placenta and produces hCG
what is hatching?
local digestion of zona pellucida by enzyme produced in trophoblast cells
where does hatching occur?
opposite the inner cell mass (embryoblast)
why does hatching occur opposite the inner cell mass?
minimise the risk of enzymatic damage to the embryo
what happens after the blastocyst has hatched?
escaped from ZP
blastocyst begins process of implantation
when does implantation occur?
zygote (fuse of male and female perinucleus) –> blastocyst (no longer totipotent)
days 14-21 of uterine cycle
what happens prior to implantation?
progesterone priming of endometrium (progesterone prepares the lining of endometrium - further thicken)
conceptus nourished in intrauterine fluid (2-3days ‘floating’ in uterus)
when does implantation commence?
6 days after ovulation
