Implantation, Placentas and Hormonal Changes in Pregnancy Flashcards
what is the trophoblast
Cells of the blastocyst that invade the endometrium and myometrium and will become the placenta.
The trophoblast secretes beta-hCG initially
what is the chorion
the outermost membrane surrounding an embryo.
goes on to become placenta
what is the amnion
the amniotic sac in which the baby sits
what happens to the oocyte once it becomes fertilised
- egg fertilised in ampullary region of uterine tube
- zygote wafted down uterine tube and starts to divide
- Day 4 = 32 cells. becomes morula
- morula is compacted. becomes blastocyst.
- blastocyst enters uterus at day 5/6
what is the morula
early stage embryo consisting of cells (called blastomeres) in a solid ball contained within the zona pellucida.
only 32 cells
what is the structure of the blastocyst
- has an inner cell mass stuck to its inner wall
- surrounded on inside by blastocoele
- trophoblast lines structure
- has small zona pellucida around it.
what happens if embryo is implanted too early
unable to implant
what happens if embryo is implanted too late
if delayed in travelling down uterine tube, can implant in uterine wall = ectopic pregnancy
what is the luteal phase
occurs after ovulation and before your period starts
at day 20 (period start) of menstrual cycle, what is the structure of the uterus
endometrium is thick, approaching thickest levels
- very vascular. glands well differentiated.
- endometrium ready to receive the blastocyst.
- progesterone levels increasing
what are the 4 main stages of implantation and placentation
- Differentiation of the trophoblast
- Trophoblastic invasion of decidua and myometrium
- Remodelling of the maternal vasculature in the uterus
- Development of vasculature within the trophoblast
what is meant by placentation
formation of placenta in a woman’s uterus
when, roughly, is the window of implantation
day 5-6
window is about 24-36 hours
which structure produced b-hCG
trophoblast
what is the role of b-hCG in pregnancy
- is maternal recognition mechanism of pregnancy
- binds to and maintains corpus luteum
- by maintaining CL, progesterone and oestrogen production continues
- former prevents menstruation
what is the corpus luteum
corpus luteum is a temporary endocrine structure involved in ovulation and early pregnancy
what is meant by decidualisation
a process that results in significant changes to cells of the endometrium in preparation for, and during, pregnancy.
what hormone allows for decidualisation
progesterone
what hormone is the basis of pregnancy tests
b-HCG
for how long is b-hCG needed to maintain the corpus luteum
7-8 weeks.
However hCG doesn’t decrease to zero at all.
at what point are b-hCH levels at their peak
usually maximal b-hCG levels by 9-11 weeks
and then start to drop again
why may clinicians need a qualitative value of b-hCH and how do they measure it
measure serum b-hCG
useful in monitoring:
early pregnancy complications such as ectopic pregnancy and miscarriage
what takes over the role of corpus luteum at 8 weeks
placenta
what is b-hCG decreasing in early pregnancy indicative of
miscarriage
