Implantation, placentation and hormone changes in pregnancy Flashcards
(26 cards)
What is a trophoblast?
- cells of the blastocyst that invade the endometrium and myometrium
When is the endometrium and myometrium invaded by the blastocyst?
- 5-6 days post fertilisation
What do trophoblasts become?
syncitioblasts
What do syncitioblasts do?
secrete beta hCG
What is the chorion?
layer of blastocyst that becomes the placenta
What is the amnion?
layer of the blastocyst that becomes the amniotic sac which contains the amniotic fluid
What does a fertilized embryo become?
- moves down fallopian tube
- develops into ball of cells
- called morula
- by day 4
What does the morula develop into?
- develops into an inner cell mass
- this develops into the baby
- it has blastocoel cavity and layer cells
What does trophectoderm develop into?
placenta
What processes need to happen in order for the placenta to develop?
- differentiation of the trophoblast
- trophoblast needs to invade the decidua of myometrium
- remodeling of the maternal vasculature
What is the decidua?
thick layer of modified mucous membrane which lines the uterus during pregnancy
Why is there remodelling of the maternal vasculature for the placenta to develop?
- uterus has tight small spiral arteries to reduce blood volume lost during menses
- tiny vessels not good enough for baby
- transform to bigger vessels to accomodate the baby
What is the window of implantation?
- narrow time point where implantation can occur
- if embryo implant too early or too later= risky
If a woman has a longer window of implantation, what happens?
- recurrent pregnancy losses
- bc low quality embryos are accepted to be implanted
- embryos might have aneuploidy
What is the role of bhCG?
- signals to the corpus luteum that there is a pregnancy
- corpus luteum is maintained
What does the corpus luteum do?
- secrete progesterone
- decidualizes endometrium
When does the corpus luteum stop playing a role in pregnancy?
- after 12 weeks
- placenta itself establishes steroidogenesis and takes over from the corpus luteum
What is bhCG?
- hormone
- basis of urinary pregnancy test
When is the amount of bhCG in the body maximum?
9-11 weeks
Why is serum bhCG checked?
- useful to monitor early pregnancy complications
- falling bhCG= ectopic/miscarriage= failing preggo
- doubling bhCG= SUCCESSFUL uterine preggo
What does the placenta act like?
- an endocrine organ
- remove CO2, urea, ammonia minerals, other waste
- barrier
What does the placenta secrete?
- steroid hormones like oestrogen and progesterone
- HPL
Why is placenta useful in baby lungs and kidneys?
transfer oxygen, carbohydrates, fats, amino acids, vitamins, minerals and antibodies (passive immunity)
that are required to develop the ball of cells into a baby
How is the placenta adapted?
- huge maternal uterine blood supply (by end of pregnancy, motherm feeding 750mls blood/minute to baby)
- blood delivered at low pressure (gentle over villi)
- huge function reserve
- high surface area contact with maternal blood
- transport system in placenta= adapted and efficient
