Session 8- The placenta Flashcards
when does the placenta begin to develop
second week of development
what develops from the outer cell mass
syncytiotrophoblast
cytotrophoblast
what develops from the inner cell mass
epiblast
hypoblast
what is the inner cell mass
embryoblast
what is the outer cell mass
trophoblast
how do the embryonic sacs change
yolk sac disappears
amniotic sac enlarges
chorionic sac is occupied by the expanding amniotic sac
what does implanation acheive
basic unit of exchange
anchor placenta
establish maternal blood flow within the placenta
how is the basic unit of exhange established
primary vili- early finger like prjections of trophoblast
secondary villi- invasion of mesenchyme into core
tertiary villi- invasion of mesenchyme core by fetal vessels
what happens to the placental membrane as the needs of the fetus increase
becomes progressively thinner to optimise transport
what does the placenta develop from
projections around the outer surface of the membrane
balanced over the entire surface
as growth occurs the projections are concentrated into a single disc-like space which goes onto become the placenta
what is the decidua
the cells of the endometrium that become speacilized to modulate the degree of invasion of the conceptus once it has implanted through decidualisation
what happens if the conceptus implants in an area where there is no decidua
there is no inhibition of decidualisation and therefore no control ober extent of invasion
what happens if the implantation occurs in the correct place but the decidual reaction is suboptimal
range of complications where the pregancy is either nor maintaied or spectrum of placenal insufficiency inclduing pre-eclampsia
how are waste products taken from the fetus
through paired umbilical arteries through the villi
how are waste products taken from the fetus
through paired umbilical arteries through the villi
how is oxygen and nutrienys taken to the fetus
umbilical vein
what sustains the corpus luteum in the first trimester
hCG
what takes over from the corpus luteum
the placenta produces steriod hormones so that when sufficiently large it takes on the role of the corpus lutrum after the fist triester and produces enough progesterone and oestrogen to keep the HPG axis in the pregnant state
how do placental hormonea affect maternal metabolism
progesterone promotes an increase in appetote to allow an increased fat depostion to hep support the fetuw and breastfeeding
what does hPL do
help maintain a diabetogenic state to caus einsulin resistance in the mother increasing the glucose availibility to the fetus
what immunoglobulins can cross the olacenta
IgG
what are teratogens
something that can cause birth defects or abnormalities in a developing embryo or fetus upon exposure. Teratogens include some medications, recreational drugs, tobacco products, chemicals, alcohol, certain infections, and in some cases, health problems such as uncontrolled diabetes in pregnant people.
when do teratogens have the greatest effect
embryonic state as this is a key time for devlpment
weeks 3-8
by what process is immunoglobin trasnported across the placenta
receptor mediated endocytosis
