Placenta Flashcards
Implantation and placenta formation occur with invasion of the endometrium during what phase?
secretory phase
What does the fertilized egg form prior to implantation?
early blastocyst with an inner cell mass and a trophoblast
What day does implantation typically occur?
day 6 post fertilization
What region of the blastocyst makes contact with the endometrium?
the embryonic pole
What does the trophoblast do in the region attached to the endometrium?
the cells int hat area become cytotrophoblasts and they will give rise to the syncytiotrophoblast, which is an invasion into the endometrial lining
Which are mitotically active - the cytotrophoblasts or the syncytiotrophoblasts?
cytotrophoblasts
Describe te syncytiotrophoblast
it’s really a syncytia - there are no cell boundaries - it’s just a mass that invades into the epithelium
Eventually, the developing fetus will bore further into the endmetrial stroma. WHat happens to the endometrial capillaries and blands?
THey get destroyed and end up as lacuna in the syncytiotrophoblast
WHat do these lacunae do eventually?
fuse to form a lacunar network (eventually the intervillous spaces)
At what point (day) has the embryo completely bored its way into the stroma?
day 9-11
What will the lacunae contain?
maternal blood and endometrial gland secretions
What will the cytotrphoblast build out to grow?
they will make pillars out into the interface between the syncytiotrophoblast, and the endometrium stroma. THese are the primary villi!
eventually they will get there and will form an outer shell aroundthe syncytioblast
What do the chorioni villi eventually consist of? THree types of cells….
extraembryonic mesoderm
cytotorphoblast
syncytiotrophoblast
Primary villin have only what?
syncytiotrophoblast on the outside and cytotorphoblast on the inside - no extraembronic mesoderm yet
At what point do the villi have mesoderm ingrowth into the core?
secondary villi
What happens for the villi to become tertiary?
the mesoderm core will become vascularized
Anchoring villi are what?
a subtype of tertiary villi with a cytotorphoblastic shell
this occurs via invasion of cyto through the syncytio so that the cytotorphoblast cells will make direct contact with the decidual cells
What do the cytotorphoblasts form after they penetrate through the syncytriotrophoblast?
the cytotrophoblastic shell
What is the difference between an anchoring villus and a free villus?
the anchoring villus will be anchored to the cytotorphoblastic shell while the free villus are free
Describe the decidual reaction?
transformation of endometrial stromal cells shortly after the embryo burrows in
the cells swell due to glycogen and lipid accumulation
the transformation spreads throughout superficial layers of the endometrium
What do we call the oart of the placenta that has the most decidual change - where it burrows?
the decidual basalis - between the conceptus and myometrium - constitues the maternal portion fo the placenta
What is the decidua capsularis?
the decidua between the conceptus and uterine lumen
it becomes attenuated and smooth - it’s continuous with the decidual basalis and the part of the decidual associated with the rest of the wall
What is the name for the decidua associated with the remainder of the uterine wall?
decidual parietalis
What are cotyledons?
partitioning of the decidual basalis - about 15-30 lobules divided by septae
within each lobule you expect to see 2-4 tertiary villi and their branches
Describe fetal placental circulation in general?
umbilical arteries - chorionic arteries - villar capillaries - chorionic veins
What supplies the placenta from the mom?
the spiral arteries of the uterus —-into the intervillous spaces —–drained by the endometrial veins
After the first trimester, what happens to the placental barrier/
the cytotorphoblast and the mesoderm diminish significantly, leaving just the syncytiotrophoblast and basal lamina and then fetal capillaries
becomes very attenuated
What infections can pass through the placental barrier?
TORCH Toxoplasmosis Other (hep B, Coxsackie, syphilis, VZV, HIV, PB19) Rubella CMV HSV
What is the main placental hormone in the beginning of pregnancy
HCG
What does that hCG do?
maintains corpu sluteum and its production of progesterone and estrogen
What are the two steroidal hormones produced by the synctiotrophoblast cells?
progesterone after the 1st trimester
estrogen
THe placenta cannot make the precursor for estrogen, so where does it get it?
the androgens form the fetal adrenal cortex!
Human placental lactogen is also called what?
chorionic somatomammotropin
What is HPL associated with?
growth, lactation and lipid/carb metabolism
What hormones are produced by the decidual cells?
prolactin, prostaglandins, and relaxin
