Pregnancy, parturition and late fetal development Flashcards
What is histiotrophic nutrition?
derivation of nutrients from uterine gland secretions, breakdown of maternal capillaries and breakdown of surrounding endometrial tissues
When does the foetus switch to haemotrophic support and how does it work?
- at the start of the 2nd trimester/12th week of gestation
- derives nutrients from maternal blood
- uptick in foetal growth
- haemochorial-type placenta–> maternal blood directly contacts foetal membrane (chorion)
What is the connecting stalk?
extra-embryonic tissue that grows from embryo, connecting conceptus w/ the chorion
What are the trophoblastic lacunae?
- large spaces in the syncytiotrophoblast filled w/ maternal blood formed by breakdown of maternal capillaries and uterine glands
- become intervillous spaces/maternal blood spaces
What are fetal membranes?
extra-embryonic tissues that form a tough but flexible sac that encapsulates the foetus and forms the basis of the maternal-fetal interface
What is the amnion?
- arises from epiblast
- forms a closed, avascular sac w/ developing embryo at one end
- begins to secrete amniotic fluid from 5th week–> forms fluid filled sac that encapsulates and protects foetus
What is the chorion?
- outer foetal membrane
- formed from yolk sac and part of trophoblast
- highly vascularised
- gives rise to chorionic villi- outgrowths of cytotrophoblast that form the basis of the foetal side of the placenta
What are the 2 layers of the amniotic sac?
amnion on the inside, chorion on the outside (expansion due to fluid accumulation forces them into contact)
What is the allantois?
- outgrowth of yolk sac
- grows along connecting stalk from embryo to chorion
- becomes coated in mesoderm and vascularises to form umbilical cord
What are primary chorionic villi?
outgrowths/projections of the cytotrophoblast (which sits on the outside of the chorion) that push through the syncytiotrophoblast into the maternal endometrium
