embryology-05-placenta and membranes
Terms
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- placenta
- apposition of fetal and parental tissues for purposes of physiological exchange and hormonal production
- what does the placenta do?
- nutrient and gas exchange between mother and fetus
- when is placenta formed
- when syncytiotrophoblast is invading endometrium
- what does trophoblast become in the placenta?
- villous chorion
- main components that form placenta?
- syncytiotrophoblast and cytotrophoblast
- where does placenta form within uterus?
- where decidua basalis is (i.e. where embryo has implanted – this is where material exchange takes place between mother & fetus)
- layers of placental “barrier”
- maternal blood, syncytiotrophoblast, cytotropoblast, extracellular space, endothelium of fetal blood vessels, fetal blood
- before the formation of the placenta, how does the fetus survive
- from uterine secretions from the uterine glands – up until day 13
- endometrium called what in pregnancy
- endometrium decidua
- what is the baby encased within
- tough layer of membrane – amnion
- chorion def.
- extra-embryonic mesoderm and two layers of trophoblast – forms the chorionic sac
- what is contained within the chorion
- the embryo with amniotic and yolk sacs are susbended by a connecting sac within the chorionic cavity
- inspection of placenta – look for?
- IS IT whole, divided into cotyledons, (which could break off in uterus)VESSELS: umbilicus in middle, 2A, 1V
- placenta measurement at 10wks
- 6.5mm
- placenta measurement at 15 weeks
- 15cm
- special about placenta?
- HIGHLY VASCULAR – huge surf. area exh. site for nutrients
- If one umbilical artery instead of two?
- could be something wrong with baby
- If too many red cells in baby – problem?
- potential for clotting
- only single artery in placenta - % and type of problems
- 16%premature, 17%abnormal, 34% small baby
- early form of monozygotic twin
- 2 different blastocysts from same egg (cytokinesis)
- most common form of monozygotic twin
- one blastocyst, two amniotic cavities, shared placenta
- later form of monozygotic twin can give rise to
- siamese twins – 2 bilaminar discs within 1 blastocyst
- Of 100 good eggs, % that wonÂ’t fertilize
- 15%
- of 100 good eggs, % that wonÂ’t implant
- 15%
- of 100 good eggs, % that cause cessation of menses
- 42% (i.e. pregnancy survives)
- of 100 good eggs, % that will die in wks 3 – 6
- 8%
- of 100 good eggs, % that will be born late or stillborn
- 3
- of 100 good eggs, how many born alive
- 31
- of the 31 live-born from 100 good eggs, how many will die or be abnormal
- 3 abnormal, 1 may die
- surviving pregnancies, statistically, from 100 good eggs.
- 28 normal.
- what might cause cessation of pregnancies?
- chromosome abnormality or mutation 25%, radiation 1%, infections 2 – 3%, drugs and chemicals 4 – 5%, combinations & unknowns 60 – 70%
- 60 – 70% of early abortions due to
- chromosomal disorders: trisomy 50%, polyploidy 25%, 45 + X 25%
- terathanasia
- monster death: tera= monster, thanatos=death
- Of spina bifida cases, what % dies?
- 90%
- Teratology principles – effects of teratogens vary how
- with genetic makeup, time of exposure – most critical weeks are early on, esp. 1st trimester, dosage
- complications with teratogens
- may not effect mother at all, single teratogen may produce many different malformations, several teratogens may produce same defect, but by different mechanisms
- common potent teratogens
- Retinoids and skin care
- Retinoids cause defects of
- CNS, face, ears, heart, kindey, esophagus, thymus. Cause spontaneous abortions.
- Animal testing of teratogens
- doesn’t accurately reflect human results – isn’t useful due to genetic differences