Flashcards in Lecture 12 - Placenta II Deck (26):
secretion from uterine glands in early pregnancy that enters intervillous space
Premature blood flow and miscarraige?
increased blood flow in miscarraiges 7-11 weeks, no difference @ 12-13 weeks, distributed centrally and across placenta rather than flowing at periphery
trophoblast cel type found mainly in first trimester underlying the syncytiotrophoblast
single cell, surface layer of placenta formed by fusion of villous cytotrophoblast, does not replicate but is replaced by fusion of additional villous cytotrophoblast
differentiated cells that have migrated out of the villous placenta towards maternal tissue
Structural changes of placenta during gestation?
stroma of villi become more cellular and vascularise (early), villous cytotrophoblast thins down (2nd trimester), villous cytotrophoblast is sparse (3rd trimester), branching of villi increases, then size of placenta increases
Decidua parts (maternal contribution to placenta)?
decidua basalis (underly implantation site), decidua capsularis (overlay implantation site), decidua peritalis (around remainder of uterus)
as gestation progresses, amniotic cavity enlarges and compresses the uterine cavity, decidua capsularis fuses with peritalis
amnion (avascular, covers cord and placenta), chorion (fetal vessels)
formed from yolk sac, and allantois (which vessels are fromed from), 2 arteries 1 vein, Wharton's jelly, myofibroblasts, mucopolysaccharides
Placental adaptations to increase transport?
large villous surface area, syncytiotrophoblasts have microvilli for increased S.A, 3rd trimester most villi are samll tertiary villi and fetal capillaries are closley apposed to syncytiotrophoblast
Placenta gas transfer?
greater affinity for oxygen Hbf, greater saturation at same pressure, also greater amount
as maternal blood picks up fetal metabolites the pH drops, dropping affinity for oxygen; opposite effect for the etal blood therefore double Bohr
The Haldane effect?
the capacity of hemoglobin to bind CO2 is related to amount of bound oxygen, therefore increases as maternal blood loses oxyge, opposite effect for fetus, double Haldane effect
Functions of amniotic fluid?
buoyant medium allows symmetric growth, cushions embryo/fetus, prevents adhesion of fetus with membranes, allows fetus movement (muscle development), development of GI/respiratory tracts (swallowing/breathing)
Source of amniotic fluid?
initially filtrate of maternal plasma, major fetal contribution, after 20 weeks primarily fetal urine
Amniotic fluid recycling?
leaves mainly via fetal swallowing, moves across fetal skin prior to 24 weeks, across fetal membranes into maternal circulation (minor) and into fetal vessels of placenta and umbilical cord (major)
excessive amniotic fluid due to impaired swallowing, found mainly in cases of diabetic pregnancy
lack of amniotic fluid likely due to kidney problems
amniocentesis, chorionic villi sampling, cell-free fetal DNA flowing
Diseases that placenta protects from?
hepB, rabies, measles, malaria (clogging however)
Diseases that placenta does not prevent from?
HIV, small pox, rubella, toxoplasmosis
Placenta and drug transport?
affects organogenesis (days 20-70 after LMP) - thalidomide (limb growth), diethylstillbestrol (cancer)
glucocorticoid give to mother to prevent respiratory distress syndrome in fetus
Drugs safe for fetus?
paracetamol, aspirin, heparin