Placenta Flashcards
functional unit of placenta
fetal cotyledon
Mature placenta
~120 fetal cotyledons
What is a cotyledon made up of?
It has a primary villus stem that rises from chorionic plate and is supplied by fetal vessels.
Primary stem divides into secondary and tertiary stems that form terminal villi.
Terminal villi
site of maternal-fetal exchange
Where does the cotyledon develop
around maternal spiral arteries
Centre of cotyledon is…
hollow
How maternal-fetal exchange takes place?
- During maternal systole,maternal spiral arteries shoot blood into inter-cotyledon space.
- Blood rises to chorionic plate and disperses over terminal villi, becomes desaturated in O2 and picks up CO2 and waste products.
3.Desaturated blood filters into venous channels into maternal veins
Separation of fetal/maternal blood via
- trophoblastic tissue
- connective tissue
- endothelium of fetal capillaries
Normal placentation
maternal spiral arteries are invaded by trophoblastic celss within 12 wks.
They replace smooth muscle wall of vessels making them wider with higher capacity and less resistance. This process is complete @20 wks.
Maternal blood flow during 1st trimester
50ml/min
Maternal blood flow @ term
500-750 ml/min
Abnormal placenta
partial/full failure of invasion of trophoblastic cells into spiral arteries. So smooth muscle wall of arteries remain (not as wide has less capacity and more resistance than desired )
Why: unknown possibly immune intolerance
Effect of failure or partial/failure of invasion of trophoblastic cells
placenta has gross morphological changes.
infarcted area due to spiral artery occlusion by thrombosis.
Basal Heamatomas due to rupture of spiral artery
Multiple infarcts =
IUFD + FGR
