THE PLACENTA Fetal blood flows from the fetus through the umbilical cord into the blood vessels of the villi.
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The placenta is made up of functional units called chorionic villi.
Maternal blood from the uterine artery enters the intervillous spaces, bathing the villi.
The chorionic villi are highly branched, tree-like structures that contain blood vessels. Exchange between the maternal and fetal circulations occurs across the villi.
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