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What are cotyledons in a human placenta?
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prenatal development
An ultrasound image of a human fetus.
In the context of human prenatal development, cotyledons are the 15 to 20 distinct compartments that make up the placenta.
These compartments are formed by dividing partitions that project into the intervillous space from the decidual side of the placenta. Within these structures, chorionic villi and their branches form a complex, treelike mass bathed in maternal blood. This arrangement is essential for the placental barrier, which facilitates the efficient exchange of nutrients, oxygen, and waste products between the maternal and fetal bloodstreams without the two blood supplies mixing.1