Figure 3.

The intervillous circulation: Following pregnancy-associated vascular remodeling, the spiral arteries are known as the uteroplacental vessels. The uteroplacental vessels provide blood to the intervillous space, where the maternal blood is free to interact with the fetal villous tree. Although the term “cotyledon” has sometimes been used to refer to the incomplete partitions of the placenta, the human placenta is not truly cotyledonary and thus the term “functional cotyledon” is more appropriate.