| The cotyledonary placenta is characterized by numerous “button-like” structures distributed across the surface of the chorion. These are called fetal cotyledons. When they join with the maternal caruncle they form a placentome. A convex cotyledon becomes covered with the chorion. Many finger-like villi (red) originating from the chorionic tissue protrude toward the lumen of the uterus. In the concave cotyledon, the chorionic tissue pushes inward, forming a concave interface between the chorion and the maternal caruncle. |