In endotheliochorial placentae, the aggressive nature of the chorion results in the __1__ of uterine epithelial cells and the ___2___ penetrate into the underlying uterine connective tissue. Modified chorionic cells at the base of each villus form a fused unit or syncytium, the __3__. The __3__ surrounds the endothelium of the adjacent uterine capillaries and is responsible for __4__ nutrition. __5__ nutrition occurs at the tips of the fetal villi and in the adjacent avillous areas. Intra-epithelial capillaries are also present.