Figure 2From: hCG, the wonder of today's scienceFormation of villous trophoblast. A. Cytotrophoblast columns in early implanted embryo. B. Extension of columns and differentiation of peripheral cells. B. and C. Folding of extensions caused by shape of syncytiotrophoblast cells. C and D formation of trophoblastic villi. No vascular supply, spiral arteries or fetal vasculature is shown.Back to article page