part of develops from extraembryonic structure embryonic structure chorion membrane chorionic plate chorionic villus chorionic villous SCTID:360403003 chorionic villus embryonic part of placenta NCIT:C34125 villous chorion embryonic placenta placental villous fetal placenta EHDAA2:0004717 chorionic villi villous of placenta fetal part of placenta Wikipedia:Chorionic_villi MESH:D002824 BTO:0001161 placental villus One of the minute vascular projections of the fetal chorion that combines with maternal uterine tissue to form the placenta. placental villi