has part has part has_part anatomical structure embryonic structure conceptus embryo plus adnexa The embryo and its adnexa (appendages or adjunct parts) or associated membranes (i.e. the products of conception) The conceptus includes all structures that develop from the zygote, both embryonic and extraembryonic. It includes the embryo as well as the embryonic part of the placenta and its associated membranes - amnion, chorion (gestational sac), and yolk sac[WP]. entire extraembryonic component