has part has part has_part characteristic of has modifier abnormal extraembryonic tissue physiology abnormal visceral yolk sac physiology 2018-01-10T16:24:20Z any functional anomaly of the extraembryonic tissue membrane, formed from the visceral endoderm and the extraembryonic mesoderm, which is located ventral to the embryonic disc and is connected to the presumptive midgut of the embryo; the yolk that it contains is the site of embryonic hematopoiesis and vitelline circulation is involved in early embryonic circulation; it is the origin of the primordial germ cells MP:0020517 abnormal functionality visceral yolk sac