has part has part has_part characteristic of has modifier abnormal visceral yolk sac morphology small visceral yolk sac small secondary yolk sac reduced size 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 small umbilical vesicle small vitelline sac small yolk sac MPheno.ontology MP:0012131 2013-10-08T15:46:33Z csmith abnormal decreased size visceral yolk sac