Visceral yolk sac

Definition

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.

Also known as secondary yolk sac, umbilical vesicle, vitelline sac — per UBERON

The Visceral yolk sac is a part of the None.