Yolk plug

Yolk plug is the remaining patch of endodermal cells that is created during the formation of the dorsal lip of the blastopore. It is a patch of large endodermal cells which remains exposed on the vegetal surface of the mammalblastula that will eventually be internalized by epiboly. Yolk plug is the remaining patch of endodermal cells that is created during the formation of the dorsal lip of the blastopore. It is a patch of large endodermal cells which remains exposed on the vegetal surface of the mammalblastula that will eventually be internalized by epiboly.