the yellow spherical part of an egg that is surrounded by the albumen

nutritive material of an ovum stored for the nutrition of an embryo (especially the yellow mass of a bird or reptile egg)

membranous structure that functions as the circulatory system in mammalian embryos until the heart becomes functional

membranous structure enclosing the yolk of eggs in birds, reptiles, marsupials, and some fishes; circulates nutrients to the developing embryo