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Bird Egg Anatomy

A bird's egg is a complex structure that houses the growing embryo and contains all the nutrition that is needed before the chick is ready to hatch. Each component of the egg performs specific functions in the development of the embryo. The embryo is the immature developing chick. The amnion is a membrane that initially covers the embryo and eventually fills with amniotic fluid, provides the embryo with protection against shock from movement. The allantois helps the embryo obtain oxygen and handles metabolic waste. The chorion, together with the amnion, forms the amniotic sac and encloses the amnion, vitellus, and the embryo. The vitellus, or yolk, is the nutrient-bearing portion of the egg, containing most of its fat, minerals, and many of its proteins and blood vessels. The air cell usually rests between the outer and inner membranes at the egg's larger end.