Ultrastructure of the developing gizzard epithelium in the chick embryo.

Abstract

The fine structure of the gizzard epithelium is described at different stages in the development of the chick embryo. The elaborate apical processes, a characteristic feature, take part in secretion at thirteen days, but do not seem to have this function at nine and ten days. The formation of glands begins at thirteen days but the adult fine structure of the gland cells is not attained until hatching. The distinct surface layer present between thirteen and seventeen days may have a protective function.