amnioserosa formation
Formation of the amnioserosa, an epithelium that occupies a hole in the embryonic dorsal epidermis. This occurs by the transformation of a narrow strip of cells at the dorsal midline of the blastoderm from columnar to squamous cells, accompanied by a lateral shift.
GO:0048646
anatomical structure formation involved in morphogenesis
is_a
GO:0010004
gastrulation involving germ band extension
part_of