A region anterior to the head in a vertebrate embryo in which mesoderm is lacking.
The opaque peripheral area of the blastoderm of birds and reptiles, continuous with the yolk.
The central transparent area of the blastoderm of birds and reptiles, overlying the subgerminal cavity.
of an organism prior to birth or hatching; "in the embryonic stage"; "embryologic development"
A ventral fold formed by rapid growth of the head of the embryo over the embryonic disk, resulting in the formation of the foregut accompanied by anteroposterior reversal of the anterior part of the embryonic disk.
A longitudinal groove between the neural folds of the vertebrate embryo before the neural tube is completed.
The thickened dorsal plate of ectoderm that differentiates into the neural tube.
a cord-like formation in the body
Thickening formed by a group of cells at the anterior end of the primitive streak in vertebrate gastrulas
A dense, opaque band of ectoderm in the bilaminar blastoderm associated with the morphogenetic movements and proliferation of the mesoderm and notochord; indicates the first trace of the vertebrate embryo.