The Textural Aspects of Vessel Formation during Embryo Development and Their Relation to Gastrulation Movements.

We have investigated the microscopic physical inhomogeneity ("texture") of the avian embryo in vivo by shadowgraph. This noninvasive technique allows one to correlate the shape of blood vessels to the physical, micro-structural, pattern that exists in the embryo prior to vessel appearance. Before any vessel forms, vascular paths are present and are prepatterned, by fields of cellular orientations and lumen anisotropies. We find the origin of this prepattern in the movements of the embryo during gastrulation, and the related deformation and force field, which establish both the animal and vascular pattern.