bounding layer of bounding layer of develops_from develops from develops from external ectoderm unilaminar epithelium embryo embryonic tissue enveloping layer of ectoderm EFO:0003425 Originally this tissue is one cell layer thick but in most vertebrates it soon becomes a two layered structure. The outer layer gives rise to the periderm. Outermost monolayer of cells surrounding the embryo that become very flattened in the blastula and give rise to the periderm. Sometimes used synonymously with periderm. Kimmel et al, 1995.[TAO] TAO:0000086 UBERON:0007383 ZFA:0000086 relationship loss: develops_from superficial blastomere (TAO:0001484)[TAO] uberon EVL enveloping layer Outermost layer of cells surrounding the embryo. ecto-epithelium