nounmass nounZoology Embryology
The outermost layer of cells or tissue of an embryo in early development, or the parts derived from this, which include the epidermis, nerve tissue, and nephridia.
- ‘The presumptive neural tube tissues consist of a layer of ectoderm along the dorsal midline of the embryo, between the notochord and an outer layer of epidermis.’
- ‘The branchial arches begin as cylindrical cores of mesenchyme sandwiched between continuous sheets of epidermal ectoderm and internal endoderm.’
- ‘The anthozoans are diploblastic animals developing from two epithelial germ cell layers: the ectoderm, facing the seawater, and the endoderm, facing the gastrovascular cavity or coelenteron.’
- ‘At a tissue level, an adult hydra is essentially a tube composed of two tissue layers, the ectoderm and the endoderm, which extend throughout the animal.’
- ‘It is involved in mesoderm development and differentiation of the neural ectoderm into epidermoblasts and neuroblasts.’
Mid 19th century from ecto-‘outside’ + Greek derma ‘skin’.
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