One of the mysteries of the English language finally explained.
nounmass nounEmbryology Zoology
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.’
- ‘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.’
- ‘The branchial arches begin as cylindrical cores of mesenchyme sandwiched between continuous sheets of epidermal ectoderm and internal endoderm.’
- ‘It is involved in mesoderm development and differentiation of the neural ectoderm into epidermoblasts and neuroblasts.’
- ‘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.’
Mid 19th century: from ecto- ‘outside’ + Greek derma ‘skin’.
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