| 词汇 | ectoderm |
| 释义 | ectoderm noun[ C ] uk /ˈek.tə.dɜːm/ us /ˈek.tə.dɝːm/ the cells in the embryo of a human or animal that develop into skin, hair, and the nervous system外胚层 Cells actin anaphase anti-platelet assort axoplasm histography homologous chromosomes infiltration intercellular intermitotic nerve fibre neurofibril neurofibrillary neuroglia neuroglial tetrad thrombocyte thymocyte turgor unciliated And only the epidermis, or outer layer of our skin, and the nervous system and parts of our sense-organs have arisen from the ectoderm. In the first embryonic structure they are merely a pair of simple cutaneous glands, or depressions in the ectoderm. In the normal development of the tadpole from the egg, as in all other vertebrate animals, the lens is formed from the outer skin or ectoderm of the head. The outer envelope of dark smaller cells forms the ectoderm or skin-layer. We find the first differentiation of epithelial and stinging cells, or of muscular and neural cells, in the thick ectoderm of the hydra. ectoderm | American Dictionaryectoderm noun[ C ] us/ˈek·təˌdɜrm/ biology the cells in the embryo (= growing organism before it is born) of a human or animal that develop into skin, hair, and the nervous system Examples of ectodermectoderm By the 10-somite stage, there is strong staining in the lateral ectoderm and caudal dorsal neural tube. The chicken spalt4 gene (csal4) is expressed in the neural tube, migrating neural crest, branchial arches and, transiently, in the cranial ectoderm. Players remain pluripotential like stem cells, yet to make their way toward differentiation as infielders (mesoderm), outfielders (ectoderm), or pitchers or catchers (endoderm). The neural ectoderm thickens to become the neural plate, which invaginates to form the neural tube. They are formed by surface ectoderm and pharyngeal endoderm and are populated by paraxial mesoderm and cranial neural crest cells. During the next few days the outer surface of the embryo (or ectoderm) folds in upon itself to form the neural tube. During this complex developmental process, the outer embryonic ectoderm and its underlying mesoderm give rise to the epidermal and dermal components, which essentially build up the hair follicle unit. Presumptive neural crest cells initially lie in the neural folds at the juncture between the neural and non-neural ectoderm and then within the dorsal neural tube after its closure. At this point, there are two layers of cells - the ectoderm (outermost) and the endoderm (innermost) layers. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. It is not a teratoma, however, which is a neoplasm comprising all three germ cell layers (ectoderm, endoderm, mesoderm). From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. This leads to the specification of non-neural ectoderm and later in the blastula stage to anmioserosa. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Embryos have three layers: endoderm, mesoderm and ectoderm. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. Each structure originates form different germinative layers or tissues: the ectoderm, endoderm and mesenchyme. From Wikipedia This example is from Wikipedia and may be reused under a CC BY-SA license. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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