a tube of ectodermal tissue in the embryo from which the brain and spinal cord develop
双语例句
These are not derived from the neural crest, instead an outpouching of the neural tube generates the optic cup which, in turn, forms the retina. 不过视网膜上皮的黑色素细胞是其中的例外,它们并非由神经脊产生,而是在神经管外囊生成的视杯产生。