外胚层

The primitie mouth, or stomodeum, is a slight depression on the surface of the ectoderm.

原始（凹）是外胚层表面一个轻微凹陷。

Ectodermal dysplasia appears in two froms, hidrotic and anhidrotic, according to clinical features and hereditary characteristics.

摘要外胚层异常症，依照临床表徵及遗传特性，可分成无汗型与出汗型大类。

Bilateral oal thickenings of the surface ectoderm, called nasal placodes, then deelop on each side of the inferior part of the frontonasal prominence.

外胚层表面呈双边卵圆形增厚形成鼻板，然后发展成为额鼻隆起下半部分。