The surface ectoderm is a single-layered epithelium originating from the lateral portions of the ectoderm. The ectoderm, derived from the epiblast, rapidly differentiates into the central neural ectoderm and the lateral surface ectoderm. Surface versus neural ectoderm fate choice is regulated by the presence of WNTs that inhibit neuralizing FGF signaling, thereby enabling BMP activity to establish surface ectoderm commitment. As soon as invagination of the neural ectoderm and formation of the neural tube progress, the two symmetric wings of the surface ectoderm come together and fuse over the newly closed neural tube. The surface ectoderm proliferates and covers the entire embryo until the epidermis is formed.
The major contribution of the surface ectoderm to embryonic organogenesis is in formation of the epidermis and its appendages, including hair, sebaceous gland and nails. In addition, in the mouse, the surface ectoderm gives rise to the epithelium, including the tooth, olfactory epithelium, lens and cornea epithelium, and the inner ear otocyst.