Derivatives of the ectoderm
Cells that remain in the epiblast layer and do not migrate via the primitive node or the primitive streak form the ectodermal germ layer. The ectoderm differentiates into neuroectoderm and surface ectoderm.
The neuroectoderm lying above the primitive node and symmetrically to the axial structures now becomes specified. The first differentiation step is the formation of the neural plate, which gives rise to the major part of the central nervous system. The ectoderm around the neural plate becomes the surface ectoderm. This becomes very thin, unlike the primordium of the nervous system. Due to this, the border between the neuroectoderm and surface ectoderm becomes easy to see. The neuro-ectodermal transition lies at this border. Cells of the neural crest migrate from this zone and reach the interior of the embryonic body, where they differentiate in various cell types.

The major part of the central and peripheral nervous system arises from the neuroectoderm and the neural crest. The surface ectoderm forms the epidermis of the skin; the skin appendages (hairs, sweat glands, sebaceous glands, and nails); the mammary glands; the epithelium of oral, nasal and paranasal cavities; the respiratory epithelium of the nose; the anterior lobe of the hypophysis; the dental enamel, and the parotid gland. Additional local thickenings develop in the surface ectoderm, called the placodes. Three of these placodes are especially important: the otic placode, the lens placode, and the nasal placode (olfactory placode).