Nasmyth's membrane or enamel cuticle, structure of embryological origin is composed of keratin which gives rise to the enamel organ.

Keratin is also present in epithelial cells of tooth germ and a thin film of keratin is present on the tooth erupted recently (Nasmyth's membrane or enamel cuticle).

Primary enamel cuticle, also called Nasmyth's membrane, is thin membrane of tissue also known as reduced enamel epithelium produced by the ameloblast, that covers the tooth once it has erupted.