Epithelium

uppermost cell layer(s) of skin and mucous membranes.

Depending on their location, the epithelial cells are multiform in form and function (e.g. keratinizing squamous epithelium of the skin or secreting or resorbing). cylinder epithelium of the Nierentubuli).

https://de.wikipedia.org/wiki/Epithel _{(Wikipedia CC-by-sa-3.0)}