Q. What are the epithelial tissues? What is their general function and how is that function associated to the features of the tissue?

Epithelial tissues also called as epithelia are tissues specialized in the covering of internal and external surfaces of the body. The general function of the epithelium is to provide impermeability and protection or selective permeability to the covered structure.

This justifies the epithelium's typical features: the cellular juxtaposition forming layers of very proximate cells with none intercellular or diminished space between each two neighbor cells.