Describe the epithelial tissue. How are its two main types different from each other?

This tissue has a free surface facing either environment outside or bodyfluid inside. Thus it acts either as a covering or the lining.

The cells are compactly packed without intercellular spaces and matrix.

Simple epithelial is composed of a single layer of cells and function as a lining of body cavity, duct or tubes. The compound epithelium has two or more layers of cells and has protective function.