Epithelial Tissues is the tissue that forms a protective covering on an external or internal surfaces of the animals. The cells are tightly packed and form a continuos sheet.  These tissue have no intercellular spaces and have small amount od cementing material between them. An epithelial tissue may be composed of one (simple epithelium) or more layers of cells (compound epithelium). The skin, surface layers of mouth, alimentary canal, lungs etc. are made of epithelial tissues. It also forms a barrier to keep different body system separate and also regulates the exchange of materials between the body and the external enviroment.