Epithelial tissue: The tissue present as a covering and protection layer over the complete animal body is termed as epithelial tissue.

It is classified on the basis of cell shape and arrangement as follows:

i. Simple squamous epithelium- It consists of those epithelial cells which are extremely thin, flat and forms delicate lining.

For example- Oesophagus, the lining of mouth are covered with simple squamous epithelium.

ii. Stratified squamous epithelium- When thin and flat epithelial cells are present in many layers as they are present in the skin which prevents wearing and tearing, it is termed as Stratified squamous epithelium.

iii. Columnar epithelial cells- Columnar here refers to pillar-like. In this tall epithelial cells are present which helps in the movement across an epithelial barrier. They are present in parts where absorption and secretion occurs.

For example- It is present in the inner lining of the intestine.

iv. Cuboidal epithelial cells- In this cube-like epithelial cells are arranged which provide mechanical support. It forms linings of the kidneys, ducts of salivary glands etc.

v. Glandular epithelial cells- In this epithelial cell acquire specialization and starts the secretion process. Sometimes they fold inward and forms multicellular gland. This type of epithelial tissues is termed as glandular epithelial tissue.

Following picture depicts different types of epithelial tissue: