Epithelial cells of following types:

(a) Simple squamous epithelium:

It located in the lining of Air sacs of lungs and the lining of the heart and blood vessels. It allows materials to pass through by diffusion and filtration and secretion.

(b) Simple cuboidal epithelium:

It is present in ducts and secretory portions of small glands and in kidney. It function is to secretes and absorbs.

(c) Simple columnar epithelium:

It is present in respiratory tract such as bronchi, lining of uterus and in the digestive tract. It absorbs and secretes mucous and enzymes.

(d) Stratified cuboidal epithelium:

It is present in different glands such as sweat, salivary and mammary glands. It helps in protection.

(e) Stratified columnar epithelium:

It is present in the male urethra and in the ducts of some glands. It helps in secretion and protection.