Epithelial tissue

Epithelial tissues are thin tissues that cover all the exposed surfaces of the body. They form the external skin, the inner lining of the mouth, digestive tract, secretory glands, the lining of hollow parts of every organ such as the heart, lungs, eyes, ears, the urogenital tract, as well as the ventricular system of the brain and central canals of the spinal cord.

The main functions of simple epithelial tissues are:

(i) The cells form the outer layer of skin. They protect the underlying cells from drying, injury, infection and chemical effects.

(ii) They regulate the exchange of materials between the body and the external environment. 

(iii) They help in absorption of water and other nutrients, especially in alimentary canal.

(iv) They help in the elimination of waste products.

(v) Some of them are greatly specialized (glandular cells) and perform secretory function.