Describe the structure and functions of epithelium.

The covering or protective tissues in the animal body are epithelial tissues. Epithelium

covers most organs and cavities within the body. The cells of epithelium tissue are closely packed without intercellular spaces. They cover external body surface and line the various body cavities, internal organs and blood vessels. The lower most layer rests on a non-cellular basement membrane.

Exchange of various materials can occur across the epithelial tissues by diffusion. One side of the cells is in contact with the basement membrane while the other surface of the tissue is in contact with the atmosphere either directly (as in skin) or indirectly (as in lungs and alimentary canal).

Functions of epithelial tissue:

(i) Protection: Epithelial tissue protects the underlying parts from germs, harmful chemicals and injury. The skin, which protects the body, is also made of squamous epithelium.

(ii) Absorption: Epithelial lining of intestine absorb digested food.

(iii) Excretion: Epithelial lining of kidneys help in excretion of nitrogenous waste materials.

(iv) Secretion: Epithelial lining of endocrine glands secrete useful substances.