1. Squamous Epithelium is made up of thin, flat cells with prominent nuclei. It forms delicate lining of the buccal cavity, alveoli of lungs, proximal tubule of kidneys, blood vessels and covering of the skin and tongue. It protects the body from mechanical injury, drying and invasion of germs. It also helps in filtration by forming a selectively permeable membrane surface.
2. Cuboidal Epithelium is composed of single layer of cubical cells. The nucleus is round and lies in the centre. This tissue is present in the thyroid vesicles, salivary glands, sweat glands and exocrine pancreas. It is also found in the intestine and tubular part of the nephron (kidney tubules) as microvilli that increase the absorptive surface area. Their main function is secretion and absorption.
3. Columnar Epithelium is composed of a single layer of slender, elongated and pillar like cells. Their nuclei are located at the base. It is found lining the stomach, gall bladder, bile duct, small intestine, colon, oviducts and also forms the mucous membrane. They are mainly involved in secretion and absorption.
4. Ciliated Epithelium Certain columnar cells bear numerous delicate hair-like outgrowths called cilia and are called ciliated epithelium. Their function is to move particles or mucus in a specific direction over the epithelium. It is seen in the trachea of wind-pipe, bronchioles of the respiratory tract, kidney tubules and fallopian tubes of oviducts.
5. Glandular Epithelium Epithelial cells are often modified to form specialized gland cells that secrete chemical substances at the epithelial surface. Sometimes a portion of the epithelial tissue folds inward to form a multicellular gland, which lines the gastric glands, pancreatic tubules and intestinal glands.
