Epithelium

{ep-e-thef-le-um) [ett’l, upon; OfjAfj, nipple]. A term applied to the group of cells that forms the epidermis, that lines all canals having communication with the external air, and that are specialized for secretion in certain glands, as the liver, kidneys, etc. Epithelium is divided according to the shape and arrangement of the cells into columnar, cuboidal, flat, pavement, squamous, stratified, te ellated, and transitional epithelium; according to function into protective and glandular or secreting. E., Ciliated, a form in which the cells bear vibratile filaments or cilia on their free extremities. E., Transitional, that intermediate between simple and stratified. 263