Epitheliale

Epitheliale is a term used in anatomy and histology to describe epithelial tissue—the cellular sheets that line surfaces, cavities, and glands. In English the corresponding adjective is epithelial; epitheliale appears in Italian, Latin, and some formal contexts to indicate a relationship to epithelium.

Epithelia are composed of tightly joined cells arranged in continuous layers and rest on a basement membrane. They are avascular and obtain nutrients by diffusion from underlying connective tissue. Epithelial cells show polarity, with an apical surface facing the lumen or exterior and a basal surface attached to the basement membrane. These tissues function as protective barriers, regulate exchange between compartments, secrete substances, and provide sensation.

Classification follows two main schemes. By number of cell layers: simple epithelia (one cell layer) and stratified epithelia (two or more). Pseudostratified epithelia appear multi-layered but all cells contact the basement membrane. By cell shape: squamous (flat), cuboidal (cube-shaped), and columnar (tall). Transitional epithelium specializes to accommodate distension, as in the urinary tract. Many epithelia have specialized features such as microvilli for absorption, cilia for movement of mucus, and intercellular junctions (tight junctions, adherens junctions, desmosomes) that maintain integrity.

Locations include the skin epidermis (keratinized stratified squamous), the lining of the digestive tract (simple columnar with microvilli), the respiratory tract (pseudostratified ciliated columnar), kidney tubules (simple cuboidal), and ducts of many glands. Epithelia are the origin of many cancers (carcinomas) and can undergo metaplasia or dysplasia in response to injury, while retaining high regenerative capacity.