Final answer:
Epithelial tissue refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands.
Step-by-step explanation:
Epithelial tissue, also referred to as epithelium, refers to the sheets of cells that cover exterior surfaces of the body, lines internal cavities and passageways, and forms certain glands. Most epithelial tissues are essentially large sheets of cells covering all the surfaces of the body exposed to the outside world and lining the outside of organs. Epithelium also forms much of the glandular tissue of the body.