epithelial

noun, plural ep·i·the·li·ums, ep·i·the·li·a [ep-uh–thee-lee-uh] /ˌɛp əˈθi li ə/. Biology.

any animal tissue that covers a surface, or lines a cavity or the like, and that, in addition, performs any of various secretory, transporting, or regulatory functions.

noun plural -liums or -lia (-lɪə)

an animal tissue consisting of one or more layers of closely packed cells covering the external and internal surfaces of the body. The cells vary in structure according to their function, which may be protective, secretory, or absorptive

1748, Modern Latin (Frederick Ruysch), from Greek epi “upon” (see epi-) + thele “teat, nipple” (see fecund). Related: Epithelial.

n. pl. ep•i•the•li•a (-lē-ə)

Membranous tissue composed of one or more layers of cells separated by very little intercellular substance and forming the covering of most internal and external surfaces of the body and its organs.

Plural epithelia

The thin, membranous tissue that lines most of the internal and external surfaces of an animal’s body. Epithelium is composed of one or more layers of densely packed cells. In vertebrates, it lines the outer layer of the skin (epidermis), the surface of most body cavities, and the lumen of fluid-filled organs, such as the gut or intestine.