Membranous tissue covering internal organs and other internal surfaces of the body WordNet 3.0 & Open English WordNet

Epithelium or epithelial tissue is a thin, continuous, protective layer of compactly packed cells with a little intercellular matrix. Wikipedia

Tissue lining the surfaces of organs in animals Wikidata

Tissue, which consists of one or more layers of epithelial cells and a basement membrane; it covers the external surface of the body and lines the internal surfaces of the anatomical structures. Examples: simple squamous epithelium, glandular cuboidal epithelium, transitional epithelium, myoepithelium. OmegaWiki

A membranous tissue composed of one or more layers of cells which forms the covering of most internal and external surfaces of the body and its organs: internally including the lining of vessels and other small cavities, and externally being the skin. Wiktionary

Membranous tissue. Wiktionary (translation)