õhuke rakkude kiht, mis koosneb tugevalt üksteisele kinnitunud rakkudest ning mis katab välimist keha pinda või selle sisemisi õõnsusi, Epithelial is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. Epithelial tissues line the cavities and surfaces of blood vessels and organs throughout the body.
