Answer:
Epithelial tissue is composed of cells laid out in sheets with strong cell-to-cell attachments. These protein connections hold the cells together to form a tightly connected layer that is avascular but innervated in nature.
The epithelial cells are nourished by substances diffusing from blood vessels in the underlying connective tissue. One side of the epithelial cell is oriented towards the surface of the tissue, body cavity, or external environment and the other surface is joined to a basement membrane. The basement layer is non-cellular in nature and helps to cement the epithelial tissue to the underlying structures.