👉 Epithelial tissue is a type of connective tissue that serves as an outer layer around organs and other tissues. It is characterized by its ability to form barriers, such as the lining of blood vessels or the lining of the mouth, and it has a specialized structure called an epithelium. The term "epithelize" refers to the process where an epithelial cell forms a protective barrier over another layer of cells, which in this case is the underlying connective tissue.