wikipedia-In biology and medicine, an epithelium is a tissue composed of cells that line the cavities and surfaces of structures throughout the body. Many glands are also formed from epithelial tissue. It lies on top of connective tissue, and the two layers are separated by a basement membrane. When they say line the cavities and structures do the mean inside or outside. Does epithelium create a membrane outside(is it the outermost membrane) or is it inside the membrane like villi in the intestine. What does the term line in imply. Thank you!!