membranous tissue covering internal organs and other internal surfaces of the body
"The pathologist examined a biopsy to see if the damaged epithelium had successfully regenerated after removing the ulcerated lining."
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.
"The biopsy showed that a benign growth had developed within the epithelium lining the patient's nasal cavity."