what are epithelial cells

epithelial cells are arranged in tightly packed layers that line the surfaces and cavities of tissues and organs throughout the body. Of the four major tissue types found in the human and animal body, epithelial cells are by far the most prolific. Epithelial cells also comprise key structures of exocrine and endocrine glands. The basic function of epithelial cells is to provide a protective layer for the organ they enclose, but they functions are diverse and include secretion, selective absorption, filtration, protection and detection of sensation.