A type of tissue that covers body surfaces and lines body cavities, serving protective, secretory, and absorptive functions. It forms the outer layer of skin and inner lining of organs.
From Greek 'epi' (upon) and 'thele' (nipple), literally meaning 'upon the nipple'. Coined in the 18th century by anatomist Albrecht von Haller, who first observed this tissue type on nipple surfaces before recognizing its presence throughout the body.
Epithelial tissue is remarkable for its regenerative capacity, completely renewing itself every few days in some areas like the intestinal lining. The original Greek naming, referring to nipple tissue, shows how early anatomists used familiar body parts as reference points for understanding broader biological principles.
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