Epithelial cells are constantly being replaced and regenerated during an animal’s lifetime, which is why some people say in jest, “As humans, we become a ‘different person’ every so often.” For example, the epidermis (outer layer of the skin) is renewed every two weeks; the epithelial lining of the stomach is replaced every two to three days; and the liver, a gland consisting of epithelial tissues, easily regenerates after portions are removed surgically.