Epithelial cells are specialized cells that form the outer layer of tissues in the body, known as epithelia. They serve as a protective barrier, covering surfaces such as the skin, lining of organs, and cavities. These cells are tightly packed together, which helps prevent the entry of pathogens and harmful substances. In addition to protection, epithelial cells play important roles in absorption, secretion, and sensation. For example, in the intestines, they help absorb nutrients, while in the lungs, they facilitate gas exchange. Their diverse functions are essential for maintaining overall health and homeostasis in the body.