Epithelia are layers of cells that cover or line various surfaces in the body. There are different types of epithelia that can be categorized based on their structure and function. Some synonyms for epithelia include epithelial tissues, surface tissues, covering tissues, and lining tissues. The term "mucosa" is also commonly used to refer to epithelia that line the body's internal surfaces, such as those in the digestive and respiratory systems. Additionally, the term "epidermis" specifically refers to the outermost layer of skin, which is composed of epithelial cells. Understanding the different types and functions of epithelia is important in understanding various aspects of human biology and health.