What is the primary function of epithelial tissue?

• A. Lines inside and outside surfaces, such as skin and the lining of the digestive tract
• B. Provides structural support for joints
• C. Transmits nerve impulses
• D. Stores minerals and fats

Answer: (A)

The main function being tested is the role of epithelial tissue as a lining and protective barrier for surfaces and cavities. Epithelial tissue forms the coverings of the skin and lines the inside of hollow organs and passages such as the digestive tract, airways, and blood vessels. This arrangement creates a protective shield for underlying tissues and also governs what can pass through the surface, enabling absorption, secretion, and selective permeability in different areas. Depending on the location, epithelial cells can be thin and flat to allow diffusion (as in the lining of vessels) or thicker and multilayered to protect (as in the skin). Because other tissues have different primary roles—connective tissue provides structure, nervous tissue transmits impulses, and adipose/bone store minerals and fats—the description of epithelial tissue fits best as lining and protecting surfaces.