What is the primary function of epithelial cells?

Epithelial cells serve the essential role of covering surfaces and lining cavities throughout the body, providing protection and structural integrity against mechanical injury, pathogens, and harmful substances. They form barriers that regulate the exchange of materials and fluids, allowing selective permeability, which is crucial for maintaining homeostasis. Epithelial tissue also plays a role in absorption, secretion, and sensation, making it vital for processes like nutrient uptake in the intestines and the secretion of hormones from glands. Given these functions, the primary role of epithelial cells is indeed to cover, line, and protect various body surfaces.