Epithelial tissue is characterized by closely packed cells with minimal extracellular matrix. It serves as a protective barrier and is involved in absorption, secretion, and sensation. Epithelial cells have distinct polarity, with an apical surface facing the lumen and a basal surface attached to the basement membrane. They can be classified based on cell shape (squamous, cuboidal, columnar) and the number of cell layers (simple, stratified).
