Columnar epithelial cells are a type of epithelial tissue characterized by their tall, column-like shape. They are primarily found lining the surfaces of organs and structures within the body, such as the intestines and respiratory tract. These cells play a crucial role in absorption, secretion, and protection, often containing specialized structures like microvilli or cilia to enhance their functions. These cells can be classified into different types, including simple columnar epithelium and stratified columnar epithelium. Simple columnar epithelium consists of a single layer of cells, while stratified columnar epithelium has multiple layers. The presence of goblet cells within this tissue type allows for the secretion of mucus, aiding in lubrication and protection of underlying tissues.