* Squamous cells are flat and thin, like pavement tiles. They are found in areas where diffusion or filtration is important, like the lining of blood vessels (endothelium), the air sacs of the lungs (alveoli), and the surface of the skin (epidermis).
* Columnar cells are tall and cylindrical, resembling columns. They are often found in areas involved in absorption or secretion, like the lining of the digestive tract (intestine) and the lining of the respiratory tract (trachea).
So, squamous cells are not a type of columnar cell, but rather a separate category of epithelial cells with a different structure and function.
