Definition of guano. : a fertilizer containing the accumulated excrement of seabirds or bats; broadly : excrement especially of seabirds or bats.
Developmental Biology Online. Epithelial tissues come in three basic types: squamous, cuboidal and columnar. These three types of tissue are seen in either simple (only one cell layer thick) or stratified (many cells in thickness) arrangements.
Epithelial cells are specialized cells which line many different kinds of tissue. Columnar epithelial cells are named because they are somewhat rectangular in shape and resemble a column in their orientation. Columnar epithelial cells are often specialized so that they can have a variety of different functions in the tissues which they line.