Pseudociliated columnar epithelium is mainly located on the inner surface of the respiratory tract and has protective and secretory functions. Pseudociliated columnar epithelium is a single layer of epithelium composed of columnar cells, spindle-shaped cells, cup-shaped cells and cone-shaped cells. Because these cells are not equal in height, their nuclei are arranged in a jagged manner, which seems to be a complex layer in the vertical section, so it is called “pseudo-complex layer”, and the free surface of the columnar cells is accompanied by cilia that can be oscillated. Pseudocomplex ciliated columnar epithelium is mainly distributed in the inner surface of the respiratory tract, such as the nasal cavity, larynx, trachea and bronchial tubes. In the columnar ciliated epithelial cells, sandwiched between a mucus-secreting cup-shaped cells, the mucus can remove dust, foreign bodies, to protect the respiratory tract.