Pseudocomplex ciliated columnar epithelium is mainly found on the inner surfaces of the respiratory tract, such as the nasal cavity, larynx, trachea, and bronchi. Pseudociliated columnar epithelium is composed of columnar cells, squamous cells, and cone-shaped cells, the basal layer of each cell is attached to the basement membrane, and there are oscillating cilia attached to the free surface of the columnar epithelium, which is mainly distributed on the inner surface of the respiratory tract. In the pseudo-complex ciliated columnar epithelium between the distribution of mucus-secreting cup-shaped cells, the secretion of mucus can be attached to and remove dust, bacteria and other foreign matter, with the help of cilia rhythmic swing, the mucus containing dust and bacteria will be discharged to the larynx. In addition, mucus also has the effect of moisturizing dry air.