❯❯ MEDICAL APPLICATION
The chronic presence or accumulation of toxins that
occur with heavy cigarette smoking or industrial air
pollution affects the respiratory epithelium beginning
in the nasal cavities. Immobilization of the cilia causes
failure to clear mucus containing filtered material and
exacerbates the problem, leading eventually to the
likelihood of squamous metaplasia of the epithelium.
A change from pseudostratified ciliated columnar to
stratified squamous epithelium can occur, particularly in
the mucosa of bronchi. This can produce precancerous
cell dysplasia in this tissue.