Smokers occasionally get stratified squamous epithelium lining their airways.
This is largely the result of genetic mutations, rather than being for protection (as some people may tell you.)
When one morphologically normal type of epithelium is replaced by another, it's called "metaplasia".
This is bronchus from a smoker. There is some blood free in the lumen of the bronchus.
With your study partners, find:
Hotshots: Find a carbon-laden macrophage in the bronchial lumen.
Kansas City University of Medicine and Biosciences