In the lungs of smokers, a process called metaplasia occurs in which the normal lining cells of the lung are replaced by squamous metaplastic cells (many layers of squamous epithelial cells)....

In the lungs of smokers, a process called metaplasia occurs in which the normal lining cells of the lung are replaced by squamous metaplastic cells (many layers of squamous epithelial cells). Functionally, why is this an undesirable body reaction to tobacco smoke?

HINT Your answer should mention the structure and function of the normal lining cells of the lung.