Having trouble with this question and another one

[nettenette]

in the lungs of smokers, process called metaplasia occurs where normal lining cells of the lung are replaced by squamous metaplastic cells functionally, why is this an undesirable body reaction to tobacco smoke?

[boxtops]

..because it causes loss of function in the cells and can lead to cancer - have a look at http://en.wikipedia.org/wiki/Metaplasia