What cellular change is primarily observed in the lungs of smokers?

Squamous metaplasia is a key cellular change observed in the lungs of smokers due to the chronic irritation caused by exposure to tobacco smoke. This condition involves the transformation of the normal respiratory epithelium, which is typically ciliated pseudostratified columnar epithelium, into a stratified squamous epithelium. This adaptive response occurs in an effort to protect the underlying tissues from the harmful effects of smoke, which includes toxic chemicals and particulates.

The presence of squamous metaplasia indicates a pathological alteration that can serve as a precursor to more serious conditions, such as dysplasia or carcinoma, particularly in the context of chronic exposure. This metaplastic change is commonly seen in the bronchial epithelium of chronic smokers and is a hallmark of smoke-related lung pathology.

Other changes, such as columnar metaplasia, primarily refer to different types of epithelial transformation that are not the primary response to cigarette smoke. Adenomatous hyperplasia and fibrous hyperplasia involve proliferative changes that are not characteristic of the typical response seen in smokers' lungs. Instead, the dominant and well-documented alteration is the development of squamous metaplasia due to the chronic irritation from smoke