What type of cellular metaplasia is expected in a patient with a long history of tobacco smoking?

In a patient with a long history of tobacco smoking, squamous metaplasia is commonly observed. This phenomenon occurs as a response to chronic irritation and inflammation caused by cigarette smoke. The normal respiratory epithelium, which is typically ciliated columnar, undergoes transformation into stratified squamous epithelium to protect against harmful substances.

Squamous metaplasia offers a more resilient barrier in the airways but can compromise the normal functions of the respiratory epithelium, such as mucus production and clearance of pathogens. This adaptive response, while providing immediate protection, is linked to an increased risk of further complications, including chronic bronchitis and potentially malignant changes, as the squamous cells may eventually become dysplastic with prolonged exposure to carcinogens found in tobacco smoke.

This understanding of squamous metaplasia in the context of smoking-related pathophysiology highlights the body's ability to adapt under chronic stress, albeit sometimes at the cost of increased susceptibility to disease.