metaplazia

Metaplasia is a reversible, cellular adaptation where one mature cell type is replaced by another mature cell type. This change is a response to chronic irritation or stress, allowing the tissue to better withstand the adverse conditions. The new cell type is generally more resistant to the stressor than the original cells. However, this adaptation comes at the cost of losing the original cell type's specialized function. For example, in the respiratory tract of smokers, the normal ciliated columnar epithelium may be replaced by squamous epithelium. The squamous cells are more robust against the irritants in smoke, but they lack cilia, impairing the clearance of mucus and debris.

Metaplasia is not a neoplastic (cancerous) process itself, but it can be a precursor to malignancy. If the stressful stimulus persists, the metaplastic tissue may undergo further changes, eventually leading to dysplasia and then carcinoma. Common sites for metaplasia include the cervix, respiratory tract, esophagus, and urinary bladder. The specific type of metaplasia depends on the tissue involved and the nature of the stimulus. Examples include squamous metaplasia, intestinal metaplasia (also known as goblet cell metaplasia), and osseous metaplasia (bone formation in soft tissues). Treatment involves identifying and removing the underlying cause of the stress.