Squamous metaplasia occurs typically in
A. bronchi of chronic smokers.B. skin exposed to sunlight.
C. chronic gastritis
D. Barrett esophagus.
Ans. A. Long-term smoking irritates the normal columnar bronchial epit helium, which undergoes squamous metaplasia
(i.e., it transforms into stratified squamous epithelium). Skin cannot undergo
squamous metaplasia, because it is already lined by stratified squamous
epithelium. The term callus refers to thickening of the skin (e.g., as would be
caused by ill-fitting shoes); it is
an example of hyperplasia rather than metaplasia. Barrett’s esophagus
represents a form of glandular metaplasia in which the normal squamous
epithelium of the esophagus changes into gastric or intestinal epithelium. In
chronic gastritis the normal gastric mucosa changes into intestinal epithelium
but is not converted into squamous epithelium.
