Squamous metaplasia occurs typically in
A. bronchi of chronic smokers.B. skin exposed to sunlight.
C. Barrett esophagus.
D. chronic gastritis.
The
answer is
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 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.
