Epithelial Metaplasia
Barrett’s esophagus
Metaplasia means the conversion, in
postnatal life, of one cell type to another.
Metaplasia is important for two reasons.
1) We understand the normal developmental biology
of the tissues that interconvert.
2) Metaplasia predisposes to certain forms of
neoplasia.
One of the examples of metaplasia is
Barrett's metaplasia or the appearance of intestinal-like columnar tissue in
the oesophagus.
Barrett's
metaplasia develops as a result of gastro–oesophageal reflux and is considered
the precursor lesion for oesophageal adenocarcinoma. Barrett’s esophagus
is a condition marked by an abnormality in the lining of the lower esophagus.
It is believed to be due to severe, longstanding, gastroesophageal reflux
disease (GERD).
Normally, the
esophageal lining (the epithelium) consists of flat, layered cells similar to
those in the skin. This squamous epitheliumtops abruptly at the junction of the
esophagus with the stomach near the lower end of the lower esophageal
sphincter. The epithelium of the rest of the gut, down to the anus, consists of
a single layer of side-by-side rectangular cells, which is called columnar
epithelium. In some people, the
transition from squamous to columnar epithelium occurs higher within the
esophagus than normal. There may also be islands of columnar epithelium above
the normal junction of the stomach and esophagus. The process of cell change
from flat, layered squamous to tall columnar epithelium is an example of
metaplasia.
Columnar cells
are more resistant to acid and pepsin and the metaplasia may be a defense
against refluxed acid.
http://www.sciencedirect.com/science/article/pii/S0304419X07000078
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