Examine a longitudinal section of
the esophago-gastric junction. Note the abrupt, major
change in the lining epithelium and the effect this has on the
underlying mucosa.
WWhat does the histology of the esophagus tell you about the
protective functions of this organ?
Clinical note: If the
muscularis of the lower esophagus fails to maintain the state of
partial contraction that normally prevents reflux of the gastric
contents upward, heartburn results. Since the esophageal mucosa
lacks a thick blanket of protective mucus, acidic gastric juices
irritate it, causing painful esophagitis. If chronic, this is called
gastro-esophageal reflux disorder (GERD) and can lead to metaplasia
of stratified squamous epithelium into a simple columnar, mucous
epithelium. (Image courtesy of
WebMD)
Now to the stomach. |