A 36-year-old Asian male complains of difficulty swallowing. Esophagoscopy reveals a polypoid mass that is subsequently biopsied. In addition to tumor cells, the esophageal biopsy show normal smooth muscle and striated muscle in the same section. Which portion of the oesophagus was the source of this biopsy?
a. Lower oesophageal sphincter
b. Lower third of the oesophagus
c. Middle third of the oesophagus
d. Upper oesophageal sphincter
The Correct option is C
Explanation with High Yield Facts:
The muscularis of the upper third of the esophagus is composed entirely of striated muscle. The middle third (choice C) contains both striated and smooth muscle. The lower third (choice B) and lower esophageal sphincter (choice A) contain only smooth muscle. There is no such thing as the upper esophageal sphincter (choice D).
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