What is the special function of the mucosa in the esophagus that explains why it is relatively thick and smooth while in most areas of the digestive tract the mucosa is relatively thin and folded?

Answer;

To protect the rest of the esophagus from sharp food particles and stomach acid.

Explanation;

The mucosa is the innermost layer, and functions in absorption and secretion. It is composed of epithelium cells and a thin connective tissue.

It contains specialized goblet cells that secrete sticky mucus throughout the GI tract, that prevents the corrosion of the stomach walls and esophagus from sharp food particles and the acids from the stomach.