The wall of the esophagus is composed of four layers (inner to outer): mucosa, submucosa, muscularis propria and adventitia, reflecting the general structural organization of the entire gastrointestinal tract.  The mucosa is composed of three components (inner to outer): a non-keratinizing stratified squamous epithelium, a lamina propria and the muscularis muscosa.  The submucosa is composed of loose connective tissue, blood vessels, lymphatics, lymphoid follicles, the meissner plexus of nerves and submucosal glands.  The submucosal glands secrete mucus which functions to lubricate the esophagus and protect the epithelial layers from the harsh environment to which it is exposed, e.g., food and gastric acid.  The muscularis propria consists of an inner circular muscle layer and an outer longitudinal muscle layer with an intervening myenteric (auerbach) plexus.  Contraction of the circular muscle layer causes an increase in luminal pressure, while contraction of the longitudinal muscle layer causes shortening of the esophagus.  The muscularis propria of the esophagus is unique in that the proximal 1/3 is composed of skeletal muscle, the middle 1/3 is composed of both smooth and skeletal muscle and the distal 1/3 is composed of only smooth muscle.  The adventitia is the connective tissue fascia layer that surrounds the esophagus (1).