The enteric nervous system (ENS) arises from neural crest cells of the primarily vagal origin and consists of a nerve plexus embedded in the intestinal wall, extending across the whole gastrointestinal tract from the esophagus to the anus. It is estimated that the human ENS contains about 100–500 million neurons. This is the largest accumulation of nerve cells in the human body (23–25). Since the ENS is similar to the brain regarding structure, function, and chemical coding, it has been describe