| [ Summary ] |
Although it is not anatomically apparent, the lower esophageal sphincter (LES) exists as a functional sphincter and formsa high pressure zone. The LES contracts and relaxes to propel the food bolus downstream and in preventing retrograde flow. The innervation of the LES is performed by the central nervous system, the sympathetic nerves, the parasympathetic nerves and the enteric nervous system (ENS). The ENS resides in the submucosa, between the circular and longitudinal muscle layers of the bowel wall. Many neurotransmitters are recognized to be located in the LES. Prominent transmitters are acetylcholine, substans P, VIP and nitric oxide. LES relaxation, not triggered by swallowing is called transient LES relaxation (TLESR). Gastroesophageal reflux (GER) often occurs during TLESR. In addition, TLESR is the most frequent mechanism underlying GER. Our current understanding of LES is incomplete. However, it is supposed that LES disoders may cause a variety of diseases. |