An increasing number of peptides with a dual localization in endocrine cells and peripheral nerves in the walls of the gastrointestinal tract has now been recognized. The parasympathetic nerve supply to the stomach is derived from the anterior and posterior vagal trunks and their branches.
Afferent fibres are also present in the vagi, which are mixed nerves.
The anterior vagal trunk, which is derived mainly from the left vagus nerve but which includes fibres from the right vagus and also some sympathetic fibres from the splanchnic nerves, enters the abdominal cavity through the oesophageal hiatus in the diaphragm. It is usually single but may be divided into two or even three trunks. Having supplied several fine twigs to the lower end of the oesophagus and cardiac part of the stomach, the anterior trunk breaks up into its main branches. These nerves do not form a plexus and can be dissected separately. A few filaments from the sympathetic supply join these direct branches via the coeliac plexus.