Innervation of Stomach and Proximal Duodenum

Parasympathetic Fibers. The two vagus nerves form an esophageal plexus around the lower esophagus, which is reinforced by twigs from the thoracic parts of the sympathetic trunks and from the greater (major) and lesser (minor) thoracic splanchnic nerves. Before reaching the diaphragm, the meshes of the esophageal plexus are reconstituted to form anterior and posterior vagal trunks. In general, more fibers from the left vagus enter the anterior trunk, whereas the posterior trunk contains more fibers from the right vagus, although the anatomic relationships are highly variable. The vagal trunks give off gastric, pyloric, hepatic, and celiac branches.

Anterior and posterior gastric branches supply the corresponding surfaces of the stomach. They run between the layers of the lesser omentum and give off branches that radiate over the surfaces of the stomach and can be traced for some distance in the subperitoneal tissue before they sink into muscle coats; no definite anterior or posterior gastric plexuses exist. Often, one branch on both the anterior and posterior aspects is larger than the others—the greater anterior and greater posterior gastric nerves. Pyloric branches arise from the anterior vagal trunk or its greater anterior gastric branch and supply the pyloric antrum, pylorus, and superior (first) part of the duodenum. Hepatic branches are provided by both vagal trunks; that from the anterior trunk arises near the gastric cardiac ostium and is called the hepatogastric nerve because it supplies offshoots to the hepatic plexus and stomach (there may be more than one hepatogastric nerve). The hepatic contribution from the posterior vagal trunk usually reaches the hepatic plexus through its celiac branch. Both vagal trunks give off celiac branches, and the posterior branch is larger than the anterior. All efferent (preganglionic) vagal fibers ending in the stomach make synaptic contacts with ganglionic neurons in the gastric parts of the myenteric and submucous plexuses; the resulting postganglionic fibers are distributed to the gastric musculature, glands, and vessels, where they exert both motor and secretory effects (see Plate 7-17).

Afferent Fibers. Afferent parasympathetic and sympathetic fibers pursue reverse routes to those described for vagal and sympathetic efferent fibers.

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