Innervation of Esophagus
The esophagus is innervated by the vagus nerve as well as several sympathetic nerves. The vagus nerve innervates the glands and muscles of the esophagus, and the sympathetic input primarily innervates the capillary sphincters associated with the organ’s blood supply.
Nerves of esophagus
The vagus nerve conveys both motor and sensory fibers between the nuclei of the medulla oblongata and esophagus. Like the pharynx, the skeletal muscle of the upper esophagus is voluntary and the axons that innervate these fibers arise primarily from nerve cell bodies in the nucleus ambiguus. However, the amount of smooth muscle within the muscularis externa of the esophagus becomes more pronounced as one moves inferiorly and it is primarily innervated by axons from the dorsal vagal motor nucleus.
In the neck, where skeletal muscle predominates, the esophagus receives somatomotor axons from the recurrent laryngeal nerves that run superiorly between the esophagus and trachea. On the right side the recurrent laryngeal nerve arises from the vagus nerve at the root of the neck and turns superiorly bypassing inferior to the right subclavian artery before ascending. The left recurrent laryngeal nerve arises from the left vagus nerve opposite the aortic arch and curves beneath the arch of the aorta to reach the groove between the trachea and esophagus. Some inconstant filaments pass to the esophagus from the main vagus nerves that lie in the carotid sheath behind and between the common carotid artery and internal jugular vein.
In the thorax, the esophagus receives filaments from the left recurrent laryngeal nerve and both vagus nerves. The vagus nerves descend posterior to the bronchi, giving off branches that unite with axons from the sympathetic trunk to form the smaller anterior and larger posterior pulmonary plexuses. Below the bronchi each vagus nerve usually splits into two to four branches, which apply themselves to the surface of the esophagus in the posterior mediastinum. The branches from the right and left vagus nerves rotate posteriorly and anteriorly (respectively) as they divide and reunite to form an openmeshed esophageal plexus containing small ganglia. At a variable distance above the esophageal hiatus in the diaphragm, the meshes of the plexus become reconstituted into an anterior vagal trunk and posterior vagal trunk, embedded in the anterior and posterior wall of the lowest part of the esophageal wall. Offshoots from the esophageal plexus and from the anterior and posterior vagal trunks sink into the esophageal wall. Common variations in the plexus and in the vagal trunks are of especial significance to anyone performing vagotomy, and the surgeon should remember that there may be more than one anterior or posterior vagal trunk. The vagus nerves and their resultant trunks interdigitate with filaments from the sympathetic trunks so that, from the neck downward, they are really mixed parasympatheticsympathetic plexuses.
Intrinsic nerves and variations in nerves of esophagus
The sympathetic preganglionic fibers are the axons that originate in the intermediolateral cell column, located mainly in the fourth to sixth thoracic segments of the spinal cord. These presynaptic axons emerge in the anterior spinal nerve roots corresponding to the segments containing their parent cells. They leave the spinal nerves via white rami communicans and pass to the ganglionic nerve cell bodies located in the sympathetic trunk. Some fibers form synapses with cells in the mid thoracic ganglia, but others pass to higher and lower ganglia in the trunk before synapsing. Postsynaptic axons exiting the sympathetic trunk reach the esophagus through branches from the sympathetic trunks. The afferent impulses are conveyed in fibers that pursue an antiparallel route, but they do not relay in the sympathetic trunk. Instead they pass through the trunk without synapsing, travel through the white rami communicans to reach the spinal nerve, and then travel along the posterior nerve roots before reaching the posterior horn of the spinal cord. Their pseudounipolar nerve cell bodies are located in the posterior (dorsal) root ganglia.
The uppermost part of the esophagus is supplied by offshoots from the pharyngeal plexus that contain postsynaptic sympathetic axons. More inferiorly, it receives axons from the cardiac branches of the superior cervical ganglia and occasionally from the middle cervical or vertebral ganglion of the sympathetic trunk. Other fibers reach the esophagus in the delicate nerve plexuses accompanying the arteries that supply it. In the upper thorax, esophageal axons are supplied by the stellate ganglia or ansa subclavia, and the delicate thoracic cardiac nerves are often associated with fibers for the esophagus, trachea, aorta, and pulmonary structures.
In the lower thorax, axons pass from the greater (thoracic) splanchnic nerves to the nearby esophageal plexus. The greater splanchnic nerves generally arise by three or four larger roots and an inconstant number of smaller rootlets from the fifth to the ninth thoracic ganglia of the sympathetic trunk, although there is significant variation. The roots and rootlets pass obliquely anteriorly, medially, and inferiorly across the sides of the thoracic vertebral bodies and intervertebral disks and coalesce to form a nerve of considerable size. On each side the nerve enters the abdomen by piercing the homolateral diaphragmatic crus or, less often, by passing between the lateral margins of the crura and the fibers arising from the medial arcuate ligament. The intraabdominal course is short, and each nerve breaks up into branches that end mainly in the celiac ganglion. The lesser and least thoracic splanchnic nerves terminate mainly in the aorticorenal and superior mesenteric ganglia. Filaments from the terminal part of the left greater splanchnic nerve reach the abdominal part of the esophagus.