SUMMARY
In summary, the autonomic innervation of thoracic viscera is derived from both parasympathetic and sympathetic systems. Autonomic fibers form the cardiac, pulmonary and esophageal plexuses.
Sympathetic fibers supplying thoracic viscera arise from the lateral horn of the upper thoracic spinal cord segments as preganglionic fibers, some of which ascend in the cervical sympathetic trunk and synapse in cervical ganglia. Postganglionic fibers then descend through the neck as cardiac branches and end in the cardiac plexus of the heart. Other sympathetic fibers synapse in the upper thoracic sympathetic trunk and the postganglionic fibers travel to the thoracic viscera as small thoracic visceral nerves ending in the cardiac, pulmonary and esophageal plexuses. The sympathetics speed the heart, increase its output, constrict blood vessels and dilate bronchi.
The parasympathetic supply to thoracic viscera is carried via the vagus nerve (CN X), which descends through the neck and into the chest. It gives rise to branches that reach the cardiac, pulmonary and esophageal plexuses. The parasympathetics slow the heart and decrease its output, constrict bronchioles in the lungs and provide for contraction (peristalsis) of the esophagus.
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