Lungs and Ventilation Pathway LO6

6. Review the autonomic innervation of the thoracic viscera.

Thoracic viscera are affected by sympathetic and parasympathetic innervation. In general, all thoracic viscera derive sympathetic innervation from T1-T5/6 spinal cord levels, while parasympathetic innervation is derived from the vagus n. (CN X).

There are three main autonomic plexuses associated with thoracic viscera: cardiac, pulmonary, and esophageal. All plexuses are continuous.

Cardiac plexus: there are two parts of the cardiac plexus: superficial (located inferior to arch of aorta and sandwiched between arch and pulmonary trunk) & deep (located between arch of aorta and tracheal bifurcation).

    • Sympathetic function: dilate coronary arteries and accelerates heart rate
    • Parasympathetic function: constrict coronary arteries and slows heart rate

Pulmonary plexus: located anterior and posterior to the root of the lungs; continuous with cardiac plexus (easily observable at tracheal bifurcation) and esophageal plexus

    • Sympathetic function: bronchodilation and constriction of pulmonary vasculature
    • Parasympathetic function: maintenance of tone or bronchoconstriction of smooth muscle of bronchi and dilation of pulmonary vasculature

Esophageal plexus: surrounding the inferior 2/3rds of the esophagus (inferior to root of lungs)

    • Sympathetic function: vasoconstriction of esophageal vasculature
    • Parasympathetic function: peristalsis of smooth muscle
    • The superior 1/3rd of the esophagus is composed of skeletal muscle and is innervated by the recurrent laryngeal n. and sympathetic fibers