It innervates the bronchial tree and the visceral pleura.
According to the relation of nerves to the root of the lung, the pulmonary plexus is divided into the anterior pulmonary plexus, which lies in front of the lung and the posterior pulmonary plexus, which lies behind the lung.
[1] Innervation of the bronchial tree regulates contraction of bronchial smooth muscles, mucous secretions from submucosal glands, vascular permeability, and blood flow.
[2] Sensory fiber innervation of the visceral pleura is thought to allow stretch detection.
[3][4][5] This article incorporates text in the public domain from page 913 of the 20th edition of Gray's Anatomy (1918)