Corpus: Pulmonary plexus

The pulmonary plexus is a nerve plexus responsible for the autonomic innervation of the main bronchi (right and left) and subsequent sections of the bronchial tree.

The pulmonary plexus is composed of two components:

• Parasympathetic bronchial branches from the vagus nerve and fibres from the recurrent laryngeal nerve.
• Sympathetic fibres from the sympathetic trunk, mainly from the cervicothoracic ganglion and upper thoracic ganglia.

The fibres are distributed on the ventral and dorsal sides of the main bronchi, with the dorsal component being more pronounced. From the main bronchi, the fibres travel alongside the pulmonary vessels into the lung tissue. Numerous small parasympathetic ganglia are scattered throughout the plexus, connecting the bronchial branches to postganglionic fibres. The number of ganglia decreases as the distance from the pulmonary hilus increases.

The pulmonary plexus also communicates with the thoracic aortic plexus.

The pulmonary plexus regulates the dead space volume of respiration. The visceromotor fibres control the smooth muscles of the bronchi. Parasympathetic stimulation leads to bronchoconstriction, reducing dead space volume during rest. In contrast, sympathetic stimulation causes bronchodilation, increasing dead space volume.

Sensory fibres, primarily via the vagus nerve, transmit stretch and pain stimuli to the respiratory centre. When lung volume exceeds 1.5 litres, the Hering-Breuer reflex is triggered to prevent over-expansion of the lungs.

Some afferent fibres from the oesophagus connect to fibres of the pulmonary plexus in the brainstem. As a result, gastro-oesophageal reflux disease (GERD) can lead to bronchoconstriction, explaining the association between reflux oesophagitis and chronic cough.