vagus nerves and phrenic nerves | Medicoze

The vagus nerve

The right vagus enters the thorax posterolateral to the right brachiocephalic artery and descends lateral to the trachea under the mediastinal pleura to the back of the right main bronchus, where it gives branches, first to the pulmonary plexus and then to the oesophageal plexus. The left vagus enters the thorax between the left common carotid and subclavian arteries and descends across the left of the aortic arch, where it gives off its recurrent laryngeal branch, before passing behind the left lung root to the oesophagus. The two vagi form the oesophageal plexus, from which emerge anterior and posterior gastric nerves containing fibres of both vagi and sympathetic nerves, which descend to pass through the oesophageal opening of the diaphragm. The nerves supply the stomach, duodenum, pancreas and liver, and contribute branches via the coeliac plexus to other viscera.

Branches

The left recurrent laryngeal nerve winds around the ligamentum arteriosum and aortic arch and ascends between the trachea and oesophagus into the neck ,providing cardiac branches to the cardiac plexus and branches to the pulmonary and oesophageal plexuses.

The phrenic nerves

The phrenic nerves arise from the ventral rami of C3, C4 and C5 and descend from the neck through the thorax in front of each lung root.The right phrenic nerve enters the thorax lateral to the right brachiocephalic vein, descends on the pericardium over the superior vena cava, right atrium and inferior vena cava, and passes through the caval opening of the diaphragm. Throughout, it is covered laterally by mediastinal leura. The left phrenic nerve enters between the left subclavian artery and left brachiocephalic vein, descending across the aortic arch and pericardium over the left ventricle to reach and pierce the left diaphragm. It is covered laterally by mediastinal pleura. Both nerves are motor to the diaphragm and supply sensory branches to the mediastinal and diaphragmatic pleura, the pericardium and the peritoneum.Pain arising from inflammation of the diaphragmatic pleura is classically referred to skin over the shoulder tip, which is supplied by nerves derived, like the phrenic nerve,from the C4 spinal segment.