Several nerves such as the intercostal, vagus, and phrenic nerves and sympathetic trunks are present in the thorax.

Sympathetic Trunks

The right and left sympathetic trunks lie on either side of the vertebral column in the posterior mediastinum. They cross the neck of the first rib, the heads of ribs 2-10, and the bodies of the eleventh and twelfth vertebrae. They then pass behind the diaphragm into the abdomen. Twelve indistinct ganglia, one for each spinal nerve, swell each thoracic trunk. Often, the ganglia of the first nerve is incorporated with the inferior cervical ganglion to form the stellate ganglion. Preganglionic axons originating from the thoracic and upper three lumbar segments of the spinal cord exit through the ventral root of each spinal nerve and leave it as white rami communicantes. After synapsing in the sympathetic ganglia, the post-ganglionic axons are distributed to their target tissues via one of three roots;

They may follow arteries, supplying the arteries themselves as they run along them on the way to their targets
They may rejoin the spinal nerve as grey rami communicantes and be distributed through them. Sympathetic preganglionic axons are myelinated whereas post-ganglionic axons are not, accounting for the colour difference between the white and grey rami
In the thorax, the lower seven ganglia have additional branches which are grouped into three splanchnic nerves that innervate the gastrointestinal tract. The first five thoracic ganglia send branches to the heart and great vessels, lungs, and esophagus.

Vagus Nerves

The right and left vagus nerves are asymmetrical due to asymmetry of the great vessels in the thorax.

The right vagus crosses in front of the subclavian artery in the root of the neck where it gives off its recurrent laryngeal branch. It enters the thorax behind the right brachiocephalic vein, then descends in contact with the trachea, and passes behind the root of the lung where it sends branches to the pulmonary plexus. It then passes on to the posterior surface of the esophagus and passes with it into the abdomen.

The left vagus enters the thorax between left subclavian and common carotid arteries. As the nerve crosses the aortic arch, it gives off the left recurrent laryngeal nerve which passes below the arch behind the ligamentum arteriosum and then ascends in the groove between the trachea and the esophagus. The main nerve trunk runs behind the root of the left lung where it contributes to the pulmonary plexus. It then runs on the anterior surface of the esophagus into the abdomen. Both vagus nerves give cardiac branches in the cervical part of their course which then descend into the heart. The two nerves supply the lungs and the esophagus through the pulmonary and esophageal plexuses as they pass through the thorax. They supply the abdominal viscera once in the abdominal cavity.

Phrenic Nerves

The phrenic nerves are derived from the ventral rami of the third to fifth cervical nerves (C3, C4 and C5) and form then motor nerve supply to the diaphragm which originated embryologically in the neck region. Each nerve passes downwards to enter the thoracic inlet between the subclavian artery and vein, they descend between the mediastinum pleura and pericardium. When they reach the diaphragm, they pass through the caval opening to supply sensory innervations to the peritoneum on the inferior surfaces of the diaphragm. The phrenic nerves also sensory to the mediastinal and diaphragmatic pleural and the fibrous and parietal layer of the serous pericardium. The thoracic nerves may be involved in diseases affecting the thorax and its contents.

Nerves of the Thorax

Intercostal nerves are the pulmonary rami of T1-T11 and run in the costal groove between the internal intercostal muscles and the innermost intercostal muscles.
The subcostal nerve is the ventral primary ramus of T12.
Intercostal nerve injury is evidenced by a sucking in (upon inspiration) and bulging out (upon expiration) of the affected intercostal space.

Innervation