Regarding the phrenic nerves:

The correct statement is that the phrenic nerves are always in contact with the pleura laterally.
The Phrenic Nerves
The phrenic nerves, one on each side, originate primarily from the ventral rami of the C3, C4, and C5 spinal nerves. They are crucial for breathing as they provide motor innervation to the diaphragm, the primary muscle of respiration. They also provide sensory innervation to the central part of the diaphragm, the mediastinal pleura, and the pericardium.
Incorrect Options Explained
* A. Pass behind anterior scalene muscle: This is incorrect. The phrenic nerve descends along the anterior surface of the anterior scalene muscle. This is a key anatomical landmark used to identify the nerve.
* B. The right nerve pierces the muscular part of the diaphragm: This is incorrect. The phrenic nerves, both right and left, pass through the diaphragm to reach its inferior surface. The right phrenic nerve passes through the caval opening in the central tendon of the diaphragm, along with the inferior vena cava. The left phrenic nerve pierces the muscular part of the diaphragm separately, to the left of the pericardium.
* D. Run in mediastinum behind the lung root: This is incorrect. The phrenic nerves run anterior to the lung roots (the structures that connect the lungs to the mediastinum, including the bronchi and pulmonary arteries/veins). The vagus nerves, in contrast, run posterior to the lung roots.
* E. Split into four main branches – anterior, posterior, medial and lateral: This is incorrect. The phrenic nerves do not split into these specific branches. After reaching the diaphragm, they divide into several smaller terminal branches that supply the different parts of the diaphragm.