Phrenic nerve
Latin: Nervus phrenicus sinistra
Paired structure: one on the left and one on the right side of the body.
View the phrenic nerve in 3DRoots
C3, C4, C5 — 'C3, 4, 5 keeps the diaphragm alive'.
Course
Descends on the anterior scalene under the prevertebral fascia, crosses it obliquely from lateral to medial, passes behind the subclavian vein, then traverses the mediastinum between the pericardium and the pleura anterior to the lung root, to reach and pierce the diaphragm's dome.
Motor supply
The left hemidiaphragm — each phrenic nerve is the sole motor supply to its half of the diaphragm.
Sensory supply
The pericardium, mediastinal pleura and the diaphragm's central tendon; the peritoneum of the central diaphragm.
Clinical relevance
Irritation refers pain to the shoulder tip (C4 dermatome) — the Kehr sign of splenic rupture; cervical cord injuries at or above C3 abolish spontaneous breathing. Hiccups are involuntary spasms of the diaphragm driven through the phrenic nerves.
Educational anatomy reference, not medical advice. About this content.