What are the sensory innervation sources of the diaphragm?

• A. Phrenic nerves
• B. Intercostal nerves
• C. Vagus nerves
• D. Phrenic and intercostal nerves

Answer: (D)

Sensory input from the diaphragm comes from two sources depending on the part of the muscle and its coverings. The central part, including the central diaphragmatic pleura and peritoneum, carries somatic sensation via the phrenic nerves. The peripheral parts of the diaphragm, especially the diaphragmatic surface near the edges, receive sensory fibers from the lower intercostal nerves. The vagus nerve provides autonomic innervation to thoracic viscera but does not contribute significant diaphragmatic sensory input. Clinically, irritation of diaphragmatic pleura or peritoneum often refers pain to the shoulder because phrenic nerve afferents enter the spinal cord at C3–C5.