Background
The diaphragm, the most important muscle of ventilation, develops negative intrathoracic pressure to initiate ventilation. Innervated by cervical motor neurons C3-C5 via the phrenic nerves, these two nerves provide both sensory and motor function to the diaphragm.
With contraction, the cone-shaped muscle of the diaphragm decreases intrapleural pressure during inspiration and thereby facilitates movement of air into the lungs. Diaphragmatic paralysis is an uncommon, yet underdiagnosed cause of dyspnea.