The visceral pleura does not contain any noci-ceptors or pain receptors. The parietal pleura is innervated by somatic nerves that sense pain when the parietal pleura is inflamed. Inflammation that occurs at the periphery of the lung parenchyma can extend into the pleural space and involve the parietal pleura, thereby activating the somatic pain receptors and resulting in pleuritic pain. Parietal pleurae of the outer rib cage and lateral aspect of each hemidiaphragm are innervated by intercostal nerves. Pain is localized to the cutaneous distribution of those nerves. The phrenic nerve supplies innervations to the central part of each hemidiaphragm; when these fibers are activated, the sensation of pain is referred to the ipsilateral neck or shoulder.^[1]