Sensor cells and nerve terminals in some gut-derived organs: a review

The intestinal mucosa is supplied with intraepithelial sensor paraneurons and with nerve fibers restricted in the lamina propria. The present study compares some gut-derived and -related organs in regard to their neuroparaneuronal elements deviated in structure and function from those in the gut. At the light microscopic level the urethra contains intraepithelial sensor paraneurons with ramified cell base containing serotonin and sensory nerves penetrating the epithelium to reach the lumen. The trachea and bronchi contain, besides sensor paraneurons, numerous sensory nerves within the basal layer of the epithelium. These nerves are proposed to form a sensory complex, being associated with the epithelial cells. The respiratory portion of the nasal mucosa lacks intraepithelial paraneurons, while revealing numerous sensory nerves passing through the epithelium to directly detect stimulants in the air.