Structure and function of the vomeronasal organ.

The vomeronasal organ (VNO) is a complex of different structures that forward specific chemical signals commonly called pheromones to the central nervous system. In some macrosmatic animals, e.g. rodents, the VNO consists of vomeronasal receptor neurons located in a sensory epithelium of the vomeronasal duct, their afferent axons connecting the duct with the accessory olfactory bulb, associated glands and ganglionic cells in the nasal septal mucosa. The organ's main task is to influence mating and social behavior. In humans, the VNO does not exist, at least not in its complexity. Although developed in early fetal life, all structures except the vomeronasal duct undergo regression. The orifice of this duct can be easily observed by nasal endoscopy. Histochemically, it is lined with a remarkable pseudostratified epithelium, the nature and significance of which are still unclear. Recent studies indicate that pheromone-like compounds are most likely registered at the level of olfactory receptor cells, rendering the chemical information system more independent of specific organ structures.