Human Vomeronasal Organ
The diagram shows the location of the vomeronasal organ in adult humans. There is no obvious bulge in the nasal septum indicating its position. The duct opening (VNO pit), that can be observed with an endoscope in most adult humans, is at the anterior end (black dot next to arrowhead). There is no evidence for true vomeronasal sensory nerves connecting the organ to the brain. There are nerves running behind the VNO and extending back to the brain (? on the diagram) but they may be only Nervus terminalis, trigeminal and autonomic nerve branches (See also Extended-text). The organ shows some differences in structure compared with other mammalian organs. It has no obvious thick sensory epithelium but does have a few cells that have been described as similar to bipolar sensory neurons but lacking an axon. The location and structure suggest that the human organ, if functional, might be stimulated by airborne chemicals rather than by stimuli dissolved in mucus. Studies of the human genome indicate that a gene thought to be essential for vomeronasal sensory neuron function in other species is non-functional in humans, apes and other old-world primates. The accessory olfactory bulbs, to which VN nerves normally project in mammals, also have not been identified in humans, raising additional questions about human VNO function. The central target of VNO input in mammals, the cortico-medial amygdala, is present in humans (see diagram) and does receive chemosensory input (from the main olfactory system). It surely shares some functions with the amygdala in other mammals but it is not yet clear whether these include the receipt of purely vomeronasal input, or the analysis of pheromone-related information (whether or not from the vomeronasal system). (See "Human Vomeronasal Organ" and Extended-text for more details. See "Mammalian Vomeronasal Organ" for information on better studied systems). Select other topics from the list, or go to Extended text.