The vomeronasal organ or Jacobson's organ (sometimes misspelled "Jacobsen's") is an auxiliary olfactory sense organ in some vertebrates, all of which are tetrapods. It is located in the vomer bone, between the nose and the mouth. The sensory neurons within the vomeronasal organ detect distinct chemical compounds, usually large molecules. Snakes use it to smell prey, sticking their tongue out and touching it to the opening to the organ. Some mammals use a distinctive facial movement called flehmen to direct compounds to this organ, while in some other mammals the entire organ contracts or pumps to draw in compounds.

Most animals with a vomeronasal organ utilize it in the detection of pheromones, though some pheromones are detected by the regular olfactory organ, and the vomeronasal organ seems to detect other compounds in addition to pheromones.

Some scientists believe that in humans the vomeronasal organ is nonfunctional and regresses before birth, as is the case with some other higher animals, including cetaceans, some bats, and apes. These scientists also believe that in adult humans, there is no neural connection between the organ and the brain. Nevertheless, some evidence suggests that the vomeronasal organ does not atrophy and remains functional throughout a person's life. Thus, its function in these organisms and in humans, if indeed real, is still somewhat mysterious.

See also : Nepetalactone

External links

Neuroscience Program FSU (http://athena.neuro.fsu.edu/research/vomeronasal/extendedText.htm)

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