The vomeronasal organ (VNO) 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. Olfaction, the sense of smell, is the detection of chemicals dissolved in air (or, by animals that breathe water, in water). ... Typical classes Petromyzontidae (lampreys) Placodermi - extinct Chondrichthyes (cartilaginous fish) Acanthodii - extinct Actinopterygii (ray-finned fish) Actinistia (coelacanths) Dipnoi (lungfish) Amphibia (amphibians) Reptilia (reptiles) Aves (birds) Mammalia (mammals) Vertebrata is a subphylum of chordates, specifically, those with backbones or spinal columns. ... Classes Synapsida Sauropsida Amphibia A tetrapod (Greek tetrapoda, four-legged) is a vertebrate animal having four feet, legs or leglike appendages. ... The vomer bone is one of the unpaired facial bones of the skull. ... Neurons (also called nerve cells) are the primary cells of the nervous system. ... A chemical compound is a chemical substance formed from two or more elements, with a fixed ratio determining the composition. ... Families Acrochordidae Aniliidae Anomalepididae Anomochilidae Atractaspididae Boidae Bolyeriidae Colubridae Cylindrophiidae Elapidae Hydrophiidae Leptotyphlopidae Loxocemidae Pythonidae Tropidophiidae Typhlopidae Uropeltidae Viperidae Xenopeltidae Snakes are cold blooded legless reptiles closely related to lizards, which share the order Squamata. ... Alternative meaning: Tongue, Highland The tongue is the large bundle of muscles on the floor of the mouth that manipulates food for chewing and swallowing. ... The Flehmen response is a particular type of curling of the lips in ungulates, felids, and many other mammals, which facilitates the transfer of chemicals into the vomeronasal organ. ...

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. Fanning honeybee exposes Nasonov gland (white-at tip of abdomen) releasing pheromone to entice swarm into an empty hive A pheromone is any chemical produced by a living organism that transmits a message to other members of the same species. ...

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. Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. ... Suborders Mysticeti Odontoceti (see text) The order Cetacea includes whales, dolphins and porpoises. ... Families Pteropodidae Emballonuridae Rhinopomatidae Craseonycteridae Rhinolophidae Nycteridae Megadermatidae Vespertilionidae Molossidae Antrozoidae Natalidae Myzopodidae Thyropteridae Furipteridae Noctilionidae Mystacinidae Mormoopidae Phyllostomidae Bats are flying mammals in the order Chiroptera with forelimbs developed as wings. ... Families Hylobatidae Hominidae Apes are the members of the Hominoidea superfamily of primates, including humans. ...

See also : Nepetalactone

Nepetalactone is a lactone chemical compound first isolated in the plant catnip, Nepeta cataria (apparently named after the Italian town of Nepete). ...

External links

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