The vomeronasal organ (VNO) or Jacobson's organ[1] is an auxiliary olfactory sense
organ in some tetrapods. It is the first processing stage of the accessory olfactory system. In adults, it is located in the vomer
bone, between the nose and the mouth. It develops from the nasal (olfactory) placode, at
the anterior edge of the neural plate (cranial nerve
zero).
Function
The function of this organ is somewhat mysterious. The sensory neurons within the vomeronasal
organ detect distinct scents containing chemical compounds, which are often, but not
always, large non-volatile molecules. No further evidence of a functional use of the organ has been found to date.
In animals (other than humans)
The vomeronasal organ is used in the detection of pheromones by some animals such as
mice, although some pheromones are detected by the main olfactory epithelium, and the vomeronasal organ detects other compounds in addition to
pheromones.
Snakes use this organ to sense prey, sticking their tongue out
to gather scents and touching it to the opening of the organ when the tongue is retracted. Elephants transfer chemosensory stimuli to the vomeronasal opening in the roof of their mouths using the
prehensile structure, sometimes called a "finger", at the tips of their trunks. Some mammals use a distinctive facial movement
called the flehmen response to direct inhaled compounds to this organ. House cats often may be seen making this grimace when examining a scent that interests them. In some other mammals,
the entire organ contracts or pumps in order to draw in the scents.
In humans
Anatomical studies demonstrate that in humans the vomeronasal organ regresses during fetal
development, as is the case with some other mammals, including apes, cetaceans, and some bats. There is no evidence of a neural connection between the
organ and the brain in adult humans. Nevertheless, a small pit may be found in the nasal
septum of some people, and some researchers have argued that this pit represents a functional vomeronasal organ. Thus, its
possible presence in adult humans remains controversial.
See also
References
- ^ Bhatnagar KP, Smith
TD (2003). "The human vomeronasal organ. V. An interpretation of its discovery by Ruysch, Jacobson, or Kölliker, with an English
translation of Kölliker (1877)". Anatomical record. Part B, New anatomist 270 (1): 4–15. PMID
12884838.
External links
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