Frontal section of nasal cavities of a human embryo 28 mm. long (Vomeronasal organ of Jacobson labeled at right)
Latin	organum vomeronasale
	subject #223 996
Precursor	olfactory placode
Dorlands/Elsevier	o_06/12596317

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

• Olfaction
• Accessory olfactory system
• Olfactory system
• Flehmen response
• Pheromone
• Odor
• Vomeronasal cartilage

References

External links

• Neuroscience Program FSU
• Annals of New York Academy of Science, 1998.

•  • [ e] General anatomy of head and neck - head
Face/Occiput	Forehead • Eye • Ear • Temple • Cheek • Chin
External nose	Nostril • Nasal septum • Cartilages (Accessory nasal, of the septum, Greater alar, Lateral nasal, Lesser alar, Vomeronasal)  • Olfactory glands
Nasal cavity	Choana • Turbinate • Sphenoethmoidal recess • Ethmoid bulla • Hiatus semilunaris • Ostium maxillare • Inferior meatus • Vomeronasal organ • Paranasal sinus
Mouth/oral cavity	Lip • Philtrum • Jaw • Pterygomandibular raphe
Teeth	Permanent (Incisor, Canine, Premolar, Molar)  • Deciduous
Tongue	Plica fimbriata • Median sulcus • Foramen cecum • Terminal sulcus • Frenulum linguae • Anterior tongue • Posterior tongue
Palate/roof of mouth	Hard palate • Soft palate • Palatine raphe • Incisive papilla • Uvula • Pharyngeal recess • Arches: (Palatoglossal • Palatopharyngeal)
Salivary glands	(Parotid • Sublingual • Submandibular) • Ducts: Submandibular • Parotid
fascia	Masseteric fascia • Temporal fascia • Galea aponeurotica • Scalp