an accessory olfactory organ located above the anterior roof of the mouth, just behind the upper lip. used to detect less volatile pheromones which are fluid-borne. the pheromones enter the vomeronasal organ through the nasopalatine (incisive) ducts, located in the oral cavity.

plays a prominent role in male courtship behavior for many mammalian species, including cattle, sheep, and horses. see also flehmen response.