A nostril (or naris, pl. nares, pronounced ˈnɛər iz) is one of the two channels of the nose, from the point where they bifurcate to the external opening. In birds and mammals, they contain branched bones or cartilages called turbinates, whose function is to warm air on inhalation and remove moisture on exhalation. Fish do not breathe through their noses, but they do have two small holes used for smelling which may, indeed, be called nostrils.
The Procellariiformes are distinguished from other birds by having tubular extensions of their nostrils.
The nostrils are separated by the septum. The septum can sometimes be deviated, causing one nostril to appear larger than the other. With extreme damage to the septum, the two nostrils are no longer separated and form a single larger external opening.1
Like other tetrapods, humans have two external nostrils and two additional nostrils inside the head. These internal nostrils are called "choanae" and each contains approximately 1000 strands of nasal hair. They also connect the nose to the throat, aiding in respiration. Though all four were outside the head of our fish ancestors, they migrated back inside as evidenced by the discovery of Kenichthys campbelli, a 395 million-year-old fossilized fish which shows this migration in progress. It has two nostrils between its front teeth, similar to human embryos at an early stage. If these fail to join up, the result is a cleft palate.2
It is possible for humans to smell different olfactory inputs in the two nostrils and experience a perceptual rivalry akin to that of binocular rivalry when there are two different inputs to the two eyes.3
- Barnes, Anthony (6 June 2000). "Cocaine destroyed my nose, admits 'EastEnders' star". The Independent (London). Archived from the original on 24 April 2009. Retrieved 1 May 2012.
- Lloyd, John; Mitchinson, John (2008). The Book of General Ignorance. London: Faber and Faber. pp. 2, 299. ISBN 978-0-571-24139-2. OCLC 191753333. Retrieved 16 July 2011.
- Zhou, Wen; Chen, Denise (29 September 2009). "Binaral rivalry between the nostrils and in the cortex". Current Biology 19 (18): 1561–5. doi:10.1016/j.cub.2009.07.052. PMC 2901510. PMID 19699095. Retrieved 1 May 2012.
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