Editing Nostril

{{Short description|Nose orifice that enables the entry and exit of air}}
{{redirect|Nares|the nostrils of a bird|Beak#Nares|other uses|Nares (disambiguation)}}
{{redirect|Naris|Prince Naris of Siam|Narisara Nuwattiwong}}
{{Infobox anatomy
 | Name = Nostril
 | Image = File:Human Nostrils 01.JPG
 | Caption = Human nostrils
 | Latin = naris
 | Width  =
 | Precursor=
 | System  = [[Olfactory system]]
 | Part_of = [[Nose]]
 | Artery  =
 | Vein   = 
 | Nerve  =
 | Lymph  =
 }}

A '''nostril''' (or '''naris''' {{IPAc-en|ˈ|n|ɛər|ᵻ|s}}, {{plural form}}: '''nares''' {{IPAc-en|ˈ|n|ɛər|iː|z}}) is either of the two [[orifices]] of the [[nose]]. They enable the entry and exit of air and other gasses through the [[nasal cavities]].  In [[bird]]s and [[mammal]]s, they contain branched bones or cartilages called [[turbinate]]s, whose function is to warm air on inhalation and remove moisture on exhalation. [[Fish]] do not breathe through noses, but they do have two small holes used for [[olfaction|smelling]], which can also be referred to as nostrils (with the exception of [[Cyclostomi]], which have just one nostril).

In [[human]]s, the [[nasal cycle]] is the normal [[Ultradian|ultradian cycle]] of each nostril's blood vessels becoming engorged in swelling, then shrinking.

The nostrils are separated by the [[Nasal septum|septum]]. The septum can sometimes be [[Deviated septum|deviated]], causing one nostril to appear larger than the other.  With extreme damage to the septum and columella, the two nostrils are no longer separated and form a single larger external opening.

Like other [[tetrapod]]s, humans have two external nostrils (anterior nares) and two additional nostrils at the back of the nasal cavity, inside the head (posterior nares, posterior nasal apertures or [[choana]]e). They also connect the nose to the throat (the nasopharynx), aiding in respiration. Though all four nostrils were on the outside of the head of the aquatic ancestors of modern tetrapods, the nostrils for outgoing water (excurrent nostrils) migrated to the inside of the mouth, as evidenced by the discovery of ''[[Kenichthys|Kenichthys campbelli]]'', a 395-million-year-old fossilized [[Sarcopterygii|lobe-finned fish]] which shows this migration in progress. It has two nostrils between its front teeth, similar to human [[embryo]]s at an early stage. If these fail to join up, the result is a [[cleft palate]].<ref>{{cite book
|last1=Lloyd
|first1=John
|author-link1=John Lloyd (producer)
|last2=Mitchinson
|first2=John 
|author-link2=John Mitchinson (researcher)
|title=The Book of General Ignorance
|url=https://books.google.com/books?id=4AhXPgAACAAJ
|access-date=16 July 2011
|date=2008
|publisher=[[Faber and Faber]]
|location=London
|isbn=978-0-571-24139-2
|oclc=191753333
|pages=2, 299}}</ref>

Each external nostril contains approximately 1,000 strands of [[nasal hair]], which function to filter foreign particles such as pollen and dust.<ref>{{cite book |last1=Blume-Peytavi |first1=Ulrike |last2=Whiting |first2=David A. |last3=Trüeb |first3=Ralph M. |title=Hair Growth and Disorders |year=2008 |publisher=Springer |location=Berlin |isbn=978-3540469087 |page=10}}</ref>

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.<ref>{{cite journal |last1=Zhou |first1=Wen |last2=Chen |first2=Denise |date=29 September 2009 |title=Binaral rivalry between the nostrils and in the cortex |journal=[[Current Biology]] |volume=19 |issue=18 |pages=1561–5 |doi=10.1016/j.cub.2009.07.052 |pmid=19699095 |pmc=2901510 |bibcode=2009CBio...19.1561Z }}</ref> Furthermore, scent information from the two nostrils leads to two types of neural activity<ref>{{Cite journal |last1=Dikeçligil |first1=Gülce Nazlı |last2=Yang |first2=Andrew I. |last3=Sanghani |first3=Nisha |last4=Lucas |first4=Timothy |last5=Chen |first5=H. Isaac |last6=Davis |first6=Kathryn A. |last7=Gottfried |first7=Jay A. |date=November 2023 |title=Odor representations from the two nostrils are temporally segregated in human piriform cortex |journal=Current Biology |volume=33 |issue=24 |pages=5275–5287.e5 |language=en |doi=10.1016/j.cub.2023.10.021|pmid=36824705 |pmc=9948982 |bibcode=2023CBio...33E5275D }}</ref> with the first cycle corresponding to the ipsilateral and the second cycle corresponding to the contralateral odor representations.  In some cultures the extreme wide flaring of the nostrils accompanied by the baring of the upper teeth is often referred to as "doing the nostrils."

The [[Procellariiformes]] are distinguished from other birds by having tubular extensions of their nostrils.

Widely-spaced nostrils, like those of the [[hammerhead shark]], may be useful in determining the direction of an odour's source.<ref>{{cite journal |last1=Gardiner |first1=Jayne M. |last2=Atema |first2=Jelle |title=The Function of Bilateral Odor Arrival Time Differences in Olfactory Orientation of Sharks |journal=Current Biology |date=July 2010 |volume=20 |issue=13 |pages=1187–1191 |doi=10.1016/j.cub.2010.04.053 |pmid=20541411 |s2cid=13530789 |doi-access=free |bibcode=2010CBio...20.1187G }}</ref><ref name="Cell culture">{{cite journal |title=Cell Culture |journal=Cell |date=August 2010 |volume=142 |issue=4 |pages=501–503 |doi=10.1016/j.cell.2010.08.009 |s2cid=357010 |doi-access=free }}</ref>

==See also==
* [[Dilator naris muscle]]
* [[Nasal cycle]]
* [[Piriform aperture]]

==References== 
{{Reflist}}

==External links==
{{Wiktionary}}
* {{DorlandsDict|six/000070199|nares}}

{{Nose anatomy}}
{{Authority control}}

[[Category:Nose]]
[[Category:Facial features]]
[[Category:Otorhinolaryngology]]
[[Category:Respiratory system anatomy]]