Editing Axilla

{{short description|Area of the human body beneath the joint between arm and torso}}
{{About|the anatomical body part|the 5th century BCE Roman consul|Gaius Servilius Axilla}}{{Redirect2|Underarm|Underarms|}}
{{Infobox anatomy
| Name        = Axilla
| Latin       = axilla
| Caption     =
| Image2      = ArmpitHair2.jpg
| Caption2    = Human axilla
| Precursor   =
| System      =
| Artery      = [[Axillary artery]]
| Vein        = [[Axillary vein]]
| Nerve       = [[Axillary nerve]], [[medial cord]], [[posterior cord]], [[lateral cord]]
| Lymph       = [[Axillary lymph nodes]]
}}
The '''axilla''' ({{plural form}}: '''axillae''' or '''axillas'''; also known as the '''armpit''', '''underarm'''  or '''oxter''') is the area on the [[human body]] directly under the [[shoulder joint]]. It includes the '''axillary space''', an [[anatomical space]] within the [[shoulder girdle]] between the [[arm]] and the [[thoracic cage]], bounded superiorly by the imaginary [[plane (geometry)|plane]] between the superior borders of the [[first rib]], [[clavicle]] and [[scapula]] (above which are considered part of the [[neck]]), medially by the [[serratus anterior muscle]] and [[thoracolumbar fascia]], anteriorly by the [[pectoral muscles]] and posteriorly by the [[subscapularis]], [[teres major]] and [[latissimus dorsi muscle]].

The soft skin covering the lateral axilla contains many [[underarm hair|hair]] and [[sweat gland]]s. In humans, the formation of [[body odor]] happens mostly in the axilla.<ref>{{cite book| last1=Turkington| first1=Carol| last2=Dover| first2=Jeffrey S.| title=The encyclopedia of skin and skin disorders| year=2007| publisher=Facts on File|location=New York| isbn=978-0-8160-6403-8| pages=363| edition=3rd}}</ref> These odorant substances have been suggested by some to serve as [[pheromone]]s, which play a role related to [[mate selection]], although this is a controversial topic within the scientific community.<ref>{{Cite journal|last=Drea|first=Christine M.|date=February 2015|title=D'scent of man: A comparative survey of primate chemosignaling in relation to sex|journal=Hormones and Behavior|language=en|volume=68|pages=117–133|doi=10.1016/j.yhbeh.2014.08.001|pmid=25118943|s2cid=2973690}}</ref> The underarms seem more important than the [[pubic area]] for emitting body odor, which may be related to human [[bipedalism]].<ref name=Oxford2007>The Oxford Handbook of Evolutionary Psychology, Edited by Robin Dunbar and Louise Barret, Oxford University Press, 2007, Chapter 22 Body odours and body odour preferences in humans by Claus Wedekind</ref>

==Structure==
===Boundaries===
Anatomically, the boundaries of the ''axilla'' are:

{| class="wikitable"
|  ||  ''superiorly'': by the outer border of [[first rib]], superior border of [[scapula]], and posterior border of [[clavicle]]<ref name="titleAnaesthesia UK :AnaesthesiaUK: Applied anatomy for upper limb blocks">{{cite web|url=http://www.anaesthesiauk.com/article.aspx?articleid=100359 |title=Anaesthesia UK :AnaesthesiaUK: Applied anatomy for upper limb blocks |access-date=2007-12-23 |url-status=usurped |archive-url=https://web.archive.org/web/20081016012019/http://www.anaesthesiauk.com/article.aspx?articleid=100359 |archive-date=2008-10-16 }}</ref> ||
|-
| ''medially'':  [[serratus anterior muscle|serratus anterior]]<ref name="titleLAB #4 PECTORAL REGION & Introduction to the Axilla">{{cite web |url=http://anatomy.iupui.edu/courses/gross-D501/Lab%20Instructions/Lab%204%20pectoral2%20%20region.htm |title=LAB #4 PECTORAL REGION & Introduction to the Axilla |access-date=2007-12-23 }}</ref>  and by the [[rib]]cage
|| ''anteriorly'': by the [[pectoralis major muscle|pectoralis major]], [[pectoralis minor muscle|minor]],<ref name="titleDissector Answers - Axilla and Arm">{{cite web|url=http://anatomy.med.umich.edu/limbs/axilla_ans.html#2o |title=Dissector Answers - Axilla and Arm |access-date=2007-12-23 |archive-url=https://web.archive.org/web/20071210033208/http://anatomy.med.umich.edu/limbs/axilla_ans.html |archive-date=2007-12-10 |url-status=dead }}</ref> and [[subclavius muscle|subclavius]]<ref name="titleLAB #4 PECTORAL REGION & Introduction to the Axilla"/>

''posteriorly'': by the [[subscapularis muscle|subscapularis]] above, and [[teres major]] and [[latissimus dorsi]] below<ref name="titleLAB #4 PECTORAL REGION & Introduction to the Axilla"/> 
|| ''laterally'': by the [[humerus]] and the surrounding muscles of the arm [[coracobrachialis muscle|(coracobrachialis]] and [[biceps brachii muscle|biceps brachii]])<ref>{{Cite book|last1=Stingl|first1=Josef|title=Regional Anatomy|last2=Grim|first2=Miloš|last3=Druga|first3=Rastislav|publisher=Galén|year=2012|isbn=978-80-7262-931-2|location=Prague|pages=95|display-authors=1}}</ref>
|-
|  || ''floor/base'': by the skin<ref name="titleAnaesthesia UK :AnaesthesiaUK: Applied anatomy for upper limb blocks"/> (visible surface of axilla) ||
|}
The lower posterior boundary is called the '''posterior axillary fold''' and this is a compound structure consisting of the [[latissimus dorsi]] and [[teres major]] muscles.<ref name="NormanAnatomy|lesson3axilla">{{NormanAnatomy|lesson3axilla}}</ref> It can descend after weight loss.<ref name=pmid17602378>{{cite journal |doi=10.1055/s-2007-965236 |pmid=17602378 |title=Body Contouring of the Arms and Brachioplasty |journal=Handchirurgie · Mikrochirurgie · Plastische Chirurgie |volume=39 |issue=3 |pages=168–72 |year=2007 |last1=Hurwitz |first1=D. |last2=Neavin |first2=T. }}</ref>

The anterior boundary is called the '''anterior axillary fold''' and this is rounded in shape and formed by the lower border of the [[pectoralis major]]. 
Some sources also include the [[pectoralis minor]].<ref name="NormanAnatomy|lesson3axilla"/> It can elongate after weight loss.<ref name=pmid17602378/>

The contents of the axilla include the [[axillary vein]] and [[Axillary artery|artery]], as well as the [[brachial plexus]], [[lymph nodes]] and fat.
The axilla is the space between the side of the [[thorax]] and the upper arm.

===Contents===

* [[Axillary artery]] and its branches
* [[Axillary vein]] and its tributaries
* Infraclavicular part of the [[brachial plexus]]
* Long [[Thoracic nerves|thoracic]] and [[intercostobrachial nerve]]s
* Five groups of axillary [[lymph node]]s and the associated [[Lymphatic system|lymphatics]]
* Axillary [[Loose connective tissue|fat and areolar tissue]] in which the other contents are embedded

{{gallery|title=Anatomy of the axilla|width=150
|Image:Gray410.png|Superficial muscles of the chest and front of the arm.
|Image:Gray523.png|Axillary artery and its branches - anterior view of right upper limb and thorax.
|Image:Gray576.png|The veins of the right axilla, viewed from in front.
|Image:Gray809.png|The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front.
|Image:Gray1215.png|The left side of the thorax.
|File:Slide6dj.JPG|Axilla
|File:Slide18d.JPG|Axilla
|File:Slide7bbbb.JPG|Axilla
|File:Slide5DDDD.JPG|Axilla
|File:Slide11DDD.JPG|Axilla
|File:Slide3EE.JPG|Axilla
|File:Slide10JJJ.JPG|Axilla
}}

==Society and culture==
The term "underarm" typically refers to the outer surface of the axilla. However, the terms are sometimes used interchangeably in casual contexts. Colloquially, ''underarm '' refers to the hollow beneath the junction of the arm and shoulder.<ref name="titleDefinition of armpit - Merriam-Webster Online Dictionary">{{cite web |url=http://www.m-w.com/dictionary/armpit |title=Definition of armpit - Merriam-Webster Online Dictionary |access-date=2007-12-23 | archive-url= https://web.archive.org/web/20071215090010/http://www.m-w.com/dictionary/armpit| archive-date= 15 December 2007 | url-status= live}}</ref>

===Tickling===
{{Main|Tickling}}
The underarm is a ticklish area due to the number of nerves it contains. Most people find this area to be particularly unpleasant when [[tickling|tickled]].{{Citation needed|date=February 2025}}

===Underarm hair===
{{Main|Underarm hair}}

[[Underarm hair]] usually grows in the underarms of both [[female]]s and [[male]]s, beginning in [[puberty|adolescence]].

In some modern [[Western cultures]], it is common for older women to remove underarm hair. Some view this practice as an [[aesthetics|aesthetic]] matter, while others view its removal for health-related concerns.<ref>{{cite journal|display-authors=3 |last1=Lanzalaco |first1=Anthony  |last2=Vanoosthuyze |first2=Kristina |last3=Swaile |first3=David |last4=Rocchetta |first4=Heather |last5=Spruell |first5=Russell|last6=Stark |first6=Cynthia |title=A comparative clinical study of different hair removal procedures and their impact on axillary odor reduction in men|journal=Journal of Cosmetic Dermatology
 |year=2016 |volume=5 |issue=1 |pages=58–65 |doi=10.1111/jocd.12197 |pmid=26663394 |pmc=4793925 }}</ref> As underarm hair grows quickly, removal must be performed frequently, or stubble will appear in the axilla.

In most culture and scenes, women retain their underarm hair for a variety of reasons, from subversion to egalitarianism to comfort or for hygienic reason.<ref>{{cite web |url=https://www.theguardian.com/lifeandstyle/2019/jun/24/feminist-armpit-hair-revolution-half-statement-half-ornament|title=The new feminist armpit hair revolution: half-statement, half-ornament|website=Guardian News & Media |date=24 June 2019|access-date=2021-06-22}}</ref> Conversely but uncommonly, some men choose to remove their underarm hair for aesthetic reasons or to reduce [[friction]] in [[sports]] such as [[swimming (sport)|swimming]].
{{gallery
|File:Shaved arm pit.jpg|Shaved underarm
|File:Arm pit – Juno.jpg|Natural underarm
}}

==Clinical significance==
Like other flexion surfaces of large joints ([[groin]], [[popliteal fossa]], [[cubital fossa]] and essentially the anterior part of the [[neck]]), it is an area where blood vessels and nerves pass relatively superficially, and with an increased amount of [[lymph node]]s.

===Lymphogenic spread of breast cancer===
Breast cancer typically spreads via lymphatic vessels to the [[Lymph node|lymph nodes]] found in the axilla.<ref>{{Cite journal |last=Bertozzi |first=Serena |last2=Cedolini |first2=Carla |last3=Londero |first3=Ambrogio P. |last4=Baita |first4=Barbara |last5=Giacomuzzi |first5=Francesco |last6=Capobianco |first6=Decio |last7=Tortelli |first7=Marta |last8=Uzzau |first8=Alessandro |last9=Mariuzzi |first9=Laura |last10=Risaliti |first10=Andrea |date=January 2019  |title=Sentinel lymph node biopsy in patients affected by breast ductal carcinoma in situ with and without microinvasion: Retrospective observational study |url=https://pubmed.ncbi.nlm.nih.gov/30608397/ |journal=Medicine |volume=98 |issue=1 |pages=e13831 |doi=10.1097/MD.0000000000013831 |issn=1536-5964 |pmc=6344146 |pmid=30608397}}</ref>

===Axillary intertrigo===
Excessive [[perspiration]] without adequate  air circulation can result in axillary [[intertrigo]]. Intertrigo is an inflammatory [[skin condition]] of skin folds exposed to friction or maceration in the presence of heat and moisture.<ref name="webmd">Selden, Samuel [http://emedicine.medscape.com/article/1087691-overview Intertrigo]. emedicine, WebMD. March 9, 2007. Accessed May 21, 2009.</ref> Intertrigo is worsened by infection, usually fungal ([[Candida (fungus)|Candida]] yeast species), but also bacterial or viral; warm, wet underarms promote those growths. The condition results in rash-like symptoms, [[pustule]]s, or chronic itching or burning in the underarm.<ref name="webmd" /> Intertrigo (in any site) has no racial or sexual predilection.<ref name=webmd/>  Axillary intertrigo is common among those who work in hot environments where air circulation is restricted by necessary clothing or safety equipment.<ref>{{cite web |url=https://www.webmd.com/skin-problems-and-treatments/guide/intertrigo-symptoms-causes-treatment-risk_factors_|title=Intertrigo|last=Gardner |first=Stephanie S |date=14 June 2020 |website=WebMD  |access-date=June 22, 2021}}</ref>

==See also==
*[[Deodorant]]
*[[Perspiration]]
*[[Popliteal fossa]] or "knee pit"
*[[Suspensory ligament of axilla]]

==Notes==
{{Reflist}}

==External links==
{{Wiktionary}}
{{Commons category|Armpits}}
*[http://anatomyguy.com/axilla-and-brachial-plexus/ Step by step Video dissection of the Human Axilla showing all relevant anatomy]
*[http://pie.med.utoronto.ca/ALND/ALND_content/axillaryAnatomy.html 3D animated overview of axillary anatomy (rich media)]
*{{NormanAnatomy|lesson3axilla}}
*{{NormanAnatomy|lesson3axillarywalls}}

{{Human anatomical features|state=collapsed}}
{{Authority control}}

[[Category:Upper limb anatomy]]
[[Category:Axillas| ]]