Axilla

The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the joint where the arm connects to the shoulder. It also contains many sweat glands.

"Underarm" redirects here. For the bowling style in cricket, see Underarm bowling.
Axilla
Axilla
Details
Arteryaxillary artery
Veinaxillary vein
Nerveaxillary nerve, medial cord, posterior cord, lateral cord
Lymphaxillary lymph nodes
Identifiers
LatinAxilla
MeSHD001365
TAA01.1.00.021
FMA24864
Anatomical terminology

In humans, the formation of body odor happens mostly in the armpit.[1] These odorant substances have been suggested by some to serve as pheromones, which play a role related to mating. However, this is a controversial topic within the scientific community.[2] The underarm regions seem more important than the genital region for body odor, which may be related to human bipedalism.[3]

Structure

Boundaries

Anatomically, the boundaries of the axilla are:

superiorly: by the outer border of first rib, superior border of scapula, and posterior border of clavicle[4]
medially: serratus anterior[5] and by the ribcage anteriorly: by the pectoralis major, minor,[6] and subclavius[5]

posteriorly: by the subscapularis above, and teres major and latissimus dorsi below[5]

 laterally: by the intertubercular sulcus[6] (coracobrachialis and the short head of the biceps brachii are in the axilla.)[5]
floor/base: by the skin[4] (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.[7] It can descend after weight loss.[8]

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.[7] It can elongate after weight loss.[8]

The contents of the axilla include the axillary vein and 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
Anatomy of the axilla
  • Superficial muscles of the chest and front of the arm.
  • Axillary artery and its branches - anterior view of right upper limb and thorax.
  • The veins of the right axilla, viewed from in front.
  • The right brachial plexus (infraclavicular portion) in the axillary fossa; viewed from below and in front.
  • The left side of the thorax.
  • Axilla
  • Axilla
  • Axilla
  • Axilla
  • Axilla
  • Axilla
  • 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.[9]

The term oxter is used in the Scots language and in Ireland instead of "axilla".[10]

Tickling
Main article: Tickling

The underarm can be a ticklish area, possibly due to the number of nerves it contains. Some people find this area to be particularly unpleasant when tickled.

Underarm hair
Main article: Underarm hair

Underarm hair usually grows in the underarms of both females and males, beginning in adolescence.

In some modern Western cultures, it is common for women to remove underarm hair. Some view this practice as an aesthetic matter, while others view its removal for health-related concerns. As underarm hair grows quickly, removal must be performed frequently, or stubble will appear in the axilla. In the Islamic tradition, underarm hair removal is a religious hygiene practice for both women and men. While most Muslims shave it, some pluck it, with products like wax, as it's more efficient to sustain longer periods without regrowing.

In the feminist movement, the hippie culture, and in the punk rock scene, some women retain their underarm hair for a variety of reasons, from subversion to egalitarianism to comfort. Conversely but uncommonly, some men choose to remove their underarm hair for aesthetic reasons or to reduce friction in sports such as swimming.

  • Shaved underarm
  • 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 nodes.

Lymphogenic spread of breast cancer

Breast cancer typically spreads via lymphatic vessels to the lymph nodes found in the axilla.

Axillary intertrigo

Excessive perspiration can result in axillary intertrigo. Intertrigo is an inflamed skin condition caused by heat, friction, and moisture.[11] A warm, wet underarm may accommodate the growth of pathogenic bacteria, yeasts, and fungi.[12] The condition is responsible for rash-like symptoms, pustules, or chronic itching or burning in the underarm.[11] Axillary intertrigo is common among those who work in hot environments.[12]

gollark: I see.
gollark: How does it work?
gollark: Yes. Earth had it coming.
gollark: I'm assuming "MPU" is "memristor processing unit" or something?
gollark: Less so, since you can do some of the work closer to the data and not have to move it much.

See also

Notes
  1. Turkington, Carol; Dover, Jeffrey S. (2007). The encyclopedia of skin and skin disorders (3rd ed.). New York: Facts on File. p. 363. ISBN 978-0-8160-6403-8.
  2. Drea, Christine M. (February 2015). "D'scent of man: A comparative survey of primate chemosignaling in relation to sex". Hormones and Behavior. 68: 117–133. doi:10.1016/j.yhbeh.2014.08.001. PMID 25118943.
  3. 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
  4. "Anaesthesia UK :AnaesthesiaUK: Applied anatomy for upper limb blocks". Archived from the original on 2008-10-16. Retrieved 2007-12-23.
  5. "LAB #4 PECTORAL REGION & Introduction to the Axilla". Retrieved 2007-12-23.
  6. "Dissector Answers - Axilla and Arm". Archived from the original on 2007-12-10. Retrieved 2007-12-23.
  7. lesson3axilla at The Anatomy Lesson by Wesley Norman (Georgetown University)
  8. Hurwitz, D.; Neavin, T. (2007). "Body Contouring of the Arms and Brachioplasty". Handchirurgie · Mikrochirurgie · Plastische Chirurgie. 39 (3): 168–72. doi:10.1055/s-2007-965236. PMID 17602378.
  9. "Definition of armpit - Merriam-Webster Online Dictionary". Archived from the original on 15 December 2007. Retrieved 2007-12-23.
  10. "BBC - Voices - Multilingual Nation". Archived from the original on 26 December 2007. Retrieved 2007-12-23.
  11. Selden, Samuel, MD. Intertrigo. emedicine, WebMD. March 9, 2007. Accessed May 21, 2009.
  12. Occupational Dermatoses - A Program for Physicians. National Institute for Occupational Safety and Health. April 17, 2001. Accessed May 21, 2009.
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