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 provides the under-arm sweat gland.

In humans, the formation of body odor happens mostly in the axillary region.[1] These odorant substances serve as pheromones which play a role related to mating. The underarm regions seem more important than the genital region for body odor which may be related to human bipedalism.[2]

Arm pit – Juno
Arteryaxillary artery
Veinaxillary vein
Nerveaxillary nerve, medial cord, posterior cord, lateral cord
Lymphaxillary lymph nodes
Anatomical terminology



Anatomically, the boundaries of the axilla are:

superiorly: by the outer border of first rib, superior border of scapula, and posterior border of clavicle[3]
medially: serratus anterior[4] and by the ribcage anteriorly: by the pectoralis major, minor,[5] and subclavius[4]

posteriorly: by the subscapularis above, and teres major and latissimus dorsi below[4]

laterally: by the intertubercular sulcus[5] (coracobrachialis and the short head of the biceps brachii are in the axilla.)[4]
floor/base: by the skin[3] (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.[6] It can descend after weight loss.[7]

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

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.



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.















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.[8]

The term oxter is used in the Scots language and in Ireland instead of "axilla".[9]


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

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, shaving 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 arm pit

Shaved underarm

Arm pit – Juno

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.[10] A warm, wet underarm may accommodate the growth of pathogenic bacteria, yeasts, and fungi.[11] The condition is responsible for rash-like symptoms, pustules, or chronic itching or burning in the underarm.[10] Axillary intertrigo is common among those who work in hot environments.[11]

See also


  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. ^ 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
  3. ^ a b "Anaesthesia UK :AnaesthesiaUK: Applied anatomy for upper limb blocks". Archived from the original on 2008-10-16. Retrieved 2007-12-23.
  4. ^ a b c d "LAB #4 PECTORAL REGION & Introduction to the Axilla". Retrieved 2007-12-23.
  5. ^ a b "Dissector Answers - Axilla and Arm". Archived from the original on 2007-12-10. Retrieved 2007-12-23.
  6. ^ a b lesson3axilla at The Anatomy Lesson by Wesley Norman (Georgetown University)
  7. ^ a b 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.
  8. ^ "Definition of armpit - Merriam-Webster Online Dictionary". Archived from the original on 15 December 2007. Retrieved 2007-12-23.
  9. ^ "BBC - Voices - Multilingual Nation". Archived from the original on 26 December 2007. Retrieved 2007-12-23.
  10. ^ a b Selden, Samuel, MD. Intertrigo. emedicine, WebMD. March 9, 2007. Accessed May 21, 2009.
  11. ^ a b Occupational Dermatoses - A Program for Physicians. National Institute for Occupational Safety and Health. April 17, 2001. Accessed May 21, 2009.

External links


Acanthosis is diffuse epidermal hyperplasia (thickening of the skin).

It implies increased thickness of the Malpighian layer (stratum basale and stratum spinosum).Acanthosis Nigricans is often associated with Diabetes Mellitus type 2, and is usually observed in the back of neck, axilla, and other folded regions of the skin. However, Acanthosis Nigricans can also be associated with other conditions such as Niacin toxicity.

Apocrine gland carcinoma

Apocrine gland carcinoma is a cutaneous condition characterized by skin lesions which form in the axilla or anogenital regions.

Axillary artery

In human anatomy, the axillary artery is a large blood vessel that conveys oxygenated blood to the lateral aspect of the thorax, the axilla (armpit) and the upper limb. Its origin is at the lateral margin of the first rib, before which it is called the subclavian artery.

After passing the lower margin of teres major it becomes the brachial artery.

Axillary fascia

The pectoral fascia is very thin over the upper part of the Pectoralis major, but thicker in the interval between it and the Latissimus dorsi, where it closes in the axillary space and forms the axillary fascia. Axillary fascia, together with the skin, forms the base of the axilla.

Axillary nerve

The axillary nerve or the circumflex nerve is a nerve of the human body, that originates from the brachial plexus (upper trunk, posterior division, posterior cord) at the level of the axilla (armpit) and carries nerve fibers from C5 and C6. The axillary nerve travels through the quadrangular space with the posterior circumflex humeral artery and vein.

Axillary vein

In human anatomy, the axillary vein is a large blood vessel that conveys blood from the lateral aspect of the thorax, axilla (armpit) and upper limb toward the heart. There is one axillary vein on each side of the body.

Its origin is at the lower margin of the teres major muscle and a continuation of the brachial vein.

This large vein is formed by the brachial vein and the basilic vein. At its terminal part, it is also joined by the cephalic vein. Other tributaries include the subscapular vein, circumflex humeral vein, lateral thoracic vein and thoraco-acromial vein. It terminates at the lateral margin of the first rib, at which it becomes the subclavian vein.

It is accompanied along its course by a similarly named artery, the axillary artery.

Bicipital groove

The bicipital groove (intertubercular groove, sulcus intertubercularis) is a deep groove on the humerus that separates the greater tubercle from the lesser tubercle. The bicipital groove lodges the long tendon of the biceps brachii between the tendon of the pectoralis major on the lateral lip and the tendon of the teres major on the medial lip. It also transmits a branch of the anterior humeral circumflex artery to the shoulder joint.

The insertion of the latissimus dorsi is found along the floor of the bicipital groove. The teres major inserts on the medial lip of the groove.

It runs obliquely downward, and ends near the junction of the upper with the middle third of the bone. It is the lateral wall of the axilla.

Breast ultrasound

Breast ultrasound is the use of medical ultrasonography to perform imaging of the breast.

It can be considered either a diagnostic or a screening procedure.It may be used either with or without a mammogram.It may be useful in younger women, where the denser fibrous tissue of the breast may make mammograms more difficult to interpret.Automated whole-breast ultrasound (AWBU) is an ultrasound investigation of the breast that is largely independent of the operator skill and that allows the reconstruction of volumetric images of the breast.

Using high-frequency ultrasound, a diagnostic evaluation of the lactiferous ducts by means of ultrasound (duct sonography) can be performed. In this manner, dilated ducts and intraductal masses can be made visible. Another technique for visualizing the system of lactiferous ducts is galactography, which allows a wider area of the lactiferous duct system to be visualized.A type of ultrasound examination to measure tissue stiffness, which is used to detect tumours, is elastography.

Breast ultrasound is also used to perform fine-needle aspiration biopsy and ultrasound-guided fine-needle aspiration of breast abscesses.

Some women prefer breast ultrasound over mammography because they dislike the pain felt during squeezing or fixing of breast done during mammography for X-ray views. Breast ultrasound is painless procedure.

Breast ultrasound is usually done with frequency 7 Megahertz to 14 Megahertz.

Breast ultrasound includes ultrasound of axillary tail of breast and sometime it includes ultrasound of axillae also to detect abnormal nodes in axilla because lymphatic drainage of parts of breast occur through axillary lymph nodes.

Central lymph nodes

A central or intermediate group of three or four large glands is imbedded in the adipose tissue near the base of the axilla.

Its afferent lymphatic vessels are the efferent vessels of all the preceding groups of axillary glands; its efferents pass to the subclavicular group.


A crutch is a mobility aid that transfers weight from the legs to the upper body. It is often used by people who cannot use their legs to support their weight, for reasons ranging from short-term injuries to lifelong disabilities.

Hoist (album)

Hoist (stylized as (Hoist)) is the fifth studio album by the American rock band Phish, released on March 29, 1994 by Elektra Records. At the time of its release, Hoist was Phish's best selling album to date, peaking at No. 34 on the Billboard 200 albums chart. The album was certified gold by the RIAA on August 19, 1996, and remains the band's best-selling studio release, outsold in their discography only by the platinum-certified A Live One.

The album includes "Down with Disease", the band's breakthrough single on American rock radio, reaching the top 40 of Billboard magazine's Mainstream Rock Tracks chart in June 1994. The band filmed their only official music video for the song, directed by bassist Mike Gordon, which received some airplay on MTV.

Pectoral fascia

The pectoral fascia is a thin lamina, covering the surface of the pectoralis major, and sending numerous prolongations between its fasciculi: it is attached, in the middle line, to the front of the sternum; above, to the clavicle; laterally and below it is continuous with the fascia of the shoulder, axilla, and thorax.

It is very thin over the upper part of the pectoralis major, but thicker in the interval between it and the latissimus dorsi, where it closes in the axillary space and forms the axillary fascia; it divides at the lateral margin of the latissimus dorsi into two layers, one of which passes in front of, and the other behind it; these proceed as far as the spinous processes of the thoracic vertebrae, to which they are attached.

As the fascia leaves the lower edge of the pectoralis major to cross the floor of the axilla it sends a layer upward under cover of the muscle; this lamina splits to envelop the pectoralis minor, at the upper edge of which it is continuous with the coracoclavicular fascia.

The hollow of the armpit, seen when the arm is abducted, is produced mainly by the traction of this fascia on the axillary floor, and hence the lamina is sometimes named the suspensory ligament of the axilla.

At the lower part of the thoracic region the deep fascia is well-developed, and is continuous with the fibrous sheaths of the rectus abdominis.

Posterior cutaneous nerve of arm

The posterior cutaneous nerve of arm (internal cutaneous branch of musculospiral, posterior brachial cutaneous nerve) is a branch of the radial nerve that provides sensory innervation for much of the skin on the back of the arm. It arises in the axilla.

It is of small size, and passes through the axilla to the medial side of the area supplying the skin on its dorsal surface nearly as far as the olecranon.

In its course it crosses behind and communicates with the intercostobrachial.

Subclavius muscle

The subclavius is a small triangular muscle, placed between the clavicle and the first rib.

Along with the pectoralis major and pectoralis minor muscles, the subclavius muscle makes up the anterior wall of the axilla.

Subscapular axillary lymph nodes

A posterior or subscapular group of six or seven glands is placed along the lower margin of the posterior wall of the axilla in the course of the subscapular artery.

The afferents of this group drain the skin and muscles of the lower part of the back of the neck and of the posterior thoracic wall; their efferents pass to the central group of axillary glands.

Suspensory ligament of axilla

The suspensory ligament of axilla, or Gerdy's ligament, is a suspensory ligament that connects the clavipectoral fascia to the axillary fascia. This union shapes the axilla (underarm).

Tail of Spence

The tail of Spence (Spence's tail, axillary process, axillary tail) is an extension of the tissue of the breast that extends into the axilla. It is actually an extension of the upper lateral quadrant of the breast. It passes into the axilla through an opening in the deep fascia called foramen of Langer.

It is named after the Scottish surgeon James Spence.

Underarm hair

Underarm hair, also known as axillary hair, is the hair in the underarm area (axilla).

Upper limb

The upper limb or upper extremity is the region in a vertebrate animal extending from the deltoid region up to and including the hand, including the arm, axilla and shoulder.

Torso (Trunk)

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