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{{short description|Proximal part of the free upper limb between the shoulder and the elbow}}
{{About|the upper part of the limb in humans and other animals|the British semiconductor and software design company|Arm Holdings|other uses|Arm (disambiguation)}}
{{Infobox anatomy
| Name        = Arm
| Latin       = brachium
| Image       = Extended_arm.jpg
| Caption     = The left arm of a human male
| Width       = 300px
| Precursor   = 
| System      = 
| Artery      = [[Axillary artery]]
| Vein        = [[Axillary vein]]
| Nerve       = [[Brachial plexus]]
| Lymph       = 
}}
In [[human anatomy]], the '''arm''' refers to the [[upper limb]] in common usage, although academically the term specifically means the '''upper arm'''<ref>{{Cite web |last=Gray |first=Henry |date=1918 |title=The Humerus (Arm Bone) |url=https://www.bartleby.com/107/51.html }}</ref><ref>{{Cite web |last=Forro |first=Stephen D. |date=July 31, 2021 |title=Anatomy, Shoulder and Upper Limb, Arm Structure and Function |publisher=StatPearls |pmid=29939618 |url=https://www.ncbi.nlm.nih.gov/books/NBK507841/ }}</ref> between the [[glenohumeral joint]] (shoulder joint) and the [[elbow joint]]. The distal part of the upper arm between the elbow and the [[radiocarpal joint]] ([[Wrist|wrist joint]]) is known as the [[forearm]] or "lower" arm, and the extremity beyond the wrist is the [[hand]].

By anatomical definitions, the [[bone]]s, [[ligament]]s and [[skeletal muscle]]s of the [[shoulder girdle]], as well as the [[axilla]] between them, are considered parts of the upper limb, and thus also components of the arm. The [[Latin]] term ''brachium'', which serves as a [[root word]] for naming many anatomical structures, may refer to either the upper arm as a whole or to the upper arm on its own.<ref name="Free dictionary">{{Cite web | url=http://www.thefreedictionary.com/brachium | title=brachium – free dictionary | access-date=December 2, 2013}}</ref><ref>{{cite web | url=http://dictionary.reference.com/browse/brachium | title=Dictionary.com | access-date=December 2, 2013}}</ref><ref>{{cite book | title=Encyclopaedia britannica 2013}}</ref>

==Structure==
===Bones===
[[File:Human arm bones diagram.svg|thumb|Bones of the [[upper limbs]], together with [[shoulder girdle]]s, that compose the human arm.]]
The [[humerus]] is one of the three [[long bone]]s of the arm. It joins with the [[scapula]] at the [[glenohumeral joint|shoulder joint]] and with the other long bones of the arm, the [[ulna]] and [[radius (bone)|radius]] at the [[elbow|elbow joint]].<ref name="Jacob">{{cite book|author=Sam Jacob|title=Human Anatomy: A Clinically-Orientated Approach|publisher=[[Elsevier Health Sciences]]|isbn=978-0443103735|page=5|year=2007|access-date=January 19, 2018|url=https://books.google.com/books?id=REKbRGsyStMC&pg=PA5}}</ref> The elbow is a complex [[hinge joint]] between the end of the humerus and the ends of the radius and ulna.<ref>{{Cite book|title=Sports injuries : prevention, diagnosis, treatment and rehabilitation|editor1=Doral, Mahmut Nedim |editor2=Karlsson, Jon|isbn=9783642368011|location=Berlin|oclc=1111734654|date = 2015-03-04}}</ref>

===Muscles===
The arm is divided by a [[fascia]]l layer (known as lateral and medial [[lateral intermuscular septum of arm|intermuscular septa]]) separating the muscles into two ''osteofascial compartments'': the [[Anterior compartment of the arm|anterior]] and the [[Posterior compartment of the arm|posterior compartments of the arm]]. The fascia merges with the [[periosteum]] (outer bone layer) of the humerus.<ref name=":0">{{Cite book|title=Gray's anatomy for students|last=Drake, Richard L. (Richard Lee)|others=Vogl, Wayne; Mitchell, Adam W. M.; Gray, Henry|date=15 November 2015|isbn=9780702051319|edition=  Third|location=Philadelphia, PA|oclc=881508489}}</ref>

The anterior compartment contains three muscles: [[Biceps|biceps brachii]], [[brachialis]] and [[Coracobrachialis muscle|coracobrachialis]] muscles. They are all innervated by the [[musculocutaneous nerve]]. The posterior compartment contains only the [[Triceps|triceps brachii muscle]], supplied by the [[radial nerve]].<ref>{{Cite book|title=Clinically oriented anatomy|last=Moore, Keith L.|others=Dalley, Arthur F., II,, Agur, A. M. R.|isbn=978-1451119459|edition=  Seventh|location=Philadelphia|oclc=813301028|date = 2013-02-13}}</ref><ref>{{Cite book|title=Gray's anatomy : the anatomical basis of clinical practice|editor=Standring, Susan|year=2016|isbn=9780702052309|edition=  Forty-first |location=[Philadelphia]|oclc=920806541}}</ref><ref>{{Cite web|url=https://www.kenhub.com/en/library/anatomy/elbow-and-forearm|title=Elbow and Forearm|website=Kenhub|access-date=2019-09-14}}</ref>

===Nerve supply===
{{Further|Cutaneous innervation of the upper limbs}}
[[File:Gray812and814.svg|thumb|Cutaneous innervation of the right upper extremity.]]
The [[musculocutaneous nerve]], from C5, C6, C7, is the main supplier of muscles of the anterior compartment. It originates from the lateral cord of the [[brachial plexus]] of nerves. It pierces the [[coracobrachialis]] muscle and gives off branches to the muscle, as well as to [[brachialis]] and biceps brachii. It terminates as the [[anterior cutaneous nerve of the forearm]].

The radial nerve, which is from the fifth cervical spinal nerve to the first thoracic spinal nerve, originates as the continuation of the posterior cord of the brachial plexus. This nerve enters the [[lower triangular space]] (an imaginary space bounded by, amongst others, the shaft of the humerus and the triceps brachii) of the arm and lies deep to the triceps brachii. Here it travels with the [[deep artery of arm|deep artery of the arm]], which sits in the [[radial groove]] of the humerus. This fact is very important clinically as a fracture of the shaft of the bone here can cause [[lesion]]s or even transections in the nerve.

Other nerves passing through give no supply to the arm. These include:
* The [[median nerve]], nerve origin C5-T1, which is a branch of the lateral and medial cords of the [[brachial plexus]]. This nerve continues in the arm, travelling in a plane between the biceps and triceps muscles. At the cubital fossa, this nerve is deep to the [[pronator teres]] muscle and is the most medial structure in the fossa. The nerve passes into the [[forearm]].
* The [[ulnar nerve]], origin C8-T1, is a continuation of the medial cord of the [[brachial plexus]]. This nerve passes in the same plane as the [[median nerve]], between the biceps and triceps muscles. At the elbow, this nerve travels posterior to the [[medial epicondyle of the humerus]]. This means that [[condyle (anatomy)|condylar]] [[bone fracture|fracture]]s can cause lesion to this nerve.

===Blood supply===
[[File:Gray1235.png|thumb|Main arteries of the arm.]]
The main artery in the arm is the [[brachial artery]]. This artery is a big continuation of the [[axillary artery]]. The point at which the axillary becomes the brachial is distal to the lower border of teres major. The [[brachial artery]] gives off an unimportant branch, the [[deep artery of arm]]. This branching occurs just below the lower border of [[teres major]].

The brachial artery continues to the [[cubital fossa]] in the anterior compartment of the arm. It travels in a plane between the [[biceps]] and [[triceps]] muscles, the same as the [[median nerve]] and [[basilic vein]]. It is accompanied by [[venae comitantes]] (accompanying veins). It gives branches to the muscles of the anterior compartment. The artery is in between the [[median nerve]] and the tendon of the [[biceps brachii|biceps]] muscle in the [[cubital fossa]]. It then continues into the [[forearm]].

The deep artery of the arm travels through the [[lower triangular space]] with the [[radial nerve]]. From here onwards it has an intimate relationship with the radial nerve. They are both found deep to the triceps muscle and are located on the spiral groove of the [[humerus]]. Therefore, [[bone fracture|fracture]] of the bone may not only lead to lesion of the [[radial nerve]], but also [[haematoma]] of the internal structures of the arm. The artery then continues on to [[anastomosis|anastamose]] with the [[recurrent radial]] branch of the [[brachial artery]], providing a diffuse blood supply for the [[Elbow-joint|elbow joint]].

===Veins===
The veins of the arm carry blood from the extremities of the limb, as well as drain the arm itself. The two main veins are the [[basilic vein|basilic]] and the [[cephalic vein]]s. There is a connecting vein between the two, the [[median cubital vein]], which passes through the [[cubital fossa]] and is clinically important for [[venepuncture]] (withdrawing blood).

The basilic vein travels on the medial side of the arm and terminates at the level of the seventh rib.

The cephalic vein travels on the lateral side of the arm and terminates as the axillary vein. It passes through the [[deltopectoral triangle]], a space between the deltoid and the pectoralis major muscles.

==Society and culture==
In Hindu, Buddhist and Egyptian iconography the symbol of the arm is used to illustrate the power of the sovereign. In Hindu tradition gods are depicted with several arms which carry specific symbols of their powers. It is believed that several arms depict omnipotence of gods. In popular culture Thakur did not have arms in the movie Sholay.

In West Africa, the Bambara use forearm to symbolize the spirit, which is a link between God and man.
[[File:Three Korean Communists in a fishing boat are captured by the USS Manchester off the coast of Korea. - NARA - 520792.tif|thumb|Three North Koreans surrender to {{USS|Manchester|CL-83|6}} by raising their arms]]
Symbolic gestures of raising both hands signal surrender, appeals for mercy, and justice.<ref>{{cite book|last1=Tresidder|first1=Jack|title=The Hutchinson Dictionary of Symbols|date=1997|publisher=Helicon|location=London|isbn=1-85986-059-1|page=16}}</ref>
[[File:Abydos KL 04-04 n23.jpg|thumb|The arm, as can be seen here, formed one component of [[hieroglyph]]s]]

==Clinical significance {{anchor|Fracture}}==
The [[cubital fossa]] is clinically important for [[venepuncture]] and for [[blood pressure]] measurement.<ref>{{Cite web|url=https://nurse.org/articles/how-nurses-professionally-draw-blood/|title=How To Draw Blood Like A Pro: Step-By-Step Guide|website=nurse.org|access-date=2019-09-14}}</ref>

When the arm is [[bone fracture|fractured]] this may refer to a [[humerus fracture|fracture of the humerus bone]].

Veins on the arm may be taken when a [[coronary artery bypass graft]] is needed.

==Other animals==
In other animals, the term ''arm'' can also be used for homologous or analogous structures (such as one of the paired [[forelimb]]s of a [[Quadrupedalism|four-legged animal]] or the [[cephalopod arm|arms of cephalopods]], respectively). In anatomical usage, the term ''arm'' may<ref name="Free dictionary" /> sometimes refer specifically to the segment between the shoulder and the elbow,<ref>{{cite web |url=https://www.lecturio.com/concepts/arm/|title=Arm
|website=The Lecturio Medical Concept Library |date=3 November 2020
|access-date=2021-06-22}}</ref><ref>{{MeSH name|Arm}}</ref> while the segment between the elbow and [[wrist]] is the [[forearm]]. However, in common, literary, and historical usage, ''arm'' refers to the entire upper arm from shoulder to wrist. This article uses the former definition; see [[upper limb]] for the wider definition.<ref name=":0" />

In primates, the arm is adapted for precise positioning of the [[hand]] and thus assist in the hand's manipulative tasks. The ball and socket shoulder joint allows for movement of the arms in a wide circular plane, while the structure of the two forearm bones which can rotate around each other allows for additional range of motion at that level.<ref>{{Cite journal|last1=Preuschoft|first1=Holger|last2=Hohn|first2=Bianca|last3=Scherf|first3=Heike|last4=Schmidt|first4=Manuela|last5=Krause|first5=Cornelia|last6=Witzel|first6=Ulrich|date=April 2010|title=Functional Analysis of the Primate Shoulder|journal=International Journal of Primatology|volume=31|issue=2|pages=301–320|doi=10.1007/s10764-010-9399-1|issn=0164-0291|pmc=2860095|pmid=20495602}}</ref>

==Additional images==
<gallery>

File:Arm Bones.png|Gross anatomy of the upper arm and [[elbow]].

</gallery>

==See also==
{{Anatomy-terms}}
{{Commons}}
{{Wiktionary}}
* [[Axilla]] – also known as armpit, underarm or oxter
* [[Common flexor tendon]]

==References==
{{Reflist}}

{{Human regional anatomy}}
{{navboxes
| title = Anatomy of the arm
| state = expanded
| list =
{{Bones of upper extremity}}
{{Joints of upper limbs}}
{{Muscles of upper limb}}
{{Arteries of upper limbs}}
{{Veins of the upper extremity}}
{{Lymphatics of upper limbs}}
}}

{{Authority control}}

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