# Upper limb

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Consists of the arm, forearm, and hand

Upper limb Front of right upper extremity. Back of right upper extremity. Details System Musculoskeletal Identifiers Latin membrum superius MeSH D034941 TA98 A01.1.00.019 TA2 138 FMA 7183 Anatomical terminology [edit on Wikidata]

The **upper [limbs](/source/Limb_(anatomy))** or **upper extremities** are the [forelimbs](/source/Forelimb) of an [upright-postured](/source/Upright_posture) [tetrapod](/source/Tetrapod) [vertebrate](/source/Vertebrate), extending from the [scapulae](/source/Scapula) and [clavicles](/source/Clavicle) down to and including the [digits](/source/Digit_(anatomy)), including all the [musculatures](/source/Musculature) and [ligaments](/source/Ligament) involved with the [shoulder](/source/Shoulder), [elbow](/source/Elbow), [wrist](/source/Wrist) and [knuckle](/source/Knuckle) joints.[1] In [humans](/source/Human), each upper limb is divided into the [shoulder](/source/Shoulder), [arm](/source/Arm), [elbow](/source/Elbow), [forearm](/source/Forearm), [wrist](/source/Wrist) and [hand](/source/Hand),[2][3] and is primarily used for [climbing](/source/Climbing), [lifting](/source/Manual_handling_of_loads) and [manipulating](/source/Dexterity) objects. In [anatomy](/source/Anatomy), just as [arm](/source/Arm) refers to the [upper arm](/source/Upper_arm), [leg](/source/Leg) refers to the [lower leg](/source/Lower_leg).

## Definition

In formal usage, the term "arm" only refers to the structures from the shoulder to the elbow, explicitly excluding the [forearm](/source/Forearm), and thus "upper limb" and "arm" are not synonymous.[4] However, in casual usage, the terms are often used interchangeably. The term "upper arm" is redundant in anatomy, but in informal usage is used to distinguish between the two terms.

## Structure

In the [human body](/source/Human_body#CITEREFYaxley2016), the muscles of the upper limb can be classified by origin, topography, function, or innervation. While a grouping by innervation reveals [embryological](/source/Embryology) and [phylogenetic](/source/Phylogenetics) origins, the functional-topographical classification below reflects the similarity in action between muscles (with the exception of the shoulder girdle, where muscles with similar action can vary considerably in their location and orientation.[5]

### Musculoskeletal system

#### Shoulder girdle

Bones of the shoulder girdle

Main article: [Shoulder girdle](/source/Shoulder_girdle)

The shoulder girdle[6] or pectoral girdle,[7] composed of the [clavicle](/source/Clavicle) and the [scapula](/source/Scapula), connects the upper limb to the [axial skeleton](/source/Axial_skeleton) through the [sternoclavicular joint](/source/Sternoclavicular_joint) (the only joint in the upper limb that directly articulates with the trunk), a ball and socket joint supported by the [subclavius muscle](/source/Subclavius_muscle) which acts as a dynamic [ligament](/source/Ligament). While this muscle prevents dislocation in the joint, strong forces tend to break the clavicle instead. The [acromioclavicular joint](/source/Acromioclavicular_joint), the joint between the [acromion](/source/Acromion) process on the scapula and the clavicle, is similarly strengthened by strong ligaments, especially the [coracoclavicular ligament](/source/Coracoclavicular_ligament) which prevents excessive lateral and medial movements. Between them these two joints allow a wide range of movements for the shoulder girdle, much because of the lack of a bone-to-bone contact between the scapula and the axial skeleton. The [pelvic girdle](/source/Pelvic_girdle) is, in contrast, firmly fixed to the axial skeleton, which increases stability and load-bearing capabilities. [7]

The mobility of the shoulder girdle is supported by a large number of muscles. The most important of these are muscular sheets rather than fusiform or strap-shaped muscles and they thus never act in isolation but with some fibres acting in coordination with fibres in other muscles.[7]

**Muscles**
- of shoulder girdle excluding the glenohumeral joint[5] **Migrated from head** - [Trapezius](/source/Trapezius), [sternocleidomastoideus](/source/Sternocleidomastoideus), [omohyoideus](/source/Omohyoideus) **Posterior** - [Rhomboideus major](/source/Rhomboideus_major), [rhomboideus minor](/source/Rhomboideus_minor), [levator scapulae](/source/Levator_scapulae) **Anterior** - [Subclavius](/source/Subclavius), [pectoralis minor](/source/Pectoralis_minor), [serratus anterior](/source/Serratus_anterior)

#### Shoulder joint

Shoulder joint with ligaments

The [glenohumeral joint](/source/Glenohumeral_joint) (colloquially called the shoulder joint) is the highly mobile ball and socket joint between the [glenoid cavity](/source/Glenoid_cavity) of the scapula and the head of the humerus. Lacking the passive stabilisation offered by ligaments in other joints, the glenohumeral joint is actively stabilised by the [rotator cuff](/source/Rotator_cuff), a group of short muscles stretching from the scapula to the humerus. Little inferior support is available to the joint and dislocation of the shoulder almost exclusively occurs in this direction. [8]

The large muscles acting at this joint perform multiple actions and seemingly simple movements are often the result of composite antagonist and protagonist actions from several muscles. For example, [pectoralis major](/source/Pectoralis_major) is the most important arm flexor and [latissimus dorsi](/source/Latissimus_dorsi) the most important extensor at the glenohumeral joint, but, acting together, these two muscles cancel each other's action leaving only their combined medial rotation component. On the other hand, to achieve pure flexion at the joint the [deltoid](/source/Deltoid_muscle) and [supraspinatus](/source/Supraspinatus) must cancel the adduction component and the [teres minor](/source/Teres_minor) and [infraspinatus](/source/Infraspinatus) the medial rotation component of pectoralis major. Similarly, abduction (moving the arm away from the body) is performed by different muscles at different stages. The first 10° is performed entirely by the supraspinatus, but beyond that fibres of the much stronger deltoid are in position to take over the work until 90°. To achieve the full 180° range of abduction the arm must be rotated medially and the scapula most be rotated about itself to direct the glenoid cavity upward. [8]

**Muscles**
- of shoulder joint proper[5] **Posterior** - [Supraspinatus](/source/Supraspinatus), [infraspinatus](/source/Infraspinatus), [teres minor](/source/Teres_minor), [subscapularis](/source/Subscapularis), [deltoideus](/source/Deltoideus), [latissimus dorsi](/source/Latissimus_dorsi), [teres major](/source/Teres_major) **Anterior** - [Pectoralis major](/source/Pectoralis_major), [coracobrachialis](/source/Coracobrachialis)

#### Bones of upper limb

The bones forming the human upper limb are

- Clavicle

- Scapula

- Humerus

- Radius

- Ulna

- Carpal bones - Scaphoid - Lunate - Triquetral - Pisiform - Trapezium - Trapezoid - Capitate - Hamate

- 5 Metacarpal bones

- 14 Phalanges

Upper limb bones with articular cartilage

#### Arm

Superficial muscles of the arm

Main article: [Arm](/source/Arm)

The arm proper (*brachium*), sometimes called the upper arm,[6] the region between the shoulder and the elbow, is composed of the [humerus](/source/Humerus) with the [elbow joint](/source/Elbow) at its distal end.

The elbow joint is a complex of three joints — the [humeroradial](/source/Humeroradial_joint), [humeroulnar](/source/Humeroulnar_joint), and [superior radioulnar joints](/source/Superior_radioulnar_joint) — the former two allowing flexion and extension whilst the latter, together with its [inferior namesake](/source/Inferior_radioulnar_joint), allows supination and pronation at the wrist. [Triceps](/source/Triceps_brachii) is the major extensor and [brachialis](/source/Brachialis) and [biceps](/source/Biceps_brachii) the major flexors. Biceps is, however, the major supinator and while performing this action it ceases to be an effective flexor at the elbow. [9]

**Muscles**
- of the arm[5] **Posterior** - [Triceps brachii](/source/Triceps_brachii), [anconeus](/source/Anconeus) **Anterior** - [Brachialis](/source/Brachialis), [biceps brachii](/source/Biceps_brachii)

#### Forearm

Ventral superficial muscles of the forearm

Main article: [Forearm](/source/Forearm)

The forearm ([Latin](/source/Latin_language): *antebrachium*),[6] composed of the [radius](/source/Radius_(bone)) and [ulna](/source/Ulna); the latter is the main distal part of the elbow joint, while the former composes the main proximal part of the wrist joint.

Most of the large number of muscles in the forearm are divided into the wrist, hand, and finger extensors on the dorsal side (back of hand) and the ditto flexors in the superficial layers on the ventral side (side of palm). These muscles are attached to either the [lateral](/source/Lateral_epicondyle_of_the_humerus) or [medial epicondyle](/source/Medial_epicondyle_of_the_humerus) of the humerus. They thus act on the elbow, but, because their origins are located close to the centre of rotation of the elbow, they mainly act distally at the wrist and hand. Exceptions to this simple division are [brachioradialis](/source/Brachioradialis) — a strong elbow flexor — and [palmaris longus](/source/Palmaris_longus) — a weak wrist flexor which mainly acts to tense the [palmar aponeurosis](/source/Palmar_aponeurosis). The deeper flexor muscles are extrinsic hand muscles; strong flexors at the finger joints used to produce the important power grip of the hand, whilst forced extension is less useful and the corresponding extensor thus are much weaker. [10]

Biceps is the major supinator (drive a screw in with the right arm) and [pronator teres](/source/Pronator_teres) and [pronator quadratus](/source/Pronator_quadratus) the major pronators (unscrewing) — the latter two role the radius around the ulna (hence the name of the first bone) and the former reverses this action assisted by [supinator](/source/Supinator). Because biceps is much stronger than its opponents, supination is a stronger action than pronation (hence the direction of screws). [10]

**Muscles**
- of the forearm[5] **Posterior** - (Superficial) [extensor digitorum](/source/Extensor_digitorum), [extensor digiti minimi](/source/Extensor_digiti_minimi), [extensor carpi ulnaris](/source/Extensor_carpi_ulnaris), (deep) [supinator](/source/Supinator), [abductor pollicis longus](/source/Abductor_pollicis_longus), [extensor pollicis brevis](/source/Extensor_pollicis_brevis), [extensor pollicis longus](/source/Extensor_pollicis_longus), [extensor indicis](/source/Extensor_indicis) **Anterior** - (Superficial) [pronator teres](/source/Pronator_teres), [flexor digitorum superficialis](/source/Flexor_digitorum_superficialis), [flexor carpi radialis](/source/Flexor_carpi_radialis), [flexor carpi ulnaris](/source/Flexor_carpi_ulnaris), [palmaris longus](/source/Palmaris_longus), (deep) [flexor digitorum profundus](/source/Flexor_digitorum_profundus), [flexor pollicis longus](/source/Flexor_pollicis_longus), [pronator quadratus](/source/Pronator_quadratus) **Radial** - [Brachioradialis](/source/Brachioradialis), [extensor carpi radialis longus](/source/Extensor_carpi_radialis_longus), [extensor carpi radialis brevis](/source/Extensor_carpi_radialis_brevis)

#### Wrist

Main article: [Wrist](/source/Wrist)

The [wrist](/source/Wrist) ([Latin](/source/Latin_language): *carpus*),[6] composed of the [carpal bones](/source/Carpal_bones), articulates at the wrist joint (or [radiocarpal joint](/source/Radiocarpal_joint)) proximally and the [carpometacarpal joint](/source/Carpometacarpal_joint) distally. The wrist can be divided into two components separated by the [midcarpal joints](/source/Midcarpal_joint). The small movements of the eight carpal bones during composite movements at the wrist are complex to describe, but flexion mainly occurs in the midcarpal joint whilst extension mainly occurs in the radiocarpal joint; the latter joint also providing most of adduction and abduction at the wrist. [11]

3D medical animation still shot of human wrist

How muscles act on the wrist is complex to describe. The five muscles acting on the wrist directly — [flexor carpi radialis](/source/Flexor_carpi_radialis), [flexor carpi ulnaris](/source/Flexor_carpi_ulnaris), [extensor carpi radialis](/source/Extensor_carpi_radialis_longus_muscle), [extensor carpi ulnaris](/source/Extensor_carpi_ulnaris), and [palmaris longus](/source/Palmaris_longus) — are accompanied by the tendons of the extrinsic hand muscles (i.e. the muscles acting on the fingers). Thus, every movement at the wrist is the work of a group of muscles; because the four primary wrist muscles (FCR, FCU, ECR, and ECU) are attached to the four corners of the wrist, they also produce a secondary movement (i.e. ulnar or radial deviation). To produce pure flexion or extension at the wrist, these muscle therefore must act in pairs to cancel out each other's secondary action. On the other hand, finger movements without the corresponding wrist movements require the wrist muscles to cancel out the contribution from the extrinsic hand muscles at the wrist. [11]

#### Hand

Bones of the hand

Main article: [Hand](/source/Hand)

The hand ([Latin](/source/Latin_language): *manus*),[6] the [metacarpals](/source/Metacarpus) (in the hand proper) and the [phalanges](/source/Phalanx_bones) of the fingers, form the [metacarpophalangeal joints](/source/Metacarpophalangeal_joint) (MCP, including the [knuckles](/source/Knuckle)) and [interphalangeal joints](/source/Interphalangeal_articulations_of_hand) (IP).

Of the joints between the carpus and metacarpus, the [carpometacarpal joints](/source/Carpometacarpal_joint), only the saddle-shaped joint of the thumb offers a high degree of mobility while the opposite is true for the metacarpophalangeal joints. The joints of the fingers are simple hinge joints. [11]

The primary role of the hand itself is grasping and manipulation; tasks for which the hand has been adapted to two main grips — power grip and precision grip. In a power grip an object is held against the palm and in a precision grip an object is held with the fingers, both grips are performed by intrinsic and extrinsic hand muscles together. Most importantly, the relatively strong thenar muscles of the thumb and the thumb's flexible first joint allow the special opposition movement that brings the distal thumb pad in direct contact with the distal pads of the other four digits. Opposition is a complex combination of thumb flexion and abduction that also requires the thumb to be rotated 90° about its own axis. Without this complex movement, humans would not be able to perform a precision grip. [12]

In addition, the central group of intrinsic hand muscles give important contributions to human dexterity. The palmar and dorsal interossei adduct and abduct at the MCP joints and are important in pinching. The lumbricals, attached to the tendons of the [flexor digitorum profundus](/source/Flexor_digitorum_profundus) (FDP) and [extensor digitorum communis](/source/Extensor_digitorum_communis) (FDC), flex the MCP joints while extending the IP joints and allow a smooth transfer of forces between these two muscles while extending and flexing the fingers. [12]

**Muscles**
- of the hand[5] **Metacarpal** - [Lumbricals](/source/Lumbricals_of_the_hand), [palmar introssei](/source/Palmar_interossei_muscles), [dorsal interossei](/source/Dorsal_interossei_of_the_hand) **[Thenar](/source/Thenar)** - [Abductor pollicis brevis](/source/Abductor_pollicis_brevis), [adductor pollicis](/source/Adductor_pollicis), [flexor pollicis brevis](/source/Flexor_pollicis_brevis), [opponens pollicis](/source/Opponens_pollicis) **[Hypothenar](/source/Hypothenar)** - [Abductor digiti minimi](/source/Abductor_digiti_minimi_muscle_of_hand), [flexor digiti minimi](/source/Flexor_digiti_minimi_brevis_(hand)), [opponens digiti minimi](/source/Opponens_digiti_minimi), [palmaris brevis](/source/Palmaris_brevis)

### Neurovascular system

#### Nerve supply

Branches of brachial plexus

The motor and sensory supply of the upper limb is provided by the brachial plexus which is formed by the ventral rami of spinal nerves C5-T1. In the posterior triangle of the neck these rami form three trunks from which fibers enter the axilla region (armpit) to innervate the muscles of the anterior and posterior compartments of the limb. In the axilla, cords are formed to split into branches, including the five terminal branches listed below. [13] The muscles of the upper limb are innervated segmentally proximal to distal so that the proximal muscles are innervated by higher segments (C5–C6) and the distal muscles are innervated by lower segments (C8–T1). [14]

Motor innervation of upper limb by the five terminal nerves of the [brachial plexus](/source/Brachial_plexus):[14]

- The [musculocutaneous nerve](/source/Musculocutaneous_nerve) innervates all the muscles of the [anterior compartment of the arm](/source/Anterior_compartment_of_the_arm).

- The [median nerve](/source/Median_nerve) innervates all the muscles of the [anterior compartment of the forearm](/source/Anterior_compartment_of_the_forearm) except [flexor carpi ulnaris](/source/Flexor_carpi_ulnaris) and the ulnar part of the [flexor digitorum profundus](/source/Flexor_digitorum_profundus). It also innervates the three [thenar](/source/Thenar) muscles and the first and second [lumbricals](/source/Lumbricals_of_the_hand).

- The [ulnar nerve](/source/Ulnar_nerve) innervates the muscles of the forearm and hand not innervated by the median nerve.

- The [axillary nerve](/source/Axillary_nerve) innervates the [deltoid](/source/Deltoid_muscle) and [teres minor](/source/Teres_minor).

- The [radial nerve](/source/Radial_nerve) innervates the posterior muscles of the arm and forearm

Collateral branches of the brachial plexus:[14]

- The [dorsal scapular nerve](/source/Dorsal_scapular_nerve) innervates [rhomboid major](/source/Rhomboid_major), [minor](/source/Rhomboid_minor) and [levator scapulae](/source/Levator_scapulae) .

- The [long thoracic nerve](/source/Long_thoracic_nerve) innervates [serratus anterior](/source/Serratus_anterior).

- The [suprascapular nerve](/source/Suprascapular_nerve) innervates [supraspinatus](/source/Supraspinatus) and [infraspinatus](/source/Infraspinatus)

- The [lateral pectoral nerve](/source/Lateral_pectoral_nerve) innervates [pectoralis major](/source/Pectoralis_major)

- The [medial pectoral nerve](/source/Medial_pectoral_nerve) innervates [pectoralis major](/source/Pectoralis_major) and [minor](/source/Pectoralis_minor)

- The [upper subscapular nerve](/source/Upper_subscapular_nerve) innervates [subscapularis](/source/Subscapularis)

- The [thoracodorsal nerve](/source/Thoracodorsal_nerve) innervates [latissimus dorsi](/source/Latissimus_dorsi)

- The [lower subscapular nerve](/source/Lower_subscapular_nerve) innervates [subscapularis](/source/Subscapularis) and [teres major](/source/Teres_major)

- The [medial brachial cutaneous nerve](/source/Medial_brachial_cutaneous_nerve) innervates the skin of medial arm

- The [medial antebrachial cutaneous nerve](/source/Medial_antebrachial_cutaneous_nerve) innervates the skin of medial forearm

#### Blood supply and drainage

Arteries of the upper limb:

- The [superior thoracic](https://en.wikipedia.org/w/index.php?title=Superior_thoracic&action=edit&redlink=1), [thoracoacromial](/source/Thoracoacromial), [posterior circumflex humeral](https://en.wikipedia.org/w/index.php?title=Posterior_circumflex_humeral&action=edit&redlink=1) and [subscapular](/source/Subscapular_artery) branches of the [axillary artery](/source/Axillary_artery).

- The [deep brachial](https://en.wikipedia.org/w/index.php?title=Deep_brachial&action=edit&redlink=1), [superior ulnar collateral](/source/Superior_ulnar_collateral), [inferior ulnar collateral](/source/Inferior_ulnar_collateral), [radial](/source/Radial_artery),

[ulnar](/source/Ulnar_artery), [nutrient](/source/Nutrient) and [muscular](/source/Muscular) branches of the [brachial artery](/source/Brachial_artery).

- The [radial recurrent](https://en.wikipedia.org/w/index.php?title=Radial_recurrent&action=edit&redlink=1), [muscular](/source/Muscular), [superficial palmar](https://en.wikipedia.org/w/index.php?title=Superficial_palmar&action=edit&redlink=1), [dorsal carpal](/source/Dorsal_carpal), [princeps pollicis](/source/Princeps_pollicis) and [radialis indicis](/source/Radialis_indicis) branches of the [radial artery](/source/Radial_artery).

- The [anterior ulnar recurrent](/source/Anterior_ulnar_recurrent), [posterior ulnar recurrent](/source/Posterior_ulnar_recurrent), [anterior interosseous](/source/Anterior_interosseous_artery), [posterior interosseous](/source/Posterior_interosseous) and [superficial](https://en.wikipedia.org/w/index.php?title=Superficial_artery&action=edit&redlink=1) branches of the [ulnar artery](/source/Ulnar_artery).

Veins of the upper limb.

Veins of the upper limb:

- [Basilic vein](/source/Basilic_vein)

- [Cephalic vein](/source/Cephalic_vein)

- [Median cubital vein](/source/Median_cubital_vein)

- [Median antebrachial vein](/source/Median_antebrachial_vein)

- [Dorsal venous arch](/source/Dorsal_venous_arch)

As for the upper limb blood supply, there are many anatomical variations.[15]

## Other animals

### Evolutionary variation

Main article: [Forelimb](/source/Forelimb)

This section relies largely or entirely on a single source. Relevant discussion may be found on the talk page. Please help improve this article by introducing citations to additional sources. Find sources: "Upper limb" – news · newspapers · books · scholar · JSTOR (July 2011)

Upper/front limbs of (top) [salamander](/source/Salamander), [sea turtle](/source/Sea_turtle), [crocodile](/source/Crocodile), [bird](/source/Bird), (bottom) [bat](/source/Bat), [whale](/source/Whale), [mole](/source/Mole_(animal)), and [human](/source/Human)

The skeletons of all [mammals](/source/Mammal) are based on a common [pentadactyl](/source/Pentadactyl) ("five-fingered") template but optimised for different functions. While many mammals can perform other tasks using their forelimbs, their primary use in most terrestrial mammals is one of three main modes of locomotion: [unguligrade](/source/Unguligrade) (hoof walkers), [digitigrade](/source/Digitigrade) (toe walkers), and [plantigrade](/source/Plantigrade) (sole walkers). Generally, the forelimbs are optimised for speed and stamina, but in some mammals some of the locomotion optimisation have been sacrificed for other functions, such as digging and grasping. [16]

Chimpanzees maintain some of the dexterity brachiating gibbons lack

In [primates](/source/Primate), the upper limbs provide a wide range of movement which increases manual dexterity. The limbs of [chimpanzees](/source/Common_chimpanzee), compared to those of humans, reveal their different lifestyle. The chimpanzee primarily uses two modes of locomotion: [knuckle-walking](/source/Knuckle-walking), a style of [quadrupedalism](/source/Quadrupedalism) in which the body weight is supported on the knuckles (or more properly on the middle phalanges of the fingers), and [brachiation](/source/Brachiation) (swinging from branch to branch), a style of [bipedalism](/source/Bipedalism) in which flexed fingers are used to grasp branches above the head. To meet the requirements of these styles of locomotion, the chimpanzee's finger phalanges are longer and have more robust insertion areas for the flexor tendons while the metacarpals have transverse ridges to limit dorsiflexion (stretching the fingers towards the back of the hand). The thumb is small enough to facilitate brachiation while maintaining some of the dexterity offered by an opposable thumb. In contrast, virtually all locomotion functionality has been lost in humans while predominant brachiators, such as the [gibbons](/source/Gibbon), have very reduced thumbs and inflexible wrists. [16]

A [bush pig](/source/Bush_pig), an ungulate with remaining non-weight-bearing digits, and the skeleton of the extinct [Malagasy hippopotamus](/source/Malagasy_hippopotamus)

In [ungulates](/source/Ungulate) the forelimbs are optimised to maximize speed and stamina to the extent that the limbs serve almost no other purpose. In contrast to the skeleton of human limbs, the proximal bones of ungulates are short and the distal bones long to provide length of stride; proximally, large and short muscles provide rapidity of step. The [odd-toed ungulates](/source/Odd-toed_ungulate), such as the [horse](/source/Horse), use a single third toe for weight-bearing and have significantly reduced metacarpals. [Even-toed ungulates](/source/Even-toed_ungulate), such as the [giraffe](/source/Giraffe), uses both their third and fourth toes but a single completely fused phalanx bone for weight-bearing. Ungulates whose habitat does not require fast running on hard terrain, for example the [hippopotamus](/source/Hippopotamus), have maintained four digits. [16]

A grooming [lynx](/source/Lynx) and a two-toed sloth "at home"

In species in the order [Carnivora](/source/Carnivora), some of which are [insectivores](/source/Insectivore) rather than [carnivores](/source/Carnivore), the [cats](/source/Cat) are some of the most highly evolved predators designed for speed, power, and acceleration rather than stamina. Compared to ungulates, their limbs are shorter, more muscular in the distal segments, and maintain five metacarpals and digit bones; providing a greater range of movements, a more varied function and agility (e.g. climbing, swatting, and grooming). Some insectivorous species in this order have paws specialised for specific functions. The [sloth bear](/source/Sloth_bear) uses their digits and large claws to tear logs open rather than kill prey. Other insectivorous species, such as the [giant](/source/Giant_panda) and [red pandas](/source/Red_panda), have developed large [sesamoid bones](/source/Sesamoid_bone) in their paws that serve as an extra "thumb" while others, such as the [meerkat](/source/Meerkat), uses their limbs primary for digging and have [vestigial](/source/Vestigial) first digits. [16]

The [arboreal](/source/Arboreal) [two-toed sloth](/source/Two-toed_sloth), a [South American](/source/South_America) mammal in the order [Pilosa](/source/Pilosa), have limbs so highly adapted to hanging in branches that it is unable to walk on the ground where it has to drag its own body using the large curved claws on its foredigits. [16]

## See also

- [Human skeletal changes due to bipedalism](/source/Human_skeletal_changes_due_to_bipedalism)

- [Lower limb](/source/Human_leg#Structure)

## Notes

1. **[^](#cite_ref-1)** ["Upper Extremity"](https://web.archive.org/web/20160110083023/http://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?mode=&term=Upper+Extremity&field=entry#TreeA01.378.800). [MeSH](/source/Medical_Subject_Headings). Archived from [the original](https://www.nlm.nih.gov/cgi/mesh/2011/MB_cgi?mode=&term=Upper+Extremity&field=entry#TreeA01.378.800) on January 10, 2016. Retrieved 26 June 2011.

1. **[^](#cite_ref-2)** ["Upper limb anatomy"](https://www.kenhub.com/en/library/anatomy/upper-extremity-anatomy).

1. **[^](#cite_ref-3)** Wineski, Lawrence E. (2019). *Snell's clinical anatomy by regions* (10th ed.). Wolters Kluwers. p. 215. [ISBN](/source/ISBN_(identifier)) [978-1-4963-4564-6](https://en.wikipedia.org/wiki/Special:BookSources/978-1-4963-4564-6).

1. **[^](#cite_ref-4)** ["Arm"](https://meshb.nlm.nih.gov/#/record/ui?name=ARM). MeSH. Retrieved 26 June 2011.

1. ^ [***a***](#cite_ref-Thieme-Atlas-256_5-0) [***b***](#cite_ref-Thieme-Atlas-256_5-1) [***c***](#cite_ref-Thieme-Atlas-256_5-2) [***d***](#cite_ref-Thieme-Atlas-256_5-3) [***e***](#cite_ref-Thieme-Atlas-256_5-4) [***f***](#cite_ref-Thieme-Atlas-256_5-5) [Ross & Lamperti 2006](#CITEREFRossLamperti2006), p. 256

1. ^ [***a***](#cite_ref-Thieme-Atlas-208_6-0) [***b***](#cite_ref-Thieme-Atlas-208_6-1) [***c***](#cite_ref-Thieme-Atlas-208_6-2) [***d***](#cite_ref-Thieme-Atlas-208_6-3) [***e***](#cite_ref-Thieme-Atlas-208_6-4) [Ross & Lamperti 2006](#CITEREFRossLamperti2006), p. 208

1. ^ [***a***](#cite_ref-Sellers-1_7-0) [***b***](#cite_ref-Sellers-1_7-1) [***c***](#cite_ref-Sellers-1_7-2) [Sellers 2002](#CITEREFSellers2002), pp. 1–3

1. ^ [***a***](#cite_ref-Sellers-3_8-0) [***b***](#cite_ref-Sellers-3_8-1) [Sellers 2002](#CITEREFSellers2002), pp. 3–5

1. **[^](#cite_ref-Sellers-5_9-0)** [Sellers 2002](#CITEREFSellers2002), p. 5

1. ^ [***a***](#cite_ref-Sellers-6_10-0) [***b***](#cite_ref-Sellers-6_10-1) [Sellers 2002](#CITEREFSellers2002), pp. 6–7

1. ^ [***a***](#cite_ref-Sellers-8_11-0) [***b***](#cite_ref-Sellers-8_11-1) [***c***](#cite_ref-Sellers-8_11-2) [Sellers 2002](#CITEREFSellers2002), pp. 8–9

1. ^ [***a***](#cite_ref-Sellers-10_12-0) [***b***](#cite_ref-Sellers-10_12-1) [Sellers 2002](#CITEREFSellers2002), pp. 10–11

1. **[^](#cite_ref-USMLE-summary_13-0)** [Seiden 2002](#CITEREFSeiden2002), p. 243

1. ^ [***a***](#cite_ref-USMLE_14-0) [***b***](#cite_ref-USMLE_14-1) [***c***](#cite_ref-USMLE_14-2) [Seiden 2002](#CITEREFSeiden2002), pp. 233–36

1. **[^](#cite_ref-15)** Konarik M, Musil V, Baca V, Kachlik D (November 2020). ["Upper limb principal arteries variations: A cadaveric study with terminological implication"](https://www.bjbms.org/ojs/index.php/bjbms/article/view/4643). *Bosn J Basic Med Sci*. **20** (4): 502–513. [doi](/source/Doi_(identifier)):[10.17305/bjbms.2020.4643](https://doi.org/10.17305%2Fbjbms.2020.4643). [PMC](/source/PMC_(identifier)) [7664784](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7664784). [PMID](/source/PMID_(identifier)) [32343941](https://pubmed.ncbi.nlm.nih.gov/32343941).

1. ^ [***a***](#cite_ref-Gough-Palmer-etal_16-0) [***b***](#cite_ref-Gough-Palmer-etal_16-1) [***c***](#cite_ref-Gough-Palmer-etal_16-2) [***d***](#cite_ref-Gough-Palmer-etal_16-3) [***e***](#cite_ref-Gough-Palmer-etal_16-4) [Gough-Palmer, Maclachlan & Routh 2008](#CITEREFGough-PalmerMaclachlanRouth2008), pp. 502–510

## References

- Gough-Palmer, Antony L; Maclachlan, Jody; Routh, Andrew (March 2008). ["Paws for Thought: Comparative Radiologic Anatomy of the Mammalian Forelimb"](http://radiographics.rsna.org/content/28/2/501.full.pdf) (PDF). *RadioGraphics*. **28** (2): 501–510. [doi](/source/Doi_(identifier)):[10.1148/rg.282075061](https://doi.org/10.1148%2Frg.282075061). [PMID](/source/PMID_(identifier)) [18349453](https://pubmed.ncbi.nlm.nih.gov/18349453).

- Ross, Lawrence M; Lamperti, Edward D, eds. (2006). *Thieme Atlas of Anatomy: General Anatomy and Musculoskeletal System*. Thieme. [ISBN](/source/ISBN_(identifier)) [1-58890-419-9](https://en.wikipedia.org/wiki/Special:BookSources/1-58890-419-9).

- Sellers, Bill (2002). ["Functional Anatomy of the Upper Limb"](http://mac-huwis.lut.ac.uk/~wis/lectures/). Retrieved 19 June 2011.

- Seiden, David (2002). *[USMLE Step 1](/source/USMLE_Step_1) Anatomy Notes*. Kaplan Medical.

v t e Human regional anatomy Body Skin Head Hair Face Forehead Cheek Chin Eyebrow Eye Eyelid Nose Mouth Lip Tongue Tooth Ear Jaw Mandible Occiput Scalp Temple Neck Adam's apple Throat Nape Torso (Trunk) Abdomen Waist Midriff Navel Vertebral column Back Thorax Breast Nipple Pelvis Genitalia Penis Scrotum Vulva Buttocks Anus Limbs Arm Shoulder Axilla Elbow Forearm Wrist Hand Finger Fingernail Thumb Index Middle Ring Little Leg Hip Thigh Knee Calf Foot Ankle Heel Toe Toenail Sole

v t e Bones of the arm Shoulder girdle, clavicle conoid tubercle trapezoid line costal tuberosity subclavian groove Scapula fossae (subscapular, supraspinatous, infraspinatous) notches (suprascapular, great scapular) glenoid fossa tubercles (infraglenoid, supraglenoid) spine of scapula acromion coracoid process angles (superior, inferior, lateral) Humerus upper extremity: necks (anatomical, surgical) tubercles (greater, lesser) bicipital groove body: radial sulcus deltoid tuberosity lower extremity: capitulum trochlea epicondyles (lateral, medial) supracondylar ridges (lateral, medial) fossae (radial, coronoid, olecranon) Forearm Radius near elbow (head, tuberosity) near wrist (ulnar notch, styloid process, Lister's tubercle) Ulna near elbow (tuberosity, olecranon, coronoid process, radial notch, trochlear notch) near wrist (styloid process) Hand Carpal bones scaphoid lunate triquetral pisiform trapezium trapezoid capitate hamate hamulus Metacarpal bones 1st 2nd 3rd 4th 5th Phalanges proximal intermediate distal

v t e Joints and ligaments of the arm Shoulder Sternoclavicular Anterior sternoclavicular Posterior sternoclavicular Interclavicular Costoclavicular Acromioclavicular Syndesmoses: Coracoacromial Superior transverse scapular Inferior transverse of scapula Synovial: Acromioclavicular Coracoclavicular (trapezoid conoid) Glenohumeral Capsule Coracohumeral Glenohumeral (superior, middle, and inferior) Transverse humeral Glenoid labrum Elbow Humeroradial Radial collateral Humeroulnar Ulnar collateral Proximal radioulnar Anular Oblique cord Quadrate Forearm Distal radioulnar Palmar radioulnar Dorsal radioulnar Interosseous membrane of forearm Hand Wrist/radiocarpal Dorsal radiocarpal/Palmar radiocarpal Dorsal ulnocarpal/Palmar ulnocarpal Ulnar collateral/Radial collateral Intercarpal Midcarpal Radiate carpal Dorsal intercarpal Palmar intercarpal Interosseous intercarpal Scapholunate Pisiform joint (Pisohamate Pisometacarpal) Carpometacarpal Dorsal carpometacarpal Palmar carpometacarpal thumb: Radial collateral Ulnar collateral Intermetacarpal Deep transverse metacarpal Superficial transverse metacarpal Metacarpophalangeal Collateral Palmar Interphalangeal Collateral Palmar Other Carpal tunnel Ulnar canal

v t e Muscles of the arm Shoulder deltoid rotator cuff supraspinatus infraspinatus teres minor subscapularis teres major fascia: deltoid fascia supraspinous fascia infraspinous fascia Arm (compartments) anterior coracobrachialis biceps brachialis posterior triceps brachii anconeus articularis cubiti fascia axillary sheath axillary fascia brachial fascia intermuscular septa lateral medial other spaces quadrangular space triangular space triangular interval Forearm (compartments) anterior superficial: pronator teres palmaris longus flexor carpi radialis flexor carpi ulnaris flexor digitorum superficialis deep: pronator quadratus flexor digitorum profundus flexor pollicis longus posterior superficial: mobile wad brachioradialis extensor carpi radialis longus and brevis extensor digitorum extensor digiti minimi extensor carpi ulnaris deep: supinator anatomical snuffbox abductor pollicis longus extensor pollicis brevis extensor pollicis longus extensor indicis fascia bicipital aponeurosis common tendons extensor flexor antebrachial fascia other cubital tunnel osborne's ligament Hand lateral volar thenar opponens pollicis flexor pollicis brevis abductor pollicis brevis adductor pollicis medial volar hypothenar opponens digiti minimi flexor digiti minimi brevis abductor digiti minimi palmaris brevis intermediate lumbrical interossei dorsal palmar fascia posterior: extensor retinaculum extensor expansion anterior: flexor retinaculum palmar aponeurosis

v t e Arteries of the human arm Axillary Shoulder before teres minor 1st part Superior thoracic artery 2nd part Thoracoacromial artery pectoral branch acromial branch clavicular branch deltoid branch Lateral thoracic artery 3rd part Subscapular artery scapular anastomosis circumflex scapular artery thoracodorsal artery anterior humeral circumflex artery posterior humeral circumflex artery Brachial Arm before cubital fossa profunda brachii radial collateral medial collateral ulnar collateral superior inferior Radial artery forearm radial recurrent wrist/carpus Dorsal carpal branch dorsal carpal arch Palmar carpal branch deep palmar arch hand Superficial palmar branch princeps pollicis radialis indicis artery superficial palmar arch Median artery median artery Ulnar artery forearm ulnar recurrent anterior posterior common interosseous anterior posterior interosseous recurrent wrist/carpus Dorsal carpal branch dorsal carpal arch Palmar carpal branch superficial palmar arch Arterial Arches Dorsal carpal arch dorsal metacarpal dorsal digital Palmar carpal arch superficial palmar arch common palmar digital proper palmar digital deep palmar arch palmar metacarpal

v t e Veins of the human arm General Subscapular Axillary Circumflex scapular Superficial Arm Cephalic Accessory cephalic Median cubital Basilic Median antebrachial Hand and forearm Dorsal network Intercapitular Dorsal metacarpal Superficial palmar arch Palmar digital Deep Arm Radial Ulnar Brachial Hand and forearm Deep palmar arch Palmar metacarpal

v t e Anatomy of the lymphatic system Head and neck Head Back Occipital Mastoid/retroauricular Parotid Superficial Deep preauricular infra-auricular intraglandular Front Facial buccinator nasolabial Mandibular Submandibular Submental Cervical Superficial anterior lateral Deep Deep anterior cervical pretracheal paratracheal prelaryngeal thyroid Deep lateral cervical superior deep cervical inferior deep cervical retropharyngeal jugulodigastric jugulo-omohyoid Other Anterior cervical Lateral cervical Supraclavicular Vessels Jugular trunk Arm and axilla Nodes Axillary Brachial Pectoral Subscapular Central Apical Arm Supratrochlear Deltopectoral Vessels Subclavian lymph trunk Chest Nodes Parasternal Intercostal Superior diaphragmatic Trachea and bronchi superior inferior bronchopulmonary paratracheal intrapulmonary Vessels Thoracic duct Right lymphatic duct Bronchomediastinal lymph trunk Abdomen Nodes Retroaortic Paraaortic Preaortic Celiac gastric hepatic splenic Superior mesenteric mesenteric ileocolic mesocolic Inferior mesenteric pararectal Iliac Common external internal Sacral Retroperitoneal Vessels Lumbar lymph trunk Intestinal trunk Cisterna chyli Leg Inguinal deep Cloquet's node superficial Popliteal

v t e Nerve supply of the human arm Supraclavicular root (dorsal scapular, long thoracic) upper trunk (suprascapular, to the subclavius) Infraclavicular lateral cord lateral pectoral ansa pectoralis musculocutaneous (lateral cutaneous of forearm) median/lateral root: anterior interosseous palmar recurrent common palmar digital (proper palmar digital) medial cord medial pectoral ansa pectoralis cutaneous: medial cutaneous of forearm medial cutaneous of arm ulnar: muscular palmar dorsal (dorsal digital nerves) superficial (common palmar digital, proper palmar digital) deep median/medial root: see above posterior cord subscapular (upper, lower) thoracodorsal axillary (superior lateral cutaneous of arm) radial: muscular cutaneous (posterior of arm, inferior lateral of arm, posterior of forearm) superficial (dorsal digital nerves) deep (posterior interosseous) Other Brachial plexus

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Adapted from the Wikipedia article [Upper limb](https://en.wikipedia.org/wiki/Upper_limb) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Upper_limb?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.