The upper
limb
Limb may refer to:
Science and technology
* Limb (anatomy), an appendage of a human or animal
*Limb, a large or main branch of a tree
*Limb, in astronomy, the curved edge of the apparent disk of a celestial body, e.g. lunar limb
*Limb, in botany, ...
s or upper extremities are the
forelimbs of an
upright-postured tetrapod
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids ( reptiles, including dinosaurs and therefore birds) and synapsids ( pelycosaurs, extinct t ...
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...
, extending from the
scapula
The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...
e and
clavicle
The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the r ...
s down to and including the
digits, including all the
musculatures and
ligament
A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the:
* Peritoneal l ...
s involved with the
shoulder,
elbow,
wrist
In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carp ...
and
knuckle joints. In
human
Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, cultu ...
s, each upper limb is divided into the
arm,
forearm
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...
and
hand
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each "h ...
, and is primarily used for
climbing
Climbing is the activity of using one's hands, feet, or any other part of the body to ascend a steep topographical object that can range from the world's tallest mountains (e.g. the eight thousanders), to small boulders. Climbing is done ...
,
lifting and
manipulating objects.
Definition
In formal usage, the term "arm" only refers to the structures from the shoulder to the elbow, explicitly excluding the
forearm
The forearm is the region of the upper limb between the elbow and the wrist. The term forearm is used in anatomy to distinguish it from the arm, a word which is most often used to describe the entire appendage of the upper limb, but which in ...
, and thus "upper limb" and "arm" are not synonymous. 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
The human body is the structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body.
It comprises a hea ...
the muscles of the upper limb can be classified by origin, topography, function, or innervation. While a grouping by innervation reveals
embryological and
phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups ...
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.
Musculoskeletal system
Shoulder girdle
The shoulder girdle
or pectoral girdle,
composed of the
clavicle
The clavicle, or collarbone, is a slender, S-shaped long bone approximately 6 inches (15 cm) long that serves as a strut between the shoulder blade and the sternum (breastbone). There are two clavicles, one on the left and one on the r ...
and the
scapula
The scapula (plural scapulae or scapulas), also known as the shoulder blade, is the bone that connects the humerus (upper arm bone) with the clavicle (collar bone). Like their connected bones, the scapulae are paired, with each scapula on eith ...
, connects the upper limb to the
axial skeleton through the
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 which acts as a dynamic
ligament
A ligament is the fibrous connective tissue that connects bones to other bones. It is also known as ''articular ligament'', ''articular larua'', ''fibrous ligament'', or ''true ligament''. Other ligaments in the body include the:
* Peritoneal l ...
. While this muscle prevents dislocation in the joint, strong forces tend to break the clavicle instead. The
acromioclavicular joint, the joint between the
acromion
In human anatomy, the acromion (from Greek: ''akros'', "highest", ''ōmos'', "shoulder", plural: acromia) is a bony process on the scapula (shoulder blade). Together with the coracoid process it extends laterally over the shoulder joint. The ...
process on the scapula and the clavicle, is similarly strengthened by strong ligaments, especially the
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 is, in contrast, firmly fixed to the axial skeleton, which increases stability and load-bearing capabilities.
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.
; Muscles: of shoulder girdle excluding the glenohumeral joint
:; Migrated from head:
Trapezius
The trapezius is a large paired trapezoid-shaped surface muscle that extends longitudinally from the occipital bone to the lower thoracic vertebrae of the spine and laterally to the spine of the scapula. It moves the scapula and supports th ...
,
sternocleidomastoideus,
omohyoideus
:; Posterior:
Rhomboideus major,
rhomboideus minor,
levator scapulae
:; Anterior:
Subclavius,
pectoralis minor,
serratus anterior
Shoulder joint
The
glenohumeral joint
The shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...
(colloquially called the shoulder joint) is the highly mobile ball and socket joint between the
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, 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.
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
The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
is the most important arm flexor and
latissimus dorsi
The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from ...
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 Deltoid (delta-shaped) can refer to:
* The deltoid muscle, a muscle in the shoulder
* Kite (geometry), also known as a deltoid, a type of quadrilateral
* A deltoid curve, a three-cusped hypocycloid
* A leaf shape
* The deltoid tuberosity, a part o ...
and
supraspinatus must cancel the adduction component and the
teres minor and
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.
; Muscles: of shoulder joint proper
:; Posterior:
Supraspinatus,
infraspinatus,
teres minor,
subscapularis,
deltoideus,
latissimus dorsi
The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from ...
,
teres major
:; Anterior:
Pectoralis major
The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
,
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
Arm
The arm proper (''brachium''), sometimes called the upper arm,
the region between the shoulder and the elbow, is composed of the
humerus with the
elbow joint at its distal end.
The elbow joint is a complex of three joints — the
humeroradial,
humeroulnar, and
superior radioulnar joint
The proximal radioulnar articulation, also known as the proximal radioulnar joint (PRUJ), is a synovial pivot joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament ...
s — the former two allowing flexion and extension whilst the latter, together with its
inferior namesake, allows supination and pronation at the wrist.
Triceps is the major extensor and
brachialis
The brachialis (brachialis anticus), also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow. It lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow ...
and
biceps
The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join t ...
the major flexors. Biceps is, however, the major supinator and while performing this action it ceases to be an effective flexor at the elbow.
; Muscles: of the arm
:; Posterior:
Triceps brachii,
anconeus
:; Anterior:
Brachialis
The brachialis (brachialis anticus), also known as the Teichmann muscle, is a muscle in the upper arm that flexes the elbow. It lies deeper than the biceps brachii, and makes up part of the floor of the region known as the cubital fossa (elbow ...
,
biceps brachii
The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join ...
Forearm
The forearm ( la, antebrachium),
composed of the
radius
In classical geometry, a radius (plural, : radii) of a circle or sphere is any of the line segments from its Centre (geometry), center to its perimeter, and in more modern usage, it is also their length. The name comes from the latin ''radius'', ...
and
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 or
medial epicondyle 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
The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...
— a strong elbow flexor — and
palmaris longus — a weak wrist flexor which mainly acts to tense the
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.
Biceps is the major supinator (drive a screw in with the right arm) and
pronator teres and
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. Because biceps is much stronger than its opponents, supination is a stronger action than pronation (hence the direction of screws).
; Muscles: of the forearm
:; Posterior: (Superficial)
extensor digitorum,
extensor digiti minimi,
extensor carpi ulnaris, (deep)
supinator,
abductor pollicis longus,
extensor pollicis brevis,
extensor pollicis longus
In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together ...
,
extensor indicis
In human anatomy, the extensor indicis roprius'' is a narrow, elongated skeletal muscle in the deep layer of the dorsal forearm, placed medial to, and parallel with, the extensor pollicis longus. Its tendon goes to the index finger, which it exte ...
:; Anterior: (Superficial)
pronator teres,
flexor digitorum superficialis
Flexor digitorum superficialis (''flexor digitorum sublimis'') is an extrinsic flexor muscle of the fingers at the proximal interphalangeal joints.
It is in the anterior compartment of the forearm. It is sometimes considered to be the deepest p ...
,
flexor carpi radialis,
flexor carpi ulnaris,
palmaris longus, (deep)
flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Togeth ...
,
flexor pollicis longus
The flexor pollicis longus (; FPL, Latin ''flexor'', bender; ''pollicis'', of the thumb; ''longus'', long) is a muscle in the forearm and hand that flexes the thumb. It lies in the same plane as the flexor digitorum profundus. This muscle is un ...
,
pronator quadratus
:; Radial:
Brachioradialis
The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way ...
,
extensor carpi radialis longus
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each ...
,
extensor carpi radialis brevis
Wrist
The
wrist
In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; "The wrist contains eight bones, roughly aligned in two rows, known as the carp ...
( la, carpus),
composed of the
carpal bones
The carpal bones are the eight small bones that make up the wrist (or carpus) that connects the hand to the forearm. The term "carpus" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, t ...
, articulates at the wrist joint (or
radiocarpal joint) proximally and the
carpometacarpal joint distally. The wrist can be divided into two components separated by the
midcarpal joints. 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.
How muscles act on the wrist is complex to describe. The five muscles acting on the wrist directly —
flexor carpi radialis,
flexor carpi ulnaris,
extensor carpi radialis,
extensor carpi ulnaris, and
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.
Hand
The hand ( la, manus),
the
metacarpals (in the hand proper) and the
phalanges of the fingers, form the
metacarpophalangeal joint
The metacarpophalangeal joints (MCP) are situated between the metacarpal bones and the proximal phalanges of the fingers. These joints are of the condyloid kind, formed by the reception of the rounded heads of the metacarpal bones into shallow ...
s (MCP, including the
knuckles) and
interphalangeal joints (IP).
Of the joints between the carpus and metacarpus, the
carpometacarpal joints, 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.
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.
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
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Togeth ...
(FDP) and
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.
; Muscles: of the hand
:; Metacarpal:
Lumbricals,
palmar introssei,
dorsal interossei
:;
Thenar:
Abductor pollicis brevis
The abductor pollicis brevis is a muscle in the hand that functions as an abductor of the thumb.
Structure
The abductor pollicis brevis is a flat, thin muscle located just under the skin. It is a thenar muscle, and therefore contributes to the ...
,
adductor pollicis,
flexor pollicis brevis
The flexor pollicis brevis is a muscle in the hand that flexes the thumb. It is one of three thenar muscles. It has both a superficial part and a deep part.
Origin and insertion
The muscle's superficial head arises from the distal edge of the fl ...
,
opponens pollicis
The opponens pollicis is a small, triangular muscle in the hand, which functions to oppose the thumb. It is one of the three thenar muscles. It lies deep to the abductor pollicis brevis and lateral to the flexor pollicis brevis.
Structure
The op ...
:;
Hypothenar:
Abductor digiti minimi,
flexor digiti minimi,
opponens digiti minimi,
palmaris brevis
Palmaris brevis muscle is a thin, quadrilateral muscle, placed beneath the integument of the ulnar side of the hand. It acts to fold the skin of the hypothenar eminence transversally.
Structure
Origin and insertion
Palmaris brevis muscle is lo ...
Neurovascular system
Nerve supply
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.
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).
Motor innervation of upper limb by the five terminal nerves of the
brachial plexus:
* The
musculocutaneous nerve innervates all the muscles of the
anterior compartment of the arm
The fascial compartments of arm refers to the specific anatomical term of the compartments within the upper segment of the upper limb (the arm) of the body. The upper limb is divided into two segments, the arm and the forearm. Each of these se ...
.
* The
median nerve
The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus.
The median nerve originates from the lateral and medial cords of the brachial plexus, and has cont ...
innervates all the muscles of the
anterior compartment of the forearm except
flexor carpi ulnaris and the ulnar part of the
flexor digitorum profundus
The flexor digitorum profundus is a muscle in the forearm of humans that flexes the fingers (also known as digits). It is considered an extrinsic hand muscle because it acts on the hand while its muscle belly is located in the forearm.
Togeth ...
. It also innervates the three
thenar muscles and the first and second
lumbricals.
* The
ulnar nerve innervates the muscles of the forearm and hand not innervated by the median nerve.
* The
axillary nerve innervates the
deltoid Deltoid (delta-shaped) can refer to:
* The deltoid muscle, a muscle in the shoulder
* Kite (geometry), also known as a deltoid, a type of quadrilateral
* A deltoid curve, a three-cusped hypocycloid
* A leaf shape
* The deltoid tuberosity, a part o ...
and
teres minor.
* The
radial nerve
The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial comp ...
innervates the posterior muscles of the arm and forearm
Collateral branches of the brachial plexus:
* The
dorsal scapular nerve innervates
rhomboid major,
minor and
levator scapulae .
* The
long thoracic nerve innervates
serratus anterior.
* The
suprascapular nerve innervates
supraspinatus and
infraspinatus
* The
lateral pectoral nerve innervates
pectoralis major
The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
* The
medial pectoral nerve innervates
pectoralis major
The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...
and
minor
* The
upper subscapular nerve innervates
subscapularis
* The
thoracodorsal nerve innervates
latissimus dorsi
The latissimus dorsi () is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The word latissimus dorsi (plural: ''latissimi dorsorum'') comes from ...
* The
lower subscapular nerve innervates
subscapularis and
teres major
* The
medial brachial cutaneous nerve
The medial brachial cutaneous nerve (lesser internal cutaneous nerve; medial cutaneous nerve of arm) is distributed to the skin on the medial brachial side of the arm.
Anatomy
It is the smallest branch of the brachial plexus, and arising from the ...
innervates the skin of medial arm
* The
medial antebrachial cutaneous nerve
The medial cutaneous nerve of the forearm (medial antebrachial cutaneous nerve) branches from the medial cord of the brachial plexus. It contains axons from the ventral rami of the eighth cervical (C8) and first thoracic (T1) nerves.
It gives o ...
innervates the skin of medial forearm
Blood supply and drainage
Arteries of the upper limb:
* The
superior thoracic,
thoracoacromial,
posterior circumflex humeral and
subscapular branches of the
axillary artery.
* The
deep brachial,
superior ulnar collateral,
inferior ulnar collateral
The inferior ulnar collateral artery (anastomotica magna artery) is an artery in the arm. It arises about 5 cm. above the elbow from the brachial artery.
Course
It passes medialward upon the Brachialis, and piercing the medial intermuscular s ...
,
radial,
ulnar,
nutrient
A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excre ...
and
muscular branches of the
brachial artery
The brachial artery is the major blood vessel of the (upper) arm. It is the continuation of the axillary artery beyond the lower margin of teres major muscle. It continues down the ventral surface of the arm until it reaches the cubital foss ...
.
* The
radial recurrent,
muscular,
superficial palmar,
dorsal carpal,
princeps pollicis and
radialis indicis branches of the
radial artery
In human anatomy, the radial artery is the main artery of the lateral aspect of the forearm.
Structure
The radial artery arises from the bifurcation of the brachial artery in the antecubital fossa. It runs distally on the anterior part of the f ...
.
* The
anterior ulnar recurrent,
posterior ulnar recurrent,
anterior interosseous,
posterior interosseous and
superficial branches of the
ulnar artery.
Veins of the upper limb:
*
Basilic vein
The basilic vein is a large superficial vein of the upper limb that helps drain parts of the hand and forearm. It originates on the medial ( ulnar) side of the dorsal venous network of the hand and travels up the base of the forearm, where its ...
*
Cephalic vein
*
Median cubital vein
*
Median antebrachial vein
The median antebrachial vein is a superficial vein of the (anterior) forearm. It arises from - and drains - the superficial palmar venous arch, ascending superficially along the anterior forearm before terminating by draining into either the basi ...
*
Dorsal venous arch
As for the upper limb blood supply, there are many anatomical variations.
Konarik M, Musil V, Baca V, Kachlik D. Upper limb principal arteries variations: A cadaveric study with terminological implication. Bosn J of Basic Med Sci. 2020;20(4):502-13.
DOI: https://doi.org/10.17305/bjbms.2020.4643 PMID 32343941 PMCID: PMC7664784
Other animals
Evolutionary variation
The skeletons of all mammal
Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...
s are based on a common 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 (hoof walkers), digitigrade
In terrestrial vertebrates, digitigrade () locomotion is walking or running on the toes (from the Latin ''digitus'', 'finger', and ''gradior'', 'walk'). A digitigrade animal is one that stands or walks with its toes (metatarsals) touching the groun ...
(toe walkers), and plantigrade
151px, Portion of a human skeleton, showing plantigrade habit
In terrestrial animals, plantigrade locomotion means walking with the toes and metatarsals flat on the ground. It is one of three forms of locomotion adopted by terrestrial mammals. ...
(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.
In primate
Primates are a diverse order of mammals. They are divided into the strepsirrhines, which include the lemurs, galagos, and lorisids, and the haplorhines, which include the tarsiers and the simians ( monkeys and apes, the latter includin ...
s, the upper limbs provide a wide range of movement which increases manual dexterity. The limbs of chimpanzee
The chimpanzee (''Pan troglodytes''), also known as simply the chimp, is a species of great ape native to the forest and savannah of tropical Africa. It has four confirmed subspecies and a fifth proposed subspecies. When its close relative t ...
s, compared to those of humans, reveal their different lifestyle. The chimpanzee primarily uses two modes of locomotion: knuckle-walking, a style of quadrupedalism in which the body weight is supported on the knuckles (or more properly on the middle phalanges of the fingers), and brachiation (swinging from branch to branch), a style of 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, have very reduced thumbs and inflexible wrists.
In ungulates 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, such as the horse
The horse (''Equus ferus caballus'') is a domesticated, one-toed, hoofed mammal. It belongs to the taxonomic family Equidae and is one of two extant subspecies of ''Equus ferus''. The horse has evolved over the past 45 to 55 million yea ...
, use a single third toe for weight-bearing and have significantly reduced metacarpals. Even-toed ungulates, such as the giraffe
The giraffe is a large African hoofed mammal belonging to the genus ''Giraffa''. It is the tallest living terrestrial animal and the largest ruminant on Earth. Traditionally, giraffes were thought to be one species, '' Giraffa camelopardal ...
, 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
The hippopotamus ( ; : hippopotamuses or hippopotami; ''Hippopotamus amphibius''), also called the hippo, common hippopotamus, or river hippopotamus, is a large semiaquatic mammal native to sub-Saharan Africa. It is one of only two exta ...
, have maintained four digits.
In species in the order Carnivora, some of which are insectivores rather than carnivores, the cats 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
The sloth bear (''Melursus ursinus'') is a myrmecophagous bear species native to the Indian subcontinent. It feeds on fruits, ants and termites. It is listed as vulnerable on the IUCN Red List, mainly because of habitat loss and degradation ...
uses their digits and large claws to tear logs open rather than kill prey. Other insectivorous species, such as the giant and red pandas, have developed large sesamoid bones in their paws that serve as an extra "thumb" while others, such as the meerkat
MeerKAT, originally the Karoo Array Telescope, is a radio telescope consisting of 64 antennas in the Meerkat National Park, in the Northern Cape of South Africa. In 2003, South Africa submitted an expression of interest to host the Square Ki ...
, uses their limbs primary for digging and have vestigial first digits.
The arboreal two-toed sloth, a South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the sou ...
n mammal in the order 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.
See also
* Lower limb
* Human skeletal changes due to bipedalism
Notes
References
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Limbs (anatomy)