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Upper Limb Nerves
The nerves of the upper limb arise predominantly from the brachial plexus and provide motor, sensory, proprioceptive, and articular innervation to the shoulder, arm, forearm, and hand. Major terminal nerves include the musculocutaneous, axillary, radial, median, and ulnar nerves.
Region-
SystemMusculoskeletal System
The nerves of the upper limb provide motor, sensory, proprioceptive, and articular innervation to structures extending from the shoulder girdle to the fingertips. Most arise from the brachial plexus, a network formed primarily by the anterior rami of spinal nerves C5-T1.
The five major terminal nerves of the brachial plexus are the musculocutaneous, axillary, radial, median, and ulnar nerves. Additional branches arise from the roots, trunks, and cords of the plexus to supply muscles of the shoulder girdle, thoracic wall, and scapular region.
The course of each nerve is closely related to bones, muscles, fascial compartments, and blood vessels. These anatomical relationships explain characteristic patterns of weakness and sensory loss following nerve injury.
Brachial Plexus
The brachial plexus is formed primarily by the anterior rami of C5, C6, C7, C8, and T1. Variations may include contributions from C4 or T2.
The plexus passes from the neck into the axilla and reorganizes spinal nerve fibers through a sequence of roots, trunks, divisions, cords, and terminal branches.
Organization of the Brachial Plexus
| Level | Organization |
|---|---|
| Roots | C5, C6, C7, C8, T1 |
| Trunks | Superior, middle, inferior |
| Divisions | Anterior and posterior division from each trunk |
| Cords | Lateral, posterior, medial |
| Major terminal nerves | Musculocutaneous, axillary, radial, median, ulnar |
Roots of the Brachial Plexus
The roots are the anterior rami of C5-T1. They emerge between the anterior and middle scalene muscles and travel toward the first rib.
Important branches arising directly from the roots include the dorsal scapular nerve and long thoracic nerve.
Trunks of the Brachial Plexus
The roots combine to form three trunks:
- Superior trunk: C5-C6
- Middle trunk: C7
- Inferior trunk: C8-T1
The trunks lie in the lower part of the posterior triangle of the neck before passing toward the clavicle.
Divisions of the Brachial Plexus
Each trunk divides into an anterior and posterior division. These divisions generally redistribute fibers according to the embryological flexor and extensor compartments of the upper limb.
Anterior divisions contribute predominantly to nerves supplying anterior, or flexor, compartments. Posterior divisions contribute predominantly to nerves supplying posterior, or extensor, compartments.
Cords of the Brachial Plexus
The divisions recombine to form the lateral, medial, and posterior cords. The cords are named according to their relationship to the second part of the axillary artery.
| Cord | Formation | Major Terminal Contributions |
|---|---|---|
| Lateral cord | Anterior divisions of superior and middle trunks | Musculocutaneous nerve and lateral root of median nerve |
| Medial cord | Anterior division of inferior trunk | Ulnar nerve and medial root of median nerve |
| Posterior cord | Posterior divisions of all three trunks | Axillary and radial nerves |
Major Terminal Nerves
| Nerve | Roots | Principal Motor Distribution |
|---|---|---|
| Musculocutaneous | C5-C7 | Anterior compartment of arm |
| Axillary | C5-C6 | Deltoid and teres minor |
| Radial | C5-T1 | Posterior arm and forearm |
| Median | C6-T1, sometimes C5 contribution | Most anterior forearm muscles and several intrinsic hand muscles |
| Ulnar | Primarily C8-T1 | Selected anterior forearm muscles and most intrinsic hand muscles |
Musculocutaneous Nerve
The musculocutaneous nerve arises from the lateral cord of the brachial plexus and usually contains fibers from C5-C7. It enters the anterior compartment of the arm by piercing coracobrachialis.
It then descends between biceps brachii and brachialis and continues distally as the lateral cutaneous nerve of the forearm.
Motor Supply of the Musculocutaneous Nerve
- Coracobrachialis
- Biceps brachii
- Brachialis
These muscles contribute principally to elbow flexion, while biceps brachii is also a powerful supinator of the forearm.
Sensory Supply of the Musculocutaneous Nerve
After providing its muscular branches, the musculocutaneous nerve continues as the lateral cutaneous nerve of the forearm and supplies skin over the lateral forearm.
Musculocutaneous Nerve Injury
Isolated musculocutaneous nerve injury is relatively uncommon. A lesion can weaken elbow flexion and forearm supination and may reduce sensation over the lateral forearm.
Elbow flexion is not necessarily abolished because other muscles, including brachioradialis, receive innervation from different nerves.
Axillary Nerve
The axillary nerve arises from the posterior cord of the brachial plexus and carries fibers primarily from C5-C6. It passes posteriorly through the quadrangular space with the posterior circumflex humeral vessels.
The nerve then winds around the surgical neck of the humerus deep to the deltoid.
Motor Supply of the Axillary Nerve
- Deltoid
- Teres minor
Deltoid is particularly important for abduction of the arm after the initial phase of movement, while teres minor contributes to lateral rotation of the humerus.
Sensory Supply of the Axillary Nerve
The superior lateral cutaneous nerve of the arm, a branch of the axillary nerve, supplies skin over the inferior portion of the deltoid region.
This small area is commonly used clinically when assessing axillary nerve function.
Axillary Nerve Injury
The axillary nerve is vulnerable in fractures involving the surgical neck of the humerus and in shoulder dislocations. Injury may produce deltoid weakness, impaired arm abduction, and sensory loss over the lateral shoulder region.
Long-standing denervation may cause visible flattening or wasting of the deltoid contour.
Radial Nerve
The radial nerve is the major terminal branch of the posterior cord and contains fibers from C5-T1. It provides the principal motor innervation to the extensor compartments of the arm and forearm.
In the arm, the radial nerve travels posteriorly with the profunda brachii artery and courses along the posterior surface of the humerus within the radial groove.
Radial Nerve in the Arm
The radial nerve supplies triceps brachii and anconeus and gives branches to portions of brachialis and brachioradialis. It also provides cutaneous branches to posterior and lateral regions of the arm and forearm.
After winding around the humerus, it enters the anterior aspect of the distal arm and approaches the lateral epicondylar region.
Radial Nerve at the Elbow
Near the lateral epicondyle, the radial nerve divides into superficial and deep branches. The superficial branch is primarily sensory, while the deep branch is predominantly motor.
The deep branch passes through the supinator muscle and continues as the posterior interosseous nerve.
Posterior Interosseous Nerve
The posterior interosseous nerve is the continuation of the deep branch of the radial nerve after it passes through the supinator. It supplies most of the extensor muscles in the posterior compartment of the forearm.
Because it is predominantly motor, isolated injury typically causes weakness of finger and thumb extension without the large cutaneous sensory deficit expected from a more proximal radial nerve lesion.
Superficial Branch of the Radial Nerve
The superficial radial nerve travels deep to brachioradialis through much of the forearm before becoming superficial near the wrist.
It supplies sensation to part of the dorsolateral hand and proximal dorsal aspects of the lateral digits. The distal fingertips and nail beds of these digits are supplied principally through palmar digital branches of the median nerve.
Motor Supply of the Radial Nerve
The radial nerve and its branches supply muscles responsible for extension at the elbow, wrist, fingers, and thumb, as well as several muscles contributing to forearm and elbow movements.
- Triceps brachii
- Anconeus
- Brachioradialis
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Supinator
- Extensor digitorum
- Extensor digiti minimi
- Extensor carpi ulnaris
- Abductor pollicis longus
- Extensor pollicis brevis
- Extensor pollicis longus
- Extensor indicis
Radial Nerve Injury
The deficits caused by radial nerve injury depend strongly on the level of the lesion. Proximal lesions can affect elbow, wrist, finger, and thumb extension, while more distal lesions spare progressively more proximal muscles.
Radial nerve injury associated with the humeral shaft can occur because the nerve lies close to the bone within the radial groove.
Wrist Drop
Loss of effective wrist extensor function can produce wrist drop. The wrist tends to remain flexed because the flexor muscles are no longer adequately opposed by the extensors.
Finger extension may also be impaired depending on the level of radial nerve injury.
Median Nerve
The median nerve is formed by contributions from the lateral and medial cords of the brachial plexus. It commonly contains fibers from C6-T1, with a variable contribution from C5.
The median nerve travels with the brachial artery through much of the arm but normally provides no major motor branches to muscles of the arm.
Median Nerve in the Cubital Fossa
The median nerve enters the cubital fossa medial to the brachial artery and passes into the forearm between the heads of pronator teres.
It then descends through the anterior forearm between muscle layers toward the wrist.
Motor Supply of the Median Nerve in the Forearm
The median nerve supplies most muscles of the anterior compartment of the forearm either directly or through its anterior interosseous branch.
- Pronator teres
- Flexor carpi radialis
- Palmaris longus
- Flexor digitorum superficialis
The anterior interosseous nerve supplies deeper muscles including flexor pollicis longus, pronator quadratus, and the lateral portion of flexor digitorum profundus.
Anterior Interosseous Nerve
The anterior interosseous nerve is a motor branch of the median nerve arising in the proximal forearm. It descends along the anterior interosseous membrane with the anterior interosseous vessels.
It supplies flexor pollicis longus, pronator quadratus, and the portion of flexor digitorum profundus acting on the index and commonly the middle finger.
Median Nerve at the Wrist
The median nerve enters the hand through the carpal tunnel, deep to the flexor retinaculum. Within or shortly beyond the tunnel it divides into branches supplying the thenar region and lateral digits.
The palmar cutaneous branch arises proximal to the flexor retinaculum and passes superficial to it, which is clinically important in carpal tunnel syndrome.
Median Nerve in the Hand
Within the hand, the median nerve supplies several muscles involved in fine thumb movement and the first two lumbricals.
- Abductor pollicis brevis
- Opponens pollicis
- Superficial head of flexor pollicis brevis
- First lumbrical
- Second lumbrical
Recurrent Branch of the Median Nerve
The recurrent branch of the median nerve supplies most of the thenar muscles. Its superficial location in the palm makes it clinically important during injuries and surgical procedures involving the thenar region.
Sensory Supply of the Median Nerve
The median nerve supplies much of the lateral palm and the palmar surfaces of the lateral three and a half digits. Its digital branches also supply the dorsal distal portions and nail beds of these digits.
The exact borders of cutaneous territories overlap with adjacent nerves and vary between individuals.
Carpal Tunnel Syndrome
Carpal tunnel syndrome results from compression of the median nerve within the carpal tunnel. Symptoms commonly include paresthesia, numbness, or pain affecting the median nerve digital distribution.
More advanced compression can impair thenar motor function and produce weakness of thumb opposition and abduction.
Palmar Sensation in Carpal Tunnel Syndrome
Sensation over the central thenar or proximal palmar region may be relatively preserved in isolated carpal tunnel syndrome because the palmar cutaneous branch of the median nerve arises proximal to the tunnel and travels superficial to the flexor retinaculum.
Median Nerve Injury at the Elbow
A proximal median nerve lesion can impair pronation, weaken wrist flexion, interfere with flexion of several digits, and substantially affect thumb function.
Sensory abnormalities can involve the lateral palm and lateral digits.
Anterior Interosseous Nerve Syndrome
Injury to the anterior interosseous nerve produces a predominantly motor deficit because the nerve does not provide cutaneous sensory innervation.
Weakness of flexor pollicis longus and the index component of flexor digitorum profundus can impair the ability to form a normal tip-to-tip pinch between the thumb and index finger.
Ulnar Nerve
The ulnar nerve arises from the medial cord of the brachial plexus and carries fibers predominantly from C8-T1, although contributions can vary.
It descends along the medial arm and passes posterior to the medial epicondyle of the humerus, where it is relatively superficial.
Ulnar Nerve at the Elbow
Behind the medial epicondyle, the ulnar nerve passes through a region where it can be readily compressed or traumatized. It then enters the forearm between the heads of flexor carpi ulnaris.
This superficial relationship explains the familiar tingling sensation that may radiate toward the medial hand after striking the region behind the medial epicondyle.
Motor Supply of the Ulnar Nerve in the Forearm
The ulnar nerve supplies:
- Flexor carpi ulnaris
- Medial portion of flexor digitorum profundus
The medial portion of flexor digitorum profundus primarily flexes the distal interphalangeal joints of the ring and little fingers.
Ulnar Nerve at the Wrist
The ulnar nerve enters the hand superficial to the flexor retinaculum through the region known as Guyon's canal. It then divides into superficial and deep branches.
The superficial branch is predominantly sensory, while the deep branch supplies most of the intrinsic muscles of the hand.
Motor Supply of the Ulnar Nerve in the Hand
The ulnar nerve supplies most intrinsic hand muscles, including:
- Hypothenar muscles
- Palmar interossei
- Dorsal interossei
- Third and fourth lumbricals
- Adductor pollicis
- Deep head of flexor pollicis brevis
- Palmaris brevis
Interossei
The dorsal interossei abduct the fingers away from the axial line through the middle finger, while the palmar interossei adduct the fingers toward this line.
Because both groups are supplied by the deep branch of the ulnar nerve, finger abduction and adduction provide useful clinical tests of ulnar motor function.
Sensory Supply of the Ulnar Nerve
The ulnar nerve supplies sensation to the medial portion of the hand and approximately the medial one and a half digits. Palmar and dorsal cutaneous branches arise at different levels, so the exact sensory deficit varies according to the site of injury.
Ulnar Nerve Injury
The ulnar nerve is particularly vulnerable near the medial epicondyle and at the wrist. Lesions can produce weakness of intrinsic hand muscles, impaired finger abduction and adduction, weakened grip, and sensory abnormalities affecting the medial hand.
Ulnar Claw
Ulnar nerve injury can produce a characteristic posture involving the ring and little fingers, commonly called an ulnar claw. Loss of the medial lumbricals and interossei alters the balance of forces acting across the metacarpophalangeal and interphalangeal joints.
The appearance and severity depend on the level and chronicity of the lesion.
Froment Sign
Froment sign can be used to assess weakness of adductor pollicis due to ulnar nerve dysfunction. When a patient attempts to hold an object between the thumb and index finger, compensatory flexion of the thumb interphalangeal joint may occur through median-innervated flexor pollicis longus.
Long Thoracic Nerve
The long thoracic nerve arises from the roots of the brachial plexus, typically C5-C7. It descends along the lateral thoracic wall and supplies serratus anterior.
Serratus anterior protracts the scapula, holds it against the thoracic wall, and contributes to upward rotation required for full elevation of the upper limb.
Long Thoracic Nerve Injury
Injury to the long thoracic nerve causes weakness or paralysis of serratus anterior and can produce medial scapular winging. The medial border of the scapula becomes prominent, particularly when pushing against a wall.
Dorsal Scapular Nerve
The dorsal scapular nerve commonly arises from the C5 root of the brachial plexus. It supplies the rhomboid muscles and frequently contributes to the innervation of levator scapulae.
These muscles participate in scapular retraction, elevation, and stabilization.
Suprascapular Nerve
The suprascapular nerve arises from the superior trunk, usually carrying fibers from C5-C6. It passes toward the scapula and travels through the suprascapular notch beneath the superior transverse scapular ligament.
It supplies supraspinatus and infraspinatus and provides articular branches to the shoulder region.
Motor Functions of the Suprascapular Nerve
Supraspinatus contributes to initiation of arm abduction, while infraspinatus is an important lateral rotator of the humerus.
Suprascapular nerve injury can therefore impair both movements.
Lateral Pectoral Nerve
The lateral pectoral nerve arises from the lateral cord and carries fibers mainly from C5-C7. It supplies pectoralis major and communicates with the medial pectoral nerve.
Medial Pectoral Nerve
The medial pectoral nerve arises from the medial cord, usually carrying fibers from C8-T1. It supplies pectoralis minor and contributes to the innervation of pectoralis major.
Upper and Lower Subscapular Nerves
The upper and lower subscapular nerves arise from the posterior cord. The upper subscapular nerve supplies subscapularis, while the lower subscapular nerve supplies subscapularis and teres major.
Thoracodorsal Nerve
The thoracodorsal nerve arises from the posterior cord, usually carrying fibers from C6-C8, and supplies latissimus dorsi.
Latissimus dorsi extends, adducts, and medially rotates the humerus.
Medial Cutaneous Nerve of the Arm
The medial cutaneous nerve of the arm arises from the medial cord and supplies skin over portions of the medial arm. It commonly communicates with the intercostobrachial nerve.
Medial Cutaneous Nerve of the Forearm
The medial cutaneous nerve of the forearm arises from the medial cord and provides cutaneous innervation to the medial forearm through anterior and posterior branches.
Major Nerves by Upper Limb Compartment
| Compartment or Region | Principal Nerve |
|---|---|
| Anterior arm | Musculocutaneous nerve |
| Posterior arm | Radial nerve |
| Anterior forearm | Median nerve, with ulnar nerve contribution |
| Posterior forearm | Radial nerve and posterior interosseous nerve |
| Thenar region | Predominantly median nerve |
| Interossei | Ulnar nerve |
| Most intrinsic hand muscles | Ulnar nerve |
| Deltoid | Axillary nerve |
Cutaneous Innervation of the Upper Limb
Cutaneous sensation is distributed among branches of the brachial plexus and neighboring thoracic nerves. Peripheral nerve territories should be distinguished from dermatomes because named peripheral nerves contain fibers from multiple spinal nerve levels.
| Nerve | Representative Sensory Territory |
|---|---|
| Axillary | Lateral shoulder over inferior deltoid |
| Musculocutaneous | Lateral forearm |
| Radial | Posterior arm and forearm, dorsolateral hand |
| Median | Lateral palm and lateral three and a half digits |
| Ulnar | Medial hand and medial one and a half digits |
| Medial cutaneous nerve of arm | Medial arm |
| Medial cutaneous nerve of forearm | Medial forearm |
Autonomous Sensory Zones
Because cutaneous nerve territories overlap, small regions with relatively little overlap are often selected during neurological examination.
| Nerve | Commonly Tested Region |
|---|---|
| Axillary | Skin over lateral deltoid |
| Musculocutaneous | Lateral forearm |
| Radial | Dorsal first web-space region |
| Median | Palmar surface of index fingertip |
| Ulnar | Palmar surface of little fingertip |
Dermatomes of the Upper Limb
A dermatome represents a cutaneous territory associated primarily with a spinal nerve root rather than a named peripheral nerve.
| Root | Commonly Tested Region |
|---|---|
| C5 | Lateral upper arm |
| C6 | Lateral forearm and thumb |
| C7 | Middle finger region |
| C8 | Little finger and medial distal forearm |
| T1 | Medial forearm |
| T2 | Upper medial arm and axillary region |
Dermatome boundaries overlap and vary among individuals and anatomical maps.
Myotomes of the Upper Limb
Clinical examination can use representative movements to assess major cervical spinal root contributions.
| Movement | Important Root Contribution |
|---|---|
| Shoulder abduction | C5 |
| Elbow flexion | C5-C6 |
| Wrist extension | C6-C7 |
| Elbow extension | C7-C8 |
| Finger flexion | C8 |
| Finger abduction and adduction | T1 |
Peripheral Nerve Territory Versus Dermatome
| Feature | Peripheral Nerve | Dermatome |
|---|---|---|
| Represents | Distribution of named nerve | Distribution associated with spinal root |
| Spinal levels | Usually multiple | Primarily one |
| Clinical importance | Peripheral nerve localization | Radiculopathy localization |
Reflexes of the Upper Limb
Deep tendon reflexes assess the integrity of sensory pathways, spinal cord segments, motor neurons, and peripheral nerves.
| Reflex | Major Roots | Peripheral Nerve |
|---|---|---|
| Biceps reflex | C5-C6 | Musculocutaneous nerve |
| Brachioradialis reflex | C5-C6 | Radial nerve |
| Triceps reflex | C7-C8, principally C7 | Radial nerve |
Brachial Plexus Injury
Injury to the brachial plexus can occur at different anatomical levels, including roots, trunks, divisions, cords, or terminal branches. The resulting deficits depend on which fibers are affected.
Because individual peripheral nerves contain fibers redistributed from several spinal roots, plexus lesions can produce patterns that differ from both isolated root lesions and isolated terminal nerve injuries.
Upper Trunk Injury
Injury involving the superior trunk, particularly C5-C6 fibers, can affect muscles responsible for shoulder abduction, lateral rotation, and elbow flexion.
This pattern is classically associated with Erb-Duchenne palsy, although the exact neurological deficit depends on the extent of injury.
Lower Trunk Injury
Injury involving the inferior trunk, particularly C8-T1 fibers, can disproportionately affect intrinsic hand muscles and other structures supplied by lower plexus fibers.
Severe lower plexus injury may produce marked weakness of fine hand movements.
Root Lesion Versus Peripheral Nerve Lesion
A spinal nerve root lesion typically produces weakness across muscles supplied by several peripheral nerves but sharing the same root contribution. A peripheral nerve lesion produces deficits concentrated among muscles and cutaneous territories supplied by that named nerve.
This distinction is central to neurological localization.
Common Sites of Upper Limb Nerve Injury
| Nerve | Important Vulnerable Site | Possible Major Deficit |
|---|---|---|
| Axillary | Surgical neck of humerus | Weak shoulder abduction |
| Radial | Radial groove of humerus | Wrist and finger extension weakness |
| Median | Carpal tunnel | Median sensory symptoms and thenar weakness |
| Ulnar | Medial epicondyle or cubital tunnel | Intrinsic hand weakness |
| Long thoracic | Lateral thoracic wall | Scapular winging |
Nerve Supply and Upper Limb Movements
| Movement | Major Nerves Involved |
|---|---|
| Shoulder abduction | Suprascapular and axillary nerves |
| Elbow flexion | Musculocutaneous nerve, with radial contribution through brachioradialis |
| Elbow extension | Radial nerve |
| Forearm pronation | Median nerve |
| Forearm supination | Musculocutaneous and radial nerves |
| Wrist extension | Radial nerve |
| Finger abduction and adduction | Ulnar nerve |
| Thumb opposition | Median nerve |
Articular Innervation
Upper limb peripheral nerves also provide sensory branches to joints. These articular branches contribute proprioceptive and nociceptive information from joint capsules and related structures.
Joint innervation often reflects the nerves supplying muscles that move the joint, a relationship commonly associated with Hilton's law.
Shoulder Joint Innervation
The glenohumeral joint receives articular branches from several nerves, particularly the axillary and suprascapular nerves, with additional contributions that may vary.
Elbow Joint Innervation
The elbow joint receives articular innervation from branches associated with the musculocutaneous, radial, median, and ulnar nerves.
Wrist and Hand Joint Innervation
The wrist and hand joints receive articular branches from the median, ulnar, radial, and interosseous nerves. Their contributions vary according to the specific joint and region.
Autonomic Fibers in Upper Limb Nerves
Peripheral nerves of the upper limb also carry postganglionic sympathetic fibers. These fibers regulate structures such as cutaneous blood vessels, sweat glands, and arrector pili muscles.
They reach the upper limb through spinal nerves and are distributed distally within branches of the brachial plexus.
Nerve Regeneration
Peripheral nerve axons have some capacity for regeneration following injury if the neuronal cell body survives and an appropriate pathway remains available. The success of recovery depends on the type of nerve injury, distance to the target, integrity of connective tissue pathways, and other biological factors.
Severe injuries that disrupt the nerve's structural framework may require surgical repair and can have incomplete functional recovery.
Electrodiagnostic Assessment
Nerve conduction studies and electromyography can help evaluate peripheral nerve injuries. These tests provide information about nerve conduction, muscle activation, denervation, and reinnervation.
Electrodiagnostic findings are interpreted together with anatomical knowledge and clinical examination to localize lesions.
Clinical Examination of Upper Limb Nerves
Assessment of upper limb nerve function combines motor testing, sensory examination, reflexes, and observation of muscle bulk. Individual movements can be selected to emphasize particular nerves or spinal roots.
| Nerve | Representative Motor Test | Representative Sensory Test |
|---|---|---|
| Musculocutaneous | Elbow flexion | Lateral forearm |
| Axillary | Shoulder abduction | Lateral deltoid region |
| Radial | Wrist or finger extension | Dorsal first web-space region |
| Median | Thumb opposition or abduction | Index fingertip |
| Ulnar | Finger abduction | Little fingertip |
Key Anatomical Relationships
| Nerve | Important Anatomical Relationship |
|---|---|
| Axillary | Winds around surgical neck of humerus |
| Radial | Travels in radial groove of humerus |
| Musculocutaneous | Pierces coracobrachialis |
| Median | Passes through carpal tunnel |
| Ulnar | Passes posterior to medial epicondyle |
| Suprascapular | Passes through suprascapular notch beneath superior transverse scapular ligament |
| Long thoracic | Descends superficially along lateral thoracic wall |
Summary of Major Terminal Nerve Functions
| Nerve | Major Motor Role | Representative Sensory Region |
|---|---|---|
| Musculocutaneous | Elbow flexion and contribution to supination | Lateral forearm |
| Axillary | Shoulder abduction | Lateral shoulder |
| Radial | Extension of elbow, wrist, fingers, and thumb | Posterior limb and dorsolateral hand |
| Median | Forearm pronation, many wrist and digit flexors, thenar function | Lateral palm and lateral digits |
| Ulnar | Most intrinsic hand movements and selected forearm flexors | Medial hand and medial digits |
Functional Importance
The nerves of the upper limb connect the cervical spinal cord with the muscles, joints, and skin of the shoulder, arm, forearm, and hand. The brachial plexus redistributes fibers from C5-T1 into peripheral nerves specialized for different anatomical compartments and functions.
The musculocutaneous nerve predominantly supplies the anterior arm, the radial nerve supplies the extensor compartments, the median nerve supplies most anterior forearm muscles and important thenar muscles, and the ulnar nerve supplies most intrinsic muscles of the hand. The axillary nerve provides essential innervation to the deltoid and teres minor.
The close relationships between nerves and skeletal landmarks create clinically important sites of vulnerability. The axillary nerve is associated with the surgical neck of the humerus, the radial nerve with the radial groove, the ulnar nerve with the medial epicondyle, and the median nerve with the carpal tunnel.
Understanding upper limb nerves is therefore fundamental to the study of muscle innervation, brachial plexus anatomy, upper limb compartments, hand function, dermatomes, myotomes, reflexes, peripheral nerve injuries, carpal tunnel syndrome, wrist drop, ulnar neuropathy, scapular winging, and neurological localization.
Published on October 15, 2026
Last updated on October 15, 2026
Last updated on October 15, 2026