Anatomy chapters
Muscles of the upper limb
Learn the upper-limb muscles by compartment, then connect their attachments and nerve supply to the movements you examine.
- Learn compartment, attachment, action and nerve together.
- The rotator cuff stabilises the humeral head while larger muscles move the arm.
- Median dominates forearm flexors; ulnar dominates intrinsic hand muscles.
On this page
Overview
Upper-limb muscles position the shoulder girdle, move the arm and forearm, and produce both power grip and precise finger movement. Their arrangement is easiest to learn by compartment rather than as an unconnected list.
Anterior arm muscles mainly flex the elbow and receive musculocutaneous innervation. Posterior arm muscles extend it through the radial nerve.
Most anterior forearm muscles are median-supplied; the important ulnar exceptions are flexor carpi ulnaris and the medial half of flexor digitorum profundus.
Muscles positioning the shoulder girdle
Scapular sliding on the chest wall assists overhead elevation.
| Name | Origin/roots | Supply/action | Clinical note |
|---|---|---|---|
| Trapezius | Occiput, nuchal ligament and C7–T12 spines to clavicle, acromion and scapular spine | Accessory nerve motor; elevates, retracts and upwardly rotates scapula | Weak shrug and drooping shoulder after accessory injury |
| Serratus anterior | Upper eight ribs to anterior medial scapular border | Long thoracic C5–C7; protracts, fixes and upwardly rotates scapula | Injury produces medial border winging |
| Rhomboids | Lower nuchal region and C7–T5 spines to medial scapular border | Dorsal scapular mainly C5; retract and downwardly rotate scapula | Help hold the scapula against the thorax |
| Levator scapulae | C1–C4 transverse processes to upper medial scapula | C3–C4 and dorsal scapular C5; elevates scapula | Acts with the rhomboids |
| Pectoralis minor | Ribs 3–5 to coracoid | Medial pectoral nerve; draws scapula anteriorly and inferiorly | Divides the axillary artery into three parts |
| Subclavius | First rib and costal cartilage to inferior clavicle | Nerve to subclavius C5–C6; steadies clavicle | Lies close to underlying neurovascular structures |
Trapezius and serratus anterior rotate the glenoid upwards.
Muscles moving the shoulder
| Name | Origin/roots | Supply/action | Clinical note |
|---|---|---|---|
| Pectoralis major | Medial clavicle, sternum and upper costal cartilages to lateral lip of intertubercular sulcus | Medial and lateral pectoral nerves; adducts and medially rotates arm | Forms anterior axillary fold |
| Latissimus dorsi | Lower thoracic spines, thoracolumbar fascia, iliac crest and lower ribs to floor of intertubercular sulcus | Thoracodorsal C6–C8; extends, adducts and medially rotates arm | Forms posterior axillary fold with teres major |
| Teres major | Inferior scapular region to medial lip of intertubercular sulcus | Lower subscapular C5–C6; adducts and medially rotates | Is not a rotator cuff muscle |
| Deltoid | Lateral clavicle, acromion and scapular spine to deltoid tuberosity | Axillary C5–C6; chiefly abducts arm | Anterior fibres flex; posterior fibres extend |
Clavicular pectoralis major assists flexion; sternocostal fibres extend an already flexed arm.
The cuff has four muscles; teres major is not one of them.
Rotator cuff
The cuff tendons blend with the shoulder capsule and help hold the humeral head against the glenoid. Their scapular origins correspond to their names.
| Name | Origin/roots | Supply/action | Clinical note |
|---|---|---|---|
| Supraspinatus | Supraspinous fossa to superior greater-tubercle facet | Suprascapular C5–C6; initiates abduction | Tendon passes beneath the acromion |
| Infraspinatus | Infraspinous fossa to middle greater-tubercle facet | Suprascapular C5–C6; lateral rotation | Test resisted external rotation |
| Teres minor | Lateral scapular border to inferior greater-tubercle facet | Axillary C5–C6; lateral rotation | Also borders quadrangular space |
| Subscapularis | Subscapular fossa to lesser tubercle | Upper and lower subscapular C5–C6; medial rotation | Supports anterior capsule |
SITS names supraspinatus, infraspinatus, teres minor and subscapularis.
Supraspinatus initiates abduction, deltoid continues it, and scapular rotation permits overhead elevation. Their actions overlap.
Arm and elbow muscles
| Name | Origin/roots | Supply/action | Clinical note |
|---|---|---|---|
| Biceps | Long head supraglenoid tubercle; short head coracoid; inserts radial tuberosity and forearm fascia | Musculocutaneous C5–C6; supinates and flexes elbow | Strong supinator with elbow flexed |
| Brachialis | Anterior distal humerus to coronoid process and ulnar tuberosity | Mainly musculocutaneous C5–C6; elbow flexion | Works in both pronation and supination |
| Coracobrachialis | Coracoid to medial humeral shaft | Musculocutaneous C5–C7; flexes and adducts arm | Musculocutaneous nerve pierces it |
| Triceps | Infraglenoid tubercle and posterior humerus to olecranon | Radial C6–C8; extends elbow | Long head also acts at shoulder |
| Anconeus | Lateral epicondyle to proximal posterior ulna | Radial C7–T1; assists extension and elbow stability | Small posterior elbow muscle |
| Brachioradialis | Lateral supracondylar ridge to distal radius | Radial C5–C6; elbow flexion | Best tested with forearm midway between rotation extremes |
The ulnar exceptions are FCU and the medial half of FDP.
Anterior forearm
Most superficial flexors arise at the medial epicondyle; superficialis forms the intermediate layer.
The deep layer contains profundus, flexor pollicis longus and pronator quadratus.
| Name | Origin/roots | Supply/action | Clinical note |
|---|---|---|---|
| Pronator teres | Medial epicondyle and coronoid to lateral radius | Median C6–C7; pronation | Median nerve passes between its heads |
| Flexor carpi radialis | Medial epicondyle to bases of second and third metacarpals | Median C6–C7; flexion and radial deviation | Tendon is medial to radial pulse |
| Palmaris longus | Medial epicondyle to palmar aponeurosis | Median C7–C8; tenses aponeurosis | May be absent |
| Flexor carpi ulnaris | Medial epicondyle and ulna to pisiform, then hamate and fifth metacarpal via ligaments | Ulnar C7–T1; flexion and ulnar deviation | Ulnar nerve enters between its heads |
| Flexor digitorum superficialis | Humeroulnar and radial origins to middle phalanges 2–5 | Median C7–T1; proximal interphalangeal flexion | Split tendons admit profundus |
| Flexor digitorum profundus | Ulna and interosseous membrane to distal phalanges 2–5 | Lateral half anterior interosseous; medial half ulnar, C8–T1; distal interphalangeal flexion | Dual innervation localises lesions |
| Flexor pollicis longus | Radius and interosseous membrane to distal thumb phalanx | Anterior interosseous C8–T1; thumb interphalangeal flexion | Test in the pinch circle |
| Pronator quadratus | Distal ulna to distal radius | Anterior interosseous C8–T1; pronation | Helps bind distal forearm bones |
DAB, PAD: dorsal interossei abduct; palmar interossei adduct.
Posterior forearm
Radial branches supply posterior forearm. Longus arises above the lateral epicondyle; many other extensors arise at the epicondyle.
| Name | Origin/roots | Supply/action | Clinical note |
|---|---|---|---|
| Radial wrist extensors | Lateral supracondylar ridge or epicondyle to second and third metacarpal bases | Radial/deep radial; wrist extension and radial deviation | Longus can preserve extension in posterior interosseous palsy |
| Extensor digitorum and digiti minimi | Lateral epicondyle to digital expansions | Posterior interosseous; finger metacarpophalangeal extension | Intrinsic muscles assist interphalangeal extension |
| Extensor carpi ulnaris | Lateral epicondyle and ulna to fifth metacarpal base | Posterior interosseous; extension and ulnar deviation | Balances radial wrist extensors |
| Supinator | Lateral elbow and proximal ulna to proximal radius | Deep radial; supination | Deep radial nerve traverses it |
| Abductor pollicis longus and thumb extensors | Posterior forearm bones to thumb metacarpal or phalanges | Posterior interosseous; thumb abduction and extension | Tendons define the snuffbox margins |
| Extensor indicis | Posterior distal ulna to index expansion | Posterior interosseous; index extension | Allows relatively independent index extension |
APL reaches the first metacarpal base, EPB the proximal thumb phalanx and EPL the distal phalanx.
Finger abduction is measured from the middle finger, not the thumb.
Intrinsic hand muscles
Thenar muscles abduct, flex and oppose the thumb. Abductor pollicis brevis, opponens pollicis and the superficial head of flexor pollicis brevis are usually median-supplied.
Snell groups flexor pollicis brevis with the median-supplied thenar muscles; the deep head may receive ulnar supply. Adductor pollicis is ulnar-supplied.
Hypothenar muscles move the little finger through the deep ulnar branch. Palmaris brevis receives the superficial branch.
Lumbricals arise from profundus tendons and insert into the radial side of extensor expansions. The lateral two are median-supplied; the medial two are ulnar-supplied.
They flex metacarpophalangeal joints while extending interphalangeal joints.
Interossei arise between metacarpals and attach to proximal phalanges and extensor expansions. All receive deep ulnar innervation.
Dorsal interossei abduct and palmar interossei adduct relative to the middle finger:
Surgical planes and blood supply
The thenar space lies behind index flexors and in front of adductor pollicis. Midpalmar space lies behind flexors to the other medial fingers. A fascial septum separates them; infection may spread from flexor sheaths.
Axillary/brachial branches supply proximal muscles; radial, ulnar and interosseous branches supply forearm compartments. Palmar arches supply the hand. Limb skeletal muscle comes from somitic myoblasts.
Clinical relevance
Rotator cuff tear
How it happens: A cuff tendon, commonly supraspinatus, is torn.
What you see: Abduction may be painful or weak, and controlled lowering may fail. Pain inhibition can also reduce strength, so weakness alone does not prove a tear.
Serratus anterior paralysis
How it happens: Long thoracic injury removes scapular fixation and effective upward rotation.
What you see: The medial border becomes prominent on a wall push, and full overhead elevation becomes difficult.
Tendon injuries
How it happens: A long flexor tendon or the terminal extensor mechanism is disrupted.
What you see: Profundus failure removes active distal interphalangeal flexion; a terminal extensor injury causes a drooping distal joint. Test each joint separately.
Know the ulnar exceptions to median forearm supply and the median exceptions to ulnar intrinsic hand supply. Link attachments to actions: profundus reaches the distal phalanx, while superficialis stops at the middle phalanx. Separate rotator cuff stabilisation from the larger muscles producing shoulder movement.
Quick revision
- Serratus anterior and trapezius upwardly rotate the scapula.
- The cuff comprises supraspinatus, infraspinatus, teres minor and subscapularis.
- Biceps supinates; brachialis flexes in any forearm position.
- Ulnar nerve supplies flexor carpi ulnaris and medial profundus.
- Superficialis flexes proximal, profundus distal interphalangeal joints.
- All interossei are ulnar-supplied; lumbricals flex knuckles while extending interphalangeal joints.
Sources: Snell's Clinical Anatomy by Regions, supplied Upper Limb chapter; UHS PGET Paper I MBBS Table of Specifications. Supplementary clinical testing and developmental context follow standard examination conventions and Duke Embryology where relevant. Picture links are visual study resources. Text and tables written independently for The House Job.
FAQ
Is teres major part of the rotator cuff?
No. Teres minor is a cuff muscle; teres major adducts and medially rotates the arm.
Which muscle flexes the elbow regardless of forearm rotation?
Brachialis, because its insertion is on the ulna rather than the radius.
Why can intrinsic hand weakness cause clawing?
Loss of metacarpophalangeal flexion and interphalangeal extension leaves the long extensors and flexors relatively unopposed.