Muscles (Origin, Insertion, Action) upper limp
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Here is a comprehensive reference for upper limb muscles - their origin, insertion, and action - organized by region. Source: General Anatomy and Musculoskeletal System, THIEME Atlas of Anatomy.
Upper Limb Muscles: Origin, Insertion & Action
SHOULDER GIRDLE MUSCLES
Muscles Connecting the Trunk to the Scapula
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Trapezius | External occipital protuberance, ligamentum nuchae, spinous processes C7-T12 | Clavicle (lateral third), acromion, scapular spine | Upper fibers: elevate scapula/shoulder; Middle: retract scapula; Lower: depress scapula, rotate glenoid upward | Accessory nerve (CN XI) + C3, C4 |
| Serratus anterior | Outer surfaces of ribs 1-9 | Costal surface of medial border of scapula | Protracts and rotates scapula (glenoid upward); holds scapula against chest wall | Long thoracic nerve (C5-C7) |
| Levator scapulae | Transverse processes of C1-C4 | Superior angle of scapula | Draws scapula medially upward; moves inferior angle medially (returns raised arm to neutral) | Dorsal scapular nerve + C3, C4 |
| Rhomboid minor | Spinous processes of C6-C7 | Medial border of scapula (above scapular spine) | Steadies scapula; draws scapula medially upward | Dorsal scapular nerve (C4, C5) |
| Rhomboid major | Spinous processes of T1-T4 | Medial border of scapula (below scapular spine) | Steadies scapula; draws scapula medially upward | Dorsal scapular nerve (C4, C5) |
| Subclavius | 1st rib (chondro-osseous junction) | Inferior surface of clavicle (lateral third) | Steadies the clavicle in the sternoclavicular joint | Nerve to subclavius (C5, C6) |
| Pectoralis minor | 3rd-5th ribs | Coracoid process of scapula | Draws scapula downward and rotates glenoid inferiorly; assists respiration | Medial and lateral pectoral nerves (C8, T1) |
SHOULDER JOINT MUSCLES
Rotator Cuff (SITS)
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Supraspinatus | Supraspinous fossa of scapula | Greater tubercle of humerus (superior facet) | Initiates abduction (first 15°); stabilizes humeral head | Suprascapular nerve (C4-C6) |
| Infraspinatus | Infraspinous fossa of scapula | Greater tubercle of humerus (middle facet) | External rotation; stabilizes humeral head | Suprascapular nerve (C5, C6) |
| Teres minor | Lateral border of scapula | Greater tubercle of humerus (inferior facet) | External rotation; weak adduction | Axillary nerve (C5, C6) |
| Subscapularis | Subscapular fossa | Lesser tubercle of humerus | Internal rotation; adduction; stabilizes humeral head | Upper and lower subscapular nerves (C5-C7) |
Other Shoulder Joint Muscles
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Deltoid | Clavicular part: lateral 1/3 of clavicle; Acromial part: acromion; Spinal part: scapular spine | Deltoid tuberosity of humerus | Clavicular: flexion, internal rotation, adduction; Acromial: abduction (main); Spinal: extension, external rotation, adduction | Axillary nerve (C5, C6) |
| Pectoralis major | Clavicular head: medial clavicle; Sternocostal head: sternum and costal cartilages 1-6 | Lateral lip of intertubercular groove of humerus | Flexion, adduction, internal rotation of arm; clavicular head: also assists flexion | Lateral and medial pectoral nerves (C5-T1) |
| Latissimus dorsi | Spinous processes T7-T12, thoracolumbar fascia, iliac crest, inferior 3-4 ribs | Floor of intertubercular groove (medial lip) | Extension, adduction, internal rotation of arm; depresses shoulder | Thoracodorsal nerve (C6-C8) |
| Teres major | Inferior angle of scapula (posterior surface) | Medial lip of intertubercular groove of humerus | Internal rotation, adduction, extension of arm | Lower subscapular nerve (C5-C7) |
| Coracobrachialis | Coracoid process of scapula | Medial surface of humerus (mid-shaft) | Flexion and adduction of arm at shoulder | Musculocutaneous nerve (C5-C7) |
ARM MUSCLES
Anterior (Flexors)
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Biceps brachii | Long head: supraglenoid tubercle; Short head: coracoid process of scapula | Radial tuberosity + bicipital aponeurosis into antebrachial fascia | Elbow: flexion, supination (most powerful with elbow flexed); Shoulder: flexion, stabilization of humeral head | Musculocutaneous nerve (C5-C7) |
| Brachialis | Distal half of anterior surface of humerus + medial/lateral intermuscular septa | Ulnar tuberosity | Flexion at elbow (pure flexor - the "workhorse" of elbow flexion) | Musculocutaneous nerve (C5-C7); also radial nerve branch (C5-C6) |
Posterior (Extensors)
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Triceps brachii | Long head: infraglenoid tubercle of scapula; Lateral head: posterior humerus (above radial groove); Medial head: posterior humerus (below radial groove) | Olecranon of ulna | Extension of elbow; long head assists shoulder extension and adduction | Radial nerve (C6-C8) |
| Anconeus | Lateral epicondyle of humerus | Lateral surface of olecranon and posterior ulna | Assists elbow extension; stabilizes elbow joint | Radial nerve (C7, C8) |
FOREARM MUSCLES
Anterior Compartment - Superficial Layer
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Pronator teres | Medial epicondyle (humeral head) + coronoid process of ulna (ulnar head) | Lateral surface of radius (mid-shaft) | Pronation; assists elbow flexion | Median nerve (C6, C7) |
| Flexor carpi radialis | Medial epicondyle (common flexor origin) | Base of 2nd (and 3rd) metacarpal | Wrist flexion; radial deviation (abduction) of hand | Median nerve (C6, C7) |
| Palmaris longus | Medial epicondyle | Palmar aponeurosis | Wrist flexion; tightens palmar aponeurosis | Median nerve (C7, C8) |
| Flexor carpi ulnaris | Humeral head: medial epicondyle; Ulnar head: olecranon and posterior ulna | Pisiform, hook of hamate, base of 5th metacarpal | Wrist flexion; ulnar deviation (adduction) of hand | Ulnar nerve (C7, C8) |
| Flexor digitorum superficialis | Medial epicondyle + coronoid process + anterior radius | Sides of middle phalanges of digits 2-5 | Flexion of PIP joints of digits 2-5; assists wrist flexion | Median nerve (C7, C8, T1) |
Anterior Compartment - Deep Layer
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Flexor digitorum profundus | Anterior and medial surfaces of ulna + interosseous membrane | Bases of distal phalanges of digits 2-5 | Flexion of DIP joints (and PIP, MCP); assists wrist flexion | Medial half (digits 4-5): Ulnar nerve (C7-T1); Lateral half (digits 2-3): Anterior interosseous nerve/Median (C7-T1) |
| Flexor pollicis longus | Anterior surface of radius + interosseous membrane | Base of distal phalanx of thumb | Flexion of IP and MCP joints of thumb | Anterior interosseous nerve/Median (C7, C8) |
| Pronator quadratus | Anterior surface of distal ulna | Anterior surface of distal radius | Pronation (primary pronator) | Anterior interosseous nerve/Median (C7, C8) |
Posterior Compartment - Superficial Extensors
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Extensor carpi radialis longus | Lateral supracondylar ridge of humerus | Base of 2nd metacarpal | Wrist extension; radial deviation | Radial nerve (C6, C7) |
| Extensor carpi radialis brevis | Lateral epicondyle (common extensor origin) | Base of 3rd metacarpal | Wrist extension; radial deviation | Radial nerve (C7, C8) |
| Extensor digitorum | Lateral epicondyle | Dorsal digital expansion of digits 2-5 | Extension of wrist; extension and abduction of digits 2-5 (MCP, PIP, DIP) | Radial nerve (C7, C8) |
| Extensor digiti minimi | Lateral epicondyle | Dorsal digital expansion of digit 5 | Extension of wrist; extension and abduction of 5th digit | Radial nerve (C7, C8) |
| Extensor carpi ulnaris | Lateral epicondyle + dorsal surface of ulna | Base of 5th metacarpal | Wrist extension; ulnar deviation of hand | Radial nerve (C7, C8) |
Posterior Compartment - Deep Extensors
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Supinator | Lateral epicondyle of humerus + olecranon/supinator crest of ulna + radial collateral ligament + anular ligament | Radius (between radial tuberosity and pronator teres insertion) | Supination of forearm | Radial nerve (C7, C8) |
| Abductor pollicis longus | Dorsal surfaces of radius and ulna + interosseous membrane | Base of 1st metacarpal | Thumb abduction (carpometacarpal); wrist radial deviation | Radial nerve (C7, C8) |
| Extensor pollicis brevis | Posterior surface of radius + interosseous membrane | Base of proximal phalanx of thumb | Extension of MCP and carpometacarpal joint of thumb; wrist radial deviation | Radial nerve (C7, C8) |
| Extensor pollicis longus | Posterior surface of ulna + interosseous membrane | Base of distal phalanx of thumb | Extension of IP, MCP, carpometacarpal joints of thumb; wrist radial deviation | Radial nerve (C7, C8) |
| Extensor indicis | Posterior surface of ulna + interosseous membrane | Dorsal digital expansion of index finger (digit 2) | Extension of index finger (MCP, PIP, DIP); assists wrist extension | Radial nerve (C7, C8) |
INTRINSIC HAND MUSCLES
Thenar Muscles (Thumb)
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Abductor pollicis brevis | Flexor retinaculum, scaphoid, trapezium | Base of proximal phalanx of thumb (radial side) | Abduction of thumb | Median nerve (C8, T1) |
| Flexor pollicis brevis | Flexor retinaculum, trapezium | Base of proximal phalanx of thumb | Flexion of MCP joint of thumb | Superficial head: Median; Deep head: Ulnar (C8, T1) |
| Opponens pollicis | Flexor retinaculum, trapezium | Lateral border of 1st metacarpal | Opposition of thumb | Median nerve (C8, T1) |
| Adductor pollicis | Oblique head: capitate + bases of 2nd-3rd metacarpals; Transverse head: palmar surface of 3rd metacarpal | Base of proximal phalanx of thumb (ulnar side) via sesamoid | Adduction of thumb | Ulnar nerve (C8, T1) |
Hypothenar Muscles (Little Finger)
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Abductor digiti minimi | Pisiform bone | Base of proximal phalanx of digit 5 (ulnar side) | Abduction of little finger | Ulnar nerve (C8, T1) |
| Flexor digiti minimi brevis | Hook of hamate, flexor retinaculum | Base of proximal phalanx of digit 5 | Flexion of MCP joint of little finger | Ulnar nerve (C8, T1) |
| Opponens digiti minimi | Hook of hamate, flexor retinaculum | Medial border of 5th metacarpal | Opposition of little finger | Ulnar nerve (C8, T1) |
Middle of Palm
| Muscle | Origin | Insertion | Action | Nerve |
|---|---|---|---|---|
| Lumbricals (4) | Tendons of flexor digitorum profundus (1st and 2nd: radial side of tendons 2-3; 3rd and 4th: adjacent tendons) | Radial side of dorsal digital expansion of digits 2-5 | Flex MCP joints; extend PIP and DIP joints | 1st and 2nd: Median nerve; 3rd and 4th: Ulnar nerve (C8, T1) |
| Dorsal interossei (4) | Adjacent sides of metacarpal shafts (bipennate) | Dorsal digital expansion + bases of proximal phalanges of digits 2-4 | Abduct digits (DAB); flex MCP; extend PIP/DIP | Ulnar nerve (C8, T1) |
| Palmar interossei (3) | Medial side of 2nd metacarpal; lateral sides of 4th and 5th metacarpals | Dorsal digital expansion + proximal phalanges of digits 2, 4, 5 | Adduct digits (PAD); flex MCP; extend PIP/DIP | Ulnar nerve (C8, T1) |
Key Memory Aids
- SITS = Supraspinatus, Infraspinatus, Teres minor, Subscapularis (rotator cuff)
- DAB / PAD = Dorsal interossei Abduct / Palmar interossei ADduct
- "You can flex without a median nerve but you cannot oppose" - opposition of thumb = median nerve
- Common flexor origin = medial epicondyle (superficial forearm flexors)
- Common extensor origin = lateral epicondyle (superficial forearm extensors)
- All intrinsic hand muscles are ulnar nerve EXCEPT: LOAF muscles (Lumbricals 1&2, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis superficial head) = Median nerve
Source: General Anatomy and Musculoskeletal System, THIEME Atlas of Anatomy
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