Muscles of the Upper Limb and Brachial Plexus

Vocabulary practice flashcards defining the origin, insertion, innervation, segmental spinal root supply, and action of the muscles of the upper limb (thoracic wall, back/vertebral column, scapula, arm, forearm, and hand) and the structural organization of the brachial plexus.

Pectoralis major

• Origin: Clavicle, sternum, and upper six costal cartilages.

• Insertion: Lateral lip of bicipital groove of humerus.

• Nerve supply: Medial and lateral pectoral nerves from brachial plexus (C5, 6, 7, 8; T1).

• Action: Adducts arm and rotates it medially; clavicular fibers also flex arm.

Pectoralis minor

• Origin: 3rd, 4th, and 5th ribs.

• Insertion: Coracoid process of scapula.

• Nerve supply: Medial pectoral nerve from brachial plexus (C6, 7, 8).

• Action: Depresses point of shoulder; if the scapula is fixed, it elevates the ribs of origin.

Subclavius

• Origin: 1st costal cartilage.

• Insertion: Clavicle.

• Nerve supply: Nerve to subclavius from upper trunk of brachial plexus (C5, 6).

• Action: Depresses the clavicle and steadies this bone during movements of the shoulder girdle.

Serratus anterior

• Origin: Upper eight ribs.

• Insertion: Medial border and inferior angle of scapula.

• Nerve supply: Long thoracic nerve (C5, 6, 7).

• Action: Draws the scapula forward anteriorly around the thoracic wall; rotates scapula.

Trapezius

• Origin: Occipital bone, ligamentum nuchae, spine of 7th cervical vertebra, spines of all thoracic vertebrae.

• Insertion: Upper fibers into lateral third of clavicle; middle and lower fibers into acromion and spine of scapula.

• Nerve supply: Spinal part of accessory nerve (motor) and C3 and 4 (sensory; XI cranial nerve).

• Action: Upper fibers elevate the scapula; middle fibers pull scapula medially; lower fibers pull medial border of scapula downward.

Latissimus dorsi

• Origin: Iliac crest, lumbar fascia, spines of lower six thoracic vertebrae, lower three or four ribs, and inferior angle of scapula.

• Insertion: Floor of bicipital groove of humerus.

• Nerve supply: Thoracodorsal nerve (C6, 7, 8).

• Action: Extends, adducts, and medially rotates the arm.

Levator scapulae

• Origin: Transverse processes of 1st four cervical vertebrae.

• Insertion: Medial border of scapula.

• Nerve supply: C3 and 4 and dorsal scapular nerve (C3, 4, 5).

• Action: Raises medial border of scapula.

Rhomboid minor

• Origin: Ligamentum nuchae and spines of 7th cervical and 1st thoracic vertebrae.

• Insertion: Medial border of scapula.

• Nerve supply: Dorsal scapular nerve (C4, 5).

• Action: Raises medial border of scapula upward and medially.

Rhomboid major

• Origin: Second to 5th thoracic spines.

• Insertion: Medial border of scapula.

• Nerve supply: Dorsal scapular nerve (C4, 5).

• Action: Raises medial border of scapula upward and medially.

Deltoid

• Origin: Lateral third of clavicle, acromion, spine of scapula.

• Insertion: Middle of lateral surface of shaft of humerus.

• Nerve supply: Axillary nerve (C5, 6).

• Action: Abducts arm; anterior fibers flex and medially rotate arm; posterior fibers extend and laterally rotate arm.

Supraspinatus

• Origin: Supraspinous fossa of scapula.

• Insertion: Greater tuberosity of humerus; capsule of shoulder joint.

• Nerve supply: Suprascapular nerve (C4, 5, 6).

• Action: Abducts arm and stabilizes shoulder joint.

Infraspinatus

• Origin: Infraspinous fossa of scapula.

• Insertion: Greater tuberosity of humerus; capsule of shoulder joint.

• Nerve supply: Suprascapular nerve ((C4), 5, 6).

• Action: Laterally rotates arm and stabilizes shoulder joint.

Teres major

• Origin: Lower third of lateral border of scapula.

• Insertion: Medial lip of bicipital groove of humerus.

• Nerve supply: Lower subscapular nerve (C6, 7).

• Action: Medially rotates and adducts arm and stabilizes shoulder joint.

Teres minor

• Origin: Upper two thirds of lateral border of scapula.

• Insertion: Greater tuberosity of humerus; capsule of shoulder joint.

• Nerve supply: Axillary nerve ((C4), C5, 6).

• Action: Laterally rotates arm and stabilizes shoulder joint.

Subscapularis

• Origin: Subscapular fossa.

• Insertion: Lesser tuberosity of humerus.

• Nerve supply: Upper and lower subscapular nerves (C5, 6, 7).

• Action: Medially rotates arm and stabilizes shoulder joint.

Biceps brachii

• Origin: Long head from supraglenoid tubercle of scapula; short head from coracoid process of scapula.

• Insertion: Tuberosity of radius and bicipital aponeurosis into deep fascia of forearm.

• Nerve supply: Musculocutaneous nerve (C5, 6).

• Action: Supinator of forearm and flexor of elbow joint; weak flexor of shoulder joint.

Coracobrachialis

• Origin: Coracoid process of scapula.

• Insertion: Medial aspect of shaft of humerus.

• Nerve supply: Musculocutaneous nerve (C5, 6, 7).

• Action: Flexes arm and also weak adductor.

Brachialis

• Origin: Front of lower half of humerus.

• Insertion: Coronoid process of ulna.

• Nerve supply: Musculocutaneous nerve (C5, 6).

• Action: Flexor of elbow joint.

Triceps brachii

• Origin: Long head from infraglenoid tubercle of scapula; lateral head from upper half of posterior surface of shaft of humerus; medial head from lower half of posterior surface of shaft of humerus.

• Insertion: Olecranon process of ulna.

• Nerve supply: Radial nerve (C6, 7, 8).

• Action: Extensor of elbow joint.

Pronator teres

• Origin: Humeral head from medial epicondyle of humerus; ulnar head from medial border of coronoid process of ulna.

• Insertion: Lateral aspect of shaft of radius.

• Nerve supply: Median nerve (C6, 7).

• Action: Pronation and flexion of forearm.

Flexor carpi radialis

• Origin: Medial epicondyle of humerus.

• Insertion: Bases of second and third metacarpal bones.

• Nerve supply: Median nerve (C6, 7).

• Action: Flexes and abducts hand at wrist joint.

Palmaris longus

• Origin: Medial epicondyle of humerus.

• Insertion: Flexor retinaculum and palmar aponeurosis.

• Nerve supply: Median nerve (C7, 8).

• Action: Flexes hand.

Flexor carpi ulnaris

• Origin: Humeral head from medial epicondyle of humerus; ulnar head from medial aspect of olecranon process and posterior border of ulna.

• Insertion: Pisiform bone, hook of the hamate, base at fifth metacarpal bone.

• Nerve supply: Ulnar nerve (C8; T1).

• Action: Flexes and adducts hand at wrist joint.

Flexor digitorum superficialis

• Origin: Humeroulnar head from medial epicondyle of humerus and medial border of coronoid process of ulna; radial head from oblique line on anterior surface of shaft of radius.

• Insertion: Middle phalanx of medial four fingers.

• Nerve supply: Median nerve (C7, 8; T1).

• Action: Flexes middle phalanx of fingers and assists in flexing proximal phalanx and hand.

Flexor pollicis longus

• Origin: Anterior surface of shaft of radius.

• Insertion: Distal phalanx of thumb.

• Nerve supply: Anterior interosseous branch of median nerve (C8; T1).

• Action: Flexes distal phalanx of thumb.

Flexor digitorum profundus

• Origin: Anteromedial surface of shaft of ulna.

• Insertion: Distal phalanges of medial four fingers.

• Nerve supply: Ulnar nerve (medial half) and median nerve (lateral half) (C8; T1).

• Action: Flexes distal phalanx of fingers; then assists in flexion of middle and proximal phalanges and wrist.

Pronator quadratus

• Origin: Anterior surface of shaft of ulna.

• Insertion: Anterior surface of shaft of radius.

• Nerve supply: Anterior interosseous branch of median nerve (C8; T1).

• Action: Pronates forearm.

Brachioradialis

• Origin: Lateral supracondylar ridge of humerus.

• Insertion: Base of styloid process of radius.

• Nerve supply: Radial nerve (C5, 6, 7).

• Action: Flexes forearm at elbow joint; rotates forearm to the midprone position.

Extensor carpi radialis longus

• Origin: Lateral supracondylar ridge of humerus.

• Insertion: Posterior surface of base of second metacarpal bone.

• Nerve supply: Radial nerve (C6, 7).

• Action: Extends and abducts hand at wrist joint.

Extensor carpi radialis brevis

• Origin: Lateral epicondyle of humerus.

• Insertion: Posterior surface of base of third metacarpal bone.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends and abducts hand at wrist joint.

Extensor digitorum

• Origin: Lateral epicondyle of humerus.

• Insertion: Middle and distal phalanges of medial four fingers.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends fingers and hand.

Extensor digiti minimi

• Origin: Lateral epicondyle of humerus.

• Insertion: Extensor expansion of little finger.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends metacarpophalangeal joint of little finger.

Extensor carpi ulnaris

• Origin: Lateral epicondyle of humerus.

• Insertion: Base of 5th metacarpal bone.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends and adducts hand at wrist joint.

Anconeus

• Origin: Lateral epicondyle of humerus.

• Insertion: Lateral surface of olecranon process of ulna.

• Nerve supply: Radial nerve (C7, 8; T1).

• Action: Extends elbow joint.

Supinator

• Origin: Lateral epicondyle of humerus, anular ligament of proximal radioulnar joint, and ulna.

• Insertion: Neck and shaft of radius.

• Nerve supply: Deep branch of radial nerve (C5, 6).

• Action: Supination of forearm.

Abductor pollicis longus

• Origin: Posterior surface of shafts of radius and ulna.

• Insertion: Base of first metacarpal bone.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Abducts and extends thumb.

Extensor pollicis brevis

• Origin: Posterior surface of shaft of radius.

• Insertion: Base of proximal phalanx of thumb.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends metacarpophalangeal joints of thumb.

Extensor pollicis longus

• Origin: Posterior surface of shaft of ulna.

• Insertion: Base of distal phalanx of thumb.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends distal phalanx of thumb.

Extensor indicis

• Origin: Posterior surface of shaft of ulna.

• Insertion: Extensor expansion of index finger.

• Nerve supply: Deep branch of radial nerve (C7, 8).

• Action: Extends metacarpophalangeal joint of index finger.

Palmaris brevis

• Origin: Flexor retinaculum, palmar aponeurosis.

• Insertion: Skin of palm.

• Nerve supply: Superficial branch of ulnar nerve (C8; T1).

• Action: Corrugates skin to improve grip of palm.

Lumbricals (Hand)

• Origin: Tendons of flexor digitorum profundus.

• Insertion: Extensor expansion of medial four fingers.

• Nerve supply: 1st and 2nd (lateral two) by median nerve; 3rd and 4th by deep branch of ulnar nerve (C8; T1).

• Action: Flex metacarpophalangeal joints and extend interphalangeal joints of fingers except thumb.

Palmar interossei

• Origin: First arises from base of 1st metacarpal; remaining three from anterior surface of shafts of 2nd, 4th, and 5th metacarpals.

• Insertion: Proximal phalanges of thumb and index, ring, and little fingers and dorsal extensor expansion of each finger.

• Nerve supply: Deep branch of ulnar nerve (C8; T1).

• Action: Adduct fingers toward center of third finger; flex metacarpophalangeal joints and extend interphalangeal joints.

Dorsal interossei (Hand)

• Origin: Contiguous sides of shafts of metacarpal bones.

• Insertion: Proximal phalanges of index, middle, and ring fingers and dorsal extensor expansion.

• Nerve supply: Deep branch of ulnar nerve (C8; T1).

• Action: Abduct fingers from center of third finger; flex metacarpophalangeal joints and extend interphalangeal joints.

Abductor pollicis brevis

• Origin: Scaphoid, trapezium, flexor retinaculum.

• Insertion: Base of proximal phalanx of thumb.

• Nerve supply: Median nerve (C8; T1).

• Action: Abduction of thumb.

Flexor pollicis brevis

• Origin: Flexor retinaculum.

• Insertion: Base of proximal phalanx of thumb.

• Nerve supply: Median nerve (C8; T1).

• Action: Flexes metacarpophalangeal joint of thumb.

Opponens pollicis

• Origin: Flexor retinaculum.

• Insertion: Shaft of metacarpal bone of thumb.

• Nerve supply: Median nerve (C8; T1).

• Action: Pulls thumb medially and forward across palm.

Adductor pollicis

• Origin: Oblique head from 2nd and 3rd metacarpal bones; transverse head from 3rd metacarpal bone.

• Insertion: Base of proximal phalanx of thumb.

• Nerve supply: Deep branch of ulnar nerve (C8; T1).

• Action: Adduction of thumb.

Abductor digiti minimi (Hand)

• Origin: Pisiform bone.

• Insertion: Base of proximal phalanx of little finger.

• Nerve supply: Deep branch of ulnar nerve (C8; T1).

• Action: Abducts little finger.

Flexor digiti minimi

• Origin: Flexor retinaculum.

• Insertion: Base of proximal phalanx of little finger.

• Nerve supply: Deep branch of ulnar nerve (C8; T1).

• Action: Flexes little finger.

Opponens digiti minimi

• Origin: Flexor retinaculum.

• Insertion: Medial border fifth metacarpal bone.

• Nerve supply: Deep branch of ulnar nerve (C8; T1).

• Action: Pulls 5th metacarpal forward as in cupping the palm.

Brachial plexus

A network of nerves formed by the anterior rami of cervical and thoracic spinal nerves C5, C6, C7, C8, and T1. It is organized anatomically into 5 roots, 3 trunks (upper, middle, lower), 6 divisions (anterior and posterior), and 3 cords (lateral, posterior, medial), ultimately terminating in peripheral nerves supplying the upper limb.