Makindo Medical Notes

Muscles of the Upper Limb - Listed Alphabetically:

Abductor Digiti Minimi (Hand)

Origin: Pisiform
Insertion: Base of the proximal phalanx of the 5th digit on its ulnar side
Action: Abducts the 5th digit
Innervation: Deep branch of the ulnar nerve
Artery: Ulnar a.
Notes: Located in the hypothenar compartment along with flexor digiti minimi brevis and opponens digiti minimi.

Abductor Pollicis Brevis

Origin: Flexor retinaculum, scaphoid, trapezium
Insertion: Base of the proximal phalanx of the first digit
Action: Abducts the thumb
Innervation: Recurrent branch of the median nerve
Artery: Superficial palmar branch of the radial a.
Notes: Located in the thenar compartment with flexor pollicis brevis and opponens pollicis. (Latin, pollicis = the thumb)

Abductor Pollicis Longus

Origin: Middle one-third of the posterior surface of the radius, interosseous membrane, mid-portion of posterolateral ulna
Insertion: Radial side of the base of the first metacarpal
Action: Abducts the thumb at the carpometacarpal joint
Innervation: Radial nerve, deep branch
Artery: Posterior interosseous a.
Notes: Forms the lateral border of the anatomical snuffbox with extensor pollicis brevis. (Latin, pollicis = the thumb)

Adductor Pollicis

Origin: Oblique head: capitate, base of 2nd and 3rd metacarpals; transverse head: shaft of the 3rd metacarpal
Insertion: Base of the proximal phalanx of the thumb
Action: Adducts the thumb
Innervation: Ulnar nerve, deep branch
Artery: Deep palmar arterial arch
Notes: Deep palmar arch and deep ulnar nerve pass between the two heads of adductor pollicis, in the adductor-interosseous compartment. (Latin, pollicis = the thumb)

Anconeus

Origin: Lateral epicondyle of the humerus
Insertion: Lateral side of the olecranon and upper one-fourth of the ulna
Action: Extends the forearm
Innervation: Nerve to anconeus, from the radial nerve
Artery: Interosseous recurrent a.
Notes: (Greek, anconeus = elbow)

Biceps Brachii

Origin: Short head: tip of the coracoid process of the scapula; long head: supraglenoid tubercle of the scapula
Insertion: Tuberosity of the radius
Action: Flexes the forearm, flexes the arm (long head), supinates
Innervation: Musculocutaneous nerve (C5,6)
Artery: Brachial a.
Notes: A powerful supinator, especially if the elbow is flexed.

Brachialis

Origin: Anterior surface of the lower one-half of the humerus and associated intermuscular septa
Insertion: Coronoid process of the ulna
Action: Flexes the forearm
Innervation: Musculocutaneous nerve (C5,6)
Artery: Brachial a., radial recurrent a.
Notes: A powerful flexor.

Brachioradialis

Origin: Upper two-thirds of the lateral supracondylar ridge of the humerus
Insertion: Lateral side of the base of the styloid process of the radius
Action: Flexes the elbow, assists in pronation & supination
Innervation: Radial nerve
Artery: Radial recurrent a.
Notes: Although innervated by the nerve for extensors (radial), its primary action is elbow flexion. Its neutral position is halfway between supination and pronation (elbow flexed, thumb up).

Coracobrachialis

Origin: Coracoid process of the scapula
Insertion: Medial side of the humerus at mid-shaft
Action: Flexes and adducts the arm
Innervation: Musculocutaneous nerve (C5,6)
Artery: Brachial a.
Notes: The musculocutaneous nerve passes through the coracobrachialis muscle to reach other arm flexor muscles (biceps brachii and brachialis).

Deltoid

Origin: Lateral one-third of the clavicle, acromion, lower lip of the crest of the spine of the scapula
Insertion: Deltoid tuberosity of the humerus
Action: Abducts arm; anterior fibers flex & medially rotate the arm; posterior fibers extend & laterally rotate the arm
Innervation: Axillary nerve (C5,6) from the posterior cord of the brachial plexus
Artery: Posterior circumflex humeral a.
Notes: Deltoid is the principal abductor of the arm, but it requires supraspinatus muscle to initiate this movement.

Dorsal Interosseous (Hand)

Origin: Four muscles, each arising from two adjacent metacarpal shafts
Insertion: Base of the proximal phalanx and extensor expansion on lateral side of the 2nd digit, lateral & medial sides of the 3rd digit, and medial side of the 4th digit
Action: Flexes the metacarpophalangeal joint, extends the proximal and distal interphalangeal joints of digits 2-4, abducts digits 2-4
Innervation: Ulnar nerve, deep branch
Artery: Dorsal and palmar metacarpal aa.
Notes: Bipennate muscles; remember DAB & PAD - Dorsal interosseous muscles ABduct, and Palmar interosseous muscles ADduct.

Extensor Carpi Radialis Brevis

Origin: Common extensor tendon (lateral epicondyle of the humerus)
Insertion: Dorsum of the third metacarpal bone (base)
Action: Extends the wrist, abducts the hand
Innervation: Deep radial nerve
Artery: Radial a.
Notes: Works with the extensor carpi radialis longus and flexor carpi radialis in abduction of the hand.

Extensor Carpi Radialis Longus

Origin: Lower one-third of the lateral supracondylar ridge of the humerus
Insertion: Dorsum of the second metacarpal bone (base)
Action: Extends the wrist, abducts the hand
Innervation: Radial nerve
Artery: Radial a.
Notes: Works with the extensor carpi radialis brevis and flexor carpi radialis in abduction of the hand.

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