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Erector spinae
o All originate from a broad tendon that attaches inferiorly to the posterior part of the
iliac crest, the posterior aspect of the sacrum, the sacroiliac ligaments, and the sacral
and inferior lumbar spinous processes
o Innervated by posterior rami of spinal nerves
o Extend vertebral column and head; as back is flexed, control movement by gradually
lengthening their fibers
o Laterally flex vertebral column
o Iliocostalis
 Inserts lumborum, thoracis, cervicis
 Fibers run superiorly to angles of lower ribs and cervical transverse processes
o Longissimus
 Inserts thoracis, cervicis, capitis
 Fibers run superiorly to ribs between tubercles and angles to transverse
processes in thoracic and cervical regions, and to mastoid process of temporal
bone
o Spinalis
 Inserts thoracis, cervicis, capitis
 Fibers run superiorly to spinous processes in the upper thoracic region and to
cranium
Superficial posterior axioappendicular muscles
o Trapezius
 Attaches from medial third of superior nuchal line, external occipital
protuberance, nuchal ligament and spinous processes to lateral third of clavicle,
acromnion, and spine of scapula
 Innervated by the spinal accessory nerve (XI) with motor fibers and C3, C4 spinal
nerves with pain and proprioceptive fibers
 Elevates, depresses, and retracts scapula; also rotates glenoid cavity superiorly
o Latissimus dorsi
 Attaches from spinous processes of inferior 6 thoracic vertebrae, thoracolumbar
fascia, iliac crest, and inferior 3 or 4 ribs to the floor of intertubercular groove of
humerus
 Innervated by thoracodorsal nerve (C6,C7,C8)
 Extends, adducts and medially rotates humerus; raises body towards arms
during climbing
Deep posterior axioappendicular muscles
o Levator scapulae
 Attaches from posterior tubercles of transverse processes of C1-C4 vertebrae to
the medial border of scapula superior to root of spine
 Innervated by dorsal scapular and cervical nerves (C3-C5)
 Elevates scapula and tilts its glenoid cavity inferiorly by rotating scapula
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Rhomboid minor/major
 Minor: Attaches from nuchal ligaments and spinous processes of C7 and T1
vertebrae to the smooth triangular are at medial end of scapular spine
 Major: attaches from spinous processes of T2-T5 vertebrae to the medial border
of scapula from level of spine to inferior angle
 Innervated by dorsal scapular nerve
 Retracts scapula and rotates it to depress glenoid cavity; fix scapula to thoracic
wall
Scapulohumeral muscles
o Deltoid
 Divided into unipennate anterior and posterior parts, and a multipennate
middle part
 Abducts the arm, but cannot initiate abduction; it can however act as a shunt
muscle resisting inferior displacement of the head of the humerus (carrying
suitcase)
 Anterior (assists pectoralis major in flexing) and posterior (assists latissimus
dorsi in extension) parts are used to swing arms during walking
 TEST: abduct arm against resistance starting at 15 degrees
 Supplied by axillary nerve
 Attaches to lateral third of clavicle, acromion and spine of scapula proximally
and the deltoid tuberosity of the humerus distally
o Teres Major
 Adducts and medially rotates the arm
 Can help extend arm from flexed position and stabilize humeral head in glenoid
cavity
 TEST: abducted arm is adducted against resistance
 Supplied by lower subscapular nerve
 Attaches to the dorsal surface of inferior angle of scapula proximally and the
medial lip of the intertubercular groove of humerus distally
o Rotator Cuff Muscles
 Supraspinatus
 Abducts the first 15 degrees of the arm
 TEST: abduct the arm from the fully adducted position
 Supplied by suprascapular nerve
 Attaches to the supraspinous fossa of scapula proximally and the
superior facet of the greater tubercle of humerus
 Infraspinatus
 Occupies medial ¾ of infraspinous fossa and is partly covered by deltoid
and trapezius
 Stabilizes glenohumeral joint and is a powerful lateral rotator of the
humerus
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Supplied by suprascapular nerve
Attaches to the infraspinous fossa of scapula proximally and the middle
facet of the greater tubercle of humerus
Teres Minor
 Completely hidden by deltoid and not delineated from infraspinatus
 Works with infraspinatus to laterally rotate the arm and assists in its
adduction
 Supplied by axillary nerve
 Attaches to the upper portion of lateral border of scapula proximally
and the lower facet of the greater tubercle of humerus
Subscapularis
 Primary medial rotator of arm and assists in adduction
 Supplied by upper/lower subscapular nerves
 Attaches to the subscapular fossa of the scapula proximally and the
lesser tubercle distally
Muscles of arm
o Biceps brachii
 Two heads arise proximally from tendinous attachments to processes of the
scapula (long head: supraglenoid tubercle; short head: coracoid process);
uniting just distal to middle of the arm; and forming a single biceps brachii
tendon that attaches to the radial tuberosity of the radius
 When elbow is extended it acts as a simple flexor of the forearm
 When elbow is fixed close to 90 degrees and forearm is supinated biceps
produce flexion
 When forearm is pronated the biceps is the most powerful supinator of the
forearm
 Innervated by the musculocutaneous nerve
o Brachialis
 Attaches proximally to lower anterior surface of humerus and distally to
coronoid process of ulna and ulnar tuberosity
 Lies deep to biceps
 Main flexor of forearm
 Innervated by the musculocutaneous nerve
o Coracobrachialis
 Attaches proximally to the coracoid process and distally to the middle third of
medial surface of humerus
 Flexes and adducts
 Innervated by musculoscutaneous nerve
o Triceps
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Attached proximally: long head: infraglenoid tubercle; lateral head: superior to
radial groove of humerus; medial head: inferior to radial groove. Distally
attached to posterior surface of olecranon process of ulna
 Primarily involved in extending forearm
 Long head stabilizes the adducted glenohumeral joint; resisting inferior
displacement
 Medial head is active as an extensor at all speeds
 Lateral head is the strongest but is recruited into activity primarily against
resistance
 innervated by the radial nerve
Muscles of forearm
o Superficial layer
 Pronator teres
 Attaches from coronoid process (ulnar head) and medial epicondyle
(humeral head) to middle of convexity of lateral surface of radius
 Pronates and flexes forearm at elbow
 Median nerve
 Flexor carpi radialis
 Attaches from medial epicondyle of humerus to base of 2nd metacarpal
 Flexes and abducts hand at wrist
 Median nerve
 Palmaris longus
 Attaches from medial epicondyle of humerus to distal half of flexor
retinaculum and apex of palmar aponeurosis
 Flexes hand at wrist and tenses palmar aponeurosis
 Median nerve
 Flexor carpi ulnaris
 Attaches from medial epicondyle (humeral head) and olecranon and
posterior border (ulnar head) to pisiform, hook of hamate and 5th
metacarpal
 Flexes and adducts hand at wrist
 Ulnar nerve
o Intermediate layer
 Flexor digitorum superficialis
 Attaches from medial epicondyle (humeroulnar head) and superior half
of anterior border (radial head) to shafts of middle phalanges of medial
four fingers
 Flexes middle phalanges at proximal interphalangeal joints of middle
four fingers; flexes hand and forearm
 Median nerve
o Deep layer
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Flexor digitorum profundus
 Attaches from anteromedial surface of ulna and interosseus membrane
to bases of distal phalanges of fingers
 Flexes distal interphalangeal joints and hand
 Ulnar and median nerve
 Flexor pollicis longus
 Attaches from anterior surface of radius, interosseus membrane and
coronoid process to base of distal phalanx of thumb
 Flexes phalanges of thumb
 Median nerve
 Pronator quadrus
 Attaches from anterior surface of distal ulna to anterior surface of distal
radius
 Pronates forearm
 Median nerve
Muscles of posterior forearm (all radial nerve)
o Brachioradialis
 Attaches from lateral supracondylar ridge of humerus to base of radial styloid
process
 Flexes forearm (maximal when forearm is in midpronated position)
o Extensor carpi radialis longus
 Attaches from lateral supraepicondylar ridge of humerus to dorsal aspect of
base of 2nd metacarpal
 Extends and abducts hand
o Extensor carpi radialis brevis
 Attaches from lateral epicondyle to dorsal aspect of base of 3rd metacarpal
 Extends and abducts hand
o Extensor digitorum
 Attaches from lateral epicondyle to extensor expansions of medial four fingers
 Extends medial four fingers primarily at metacarpophalangeal joints; secondarily
at interphalangeal joints
o Extensor digiti minimi
 Attaches from lateral epicondyle to extensor expansion of 5th finger
 Extends little finger
o Extensor carpi ulnaris
 Attaches from lateral epicondyle and posterior surface of ulna to base of fifth
metacarpal
 Extends and adducts hand
o Supinator
 Attaches from lateral epicondyle, radial collateral and annular ligaments,
supinator fossa and crest of ulna to lateral side of upper part of radius
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 Supinates forearm
o Abductor pollicis longus
 Attaches from interosseus membrane, middle third of posterior surfaces of
radius and ulna to lateral surface on base of first metacarpal
 Abducts thumb and hand
o Extensor pollicis longus
 Attaches from interosseus membrane and middle third of posterior surface of
ulna to base of distal phalanx of thumb
 Extends distal phalanx of thumb and abducts hand
o Extensor pollicis brevis
 Attaches from interosseus membrane and posterior surface of middle third of
radius to the base of proximal phalanx of thumb
 Extends proximal phalanx of thumb and abducts hand
Muscles of hand
o Thenar muscles
 Opponens pollicis
 Opposes thumb; draws 1st metacarpal medially to center of palm and
rotates it medially
 Recurrent branch of medial nerve
 Abductor pollicis brevis
 Abducts thumb; helps oppose it
 Recurrent branch of medial nerve
 Flexor pollicis brevis
 Flexes thumb
 Recurrent branch of medial nerve
 Adductor pollicis
 Adducts thumb
 Deep branch of ulnar nerve
o Hypothenar muscles
 Abductor digit minimi
 Abducts fifth finger
 Ulnar nerve
 Flexor digiti minimi brevis
 Flexes proximal phalanx of fifth finger
 Ulnar nerve
 Opponens digiti minimi
 Opposes little finger
 Ulnar nerve
o Short muscles
 Lumbricals
 Flex metacarpophalangeal joints and extend interphalangeal joints
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 Median nerve (1,2) and ulnar nerve (3,4)
Dorsal interossei
 Abduct fingers from axial line; flex metacarpophalangeal joints; extend
interphalangeal joints’
 Ulnar nerve
Palmar interossei
 Adduct 2nd, 4th, 5th fingers towards axial line; assist lumbricals in flexing
metacarpophalangeal joints and extending interphalangeal joints