IMAGE	MUSCLE	ORIGIN	INSERTION	ACTION	NERVE
	Pectoralis Major	Medial half of clavicle; sternum; upper six costal cartilages	Lateral lip of intertubercular groove of humerus	horizontal adduction	Medial and lateral pectoral nerves
	Pectoralis Minor	External surfaces of ribs 3-5	Coracoid process of the scapula	Raises ribs in forced inspiration; draws scapula forward and downward	Medial and lateral pectoral nerves
	Trapezius	External occipital protuberance; ligamentum nuchae; Spinous processes and surpraspinous ligaments of C7 and all thoracic vertebrae	Lateral third of clavicle; acromion and crest of spine of scapula; Inner/medial aspect of the spine of the scapula	Shrugging the shoulders	Accessory (eleventh cranial)
	Latissimus Dorsi	Spinous processes of lower six thoracic vertebrae; Lumbar vertebrae, sacral vertebrae, supraspinous ligament; Posterior part of iliac crest; lower three or four ribs; Inferior angle of the scapula	Bottom of intertubercular groove	Extends and hyper- extends the arm, drawing shoulder downward and backward; Extends, adducts and medially rotates the arm	Thoracodorsal (C6-C8)
	Levator Scapulae	Posterior tubercles of transverse processes of C1-C4	Superior angle of scapula	Elevates scapula (synergist)	Dorsal scapular
	Rhomboid Major	Spines of thoracic vertebrae 2-5; Supraspinous ligament	Medial border of the scapula below the spine	Retracts and stabilizes scapula	Dorsal scapular
	Rhomboid Minor	Spines of c7 and T1; Lower part of ligamentum nuchae	Medial border of the scapula at the root of spine	Retracts and stablizes scapula	Dorsal scapular
	Serratus Anterior	Outer surface of first 8-9 ribs	Anterior surface of medial border of scapula	Holds scapula in place against posterior thoracic wall	Long Thoracic
	Deltoid	Anterior border and superior surface of lateral third of clavicle; Lateral border of the acromion process; Lower border of the crest of the spine of the scapular	Deltoid tuberosity	Main action: abducts arm; synergist: flexes and medially rotates arm, Extends and laterally rotates arm	Axillary (C5, C6)
	Rotator Cuff (SITS)
	Supraspinatus (rotator cuff)	Supraspinous fossa of scapula	Superior facet of greater tubercle of humerus	Hyperextension of the arm	Suprascapular nerve
Infraspinatus (rotator cuff)	Infraspinous fossa of scapula	Middle facet of the greater tubercle of humerus	Lateral rotation of the arm, synergist to abduction of arm	Suprascapular nerve (C5, C6)
	Teres Minor (rotator cuff)	Upper 2/3 of the posterior surface of the lateral border of the scapula	Lower facet of the grater tubercle of humerus	Laterally rotates arm (synergist); weak synergist to adduction of arm	Axillary
	Subscapularis (rotator cuff)	Subscapular fossa on the anterior surface of scapula	Lesser tubercle of humerus	Internal rotation of the arm	Upper and lower subscapular nerves (C5, C6)
	Teres Major	Lower third of the posterior surface of the lateral border of the scapula, near inferior angle	Medial lip of intertubercular groove	Syngergist to latissimus dorsi: Adducts arm, extends arm, medially rotates arm	Lower subscapular nerve
	Brachialis	Anterior of lower half of humerus	Coronoid process of ulna; ulnar tuberosity	Primary forearm flexor	Musculocutaneous
	Biceps Brachii	Two heads: Supraglenoid tubercle of scapula & coracoid process of scapula	Radial tuberosity; bicipital aponeurosis into deep fascia on medial side of forearm	Supinates forearm in flexion; weak forearm flexor	Musculocutaneous
	Coracobrachialis	Tip of coracoid process of scapula	Middle third of the medial surface of border of humerus	Flexor of humerus at shoulder joint	Musculocutaneous
	Triceps Brachii	Long head: infraglenoid tubercle of scapula; Lateral head: upper half of posterior surface of humerus; Medial head: posterior surface of lower half of humerus (buried)	Posterior part of olecranon process of ulna	Extends forearm; long head aids in addution if arm is abducted	Radial nerve
	Superficial Group
	Pronator Teres (superficial group)	Humeral head- medial supracondylar ridge and medial epicondyle of humerus; Ulnar head- medial border of the coronoid process of ulna	Middle of lateral surface of the radius (pronator tuberosity)	Pronates and flexes forearm	Median nerve
	Flexor carpi radialus (superficial group)	Medial epicondyle of the humerus through common tendon (flexor pronator tendon)	Front of the bases of the second and third metacarpal bones	Flexes hand; radial deviation	Median nerve
	Palmaris Longus (superficial group)	Medial epicondyle of the humerus through common tendon (flexor pronator tendon)	Front of flexor retinaculum and apex of palmar aponeurosis	Flexes the hand; makes a tight fist	Median nerve
	Flexor carpi ulnaris (superficial group)	Humeral head- medial epicondyle of humerus; Ulnar head- medial margin of olecranon process of ulna, dorsal border of shaft of ulna	Pisiform bone; hook of hamate; base of fifth metacarpal	Flexes hand; ulnar deviation	Ulnar nerve
	Flexor Digitorum Superficialis (Intermediate grp)	Medial epicondyle of humerus through common tendon; medial margin of coronoid process of ulna; anterior shaft of radius	Four tendons split and connect at middle phalanges of four fingers	Primary: flexion of digits. Flexes carpal region, MCPs & PCPs of digits 2-5.	Median nerve
	Flexor Digitorum Profundus (deep)	Upper anterior & medial shaft of ulna and medial coronoid process, interosseous membrane	Front of base of distal phalanges of fingers 2-5	Flexes distal phalanges (DIPS). Synergist to MCPs & PIPs	Anerior Interosseus/Ulnar (digit flexion backup for median nerve)
	Flexor Pollicis Longus	Middle of anterior surface of shaft of radius, interosseous membrane	Palmar aspect of base of distal phalanx of thumb	Flexes the thumb	Anterior interosseous (branch of median)
	3 muscles in Anterior Compartment of Forearm- no action on digits:
	Pronator Quadratus	Anterior surface of distal part of shaft of ulna	Lower portion of anterior surface of shaft of radius, distal part of lateral border of radius	Pronates forearm and hand; works with Pronator teres for full pronation.	Anterior interosseous (branch of median)
	Supinator	Lateral epicondyle of humerus; supinator crest of ulna	Posterior and lateral surfaces of upper third of radius	supinates forearm; antagonist of pronator teres and pronator quadratus; supinator when in extension, syngergist in flexion	Radial nerve (because origin off lateral condyle)
	Brachioradialis	Upper 2/3 of lateral supracondylar ridge of humerus	Base of styloid process and lateral surface of radius	Flexes forearm (synergist to brachialis)	Radial nerve (elbow flexion backup)
	Posterior Compartment of Forearm
	Extensor Carpi Radialis (Brevis3 & Longus2)	Lateral supracondylar ridge and epicondyle of humerus	Dorsal surface of 2nd and 3rd metacarpals	extends hand; synergist in radial deviation with flexor carpi radialis; antagonist to FCR for extension/flexion	Radial
	Extensor Carpi Ulnaris	Common tendon attached to lateral epicondyle of humerus	Dorsal surface of base of 5th metacarpal bone	Extends hand; synergist in ulnar deviation with flexor carpi ulnaris	Radial nerve (because origin off lateral condyle)
	Extensor Digitorum Communis	Common tendon attached to lateral epicondyle of humerus	Lateral and dorsal surfaces of all phalanges of four fingers	Extends the fingers and wrist; extension expansion joint at distal phalanges	Radial nerve (because origin off lateral condyle)
	Extensor Indicis	Posterior surface of ulna and adjacent part of interosseous membrane	Extensor expansion on dorsal surface of proximal phalanx of index finger	Extends index finger	Radial
	Extensor Digiti Minimi	Common tendon attached to lateral epicondyle of humerus	Dorsal surface of base of first phalanx of fifth finger	Extends fifth finger (pulls out of opposition)	Radial nerve
	Abductor Pollicis Longus	Dorsal surface of shaft or radius, ulna, interosseous membrane	Dorsal surface of base of first metacarpal bone	Abducts thumb & wrist	Radial
	Extensor Pollicis Brevis	Dorsal surface of radius, adjacent part of interosseous membrane	Base of proximal phalanx of thumb	Extends thumb	Radial
	Extensor Pollicis Longus	Middle third of dorsal surface of ulna, interosseous membrane	Base of distal phalanx of thumb	Extends thumb	Radial
	Abductor pollicis Brevis (thenar eminence)	Tubercle of scaphoid, tubercle of trapezium, flexor retinaculum	Lateral aspect of base of proximal phalanx of thumb	Abducts thumb (with Abductor Pollicis Longus) and opposes thumb to other fingers	Median
	Flexor Pollicis Brevis (thenar eminence)	Flexor retinaculum and trapezium, first metacarpal bone	Medial and lateral aspect of base of proximal phalanx of thumb	Flexes MCP joint of thumb, opposes thumb	Median/Ulnar
	Opponens Pollicis (thenar eminence)	Flexor retinaculum, tubercle of trapezium	Lateral border of first metacarpal bone, wraps around entire lateral border	Rotates thumb into opposition, primary thumb opposer; separates us from animals	Median
	Adductor Pollicis	Anterior surface of 2 & 3 metacarpals, capitate and trapezoid	Medial side of proximal phalanx of thumb	adducts thumb	Ulnar
	Abductor Digiti Minimi (Hypothenar eminence)	Pisiform bone, tendon of flexor carpi ulnaris	Medial side of proximal phalanx of fifth finger	Abducts fifth finger	Ulnar
	Flexor Digiti Minimi (Hypothenar eminence)	Anterior surface of flexor retinaculum, hook of hamate	Medial side of base of proximal phalanx of fifth finger	Flexes fifth finger (extrinisic muscles, Flexor Digitorum Profundus/Superficialis are stronger flexors)	Ulnar
	Opponens Digiti Minimi (Hypothenar eminence)	Flexor retinaculum, hook of hamate	Whole length of medial border of fifth metacarpal bone	rotates fifth metacarpal bone, flexing fifth finger	Ulnar
	Lumbricales	JUST KNOW: Synergist to PIP & MCP function
	Palmar Interossei (PAD)	Palmer surface of metacarpals: ADducts digits between 2-3, 3-4, 4-5;
	Dorsal Interossei (DAB)	Dorsal surface between metacarpals; ABducts between 2-3 and 3-4 digits

MYOTOMES

The term myotome is defined as a group of muscles innervated by a single spinal nerve root. While a dermatome usually represents a distinct skin area, most roots innervate more than one muscle, and most muscles are innervated by more than one root. For example, the biceps brachii muscle performs flexion at the elbow. It is innervated by the musculocutaneous nerve, which is derived from C5, C6 and C7 nerve roots. Therefore, all three of these spinal nerve roots can be said to be associated with elbow flexion.

Depending on which resource you refer to, there is a discrepancy between the identified myotomes.

Comparing Myotomes- SCI vs Brachial Plexus Injury
SCI
With a SCI, the loss of motor and/or sensory function is due to damage to neural elements within the spinal canal.

The ASIA Myotome Levels:
The muscles were chosen because of their consistency for being innervated by the segments indicated and their ease of testing in the clinical situation, where testing in any position other than the supine position may be contraindicated.

When using the ASIA, the motor examination is completed through the testing of key muscle functions corresponding to 10 paired myotomes (C5-T1 and L2-S1). It is recommended that each key muscle function should be examined in a rostral-caudal sequence, utilizing standard supine positioning and stabilization of the individual muscles being tested. Improper positioning and stabilization can lead to substitution by other muscles and will not accurately reflect the muscle function being graded.

MYOTOMES
• C5 – Elbow flexion
• C6 – Wrist extension
• C7 – Elbow extension
• C8 – Finger flexion
• T1 – Finger abduction
• L2 – Hip flexion
• L3 – Knee extension
• L4 – Ankle dorsiflexion
• L5 – Great toe extension
• S1 – Ankle plantarflexion

Brachial Plexus Injury
With a brachial plexus lesion/injury it is the peripheral nerves outside the spinal cord that are being affected.

The cervical and thoracic myotomes (C1-T12) are tested with the patient in a seated position. When testing for a brachial plexus lesion, you want to test movement(s) which have the strongest association with each myotome. 

Example: The primary muscles involved in the action of arm abduction include the supraspinatus, deltoid, trapezius, and serratus anterior.
• Serratus Anterior, Deltoid- innervated by C5.
• Cranial nerve XI innervates the motor function of the trapezius.
• The supraspinatus muscle is supplied by the suprascapular nerve (C5 and C6)

Technique for assessing C5 myotome with BPL
C5- Shoulder abduction.
Ask the patient to raise both their arms to the side of them simultaneously as strongly as then can while the examiner provides resistance to this movement. Compare the strength of each arm.

MYOTOMES

C5 – Shoulder abduction
C6 – Elbow flexion Wrist extension
C7 – Elbow extension
C8 – Finger flexion
T1 – Finger abduction
L2 – Hip flexion
L3 – Knee extension
L4 – Ankle dorsiflexion
L5 – Great toe extension
S1 – Ankle plantarflexion