Muscles acting on the Shoulder & Arm

Trapezium

Origin: occipital protuberance, nuchal ligament, spinous processes of C7-T12

Insertion: clavicle, acromion process, spine of scapula

Action: Extends and Abducts head, rotates and adducts scapula, fixes scapula

Innervation: Accessory (XI) nerve

Latissimus dorsi

Origin: T7-12, L1-5, sacrum, iliac crest, ribs 10-12

Insertion: Intertubercular groove of the humerus

Action: extends, adducts, and medially rotates arm; depresses shoulder

Innervation: Thoracodorsal nerve

Deltoid

Origin: Clavicle, acromion process, spine of scapula

Insertion: Deltoid tuberosity of humerus

Action: Abducts, flexes, and extends arm ; medially and laterally rotates arm

Innervation: Axillary nerve

Rhomboideus major

Origin: Spines of T1-4

Insertion: inferior, medial border of scapula

Action: adducts scapula

Innervation: Dorsal scapular nerve

Rhomboideus minor

Origin: Nuchal ligament, spines of C6-7

Insertion: Medial border of of scapula at scapular spine

Action: adducts scapula

Innervation: dorsal scapular nerve

Levator scapulae

Origin: C1-4

Insertion: superior angle of scapula

Action: elevates scapula, abducts and rotates neck

Innervation: spinal nerves C3-5, dorsal scapular nerve

Supraspinatus

Origin: Supraspinous fossa

Insertion: Greater tubercle of humerus

Action: Abducts arm (stabilizes shoulder joint)

Innervation: suprascapular nerve

Infraspinatus

Origin: Infraspinous fossa

Insertion: Greater tubercle of humerus

Action: Extends and laterally rotates arm (stabilizes shoulder joint)

Innervation: Suprascapular nerve

Subscapularis

Origin: Subscapular fossa

Insertion: lesser tubercle of humerus

Action: Extends and medially rotates arm (stabilizes shoulder joint)

Innervation: subscapular nerve

Teres minor

Origin: Lateral border of scapula

Insertion: Greater tubercle of humerus

Action: Extends, laterally rotates, and adducts arm (stabilizes shoulder joint)

Innervation: Axillary nerve

Teres major

Origin: Lateral border of scapula

Insertion: Crest of lesser tubercle of humerus

Action: Extends, adducts, and medially rotates arm

Innervation: subscapular nerve

Triceps brachii

Origin: infraglenoid tuberosity of scapula, lateral and posterior surface of humerus

Insertion: olecranon process of ulna

Action: Extends and adducts arm, extends forearm

Innervation: radial nerve

Pectoralis major

Origin: Clavicle, sternum, cartilages, of ribs 1-7

Insertion: crest of greater tubercle of humerus

Action: flexes, adducts, and medially rotates arm

Innervation: anterior thoracic nerves

Pectoralis minor

Origin: Ribs 3-5

Insertion: Coracoid process of scapula

Action: Depresses glenoid cavity, raises ribs 3-5

Innervation: anterior thoracic nerves

Biceps brachii

Origin: supraglenoid tubercle, coracoid process of scapula

Insertion: radial tuberosity

Action: flexes arm, flexes forearm, supinates hand

Innervation: Musculocutaneous nerve

Coracobrachialis

Origin: Coracoid process of scapula

Insertion: midmedial shaft of humerus

Action: flexes and adducts arm

Innervation: Musculocutaneous nerve

Brachialis

Origin: anterior, distal surface of humerus

Insertion: coronoid process of ulna

Action: flexes forearm

Innervation: Musculocutaneous and radial nerves

Brachioradialis

Origin: lateral supracondylar ridge of humerus

Insertion: styloid process of radius

Action: flexes forearm

Innervation: radial nerve

Supinator

Origin: lateral epicondyle of humerus, anterior ulna

Insertion: proximal radius

Action: supinates hand

Innervation: radial nerve

Pronator teres

Origin: medial epicondyle of humerus, coronoid process of ulna

Insertion: lateral, middle shaft of radius

Action: pronates hand, flexes forearm

Innervation: median nerve

Pronator quadratus

Origin: Distal part of anterior ulna

Insertion: distal radius

Action: pronates hand

Innervation: median nerve (anterior interosseus branch)