Shoulder and Back Muscles: Origins, Insertions, Innervation, and Actions

trapezius Origin

superior nuchal line, external occipital protuberance, ligamentum nuchae, spinous processes of C7-T12

trapezius Insertion

lateral 1/3 clavicle, acromion, spine of scapula

trapezius Innervation

CN XI (spinal accessory nerve)

trapezius Action

rotates, elevates, retracts, and depresses scapula

latissimus dorsi Origin

spinous processes of T6-L5, sacrum, iliac crest, ribs 10-12

latissimus dorsi Insertion

intertubercular groove of humerus

latissimus dorsi Innervation

thoracodorsal nerve

latissimus dorsi Action

extends, adducts, and medially rotates humerus

levator scapulae Origin

transverse processes of C1-C4

levator scapulae Insertion

superior angle of scapula

levator scapulae Innervation

dorsal scapular nerve

levator scapulae Action

elevates and rotates scapula

rhomboid major and minor Origin

spinous processes of C7-T5

rhomboid major and minor Insertion

medial border of scapula

rhomboid major and minor Innervation

dorsal scapular nerve

rhomboid major and minor Action

retracts, elevates, and rotates scapula

deltoid Origin

spine of scapula, acromion, lateral 1/3 clavicle

deltoid Insertion

deltoid tuberosity

deltoid Innervation

axillary nerve

deltoid Action

abducts, flexes, extends, and rotates arm

supraspinatus Origin

supraspinous fossa

supraspinatus Insertion

superior facet of greater tubercle

supraspinatus Innervation

suprascapular nerve

supraspinatus Action

abducts arm

infraspinatus Origin

infraspinous fossa

infraspinatus Insertion

middle facet of greater tubercle

infraspinatus Innervation

suprascapular nerve

infraspinatus Action

laterally rotates arm

teres major Origin

lateral scapular border superior to inferior angle

teres major Insertion

medial lip of intertubercular sulcus

teres major Innervation

lower subscapular nerve

teres major Action

medially rotates and adducts arm; extends flexed arm

teres minor Origin

lateral scapular border superior to teres major

teres minor Insertion

inferior facet of greater tubercle

teres minor Innervation

axillary nerve

teres minor Action

laterally rotates arm

long head triceps Origin

infraglenoid tubercle of scapula

long head triceps Insertion

olecranon process

long head triceps Innervation

radial nerve

long head triceps Action

extends forearm

subscapularis Origin

subscapular fossa

subscapularis Insertion

lesser tubercle of humerus

subscapularis Innervation

upper and lower subscapular nerves

subscapularis Action

medially rotates arm

pectoralis major Origin

medial 1/2 clavicle and anterior sternum

pectoralis major Insertion

lateral lip of intertubercular sulcus

pectoralis major Innervation

medial and lateral pectoral nerves

pectoralis major Action

flexes, adducts, and medially rotates arm

pectoralis minor Origin

ribs 3-5

pectoralis minor Insertion

coracoid process

pectoralis minor Innervation

medial pectoral nerve

pectoralis minor Action

pulls shoulder down and protracts scapula

subclavius Origin

first rib

subclavius Insertion

inferior surface of clavicle

subclavius Innervation

nerve to subclavius

subclavius Action

pulls shoulder down and stabilizes sternoclavicular joint

serratus anterior Origin

lateral surface of upper 8-9 ribs

serratus anterior Insertion

costal surface of medial scapular border

serratus anterior Innervation

long thoracic nerve

serratus anterior Action

protracts, rotates, and depresses scapula