shoulder muscles pt1

pectoralis major (upper fibers)

O: anterior surface of sternal 1/2 of clavicle

I: greater tubercle of humerus

N: lateral pectoral (C 5, 6, 7)

A:

(origin fixed): shoulder flexion, medial rotation, horizontal adduction of humerus towards opposite shoulder

(insertion fixed): assists in elevation of thorax in forced inspiration

pectoralis major (lower fibers)

O: anterior surface of sternum, cartilage of adjacent ribs, aponeurosis of external obliques

I: greater tubercle of humerus

N: lateral & medial pectoral (C6,7,8 T1)

A: depresses shoulder girdle via attachment to humerus

(origin fixed): obliquely adducts & extends humerus towards opposite iliac crest, medially rotates

(insertion fixed): assists in elevation of thorax in forced inspiration

pectoralis minor

O: ribs 3,4,5 near cartilage

I: coracoid process of scapula

N: medial pectoral (C6,7,8, T1)

A: downward rotation of scapula (prevents upwards rotation), internal rotation of scapula

(origin fixed): anteriorly tilts scapula

(insertion fixed): assist in forced inspiration

subclavius

O: 1st rib and cartilage

I: undersurface of clavicle

N: subclavian (C5,6)

A: draws clavicle down & stabilizes joint

latissimus dorsi

O: spinous processes of lower thoracic vertebrae, ribs 8/9-12, through thoracolu,bar fascia from lumbar/sacral vertebrae & posterior iliac crest

I: intertubercular groove of humerus

N: thoracodorsal (C6,7,8)

A:

(origin fixed): medial rotation, adduction, extension, of shoulder, depression of shoulder girdle, assists in lateral trunk flexion, indirectly downward rotates scapula

(insertion fixed): assists in anterior/lateral pelvic tilt, assists in lumbar hyperextension, contralateral trunk rotation

teres major

O: dorsal surface inferior angle and lower third of the lateral border of scapula

I: crest of lesser tubercle of humerus

N: lower subscapular (C5,6,7)

A: medial rotation adduction, extension of shoulder, internally rotates scapula

serratus anterior

O: outer surface of ribs 1-9

I: costal surface of medial border of scapula

N: long thoracic (C5,6,7,8)

A: abduction and posteriorly tilts scapula, prevents scapular winging (assisting in external rotation of scapula)

(origin fixed): upward rotation of scapula