Posterior Muscles of Human Trunk
infraspinatus
origin: infraspinous fossa of scapula insertion: greater tubercle of humerus action: lateral rotation of arm
latissimus dorsi
origin: lower vertebrae, last 3 to 4 ribs, and iliac crest insertion: arm action: prime mover of shoulder extension; adducts and medially rotates arm
trapezius
origin: occipital bone; vertebrae insertion: acromion and spinous process of scapula; clavicle action: extension of head; superior fibers elevate scapula (as in shrugging the shoulders)
teres minor
origin: scapula insertion: greater tubercle of humerus action: lateral rotation of arm
subscapularis
origin: scapula insertion: humerus action: adduction and flexion of shoulder
teres major
origin: scapula insertion: humerus action: extension and adduction of shoulder
rhomboids -- major and minor
origin: spinous processes of vertebrae insertion: medial border of scapula action: pulls scapula medially (retraction); scapula elevation
supraspinatus
origin: supraspinous fossa of scapula insertion: greater tubercle of humerus action: abduction of shoulder
levator scapulae
origin: transverse processes of C1-C4 insertion: medial border of scapula action: elevates and adducts scapula