Muscles and actions of the shoulder girdle

Pectoralis Minor

O = Anterior surface of the 3rd and 5th ribs
I = Coracoid process of the scapula
A = Scapular depression, protraction, downward rotation and tilt

Retraction

Middle trapezius and rhomboids

Protraction

Serratus anterior and pectoralis minor

Upward Rotation

Upper trapezius, lower trapezius and serratus anterior

Lower Trapezius

O = Spinous processes of middle and lower thoracic vertebrae
I = Base of scapular spine
A = Scapular depression and upward rotation

Serratus Anterior

O = Lateral surface of the upper six ribs
I = Vertebral border of the scapula; anterior surface
A = Scapular protraction and upward rotation

Upper Trapezius

O = Occipital bone and spinous processes of upper cervical vertebrae
I = Outer 3rd of clavicle and acromion process
A = Scapular elevation and upward rotation

Rhomboids

O = Spinous processes of C7-T5
I = Vertebral border of scapula between superior and inferior angles
A = Scapular retraction, elevation and downward rotation

Downward Rotation

Rhomboids, pectoralis minor and levator scapula

Depression

Lower trapezius and pectoralis minor

Levator Scapula

O = Transverse process of first four cervical vertebrae
I = Vertebral border of scapula between superior angle and spine
A = Scapular elevation and downward rotation

Elevation

Upper trapezius, rhomboids and levator scapula

Middle Trapezius

O = Spinous processes of C7-T3
I = Scapular spine
A = Scapular retraction