Anatomy Exam 4 - Muscle Actions

Shoulder Girdle Muscles

1) Trapezius: upper, middle, and lower

2) Rhomboid

3) Levator Scapulae

4) Serratus Anterior

5) Pectoralis Minor

Trapezius

Upper fibers:

• scapular elevation

• capital extension

• contralateral rotation of head

Middle fibers:

• scapular elevation

• scapular upward rotation

• scapular retraction/adduction

Lower fibers:

• scapular depression

• scapular upward rotation

• scapular retraction/adduction

Levator Scaplae

Scapular elevation

Rhomboids

1) Scapular retraction (adduction)

2) Scapular downward rotation

3) Scapular elevation

Serratus Anterior

1) Scapular protraction (abduction)

2) Scapular upward rotation

Pectoralis Minor

1) Scapular protraction (abduction)

2) Scapular downward rotation

3) Scapular depression

Subclavius

1) Scapular protraction (abduction)

2) Scapular depression

Intrinsic GH Muscles

Originate on scapula and clavicle

• Deltoid, Coracobrachialis, teres major

• Rotator cuff group

  • Subscapularis, supraspinatus, infraspinatus and teres minor

Extrinsic GH Muscles

Latissimus Dorsi and Pectoralis Major

Deltoid

Anterior Fibers:

• GH abduction, flexion, horizontal adduction, diagonal adduction, internal rotation

Middle Fibers:

• GH abduction

Posterior Fibers:

• GH abduction, extension, horizontal abduction, diagonal abduction, external rotation

Pectoralis Major

All Fibers:

• GH horizontal adduction, adduction, and internal rotation.

Upper Fibers (clavicular head):

• GH flexion, abduction (once arm is abducted 90 degrees) and adduction (with arm below 90 degrees of abduction)

Lower Fibers (sternal head):

• GH extension from flexed position

Latissimus Dorsi

1) GH Adduction

2) GH Extension

3) GH Internal rotation

4) GH Horizontal abduction

Teres Major

1) GH extension, particularly from the flexed position to the posteriorly extended position

2) GH internal rotation

3) GH adduction, particularly from the abducted position down to the side and toward midline of body

Coracobrachialis

1) GH horizontal adduction

2) GH adduction

3) GH flexion

Rotator Cuff Muscles

Supraspinatus

Infraspinatus

Teres Minor

Subscapularis

ALL of them STABILIZE the HUMERAL HEAD

Subscapularis

1) GH adduction

2) GH internal rotation

3) GH extension

4) stabilization of humeral head

Supraspinatus

1) GH abduction

2) stabilization of humeral head

Infraspinatus

1) GH horizontal abduction

2) GH external rotation

3) GH extension

4) stabilization of humeral head

Teres Minor

1) GH horizontal abduction

2) GH external rotation

3) GH extension

4) stabilization of humerus