Shoulder Muscles

1. Shoulder Muscles • Chapter 5

2. Determination of Muscle Action • Muscle location? • Origin and insertion • What joint(s) it crosses or act on? • Where does the muscle cross the joint? (e.g. anterior, lateral, etc.) • What are the possible planes of movement and actions at that joint? (also see pages 23, 24) • What is the line of pull? • Muscles only pull on bones, they do not push bones. • Insertion is usually pulled towards the origin. • Remember, most muscle can not perform opposite actions (e.g. flexion AND extension).

3. Anterior Muscles • Coracobrachialis • Pectoralis major • Subscapularis

4. Coracobrachialis • Origin: coracoid process • Insertion: medial humerus • Actions: • Horizontal Adduction of the shoulder • flexion of the shoulder • adduction of the shoulder

6. Pectoralis Major • Origin: • Proximal clavical (clavicular head) • Sternum (sternal head) • Insertion: Intertubercular groove • Actions: • Clavicular (upper) • Internal rotation • Horizontal adduction • Flexion up to 60º • Adduction beyond 90º • Abduction below 90º • Sternal (lower) • Internal rotation • Horizontal adduction • Extension to a neutral position • Adduction

7. Pectoralis Major

8. Subscapularis • Origin: subscapular fossa • Insertion: lesser tubercle • Actions: • Internal rotation • Adduction • Extension • Other: anterior rotator cuff muscle Note: Anterior view. The ribs are removed from this image

10. Superior Muscles • Deltoid • Supraspinatus

11. Deltoid • Origin: • Anterior: distal clavicle • Middle: acromion process • Posterior: spine of scapula • Insertion: • Actions • Anterior: abduction, flexion, internal rotation, horizontal adduction • Middle: abduction • Posterior: abduction, extension, external rotation, horizontal abduction

12. Deltoid Lateral view

13. Supraspinatus • Origin: supraspinatus fossa • Insertion: greater tubercle • Action: abduction • Other: rotator cuff muscle

15. Inferior Muscles • Latissimus dorsi • Teres major

16. Latissimus Dorsi • Origin: • Insertion: intertubercular groove • Actions: • adduction • internal rotation • extension • horizontal abduction • “swimmer’s muscle”

18. Teres Major • Origin: inferior angle • Insertion: intertubercular groove • Actions: • adduction • internal rotation • extension “lats little helper”

20. Posterior Muscles • Infraspinatus • Teres minor

21. Infraspinatus • Origin: infraspinus fossa • Insertion: greater tubercle • Actions: • extension • external rotation • horizontal abduction • Other: rotator cuff muscle

23. Teres Minor • Origin: lateral border • Insertion: greater tubercle • Actions: • extension • external rotation • horizontal abduction • Other: rotator cuff

25. Rotator Cuff Muscles S.I.T.S

27. Name the horizontal adduction muscles • pectoralis major (upper and lower fibers) • corachobrachialis • anterior deltoid

28. Name the horizontal abduction muscles • posterior deltoid • infraspinatus • teres minor • latissimus dorsi

29. Name the flexor muscles • coracobrachialis • pect major (upper fibers) • anterior deltoid

30. Name the extensor muscles • latissimus dorsi • teres major • posterior deltoid • pectoralis major (lower fibers)

31. Name the adductor muscles • pect major (upper and lower fibers) • coracobrachialis • latissimus dorsi • teres major

32. Name the abductor muscles • deltoid (all fibers) • supraspinatus

33. Name the internal rotator muscles • subscapularis • latissimus dorsi • teres major • anterior deltoid