Shoulder Muscles Chapter 5 Determination of Muscle Action

Shoulder Muscles Chapter 5

Determination of Muscle Action 1. Muscle location? • Origin and insertion 2. What joint(s) it crosses or act on? • Where does the muscle cross the joint? (e. g. anterior, lateral, etc. ) 3. What are the possible planes of movement and actions at that joint? (also see pages 23, 24) 4. What is the line of pull? • Muscles only pull on bones, they do not push bones. 1. Insertion is usually pulled towards the origin. • Remember, most muscle can not perform opposite actions (e. g. flexion AND extension).

Anterior Muscles • Coracobrachialis • Pectoralis major • Subscapularis

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

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

• Pectoralis Major

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

Superior Muscles • Deltoid • Supraspinatus

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

• Deltoid Lateral view

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

Inferior Muscles • Latissimus dorsi • Teres major

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

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

Posterior Muscles • Infraspinatus • Teres minor

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

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

Rotator Cuff Muscles S. I. T. S

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

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

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

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

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

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

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