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HUMAN FUNCTIONAL ANATOMY 213

SHOULDER MOVEMENT THIS WEEKS LAB: Shoulder and hip Joints In this lecture The shoulder complex Scapulo-thoracic Glenohumeral The Clavicle Scapular movements and muscles Elevation – Depression Protraction – Retraction Upward and Downward Rotation Glenohumeral movements and muscles Rotator Cuff Muscles

Flexion – Extension Adduction – Abduction Medial and Lateral Rotation Combined movements Readings

1. Stern – Core concepts – sections 81 and 84 (plus appendices)

2. Faiz and Moffat – Anatomy at a Glance – Sections 32 and 34

3. Grants Method of Anatomy – shoulder in joints of the upper limb

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THE SHOULDER COMPLEX

MANY JOINTS INVOLVED Glenohumeral Acromioclavicular Sternoclavicular Scapulothoracic Costovertebral Costotransverse Costochondral Sternocostal Simultaneous movements of all these joints Hard to voluntarily move one joint +ve can compensate for loss of range in one joint -ve one painful joint can upset movements of the whole complex. Although there are many joints, we only normally refer to movements two joints. Scapulothoracic or scapular movements Glenohumeral We will examine the movements of the two joints separately – but be aware that the movements occur together

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SCAPULAR MOVEMENTS The scapular slides on the body wall and can move in three directions (and combinations of the those 3)

1. Elevation – Depression 2. Protraction – Retraction 3. Upward and Downward Rotation

In humans and other animals with clavicles the movements of the scapula is regulated by the clavicle. Animals with clavicles and without clavicles:

The clavicle is important in the use of the hand for grasping and manipulation. It acts as a strut that, with the muscles as “guy ropes”, forms a secure basis for movements of the arm.

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SHOULDER MUSCLES Scapular muscles Levator scapulae Serratus anterior Rhomboids Pectoralis minor Trapezius Glenohumeral muscles Supraspinatus Infraspinatus Teres minor Subscapularis Teres major Deltoid Triceps long head Biceps Coracobrachialis Both Scapular and Glenohumeral (they don’t attach to the scapula) Pectoralis major Latissimus dorsi

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SCAPULAR MOVEMENTS Elevation and Depression

Elevation = Lifting the shoulders As is shrugging (where the scapula moves) Or carrying heavy objects (where the scapula stays still or may even go down!) Muscles involved: Levator scapulae Trapezius (upper fibres) Rhomboids Depression = lowering the shoulders May be an actual lowering, or merely preventing the scapula going up (as when you support yourself with your arms) Muscles involved: Trapezius (lower fibres) Pectoralis major and minor Latissimus dorsi Gravity

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SCAPULAR MOVEMENTS Protraction and Retraction

Protraction = shoulders forwards Maybe an actual movement or stopping the shoulder being pushed backwards. Muscles involved: Serratus anterior Pectoralis minor Retraction = shoulders back May be an actual movement or … Muscles involved Rhomboids Trapezius (middle part) Rhomboids and serratus anterior form a couple that control the mediolateral position of the scapula

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SCAPULAR MOVEMENTS Upward and downward rotation

Upward rotation = makes the glenoid cavity face upwards Muscles involved Serratus anterior (lower part) Trapezius (upper and lower parts) Downward rotation = makes the glenoid cavity face downwards Muscles involved Pectoralis major Latissimus dorsi Rhomboids Gravity

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GLENOHUMERAL JOINT The glenohumeral joint is a ball and socket joint. Glenohumeral movements Flexion – Extension Adduction – Abduction Medial and Lateral Rotation Bones The bony socket is very shallow Deepened by the glenoid labrum The acromion, coracoid and coracoacromial ligament form a secondary socket that prevents upward dislocation. The ligaments are very loose to allow free movements, so the joint relies on muscles to maintain its stability The rotator cuff muscles

1. Act as dynamic ligaments to stabilise the joint in all positions.

2. They attach very close to the joint centre and so can not cause strong movements of the arm.

3. They assist other muscles (synergists) Subscapularis Supraspinatus Infraspinatus Teres minor

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GLENOHUMERAL MOVEMENTS Flexion and extension

Sagittal plane movement Flexion is the forward movement of the arm. It may be an actual movement or just a stabilising action Muscles involved Pectoralis major (clavicular part) Deltoid (anterior part) Biceps and coracobrachialis Extension is the backwards movement of the arm Muscles involved Pectoralis major (sternal part) Deltoid (posterior part) Latissimus dorsi and teres major Triceps (scapular head)

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GLENOHUMERAL MOVEMENTS Abduction and Adduction

Coronal plane movement Abduction is moving the arm away from the body It may be an actual movement or just a stabilising action Muscle Involved Middle part of Deltoid Rotator cuff muscles act as synergists Adduction is bringing the arm to the body Muscles involved Teres major, latissimus dorsi Pectoralis major Anterior and posterior deltoid Gravity

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GLENOHUMERAL MOVEMENTS Medial and lateral rotation

Medial rotation is rotation around the long axis of the humerus that moves the anterior part medially. May be the movement itself or a stabilising action like when you carry something between two hands. Muscles involved Teres major and latissimus dorsi Pectoralis major and anterior deltoid Subscapularis Lateral rotation is rotating the humerus outwards Muscles involved Posterior deltoid Infraspinatus Teres minor

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EXAMPLES OF ACTUAL MOVEMENTS

It is important to learn the movements and muscles of the scapular and glenohumeral components of the shoulder separately, and not to allow yourself to confuse the two. But, in practice the movements that we do involve both components acting together. For example: Raising the arm laterally to the vertical position

1. Glenohumeral movement can only perform half of the movement.

2. The scapula must rotate laterally as well. Pushing forwards with the hand as in opening a heavy door

1. Glenohumeral flexion (and elbow extension), performs most of the action - but.

2. The Scapula must protract as well. This pushes the whole shoulder forwards.

a. In people with paralysis of serratus anterior, as they try to push forwards the scapula moves backwards.

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SCAPULAR MUSCLES AND MOVEMENTS Elevate Depress Protract Retract Upward

rotate Downrotate

Levator scapulae

Serratus anterior

Rhomboids Pectoralis minor

Trapezius Pectoralis major

Latissimus dorsi

GLENOHUMERAL MUSCLES AND MOVEMENTS Flex Extend Abduct Adduct Medial

rotate Lateral rotate

Supraspinatus Infraspinatus Teres minor Subscapularis Teres major Deltoid Triceps (long) Biceps Coracobrachialis Pectoralis major Latissimus dorsi