Pectoral Girdle and Shoulder Muscle Movements

what makes up the sternoclavicular joint

• sternal end of clavicle

• articular disc

• manubrium of sternum

movement of sternoclavicular joint

• elevation and depression (lower angular range for depression)

• protraction (forward movement) and retraction (backward movement)

what makes up the acromioclavicular joint

• clavicle

• acromion and coracoid process of scapula

movement of acromioclavicular joint

gliding and rotation during scapular movement (overhead reaching and gliding)

what makes up the scapulothoracic joint

• convex surface of posterior thoracic cage

• concave surface of anterior scapula (attached to skeleton via acromioclavicular joint and sternoclavicular joint)

  • not true synovial joint (not surrounded by ligaments/capsule)

movement of scapulothoracic joint

• elevation

• depression

• abduction (protraction)

• adduction (retraction)

• downward rotation (medial rotation)

• upward rotation (lateral rotation)

what makes up the glenohumeral joint

• head of humerus

• glenoid cavity

• glenoid labrum (connective tissue)

• coracoid process of scapula

• acromion of scapula

• coracoacromial ligament (connects coracoid process to acromion)

enables widest range of movement bc shallow glenoid fossa can articular with enitre surface of humeral head - relatively unstable, frequently dislocated

movement of glenohumeral joint

• flexion (arm towards face)

• extension (arm away face)

• abduction

• adduction

• medial rotation

• lateral rotation

  • circumduction

how can we distinguish muscles of pectoral girdle

• those that move the scapula, those that move the arm

  • scapula further divided according to location; anterior, posterior

anterior pectoral girdle muscles that move the scapula

• pectoralis minor

• serratus anterior

posterior pectoral girdle muscles that move the scapula

• trapezius

• levator scapulae

• rhomboid major

• rhomboid minor

muscles that elevate the scapula

• trapezius (descending fibres) (P)

• levator scapulae (P)

muscles that depress the scapula

• trapezius (ascending fibres) (P)

• pectoralis minor (A)

• pectoralis major (P)

• serratus anterior (A)

muscles that retract the scapula

• trapezius (horizontal fibres) (P)

• rhomboid major (P)

• rhomboid minor (P)

muscles that protract the scapula

• serratus anterior (A)

muscles that rotate the scapula

upward rotation:

• trapezius (descending + ascending) (P)

• serratus anterior (A)

downward rotation:

• levator scapulae (P)

• pectoralis major (P)

• rhomboid major (P)

how can we group shoulder muscles that move the arm and distally attach to the humerus

extrinsic and intrinsic muscles

• extrinsic located on axial skeleton

• intrinsic located on scapula and/or clavicle

intrinsic shoulder muscles (6)

• deltoid

• teres major

• teres minor (rotator cuff)

• subscapularis (rotator cuff)

• supraspinatus (rotator cuff)

• infraspinatus (rotator cuff)

what are the rotator cuff muscles

• teres minor, subscapularis, supraspinatus, infraspinatus

• tendon surrounds head of humerus

• strengthens joint capsule

  • supraspinatus, infraspinatus + teres minor distally attach onto greater tubercle

not teres major bc doesn’t cross glenohumeral joint

why are shoulder dislocations common

increase of stability within joint comes at a cost of mobility - large range of motion in glenohumeral joint

extrinsic shoulder muscles (2)

• pectoralis minor

• latissimus dorsi

muscles that flex the arm

• deltoid

• pectoralis major

• coracobrachialis

muscles that extend the arm

• deltoid

• teres major

• latissimus dorsi

muscles that adduct the arm

• pectoralis major

• teres major

• latissimus dorsi

muscles that abduct the arm

• deltoid

• supraspinatus

muscles that medially rotate the arm

• pectoralis major

• teres major

• latissimus dorsi

• deltoid

• subscapularis

• latissimus dorsi

muscles that laterally rotate the arm

• infraspinatus

• teres minor

• deltoid

what is the intertubercular sulcus of the humerus

site of distal attachment for;

• pectoralis major

• latissimus dorsi

• teres major

what is the deltoid tuberosity

site of distal attachment for;

• deltoid

what gives rise to brachial artery

subclavian artery - axillary artery - brachial artery

what gives rise to the basilic vein

subclavian vein - axillary artery → cephalic vein and basilic vein

what is the brachial plexus

network of nerves formed by ventral rami of spinal nerves C5-T1 that join with each other, lateral to vertebral column

• 5 terminal branches (axillary, musculocutaneous, median, radial + ulnar nerve)

muscles innervated by axillary nerve

• teres minor

• deltoid