Shoulder / Pectoral Girdle Arthrology and Myology Flashcards
What are the 3 joints of the shoulder region?
Acromioclavicular joint
Sternoclavicular joint
Glenohumeral joint
Description of sternoclavicular joint?
Articulation between medial end of clavicle and superolateral angle of manubrium of sternum and adjacent part of 1st costal cartilage: larger clavicular articular surface so that clavicle projects above manubrium.
Surfaces reciprocally concavoconvex but of different radii of curvature: congruence partly improved by fibrocartilaginous intra-articular disc.
Description of acromioclavicular joint?
Flat oval articular surfaces on lateral end of clavicle and anteromedial border of acromion; both surfaces covered with fibrocartilage.
Clavicular surface faces posterolaterally, acromial surface faces anteromedially.
Description of sternoclavicular fibrous capsule?
Strong fibrous capsule attaches to articular margins of clavicle and sternum, extending inferiorly onto the upper surface of 1st costal cartilage.
Reinforced by anterior, posterior and interclavicular ligs.
Complete intra-articular fibrocartilaginos disc attaches to capsule, dividing joint into 2 separate compartments.
Synovial membrane lines each compartment.
What is the extracapsular sternoclavicular ligament and where does it attach?
Costoclavicular ligament:
→ passes from upper surface of 1st costal cartilage to inferior surface to inferior surface of medial end of clavicle.
→ limits elevation of clavicle as well as preventing excessive anterior/posterior movement of it’s medial end.
Description of acromioclavicular fibrous capsule?
Loose fibrous capsule attaches to articular margins.
Reinforced by superior and inferior acromioclavicular ligaments.
Partial fibrocartilaginous disc attaches to superior capsule in most joints.
Synovial membrane lines all non-articular surfaces.
Where is the extracapsular ligament at the ACJ and what is its role?
Coracoclavicular ligament:
Anchors lateral end of clavicle to coracoid process: conoid and trapezoid parts attach to conoid tubercle and trapezoid line respectively.
Conoid part limits forward movement and trapezoid part backward movement of clavicle → both prevent medial displacement of acromion under the lateral end of clavicle in laterally directed forces to the shoulder.
What muscles stabilise the scapula relative to the thorax during movements of the arm?
trapezius
levator scapulae
What do all the fibres of deltoid do?
abduction
What do the anterior fibres of deltoid do?
Flexion and medial rotation
What do the posterior fibres of deltoid do?
Extension and lateral rotation
What is the action of supraspinatus?
Initiates the first 20 degrees of abduction
What is the action of teres minor?
Laterally rotates the glenohumeral joint
What does infraspinatus do?
laterally rotates the glenohumeral joint
What does subscapularis do?
Medially rotates the glenohumeral joint