Ribs • 12 pairs of ribs for the walls of the bony thorax. • All ribs articulate with the vertebral column posteriorly and downward toward the anterior body surface. • True Ribs = first 7 pairs • Attach directly to the sternum by costal cartilages. • False Ribs = next 5 pairs • Attach either indirectly or not at all to the sternum • Floating Ribs = Last 2 pairs • Lack sternal attachment
Shoulder Girdle • Each shoulder girdle has 2 bones – a clavicle and a scapula. • The clavicle “collarbone” acts as a brace to hold the arm away from the top of the thorax and helps to prevent shoulder dislocation. • When the clavicle is broken the whole shoulder region caves in medially.
Shoulder Girdle • The scapulae (shoulder blades) are commonly called wings due to triangular shape. • 2 important processes: • Acromin- enlarged end of the spine of the scapula • Connects the clavicle to the acromioclavicular joint. • Coracoid Process-beak like • Anchors some of the muscles of the arm. • Suprascapular notch- serves as a nerve passageway. • Glenoid Cavity- shallow socket that receives the head of the arm bone
Shoulder Girdle Allows upper limb to have exceptionally free movement due to: • Each shoulder girdle attaches to the axial skeleton at only one point – the sternoclavicular joint. • The loose attachment of the scapula allows it to slide back and forth against the thorax as muscles act. • The glenoid cavity is shallow and the shoulder joint is poorly reinforced by ligaments • The drawback to exceptional flexibility is that the shoulder girdle is easily dislocated..