Acromion Health Dictionary

The joint formed by the upper end of the HUMERUS and the shoulder-blade or SCAPULA. The acromion process of the scapula and the outer end of the collar-bone (see CLAVICLE) form a protective bony arch above the joint, and from this arch the wide and thick deltoid muscle passes downwards, protecting the outer surface of the joint and giving to the shoulder its rounded character. The joint itself is of the ball-and-socket variety, the rounded head of the humerus being received into the hollow glenoid cavity of the scapula, which is further deepened by a rim of cartilage. One tendon of the biceps muscle passes through the joint, grooving the humerus deeply, and being attached to the upper edge of the glenoid cavity. The joint is surrounded by a loose ?brous capsule, strengthened at certain places by ligamentous bands. The main strength of the joint comes from the powerful muscles that unite the upper arm with the scapula, clavicle and ribs.

Shoulder-blade or scapula. A ?at bone, about as large as the ?at hand and ?ngers, placed on the upper and back part of the With the arm hanging by the side, the scapula extends from the second to the seventh rib, but, as the arm is raised and lowered, it slides freely over the back of the chest. On the rear surface of the bone is a strong process, the spine of the scapula. This arches upwards and forwards into the acromion process. The latter forms the bony prominence on the top of the shoulder, where it unites in a joint with the outer end of the clavicle.... shoulder

The joint that lies between the outer end of the clavicle (collarbone) and the acromion (the bony prominence at the top of the scapula (shoulderblade).... acromioclavicular joint

n. (pl. scapulas or scapulae) the shoulder blade: a triangular bone, a pair of which form the back part of the shoulder girdle (see illustration). The spine on its dorsal (back) surface ends at the acromion process at the top of the shoulder. This process turns forward and articulates with the collar bone (*clavicle) at the acromioclavicular joint; it overhangs the glenoid fossa, into which the humerus fits to form the socket of the shoulder joint. The coracoid process curves upwards and forwards from the neck of the scapula and provides attachment for ligaments and muscles. —scapular adj.... scapula