Final answer:
On a PA Oblique shoulder (Scapular Y) image, the humerus is normally superimposed over the scapula, showing the glenohumeral joint clearly, indicating a normal position.
Step-by-step explanation:
In a normal PA Oblique shoulder (Scapular Y) image, the humerus is generally demonstrated as overlapping the scapula. When positioned for the Scapular Y view, the body of the scapula, the coracoid process, and the acromion should project as a Y shape, hence the name. The arm bone or humerus should appear as a clean overlap on the scapula if there is no dislocation or fracture. The glenohumeral joint, where the humerus articulates with the glenoid cavity of the scapula, should be clearly visible, affirming a normal relationship between the humerus and the scapular.
Muscles such as the deltoid, pectoralis major, latissimus dorsi, subscapularis, supraspinatus, infraspinatus, teres major, and teres minor that are responsible for various movements of the humerus, attach onto the humerus and scapula. They also influence the appearance and position of the humerus in imaging studies, like the Scapular Y radiographic view, by determining the relative position of the humerus with respect to the scapula.