Which articular surfaces make up the shoulder joint?

The shoulder joint, also known as the glenohumeral joint, is formed by the articulation of the glenoid cavity of the scapula and the head of the humerus. This joint is a ball-and-socket type, allowing for a wide range of motion in multiple directions. The shallow glenoid cavity provides flexibility but less stability compared to other joints, which is compensated by surrounding muscles and ligaments. Thus, the glenoid cavity fits articulately with the rounded head of the humerus, enabling not only mobility but also the ability to support various movements integral to arm function, such as reaching and throwing.

The other options refer to anatomical structures that do not form the shoulder joint. The coracoid process and greater tubercle are parts of the scapula and humerus, respectively, but they do not directly articulate with one another. The acromion and scapular spine are components of the scapula that contribute to shoulder stability and muscle attachment, but they do not make up the shoulder joint itself. Lastly, the head of the radius and the ulnar notch are involved in the elbow joint, not the shoulder.