Final answer:
The proximal attachments of the long head of the biceps brachii muscle include the supraglenoid tubercle of the scapula, the superior glenoid labrum, and the radial tuberosity of the radius bone.
Step-by-step explanation:
The proximal attachments of the long head of the biceps brachii muscle include the supraglenoid tubercle of the scapula and the superior glenoid labrum of the shoulder joint. The tendon of the long head of the biceps brachii then travels through the joint capsule of the shoulder and passes through the narrow intertubercular groove (bicipital groove) of the humerus. It finally attaches to the radial tuberosity of the radius bone in the forearm.