Which muscle is NOT associated with the ulna?

The deltoid muscle is primarily associated with the shoulder and is responsible for the abduction of the arm. Its origin is from the clavicle and the scapula, and it inserts on the humerus. The deltoid is not linked to the ulna at all, as it does not cross the elbow joint or have any direct functional relationship with the forearm or ulna.

In contrast, the triceps brachii, flexor digitorum superficialis, and pronator teres all have attachments or functional relationships with the ulna. The triceps brachii, for instance, has its long head originating from the scapula and inserting on the ulna, helping with elbow extension. The flexor digitorum superficialis originates from both the humerus and ulna and is involved in finger flexion. The pronator teres also has its origins and insertions that involve the ulna and is responsible for pronating the forearm. Thus, considering these relationships, the deltoid stands out as the muscle not associated with the ulna.