Which of the following statements is true regarding the triceps brachii?

The statement that the triceps brachii primarily extends the elbow is true. The triceps brachii is a muscle located at the back of the upper arm and is primarily responsible for elbow extension. This action occurs when the muscle contracts, pulling on the olecranon process of the ulna, thereby straightening the arm. In functional terms, activities such as pushing and throwing rely heavily on the extension provided by this muscle.

The other options focus on functions or innervations that are not characteristic of the triceps brachii. Abduction of the arm is mainly performed by muscles like the deltoid. The median nerve does not innervate the triceps brachii; instead, it is innervated by the radial nerve. Finally, pronation of the forearm is primarily carried out by the pronator teres and pronator quadratus muscles, rather than the triceps brachii. Understanding these distinctions helps illustrate the specific role of the triceps in upper limb mechanics.