From which cord does the ulnar nerve arise?

• A. Medial cord
• B. Lateral cord
• C. Posterior cord
• D. Roots

Answer: (A)

The ulnar nerve comes from the medial cord of the brachial plexus. The medial cord is formed by the anterior divisions of the lower trunk, which carries fibers from C8 and T1. So the ulnar nerve contains C8–T1 fibers and travels with the medial side of the arm and forearm, passing behind the medial epicondyle to the hand. This distinguishes it from nerves that arise from the lateral or posterior cords (which give the median, musculocutaneous, radial, and axillary nerves) and from the roots directly, which don’t themselves become a single named cord.