Final answer:
The ulnar nerve originates from the cervical roots C8-T1 and passes through the brachial plexus, branching from the medial cord.
Step-by-step explanation:
The ulnar nerve arises from the cervical roots C8-T1, and travels through the brachial plexus and medial cord. The brachial plexus is responsible for the reorganization of spinal nerves C4 through T1 to form the nerves that supply the arms. Specifically, the ulnar nerve, along with the radial and median nerves, is one of the main nerves that stem from this plexus and is essential for the motor and sensory supply to parts of the arm and hand. The brachial plexus has various divisions, and one of its key components is its division into the lateral, posterior, and medial cords from which different nerves originate, including the ulnar nerve branching from the medial cord.