Final answer:
The Triceps Brachi lateral head originates from the posterior shaft of the humerus and inserts on the olecranon of the ulna. It is innervated by the radial nerve.
Step-by-step explanation:
The origin of the Triceps Brachi lateral head is the posterior shaft of the humerus, specifically at the area distal to the radial groove. Its insertion is on the olecranon of the ulna, which is a bony prominence that can be easily felt at the posterior aspect of the elbow. The triceps brachi, including its lateral head, is innervated by the radial nerve, a nerve that originates from the brachial plexus and travels down the arm to the hand.