Origin Humeroulnar head: medial epicondyle of humerus, ulnar collateral ligament, and coronoid process of ulna.Radial head: superior half of anterior border of radius Insertion Bodies of middle phalanges of fingers Action Flexes middle phalanges at PIP joints of digits 2-5. Also flexes proximal phalanges at MCP joint. Innervation Median nerve (C7, C8, T1) Arterial Supply Ulnar artery