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Origin of Oblique Fibers:  Capitate bone and bases of second and third metacarpal bones.
Origin of Transverse Fibers:  Palmar surface of third metacarpal bone

Insertion: Transverse head into ulnar side of base of proximal phalanx of thumb, and oblique head into extensor expansion

Innervation: Ulnar, C8, T1

Action: Adducts the CMC joint, and adducts and assists in flexion of the MCP joint, so that the thumb moves toward the plane of the palm. Aids in opposition of the thumb toward the little finger, may assist in extending the IP joint