Origin: Oblique head: bases of the second and the third metacarpals and the adjacenttrapezoid and capitate bones
Insertion: Medial side of the base of the proximal phalanx of the thumb and the ulnar sesamoid
Nerve: Deep branch of ulnar nerve (T1)
Action: Adducts the thumb at the carpometacarpal joint
Antagonist: Abductor pollicis longus muscle, Abductor pollicis brevis muscle
The Adductor pollicis (transversus) (Adductor transversus pollicis) is the most deeply seated of this group of muscles. It is of a triangular form arising by a broad base from the lower two-thirds of the volar surface of the third metacarpal bone; the fibers converge, to be inserted with the medial part of the Flexor pollicis brevis and the Adductor pollicis (obliquus) into the ulnar side of the base of the first phalanx of the thumb.