Adductor pollicis - Musculus adductor pollicis
Origin: Transverse head: anterior body of the third metacarpal - 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 (obliquus) (Adductor obliquus pollicis) arises by several slips from the capitate bone, the bases of the second and third metacarpals, the intercarpal ligaments, and the sheath of the tendon of the Flexor carpi radialis. From this origin the greater number of fibers pass obliquely downward and converge to a tendon, which, uniting with the tendons of the medial portion of the Flexor pollicis brevis and the transverse part of the Adductor, is inserted into the ulnar side of the base of the first phalanx of the thumb, a sesamoid bone being present in the tendon. A considerable fasciculus, however, passes more obliquely beneath the tendon of the Flexor pollicis longus to join the lateral portion of the Flexor brevis and the Abductor pollicis brevis.
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.
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).