Palmar interosseous muscle of the human thumb.

The adductor pollicis muscle was studied in fifty hands of Japanese adult cadavers of both sexes. The radial portion of the oblique head of the adductor pollicis muscle has carpal and metacarpal origins and an insertion into the wing tendon of the extensor apparatus. This portion was located dorsal to the palmar metacarpophalangeal articular nerve and superficial palmar metacarpal artery. Thus, the radial portion of the oblique head of the adductor pollicis muscle (more strictly, the slips dorsal to the palmar-penetrating twig of the ulnar nerve) is similar to the palmar interosseous muscles, except that its slips cannot be clearly distinguished from each other.