|Adductor pollicis muscle|
The superficial muscles of the left hand. Palmar view
Adductor pollicis is labelled at bottom right.
|Origin||Transverse head: anterior body of the third metacarpal|
Oblique head: bases of the second and the third metacarpals and the adjacent trapezoid and capitate bones
|Insertion||medial side of the base of the proximal phalanx of the thumb and the ulnar sesamoid|
|Artery||deep palmar arch|
|Nerve||deep branch of the ulnar nerve (T1)|
|Actions||adducts the thumb at the carpometacarpal joint|
|Antagonist||Abductor pollicis longus muscle, Abductor pollicis brevis muscle|
|Latin||Musculus adductor pollicis|
|Anatomical terms of muscle|
It is a fleshy, flat, triangular, and fan-shaped muscle deep in the thenar compartment beneath the long flexor tendons and the lumbrical muscles at the center of the palm. It overlies the metacarpal bones and the interosseous muscles. 
The oblique head (Latin: 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 head of the adductor pollicis, is inserted into the ulnar side of the base of the proximal 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 pollicis brevis and the abductor pollicis brevis. 
The transverse head (Latin: adductor transversus pollicis) is deeply seated. 
It is triangular, arising by a broad base from the lower two-thirds of the palmar surface of the third metacarpal bone; the fibers converge, to be inserted with the medial part of the flexor pollicis brevis and the oblique head into the ulnar side of the base of the proximal phalanx of the thumb. 
While adduction of the thumb (bringing it back into the plane of the palm of the hand from its previously abducted position) is mainly produced by the adductor pollicis, it can also bring the thumb to the side of the palm and index finger and the flexor pollicis brevis and the opponens pollicis help in thumb adduction.
Froment's sign is used to test for a compromised adductor pollicis muscle.
In the Pan-Homo LCA the oblique head of the adductor pollicis probably had a relatively small physiological cross sectional area (PCSA) and both heads probably acted as extensors and adductors at the carpometacarpal joint. In humans the PCSA of the oblique head is relatively enlarged and both heads act as flexors at this joint. 
Front of the left forearm. Deep muscles. (Adductor pollicis visible at bottom center.)