pollicis

Pollicis is a Latin genitive form derived from pollex, meaning the thumb. In anatomical terminology, pollicis indicates a structure relating to or belonging to the thumb and is appended to the name of muscles, tendons, or other features to specify their association with the thumb, such as flexor pollicis longus or abductor pollicis.

The term pollicis features prominently in the naming of intrinsic and extrinsic muscles that move the thumb. Intrinsic hand muscles include the thenar group—abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis—and the adductor pollicis, which lies in the palm between the metacarpals. Extrinsic muscles acting on the thumb originate in the forearm and include flexor pollicis longus; extensor pollicis longus and extensor pollicis brevis; and abductor pollicis longus. These muscles coordinate the thumb’s range of motion, including flexion, extension, abduction, adduction, and opposition.

Nerve supply varies among the pollicis muscles. The thenar muscles (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) are primarily innervated by the median nerve, while adductor pollicis is innervated by the ulnar nerve. The extrinsic pollicis muscles—such as abductor pollicis longus, flexor pollicis longus, extensor pollicis longus, and extensor pollicis brevis—receive innervation from branches of the radial nerve, particularly the posterior interosseous nerve.

Clinically, structures bearing the pollicis name are involved in conditions affecting thumb motion, including De Quervain’s tenosynovitis and carpal tunnel syndrome, which can impair thumb movement and grip.