Adductor Pollicis

Hand · Upper Limb

The Adductor Pollicis is found among the Hand muscles of the Upper Limb. Its origin is Oblique head: bases of 2nd–3rd metacarpals and capitate; Transverse head: anterior shaft of 3rd metacarpal, and it inserts onto Medial base of proximal phalanx of thumb. Its chief action is that it adduction of thumb. Its nerve supply is the Deep branch of ulnar nerve (C8, T1).

Origin, Insertion, Action & Nerve

Origin

Oblique head: bases of 2nd–3rd metacarpals and capitate; Transverse head: anterior shaft of 3rd metacarpal

Insertion

Medial base of proximal phalanx of thumb

Action

Adduction of thumb

Nerve

Deep branch of ulnar nerve (C8, T1)

Attachments explained

The Adductor Pollicis is defined first by where it attaches. Its origin is the more fixed anchor, usually the proximal or more stable end that stays put during contraction, while its insertion is the more mobile point that is pulled toward the origin when the muscle shortens.

Origin

Oblique head: bases of 2nd–3rd metacarpals and capitate; Transverse head: anterior shaft of 3rd metacarpal

Insertion

Medial base of proximal phalanx of thumb

Action & function

When the Adductor Pollicis contracts, it produces the following movement: Adduction of thumb.

As part of the Hand group of the Upper Limb, it works alongside neighbouring muscles to generate smooth, coordinated movement and to stabilise the structures it acts on.

Nerve supply & clinical relevance

The Adductor Pollicis receives its nerve supply from the Deep branch of ulnar nerve (C8, T1). This nerve carries fibres from spinal segment(s) C8, T1.

Because a muscle can only contract when its nerve is intact, injury to the Deep branch of ulnar nerve or to its spinal roots (C8, T1) can weaken or paralyse the Adductor Pollicis, impairing the movements it normally produces (adduction of thumb). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Adductor Pollicis (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Adductor Pollicis, work through them in order: picture its origin, trace the muscle to its insertion, reason out the action that shortening between those two points must create, then add the nerve that drives it.

Most students remember the Adductor Pollicis fastest by linking its action back to its attachments rather than memorising each fact in isolation. Once the origin and insertion make sense, the action usually follows logically.