Abductor Pollicis Brevis

Hand · Upper Limb

Located in the Hand of the Upper Limb, the Abductor Pollicis Brevis is a key muscle for anatomy study. Originating at Flexor retinaculum and tubercles of scaphoid and trapezium, it inserts at Lateral base of proximal phalanx of thumb. Its chief action is that it abduction of thumb. Innervation is provided by the Recurrent branch of median nerve (C8, T1).

Origin, Insertion, Action & Nerve

Origin

Flexor retinaculum and tubercles of scaphoid and trapezium

Insertion

Lateral base of proximal phalanx of thumb

Action

Abduction of thumb

Nerve

Recurrent branch of median nerve (C8, T1)

Attachments explained

The Abductor Pollicis Brevis 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

Flexor retinaculum and tubercles of scaphoid and trapezium

Insertion

Lateral base of proximal phalanx of thumb

Action & function

When the Abductor Pollicis Brevis contracts, it produces the following movement: Abduction 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 Abductor Pollicis Brevis receives its nerve supply from the Recurrent branch of median 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 Recurrent branch of median nerve or to its spinal roots (C8, T1) can weaken or paralyse the Abductor Pollicis Brevis, impairing the movements it normally produces (abduction of thumb). This is why knowing the innervation is central to localising nerve lesions in clinical practice.

How to study the Abductor Pollicis Brevis (the OIANS method)

OIANS stands for Origin, Insertion, Action and Nerve, the four facts that uniquely define every skeletal muscle. To learn the Abductor Pollicis Brevis, 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 Abductor Pollicis Brevis 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.