Superficial Head of Flexor Pollicis Brevis (Caput superficiale musculi flexoris pollicis brevis)
Educational content only — not medical advice.
Anatomy
The more superficial of the two heads of the short thumb flexor, running distally on the radial side of the long flexor tendon and inserting through the radial sesamoid. It is the median-supplied half of the muscle and the component tested when assessing the recurrent motor branch.
Origin & insertion
From the distal border of the flexor retinaculum and the trapezium, to the radial base of the proximal phalanx of the thumb with the radial sesamoid.
Action
Flexes the metacarpophalangeal joint of the thumb.
Innervation
Recurrent motor branch of the median nerve (C8–T1).
Clinical notes
Because the deep head is ulnar-supplied, this head alone answers for thumb flexion in median nerve palsy testing — overestimating it leads to missed ulnar deficits, so the examiner isolates flexion at the metacarpophalangeal joint with the carpometacarpal joint blocked.
Related structures
Educational references
FAQ
What is the role of the Superficial Head of Flexor Pollicis Brevis?
The more superficial of the two heads of the short thumb flexor, running distally on the radial side of the long flexor tendon and inserting through the radial sesamoid. It is the median-supplied half of the muscle and the component tested when assessing the recurrent motor branch.
Why is the Superficial Head of Flexor Pollicis Brevis clinically important?
Because the deep head is ulnar-supplied, this head alone answers for thumb flexion in median nerve palsy testing — overestimating it leads to missed ulnar deficits, so the examiner isolates flexion at the metacarpophalangeal joint with the carpometacarpal joint blocked.
Source & license
BodyParts3D, © The Database Center for Life Science licensed under CC Attribution 4.0 International (https://creativecommons.org/licenses/by/4.0/). license details