Corpus: Flexor pollicis brevis muscle
from latin: pollex - thumb; flectere - to bend
Definition
The flexor pollicis brevis muscle is a short, two-headed muscle that is part of the thenar muscle group of the hand.
Anatomy
Origin
The muscle has two heads with different origins. The superficial head originates from the distal edge of the flexor retinaculum and the trapezium bone. The deep head originates from the trapezium and trapezoid bones, and according to some authors, also from the ulnar side of the first metacarpal.
Insertion
The tendon of the superficial head runs along with the tendon of the flexor pollicis longus muscle and attaches via the small sesamoid bone to the radial side of the base of the thumb's proximal phalanx. The tendon of the deep head also attaches via the small sesamoid bone to the ulnar side of the base of the thumb's proximal phalanx.
Innervation
The innervation of the superficial head is provided by the median nerve from the brachial plexus (segment: C8, with contributions from C7 and Th1). The innervation of the deep head is provided by the deep branch of the ulnar nerve (segments: C8 and Th1).
Function
The flexor pollicis brevis muscle is responsible for flexion at the thumb's metacarpophalangeal joint and contributes to thumb opposition and flexion at the carpometacarpal joint.