Corpus: Abductor pollicis brevis muscle
Definition
The abductor pollicis brevis muscle is a short, flat muscle that belongs to the thenar muscles of the hand. It is located directly below the skin of the ball of the thumb.
Anatomy
Origin
The muscle originates from the trapezium bone, the scaphoid tubercle of the scaphoid bone and the ligamentous structures of the palmar side of the carpus (flexor retinaculum).
Insertion
The short tendon of the muscle is attached to the sesamoid bone at the lateral side of the base of the proximal phalanx of the thumb (digitus I). Some fibers extend into the joint capsule of the first metacarpophalangeal joint.
Innervation
The abductor pollicis brevis muscle is innervated by the median nerve from the brachial plexus (segments: C8 and Th1).
Function
The abductor pollicis brevis muscle is responsible for abduction (spreading) of the thumb from the palm. It supports the movement of opposition.