The musculus flexor longus pollicis, also known as the flexor pollicis longus or FPL, is a muscle located in the forearm that is responsible for flexing or bending the thumb. It belongs to a group of muscles known as the extrinsic muscles of the hand, which control movements of the fingers and thumb.
The term "musculus" refers to muscle, while "flexor" indicates its primary action of flexion. "Longus" signifies that it is a relatively long muscle, distinguishing it from other muscles in the forearm. "Pollicis" specifically denotes its association with the thumb.
The musculus flexor longus pollicis originates from the middle part of the anterior surface of the ulna bone, located on the inner side of the forearm. It travels downward and crosses the palm side of the wrist through a tunnel-like structure called the carpal tunnel. From there, it inserts into the base of the distal phalanx of the thumb, the bone closest to the fingertip.
When the musculus flexor longus pollicis contracts, it pulls on the tendons that run along the thumb, causing it to bend towards the palm of the hand. This motion is essential for gripping objects firmly and manipulating them with precision.
In summary, the musculus flexor longus pollicis is a forearm muscle responsible for flexing the thumb. It originates from the ulna, crosses the wrist through the carpal tunnel, and inserts into the distal phalanx of the thumb. Its contraction facilitates thumb flexion, enabling grasping and manipulation of objects.
