The Extensor Pollicis Brevis is a muscle in your forearm that plays a crucial role in the movement of your thumb. It is one of the three main muscles responsible for extending the thumb, which means it helps to straighten or move your thumb away from the palm of your hand.
This muscle starts from a specific part of your forearm bone called the radius and the interosseous membrane, which is a thin, fibrous sheet that connects the radius and ulna (the two bones of the forearm). From there, the Extensor Pollicis Brevis travels down the back of your forearm.
As it reaches your wrist, it narrows into a tendon. This tendon then passes through a tunnel-like structure on the back of the wrist called the first dorsal compartment, which it shares with another muscle called the Abductor Pollicis Longus. After passing through this compartment, the tendon of the Extensor Pollicis Brevis attaches to the base of the proximal phalanx of the thumb. This is the first of the two bones in the thumb, not including the thumb metacarpal.
When the Extensor Pollicis Brevis contracts, it extends the thumb at the metacarpophalangeal joint, which is the joint near the base of the thumb. This action is essential for various activities that involve grasping or pinching and even tasks like writing or typing.
Understanding and strengthening this muscle, along with others in the hand and forearm, can improve hand function and coordination, which is beneficial for everyday tasks and specific sports or activities that require precise thumb movements.