The Extensor Pollicis Brevis is a small muscle located in the forearm. It is part of the extensor group of muscles and is responsible for extending the thumb at the metacarpophalangeal joint. This muscle plays a crucial role in thumb movements, allowing for actions like grasping and pinching. Originating from the radius bone, the Extensor Pollicis Brevis travels along the back of the wrist and attaches to the base of the thumb's proximal phalanx. It works in conjunction with other muscles, such as the abductor pollicis longus and the extensor pollicis longus, to facilitate thumb mobility and function.