Flexor Pollicis Brevis Muscle

**Semantic type:** Body Part, Organ, or Organ Component

**Definition:** A muscle in the hand that has a superficial head that originates from the flexor retinaculum and tubercle of the trapezium bone and a deep head that originates from the trapezoid and capitate bones; it attaches to the lateral side of the base of the proximal phalanx of the thumb and functions to flex the thumb at the metacarpophalangeal joint.

**Synonyms:** - FLEXOR POLLICIS BREVIS MUSCLE