As a muscle, the flexor digiti minimi brevis (hand) helps flex the hand's fifth digit, which is also known as the pinky finger. This action is opposed by the extensor digiti minimi, which extends the pinky. The muscle originates at the hamate bone and extends to its insertion at the fifth digit. Specifically, the muscle attaches to the ulnar side of the finger, near the finger's proximal phalanx bone. The muscle receives its oxygenated blood supply from the ulnar artery. Signals from the brain arrive at the muscle via the deep branch of the ulnar nerve. Some people are born without a flexor digiti minimi brevis (hand), and in these cases, the nearby abductor digiti minimi compensates for the absence with a larger size. In human anatomy, muscles with the "brevis" distinction usually have counterpart muscle designated as "longus." However, the flexor digiti minimi brevis usually lacks this counterpart. The existence of a flexor digiti minimi longus is highly rare.