The flexor digiti minimi brevis (hand) is a muscle that helps flex the hand's fifth digit. The digit 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. It 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). In these cases, the nearby abductor digiti minimi compensates for the absence by growing larger in size.