The scaphoid and trapezium bones and the transverse carpal ligament.
Proximal phalanx of the thumb.
Superficial palmar arch.
The abductor pollicis brevis controls movement of the thumb. It helps to straighten the thumb and move the thumb away from the fingers. It also helps the tip of the thumb to touch the tips of all the other fingers of the hand.
Injury and strain to this muscle is higher due to sports like wrestling, soccer, football, skiing, etc.
Repeatedly squeezing a rolled towel with your hand and holding it in that position for 10 seconds for about 5 repetitions helps to strengthen this muscle.
This muscle gives high degree of flexibility in the thumb which is not available in other fingers.