The thumb is the first of the hand's five digits, but it is not commonly referred to as a finger. The thumb possesses a unique and wide range of motion not shared by the hand's other digits. Not only does it bend its knuckle, but the tip of the thumb can touch the tips of the fingers. This range of motion greatly assists in the ability to grasp and hold items. Anatomically, the thumb comprises of the metacarpal connected to the wrist's trapezium carpal bone. This first metacarpal connects to the proximal phalanx. This connects to the thumb's distal phalanx, which is also the tip of the digit. Unlike fingers, the thumb does not possess an intermediate phalanx bone. The thumb is generally served oxygenated blood by the princip pollicis artery. The muscles of the thumb all contain the word "pollicis," and are distinguished by extensor, flexor, oppenens, and abductor designations. This includes longus and brevis descriptions. The first dorsal interosseus also serves the thumb.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Thumb