The hand (Latin: manus) is the terminal part of the upper limb composed mainly of bones, muscles, as well as ligaments and tendons that allow for a large amount of movement and dexterity. The human hand typically has five digits: four fingers and a thumb. The skeleton of each hand is usually formed by 27 bones, not including the sesamoid bones, which varies in number in each individual.
The bones of the hand are grouped into three categories:
The carpal bones are the eight bones creating the wrist, and they are arranged in two rows. The proximal row of the carpal bones articulates with the forearm bones, namely, the radius and ulna.
The metacarpal bones are five bones that create the middle part of the hand.
Fourteen phalangeal bones are found in the fingers of each hand, as well as the feet. The skeleton of each finger consists of three phalanges - proximal, middle, distal, except for the thumb, which only has two phalanges.
The hand serves as an instrument for fine and varied movements. In these, the thumb with its skeleton, the first metacarpal bone, and two phalanges, is extremely significant. Its free movements include - besides flexion, extension, abduction, and adduction - a unique action, that of opposition, by which the thumb can be brought across the palm and to the tips of the slightly flexed fingers. This motion forms the basis for the handling of tools, weapons, and instruments.