Middle phalanges (hand)
The middle phalanges (hand), also known as the intermediate phalanges, are bones located in the fingers. Each intermediate phalanx connects to a proximal and distal phalanx. Each proximal phalanx is jointed to the metacarpal bone located in the palm, while each distal phalanx of the finger serves as the tip of the finger, as well as the home of the fingernail. This middle bone has two joints, and allows the finger to bend in two places. The intermediate phalanges are unique to fingers. The thumb does not possess such a bone, as it is only consists of a proximal and distal phalanx. There are reasons why thumbs lack middle phalanges (hand). The thumb is a unique digit in the hand, as it passes a range of motion unique to itself. Not only can the thumb rotate, but it can press against the tips of the all the fingers. Also, the thumb is much shorter than most of the other fingers.
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In Depth: Middle phalanges (hand)