The skeletal structure of the hand comprises a number of bones. The bones that are found in the hand can be divided into the carpal bones, the metacarpal bones and the phalanges, with the phalanges being the terminal bones of the hand and indeed the upper limb. There are a total of fourteen phalanges on each hand. Each finger possesses three phalanges; a proximal phalanx, a middle phalanx and a distal phalanx, with the exception of the thumb which only possesses a proximal phalanx and a distal phalanx.
In other words, each hand contains five proximal phalanges, four middle phalanges and five distal phalanges. Each phalanx has a base a shaft and a head. The base of the proximal phalanx on each finger articulates with the head of the metacarpal bones forming the metacarpophalangeal joints. On the index finger, middle finger, ring finger and little finger, the base of each middle phalanx articulates with the heads of the proximal phalanges to form the proximal interphalangeal joints. An finally, the distal interphalangeal joints are formed by the articulation of the heads of the middle phalanges of the second to fifth fingers with the base of the distal phalanges of the corresponding fingers. On the thumb, however, the interphalangeal joint is formed between the proximal phalanx and the distal phalanx.
The distal phalanges differ from the rest of the phalanges as the proximal base is noticeably wider than the distal head. This is due to the fact that each distal phalanx narrows distally. The distal surface of each distal phalanx is rough, but the palmar surface is especially rough as it is the point of insertion for the tendon of the flexor digitorum profindus muscle on the second to fifth digits and the tendon of the flexor pollicis longus on the thumb. In addition, the distal end each distal phalanx, on the palmar surface, possesses a rough spade shaped plate known as the tuberosity of the distal phalanx.
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