0.11 Skeletal system module 12: bones of the upper limb  (Page 103/64)

The upper limb is divided into three regions. These consist of the arm    , located between the shoulder and elbow joints; the forearm    , which is between the elbow and wrist joints; and the hand    , which is located distal to the wrist. There are 30 bones in each upper limb (see [link] ). The humerus    is the single bone of the upper arm, and the ulna    (medially) and the radius    (laterally) are the paired bones of the forearm. The base of the hand contains eight bones, each called a carpal bone    , and the palm of the hand is formed by five bones, each called a metacarpal bone    . The fingers and thumb contain a total of 14 bones, each of which is a phalanx bone of the hand    .

Carpal bones

The wrist and base of the hand are formed by a series of eight small carpal bones (see [link] ). These eight short bones glide over each other to provide the wrist with maximum mobility.

Bones of the wrist and hand

Metacarpal bones

The palm of the hand contains five elongated metacarpal bones . These bones lie between the carpal bones of the wrist and the bones of the fingers and thumb (see [link] ).

Phalanx bones

The fingers and thumb contain 14 bones, each of which is called a phalanx bone (plural = phalanges) , named after the ancient Greek phalanx (a rectangular block of soldiers). The thumb has two phalanges. The index finger through little finger have three phalanges each.

The long bones of the arm

Three long bones compose the arm and forearm. The humerus    makes up the anatomical arm. The humerus forms a ball and socket joint with the scapula. Two bones are found in the forearm. The radius    is lateral in anatomical position, lining up with the thumb. The ulna    forms the point of the elbow. It is medial in anatomical position and lines up with the pinky finger.