forearm to form the elbow. Its anatomical portionsinclude a head (a rounded portion that fits into a recessof the scapula) called the glenoid fossa; the shaft,which is the main part of the humerus; and the distalend, which includes the prominence (called anepicondyle) and the surfaces that articulate with thebones of the forearm.Radius and Ulna.—When the arm is in theanatomical position with the palm turned forward, theradius is on the lateral (thumb) side and the ulna is onthe medial (little finger) side of the forearm (fig. 1-22).When the hand is pronated (with the palm turneddownward), the bones rotate on each other and cross inthe middle. This pronation makes it possible to turn thewrist and hand (as when opening doors). The ulna andthe radius articulate at their proximal ends with thehumerus, at their distal ends with some of the carpalbones, and with each other at both ends.Carpal.—There are eight carpal bones, arrangedin two rows, forming the wrist.Metacarpal.—The metacarpal bones arenumbered one to five, corresponding with the fivefingers, or digits, with which they articulate. Thef i n g e r s a r e n a m e d a s f o l l o w s : 1 s t — t h u m b ;2nd—index; 3rd—middle; 4th—ring; and 5th—little.Phalanges.—The small bones of the fingers arecalled phalanges, and each one of these bones is calleda phalanx. Each finger has three phalanges, except thethumb (which has two). The phalanges are named fortheir anatomical position: The proximal phalanx is thebone closest to the hand; the distal phalanx is the boneat the end of the finger; and the middle phalanx is thebone located between the proximal and distalphalanges.LOWER EXTREMITY.—The lower extremityincludes the bones of the hip, thigh, leg, ankle, andfoot. The bones that form the framework of the lowerextremities are listed in table 1-2.1-13HEAD OF HUMERUS(GLENOID FOSSA)HUMERUSRADIUSULNASHAFT OFHUMERUSULNADISTAL END(EPICONDYLE)CARPALSMETACARPALSPHALANGESHANDSUPINATEDHANDPRONATEDHM3f0122A BFigure 1-22.—Left arm: A. Frontal view of left arm with hand supinated; B. Frontal view of left arm with hand pronated.
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