Appendicular SkeletonThe appendicular skeleton consists of the bones ofthe upper and lower extremities.UPPER EXTREMITY.—The upper extremityconsists of the bones of the shoulder, the arm, theforearm, the wrist, and the hand (figs. 1-21 and 1-22).The bones that form the framework for the upperextremities are listed in table 1-1.Clavicle.—The clavicle (commonly called thecollar bone) lies nearly horizontally above the first riband is shaped like a flat letter S. The clavicle is a thinbrace bone that fractures easily. Its inner end is roundand attached to the sternum; its outer end is flattenedand fixed to the scapula. The clavicle forms theanterior portion of the pectoral girdle (fig. 1-21). Thepectoral girdle is composed of the two clavicles andtwo scapulae (shoulder blades). It functions as asupport for the arms and serves as an attachment forseveral muscles.Scapula.—The scapula is a triangular bone that liesin the upper part of the back on both sides, between thesecond and seventh ribs, forming the posterior portionof the pectoral girdle. Its lateral corner forms part of theshoulder joint, articulating with the humerus.Humerus.—The humerus is the longest bone ofthe upper extremity and is often called the arm bone(fig. 1-22). It articulates with the pectoral girdle toform the shoulder joint, and with the bones of the1-12HM3F0120THORACICVERTEBRAMANUBRIUMBODYSTERNUMXIPHOIDPROCESSRIBSCOSTALCARTILAGESTERNALANGLETRUE RIBS(VERTEBROSTERNALRIBS)FALSERIBSFLOATING RIBS(VERTEBRAL RIBS)(VERTEBROCHONDRALRIBS)123456789101112Figure 1-20.¾Anterior view of thorax,HM3F0121STERNALENDCLAVICLEHEAD OFHUMERUSSTERNUMCOSTALCARTILAGERIBSCAPULAHUMERUSULNARADIUSFigure 1-21.—Pectoral girdle.BONECOMMONNAMETOTALNUMBERIN BODYclaviclecollar bone 2scapulashoulder blade 2humerusarm bone 2radius and ulnaforearm bones 4carpalswrist bones 16metacarpalsbones of the palm 10phalangesfinger bones 28Table 1-1.—Bones of the Upper Extremities
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