Appendicular Skeleton The appendicular skeleton consists of the bones of the upper and lower extremities. UPPER  EXTREMITY.—The   upper   extremity consists  of  the  bones  of  the  shoulder,  the  arm,  the forearm, the wrist, and the hand (figs. 1-21 and 1-22). The   bones   that   form   the   framework   for   the   upper extremities are listed in table 1-1. Clavicle.—The   clavicle   (commonly   called   the collar bone) lies nearly horizontally above the first rib and is shaped like a flat letter S. The clavicle is a thin brace bone that fractures easily. Its inner end is round and attached to the sternum; its outer end is flattened and   fixed   to   the   scapula.   The   clavicle   forms   the anterior portion of the pectoral girdle (fig. 1-21). The pectoral girdle is composed of the two clavicles and two   scapulae   (shoulder   blades).   It   functions   as   a support for the arms and serves as an attachment for several muscles. Scapula.—The scapula is a triangular bone that lies in the upper part of the back on both sides, between the second and seventh ribs, forming the posterior portion of the pectoral girdle. Its lateral corner forms part of the shoulder joint, articulating with the humerus. Humerus.—The  humerus  is  the  longest  bone  of the upper extremity and is often called the arm bone (fig.  1-22).  It  articulates  with  the  pectoral  girdle  to form  the  shoulder  joint,  and  with  the  bones  of  the 1-12 HM3F0120 THORACIC VERTEBRA MANUBRIUM BODY STERNUM XIPHOID PROCESS RIBS COSTAL CARTILAGE STERNAL ANGLE TRUE RIBS (VERTEBROSTERNAL RIBS) FALSE RIBS FLOATING RIBS (VERTEBRAL RIBS) (VERTEBROCHONDRAL RIBS) 1 2 3 4 5 6 7 8 9 10 11 12 Figure 1-20.¾Anterior view of thorax, HM3F0121 STERNAL END CLAVICLE HEAD OF HUMERUS STERNUM COSTAL CARTILAGE RIB SCAPULA HUMERUS ULNA RADIUS Figure 1-21.—Pectoral girdle. BONE COMMON NAME TOTAL NUMBER IN BODY clavicle collar bone 2 scapula shoulder blade 2 humerus arm bone 2 radius and ulna forearm bones 4 carpals wrist bones 16 metacarpals bones of the palm 10 phalanges finger bones 28 Table 1-1.—Bones of the Upper Extremities