The appendicular musculature positions and stabilizes the pectoral and pelvic girdles and moves the upper and lower limbs. There are two major groups of appendicular muscles: (1) the muscles of the shoulders and upper limbs and (2) the muscles of the pelvic girdle and lower limbs. The functions and required ranges of motion are very different from one group to another. In addition to increasing the mobility of the arms, the muscular connections between the pectoral girdle and the axial skeleton must act as shock absorbers. For example, while you jog, you can still perform delicate hand movements, because the muscular connections between the axial and appendicular skeletons smooth out the bounces in your stride. In contrast, the pelvic girdle has evolved to transfer weight from the axial to the appendicular skeleton. A muscular connection would reduce the efficiency of the transfer, and the emphasis is on strength rather than versatility. Figure 11-14 provides an introduction to the organization of the appendicular muscles. |
