Anatomy, Appendicular Skeleton

The appendicular skeleton is one of two major bone groups in the body, the other being the axial skeleton. The appendicular skeleton is comprised of the upper and lower extremities, which include the shoulder girdle and pelvis. The shoulder girdle and pelvis provide connection points between the appendicular skeleton and the axial skeleton to where mechanical loads transfer. Of the 206 bones in the adult human body, a total of 126 bones form the appendicular skeleton. The bones that contribute to the appendicular skeleton include the bones of the hands, feet, upper extremity, lower extremity, shoulder girdle, and pelvic bones. A single upper extremity includes 14 phalanges (proximal, intermediate, and distal), five metacarpals, eight carpal bones, two forearm bones (radius and ulna), the humerus, and the shoulder girdle (scapula and clavicle). A single lower extremity contains 14 phalanges (proximal, intermediate, and distal), five metatarsals, seven tarsal bones, two leg bones (fibula, tibia), the femur, and the hip bone or coxal bone (ilium, ischium, and pubis). These bones articulate with each other and are joined by a multitude of ligaments, cartilage, and tendons to form the appendicular skeleton. There are also bony prominences and protuberances that serve as muscle attachment sites on the surfaces of these bones. The appendicular skeleton is structured for a greater range of motion and locomotion generation when compared to the axial skeleton.