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The 126 bones of the limbs and their girdles, enabling movement and manipulation of the environment.
Medically reviewed & updated
The skeleton is divided into two major parts. The axial skeleton forms the central core (skull, vertebral column, and rib cage), while the appendicular skeleton comprises the bones of the limbs and the girdles that attach them to the axial skeleton. Of the roughly 206 bones in the adult body, 126 belong to the appendicular skeleton. Its primary role is movement and interaction with the environment—walking, lifting, grasping, and manipulating objects.
Each limb attaches through a girdle. The pectoral (shoulder) girdle consists of the clavicle (collarbone) and scapula (shoulder blade) on each side. It is loosely attached to the axial skeleton, which gives the upper limb a remarkably wide range of motion at the cost of some stability. The pelvic girdle, by contrast, is formed by two hip bones (each fusing the ilium, ischium, and pubis) that join the sacrum. It is strong and rigid, transmitting the weight of the upper body to the legs and protecting pelvic organs.
The upper limb includes the humerus (upper arm), the radius and ulna (forearm), and the hand—made up of carpals (wrist), metacarpals (palm), and phalanges (fingers). The intricate arrangement of the hand allows fine, precise movements and the opposable thumb that is a hallmark of human dexterity.
The lower limb includes the femur (thigh bone, the longest and strongest bone in the body), the patella (kneecap), the tibia and fibula (lower leg), and the foot—comprising tarsals (ankle), metatarsals, and phalanges (toes). These bones are built for weight-bearing, balance, and locomotion.
Because the appendicular skeleton bears mechanical stress and is involved in nearly every physical activity, its bones and joints are frequent sites of injury. Hip fractures (typically of the femoral neck) are a major concern in older adults with osteoporosis. Wrist (distal radius) fractures often result from falls onto an outstretched hand, and clavicle fractures are common in sports and falls. This page is educational and not a substitute for professional medical care.