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How are the axial skeleton and appendicular skeleton different?

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Front and back views of the human skeleton are shown side by side, with labeled bones including the skull, spine, ribs, pelvis, arms, legs, hands, and feet. Insets detail the bones of the foot and hand, highlighting major bone groups and anatomical terms. — human skeleton Front and back views of the human skeleton.

The human skeleton is divided into two primary subdivisions, the axial skeleton and the appendicular skeleton, which differ in their anatomical composition and functional roles.1

The Axial Skeleton

The axial skeleton forms the central axis of the body. It consists of 80 bones, including the skull, the vertebral column, and the rib cage. Its primary functions are to provide structural support for the trunk and to protect vital organs, such as the brain, spinal cord, heart, and lungs.21

The Appendicular Skeleton

The appendicular skeleton comprises the bones of the upper and lower limbs, as well as the pectoral girdle (shoulder) and pelvic girdle (hip). While the axial skeleton is specialized for protection and support, the appendicular skeleton is primarily adapted for motion and interaction with the environment. The girdles serve to connect the limbs to the axial skeleton, with the pelvic girdle providing a stable, weight-bearing connection and the pectoral girdle offering a highly mobile attachment for the arms.213