Which of the following parts is included in the axial skeleton?

The sacrum is a critical component of the axial skeleton, which primarily consists of the bones along the body’s central axis. The axial skeleton includes the skull, vertebral column, and rib cage, serving both structural and protective roles for the vital organs such as the brain, spinal cord, and thoracic organs.

The sacrum is a large, triangular bone at the base of the vertebral column that forms the back wall of the pelvis. It is formed by the fusion of five vertebrae (S1-S5) and articulates with the hip bones on either side, helping to support the weight of the upper body when standing and transferring that weight to the lower limbs when walking or running.

Other options, such as the humerus, pelvis, and femur, are part of the appendicular skeleton. The humerus is the bone of the upper arm, the pelvis consists of the hip bones, and the femur is the thigh bone. These bones are more involved in limb movement and are not classified as part of the axial skeleton. The distinction is important for understanding the basic structure of the human skeletal system and its functional divisions.