What structures comprise the axial skeleton?

• A. The longitudinal axis of the body, including the skull, vertebral column, ribs, collarbones and sternum.
• B. The bones of the legs, arms, hands and feet.
• C. Long bones, short bones, irregular bones, flat bones and sesamoid bones.
• D. The lipid bilayer that separates the cells.

Answer: (A)

The axial skeleton runs along the body's central axis and provides the main framework that supports the head, neck, and trunk while protecting vital organs. It includes the skull, the vertebral column, and the rib cage with the sternum, forming the structures that lie along the midline of the body. Some descriptions also mention the collarbones as part of this central axis because they connect the upper limbs to the axial skeleton, reinforcing the idea of components that support the torso and protect thoracic organs. This is why the option listing the skull, vertebral column, ribs, and sternum (along with the collarbones) best fits what the axial skeleton comprises. By contrast, the bones of the legs, arms, hands, and feet are part of the appendicular skeleton; describing bone types speaks to shapes rather than body regions, and the lipid bilayer is not related to skeletal structure.