Which term describes a muscle action that moves an extremity away from the midline of the body?

• A. Internal
• B. Central
• C. External
• D. Abduction

Answer: (D)

Abduction is the movement that moves a limb away from the body's midline. When you lift an arm out to the side or spread the fingers away from the middle of the hand, you’re performing abduction. The muscles that carry this out are the abductors, like the deltoid and supraspinatus for the shoulder, or the dorsal interossei for the hand.

Internal and external are terms related to rotation at a joint (turning a part toward or away from the midline along the joint’s axis), not the general action of moving away from the midline. Central isn’t a term used to describe limb movement. So the term that best fits the action described is abduction.