Which term refers to the muscle's fixed or proximal attachment?

• A. Insertion
• B. Origin
• C. Circular muscle
• D. Fusiform muscle

Answer: (B)

Origin is the term for the muscle’s fixed or proximal attachment. It’s where the muscle anchors to bone (often closer to the center of the body or the stationary part of the limb) and remains relatively still during contraction. The moving end that pulls on the bone is the insertion. So the origin stays put as the insertion moves toward it when the muscle contracts. For example, the sternocleidomastoid has its origin on the sternum and clavicle and inserts on the mastoid process; when it contracts, its action pulls the skull toward the sternum/clavicle. The other terms mentioned describe where a muscle attaches in a movement (insertion) or describe muscle shape (circular, fusiform), not the fixed attachment.