Which muscle draws corners of mouth outward and backward as in a grin?

• A. Masseter
• B. Buccinator
• C. Zygomaticus major
• D. Risorius

Answer: (D)

The movement described is produced by the muscle that pulls the corners of the mouth outward toward the sides of the face, creating a wide grin. That muscle is the risorius. It originates from the fascia near the masseter and inserts at the corners of the mouth, pulling them laterally (outward) and slightly backward to produce the grin-like expression. Other muscles have different primary actions: the masseter elevates the jaw for chewing; the buccinator tightens the cheek and helps move air or food, not primarily changing the mouth corners; and the zygomaticus major elevates and slightly moves the mouth corner upward for a smile, but it doesn’t pull the corners outward and backward in the same way the risorius does.