Which muscle draws the mouth up and out, resembling a smile?

The muscle that draws the mouth up and out, resembling a smile, is the risorius. This muscle is located at the side of the mouth and contributes to the expression of happiness or amusement. When it contracts, it pulls the corners of the mouth laterally, which helps create a smiling expression.

While the other muscles mentioned also play roles in facial expressions, they each have different functions. The caninus muscle mainly contributes to frowning and pulling the corner of the mouth upwards, while the zygomaticus is specifically responsible for elevating the corners of the mouth and is typically associated with a smiling expression, though it primarily focuses on upward movement. The buccinator, on the other hand, aids in chewing by keeping food between the teeth instead of making a smile. Each of these muscles supports facial expressions but their specific actions differ, with the risorius being distinctly associated with drawing the mouth outwards in a smiling motion.