Which muscle is commonly known for its role in smiling?

The muscle renowned for its role in smiling is the Risorius. This muscle is located in the facial region and plays a significant role in facial expressions. Its primary function is to pull the corners of the mouth laterally, which contributes to the expression of smiling as well as grinning.

The Risorius is important for creating that particular facial expression, particularly in conjunction with other muscles such as the Zygomaticus Major, which also assists in elevating the corners of the mouth in a smile. While options like the Zygomaticus Minor and Orbicularis Oris are involved in movements related to facial expressions and the mouth, respectively, they do not isolate the action of smiling as effectively. The Masseter, primarily a muscle of mastication, is focused on chewing rather than on expressions, making it less relevant in the context of smiling. Understanding the specific actions of these muscles clarifies the Risorius's key role in expressions of joy such as smiling.