PSI Barbering Practice Exam 2025 - Free Barbering Practice Questions and Study Guide

The risorius muscle is primarily responsible for drawing the corners of the mouth outward and backward, which creates the expression associated with grinning or smiling. It is a thin, superficial muscle located in the cheek area, and its contraction pulls the corners of the mouth laterally, facilitating a wide smile or grin.

In terms of muscle function, the zygomaticus muscle also contributes to smiling, but it specifically pulls the corners of the mouth upward rather than outward. The depressor anguli oris, on the other hand, has an opposing function; it draws the corners of the mouth downwards and is involved in frowning. Lastly, the orbicularis oris is a circular muscle around the mouth that primarily helps in closing and protruding the lips, rather than affecting the corners of the mouth’s movement in the same way that the risorius does. Therefore, the risorius is the muscle most associated with the action of grinning.